MATERIALS SCIENCE AND ENGINEERING

Knowledge of the atomic, crystalline, and microstructural characteristics of materials and use of this knowledge in the design and synthesis of new materials receive major emphasis in the research programs of the department. Equally challenging is the understanding of how these materials may be formed into useful shapes and devices.

In the area of ceramics, new scientifically based methods of fabricating optimized ceramic microstructures and macrostructures provides the underpinnings for a wide-range of research topics such as new high-temperature superconductors, deposition of ultrahard diamond films, and toughened cements and concrete.

Work in the area of metals ranges from studies on high-performance steels to basic research on intermetallic compounds and improved alloys. Fundamental studies on corrosion of metals in gaseous environments are underway to interpret the very complex surface reactions between metals and gases such as oxygen, hydrogen, or nitrogen.

Polymer research is directed at materials that tend to self-assemble in the melt or solution and can then be fabricated into shapes with outstanding mechanical properties. New kinds of biodegradable polymers are being studied with the goal of designing systems that facilitate disposal of plastics.

Studies of electronic materials include advanced research on processes to deposit single layers of molecules to tailor the properties of semiconductor devices. This knowledge will be of great value in the design of optical and magnetic devices.

New kinds of composites consisting of high-strength, modulus fibers embedded in metal, ceramic, or organic matrices are being explored with the goal of providing the foundations for the next generation of high-performance structural materials.

To meet the challenges of training and educating materials scientists for the future, a completely new curriculum has been designed for the undergraduate and graduate students in the department. As part of this program collaborative research is pursued with groups in aeronautical, chemical, civil, and mechanical engineering, physics, and chemistry.

COMBUSTION, PROPULSION, AND AUTOMOTIVE SYSTEMS

The controllable flow of energy into and out of a vehicle suspension is studied in two phases: active control and semiactive control. Active control means being able to remove and/or add energy to the suspension from an external power source. Performance comparisons between active suspensions and passive suspensions, capable of only constant energy removal rates, demonstrate the benefits of the active systems. Semiactive control means being able to control the rate of energy removal but not being able to add energy to the system. Both approaches are investigated using theory, simulation, and experiment.

Presently, components of the vehicle act independently of one another to control various aspects of the vehicle's dynamics. In this research, the dynamics of a moving vehicle are controlled by coordinating and integrating the various subsystems of the chassis. Wheel torque, steering forces, and suspension forces are combined in a synergistic approach to achieve levels of vehicle performance and safety that are superior to previous approaches. Extensive use of modern control techniques is made to determine the optimal combination of forces.

The oscillatory combustion behavior of solid propellants and energetic materials is of great interest for purposes of achieving stable combustion in solid rockets. This project is aimed at developing a new technique for determining the unsteady response function of propellants that is simpler and more reliable than the standard T- burner method. The combustion response to an unsteady radiant heat source (laser) is measured from the recoil of the propellant. A mathematical model is being developed to predict the unsteady burning rate of the propellant and test modeling assumptions.

As new energetic materials are developed for use as propellants in solid rockets, it will be necessary to consider their combustion stability at an early stage of propellant development. This will require a multidisciplinary approach including complex chemistry, combustion, and fluid dynamics. The overall objective of this project is to conduct a coordinated, multidisciplinary investigation to advance our knowledge of dynamic burning response of new combinations of energetic materials. The specific objective is to develop an understanding of the combustion behavior of new energetic materials as monopropellants and combinations of new and conventional energetic materials as composite propellants.

The objectives of this study are (1) to develop and validate a one- dimensional, premixed gas phase reaction code to be coupled with an existing condensed phase code which will calculate burning rate, temperature profile, and species profiles; (2) to use this code to investigate the domain of validity of existing activation energy asymptotics analytic results; (3) to develop new analytic results that can predict variations in steady burning rate and flame standoff distance with pressure, initial temperature, and radiant heat flux; and (4) to apply these models to steady and oscillatory (quasi-steady) burning of RDX and HMX.

The combustion of aluminum droplets in a solid rocket motor internal flowfield will be simulated using a simple vapor phase diffusion- limited droplet burning model. Two versions will be developed. First, a detailed model will be developed based on numerical solution of the governing differential equations for droplet burning in a convective, radiative environment. From the results of this detailed model, a "d2" correlation will be extracted for use in the multi- phase, reacting flowfield analysis. This correlation will include the important effects of variable ambient gas composition as well as thermal radiation.

Thermal radiation is an important mode of heat transfer in rocket motor internal flowfields. The primary source of thermal radiation is the field of submicron, liquid phase Al2O3 "smoke" particles formed by aluminum droplet combustion. In addition, pressure-broadened line radiation from molecular gases such as CO2, H2O, and HCl is also important at the elevated pressures in rockets. A hybrid radiation model will be developed with an N-flux description near the propellant surface matched with a diffusion approximation in the core region. A k-distribution technique will be used to accommodate the continuum particle radiation and the molecular gas line radiation.

The heterogeneous combustion zone near a composite propellant surface is being simulated. The first approach will be to utilize the quasi- statis approximation (quasi-steady gas and solid preheat zones). For sufficiently rapid transient events (i.e., of time scales less than the thermal relaxation time of the propellant which is on the order of 1 to 10 ms), the quasi-static of approximation fails and a second approach will be utilized: a modification of the Zeldovich-Novozhilov (ZN) method for extending steady-state burning data to the unsteady regime, still retaining the quasi-steady gas assumption.

Using a laboratory-scale, end-burning solid propellant rocket motor, ignition and combustion of injected aluminum particles are observed by spectroscopic techniques. Models are being developed to confirm the metal burning rate as a function of gas composition and pressure.

This effort is part of a large project to develop advanced simulation tools for a solid rocket motor. Under this task, we will be developing the fluid flow aspects of the project. This will include large eddy simulations of the core flow in a rocket motor.

New energetic solid propellants will contain metals such as aluminum, magnesium, and boron. Experiments in a high-pressure shock tube measuring boron ignition delay and combustion (burn) time, as well as measurements by emission spectroscopy of the transient reactive species, will impact chemical kinetic theories on reaction pathways for such two-phase mixtures.

To coordinate the overall predictions of the interior ballistics of modern solid-propellant rocket motors, simulation codes will be used to predict both steady-state and transient performance. Calculation of pressure distribution, burning rates, and overall rockets thrust will be made.

To explain rocket motor combustion instability, one must know the propellant burning rate response to pressure transients. End burning solid propellant rocket motors, where the motor throat area is modulated, will give rise to pressure fluctuations during which instantaneous burning rate, gas species, and gas temperature can be measured. Laser diagnostics and ultrasonic techniques are being used showing significant nonsteady burning rate responses.

The task of developing a multicomponent, multiphase hydrodynamic model that describes all the salient features of an underwater explosion of metal-loaded high explosives is addressed. The model represents a significant advancement over previous efforts in this area because it includes many nonideal phenomena not previously considered (e.g., combustion of metal-loaded high explosives and bubble-water interfacial transport processes). The primary purpose of this research is to develop a basic understanding of the fundamental relationship between the available energy stored in the explosive system prior to detonation and the subsequent redistribution of energy throughout the bubble and surrounding fluid.

Knowledge of the instantaneous vapor and liquid fuel distributions is important to the improvement of direct-injection engines. A fluorobenzene/DEMA exciplex system is developed for concentration measurements of lower boiling fuel, such as hexane and gasoline. Particular attention is paid to: linearity and spatial nonuniformity of the intensified camera, gain calibration and modulation transfer function of the signal collection system, fluorescence saturation, the selection of filters and of the concentrations of the two dopants to reject Mie scattering, and reduce crosstalk while enhancing the vapor signal. This system is capable of yielding qualitative liquid and quantitative vapor instantaneous spatial distributions.

To understand and improve fuel preparation of port-injection engines, multidimensional models are being developed for spray impingement on the wall, fuel film formation and transport, and atomization due to the back flow from the cylinder into the intake port upon intake valve opening. P/DPA, digital imaging, and light reflection measurements of drop size and velocity, film spreading rate, and film thickness will be conducted under controlled conditions specifically designed to provide a set of data for direct comparison with the modeled results. The calibrated models will then be used to study the port-injection and back-flow processes in the engines.

Atomization of liquid jets is of primary importance for many industrial applications. Models for prediction of instability and disintegration of liquid sheet jets and round jets are being developed. Aerodynamic instability that occurs at a disturbed two- phase interface is studied by using perturbation analysis. Detailed numerical simulation of the unstable waves on the two-phase interface is conducted to extend the analytical model well into the nonlinear breakup regime. The resulting models for both sheet jets and round jets will be incorporated into a multidimensional code for computations of internal combustion engines.

A lean, direct-injection, spark-ignition engine concept has the potential of reducing fuel consumption and increasing performance while obtaining cleaner exhaust gas and greater driver comfort. The key research need of this type of engine is to develop a better understanding and control of in-cylinder fuel injection, atomization, vaporization, and mixing. The objective of this research program is to study the fuel sprays and air-mixing process in direct-injection, four-stroke, spark-ignition engines. The latest multidimensional modeling will be used to conduct detailed studies. Direct-injection strategies currently under consideration by industry will be used, and the effects of key variables such as injector timing, atomization quality, air motion, and engine geometry will be investigated.

The heating and gasification of a fuel droplet during the intake and compression strokes of stroke-ignition engine are important for fuel/air mixture preparation and cold-start emission. The amount of the liquid droplets entering the cylinder is strongly influenced by the type of fuel used. A fuel blend was chosen in order to match the distillation curve for the gasoline. An evaporation model of multicomponent fuel droplets is developed. The model will be verified against vaporization measurements of a single droplet and exciplex measurements of low- and high-volatility fuel liquid and vapor distributions in the port-injection engine. The model will then be used to study the detailed mixture preparation process.

The diesel engine is the leading heavy-duty power plant because of its superior energy efficiency. However, diesel industries face increasingly stringent emissions regulation in both nitric oxides and particulates. A detailed understanding of combustion is required to effectively reduce emissions while maintaining engine fuel economy. A multidimensional model that has been tested extensively in various engine environments is used to characterize the fuel/air mixing and combustion in the engine. Direct-injection strategies currently under consideration by Cummins will be studied and the effects of injection rate and timing, EGR, and three-dimensionality on combustion will be investigated.

Natural gas is an attractive alternative fuel for diesel engines because of the potential for achieving high thermal efficiencies and power densities, reduced fuel costs, and reduced particulate emissions. A single-cylinder engine has been modified to provide optical access to the cylinder for measurements of fuel/air mixing, flame propagation, and NO formation using laser-induced fluorescence. In-cylinder measurements of temperatures and fuel-air ratios will be performed using coherent anti-Stokes Raman scattering. Modeling of the natural gas injection, mixing, ignition, and combustion will be conducted using a modified version of the KIVA 3 code.

We are investigating gas-phase chemistry near the deposition substrate in diamond-forming flames using spatially resolved laser diagnostics. High-quality, polycrystalline diamond films are deposited using acetylene/hydrogen/oxygen flat flames stabilized against molybdenum substrates. Coherent anti-Stokes Raman scattering is used to measure major species concentrations (H2, CO) and temperature profiles near the diamond-forming substrate. Laser-induced fluorescence and/or degenerate four-wave mixing will be used to measure the minor species H2, C2H2, and CH3, which are thought to play an important role in diamond-forming flame chemistry.

We are investigating the interaction of a vortex with a diffusion flame sheet. Vortices induced by using an acoustic speaker to drive a fuel jet cause the flame sheet to bulge outward. The induced stretch is sufficient to extinguish the flame locally. We will use advanced laser diagnostics to study the flame-vortex interaction. Temperature measurements are performed using coherent anti-Stokes Raman scattering. Concentrations of the radical species OH and CH and the pollutant species NO will be measured using laser-induced fluorescence. The experimental measurements are compared with computational fluid dynamics calculations that include detailed chemical kinetics.

Degenerate four-wave mixing (DFWM) is a promising combustion diagnostic, but lack of accurate models for lineshapes and signal intensities has impeded the quantitative application of the technique. A combined theoretical and experimental approach is used for the development and evaluation of strategies for quantitative measurements in flames. DFWM signal levels and lineshapes are calculated theoretically by solving the time-dependent density matrix equations for the DFWM process by direct numerical integration. Experimentally, DFWM measurements of OH will be performed over a wide range of flame pressures and stoichiometries for comparison with these theoretical calculations.

In a collaborative effort with General Electric Aircraft Engines, an experimental investigation of gas turbine combustor concepts is underway. Advanced nonintrusive laser diagnostics including coherent anti-Raman Stokes scattering and laser-induced fluorescence will be used to probe the mixing and combustion processes. The purpose of this research program is to "bridge the gap" from more fundamental experimental and modeling studies of turbulent mixing and combustion to the combustor design process. The technical issues that will be addressed in research at UIUC include fuel/air mixing, flame structure and stabilization, and pollutant formation.

The preparation of fuel and air mixtures during cold start conditions for port-injection systems is being investigated. Because cold start emissions of unburned hydrocarbons are strongly influenced by the presence of liquid fuel in the combustion chamber, this study seeks to develop an improved understanding of the fuel preparation process as it relates to cold start atomization and mixing. Laser diagnostics are being used to study liquid atomization, vaporization, and mixing with air in the intake port and cylinder as a function of engine variables including valve lift, air flow, manifold geometry, and fuel injector type.

A single-cylinder, four-valve, extended piston, spark-ignition engine is used to study the effects of in-cylinder flow patterns on combustion and heat loss. Shrouded inlet values are used to vary turbulence levels, while five independent cooling systems can control component operating temperatures. Fast-response thermocouples are used to measure instantaneous temperatures and heat transfer rates at various locations inside the combustion chamber. The program will examine the local heat transfer rates at incipient knock conditions on both the piston and combustion chamber.

If the pressure in underground gasoline storage tanks at filling stations increases beyond a specified level, a pressure relief valve will open and vent hydrocarbons into the atmosphere. In this research project, a model is being developed to predict the underground tank pressure as a function of various parameters including tanker refills, gasoline distribution rate, vapor return rates, temperatures, pressures, and gasoline properties. The goal of the research is to be able to predict tank pressure as a function of various operating and ambient conditions in order to minimize hydrocarbon emissions through improved storage system hardware and operating procedures.

Use of compressed natural gas is attractive for large-displacement, heavy-duty engines because of emission standards and availability. Mixing natural gas with air and the distribution of the gas-air mixture to the cylinders is important to avoid cylinder-to-cylinder variations. The velocity and concentration distributions of the gas- air mixture are being measured throughout the intake system to determine the contribution of individual components on engine performance and exhaust emissions. Improved intake system components could then be designed to minimize undesirable cycle-to-cycle variations.

University of Illinois; U.S. Department University of Illinois; National Science Foundation, DESIGN METHODOLOGY AND TRIBOLOGY

The main objective of the proposed research program is to identify effective methods for lubricating compressors of air conditioning and refrigeration systems using ozone-safe refrigerants. A number of candidate materials, especially aluminum, are experimentally investigated to determine their tribological behavior under fully lubricated or lubricant-starved condition and in environments simulating compressor operation. Possible friction, wear, and seizure models will be examined to determine their usefulness in predicting tribological behavior of these mixtures.

The objective of this study is to develop advanced methodology for modeling of earth-moving vehicles. The current software using DYNASTY, a special dynamic simulation package, is enhanced by the use of Kane's method, which greatly reduces computer time for simulation runs. In addition, attention is given to the use of neural networks in the representation of the force effects imposed by the soil in the digging process. The project has far-reaching financial implications relative to the monetary strategies of an earth-moving equipment manufacturer.

The objective of this study is to evaluate operator visibility of earth-moving equipment using Caterpillar's virtual prototyping system. This system uses real-time interactive graphics by means of the National Center for Supercomputing Applications CAVE. Equipment part designs are converted from CAD files and placed directly into the virtual environment, giving an accurate representation of the vehicle, which is controlled using a dynamics simulation package. Then, within the environment, qualitative and quantitative studies on operator visibility can be performed. By using this system first, operator visibility can be evaluated much more quickly and inexpensively than by making a physical prototype.

The objective of this project is to develop a system to calculate the optimal path from given starting and ending points for an earth-moving vehicle to follow during a typical work cycle. Constraints considered in calculating the optimal path are the vehicle geometry, vehicle performance limits, work area configuration, and vehicle jerk and acceleration limits. The applications of this research will include use as a design tool to assist engineers in determining vehicle specifications.

Much work has been performed to develop finite elements for the analysis of plates. These theories, primarily based on the Kirchoff assumptions, contain certain inconsistencies. In this study, a plate theory consistent with 3-D elasticity is developed using the theory of internal constraints. The basic assumptions of the Kirchoff plate theory are enforced as internal constraints as are the appropriate constrained constitute equations. In this way, no inconsistencies are introduced. A 3-D, 8-noded brick element is developed and yields satisfactory results in the analysis of some simple plate problems. The applicability of the element to more complicated problems is being investigated.

Controversy exists over various rate algorithms for elastoplastic analysis. The oscillatory response in simple shear had led researchers to investigate numerous stress rates for the hypoelastic material response models. It is felt that the problems encountered here are attributable to more fundamental inconsistencies in their formulations. An attempt is being made to investigate these issues by delving into the fundamental aspects of the hypoelastic formulation. Our findings will be exemplified by solving the simple shear problem using the revised theory.

First-order sensitivity expressions are derived for nonlinear thermal systems in a Eulerian reference frame with respect to surface heat flux terms. The surface region over which the flux is applied is defined through a series of design parameters. Local shape functions in the finite-element formulation are manipulated to obtain accurate sensitivity information. The method is applied to optimize laser annealing processes. The solution ensures that a desired material microstructure is obtained with minimal laser power.

A computer-aided design methodology is developed to automate the design of mechanisms. The approach uses efficiently computed design sensitivities of the generalized coordinates and reaction forces with respect to local joint positions. Sensitivities are combined with numerical optimization to optimally locate joint coordinates to minimize a cost function while satisfying constraints. These sensitivities are efficiently computed because they utilize the decomposed Jacobian from the kinematic analysis. Mathematica® is used to expedite the analytical derivations. The analytical sensitivities are verified with finite-difference sensitivities. Mechanisms with known analytical solutions are optimized for verification purposes. Finally, the design of a wheel loader bucket mechanism is studied.

The goal of this project is to develop a robust mathematical link between solid modeling and design sensitivity analysis. Two of the traditional difficulties of shape sensitivity analysis and optimization have been the troublesome and lengthy tasks of model parameterization and the evaluation of grid sensitivities essential to shape sensitivity analysis. While solid modelers and automatic mesh generation techniques have provided solutions for model parameterization, a method is being developed to analytically derive grid sensitivities from the variational geometry of a feature-based modeler.

Sensitivity analysis and optimization techniques are used to design control systems for nonlinear plants. These plants usually preclude classical/modern control strategies because of their complex nonlinear behavior. A rigorous dynamic model of the system under consideration is derived, and an open loop control law is determined minimizing the desired cost function through sensitivity analysis and optimization techniques. Unfortunately, open loop schemes never completely solve automatic control problems as they lack desirable features of feedback control such as disturbance rejection and lowered sensitivity to parameter variation. Hence, we seek to combine open- and closed-loop strategies in the overall control scheme.

Explicit design sensitivity analysis formulations for systems undergoing large elastoplastic deformations will be derived. A continuum formulation will be investigated first by applying the direct differentiation method to the continuum governing equations. Next, a discretized version both in space and time will be obtained for finite-element implementation. The derived formulations will be used to optimize metal-forming operations.

To correlate analysis results with experimental data, optimization algorithms use first-order sensitivity expressions to minimize error functions with respect to the unknown model parameters. Research is being performed to investigate the stability of this solution process. Second-order sensitivities will be derived for the nonlinear thermal conduction systems. Methods for determining stability of the inverse solution based on the condition of the Hessian matrix will be explored.

First-order design sensitivity expressions will be derived and implemented for various polymer-processing problems. The generalized Hele-Shaw model for Newtonian and power law fluids will be used in the fully coupled thermal fluid flow formulation. Initially, steady isothermal sensitivities will be developed to optimize the polymer sheet extrusion process to ensure a uniform sheet exit velocity by varying the thickness distribution inside the extrusion die. The finite-element method will be used in nonlinear numerical simulations. Extension of the method to injection and compression molding with other non-Newtonian behavior is expected.

DYNAMIC SYSTEMS AND CONTROLS

The modeling and control of fluid power systems includes electrical, mechanical, hydraulic, and pneumatic subsystems. Various types of advanced controllers are applied to these complex nonlinear systems. Applications of these systems range from automotive engine systems to earth-moving vehicles to high-speed machine tool drives.

The control of various nonlinear mechanical and electromechanical devices is studied. The techniques applied vary from standard linearization (Jacobian) to gain scheduling to nonlinear transformations (feedback linearization). The structure of the particular systems being controlled is exploited to facilitate control. The application of this is directed to the control of vehicles and manufacturing systems.

Fluid power systems are able to achieve high forces and fast response. They also tend to be quite nonlinear in nature. Through modeling, simulation, and experiment, appropriate controllers are determined to enable fluid power drives to maintain their high force capability but with an increased bandwidth and accuracy. The application of this work is the development of high-speed machine tool drives for novel machine tools and other manufacturing equipment such as injection molding machines. Force and position control algorithms are developed and implemented along with hybrid force/position approaches.

Presently, components of the vehicle act independently of one another to control various aspects of the vehicle's dynamics. In this research, the dynamics of a moving vehicle are controlled by coordinating and integrating the various subsystems of the chassis. ABS braking systems, traction control systems, lateral stability control systems, 4-wheel drive (4WD), and controllable suspensions (active or semiactive) are combined in a synergistic approach to achieve higher levels of vehicle performance. The benefits of this approach are increased vehicle performance and safety.

Fluid power systems, particularly hydraulics, have a very high power- to-weight ratio with a large dynamic bandwidth. The goal is to use advanced control methodology to increase the performance of fluid power systems in terms of force and motion control. Several linear and nonlinear control approaches are taken. Where appropriate, new methodologies are developed based on information gathered from experimental experience. The applications of these high-performance systems include active vibration isolation and manufacturing systems.

The goal of this project is to synthesize stable and robust real-time predictive control algorithms with the tuning knobs which specify trade-off between performance and robustness for use in the self- tuning applications.

The goal of this proposal is to develop mathematical models capable of predicting the temporal evolution (dynamics) of the MF-influenced free-radical transformations of the lipids. The main emphasis is on covering the range of MF strength from zero through the values where clear reproducible effects of the MF exposure are found to the values where MF exerts strong influence on the free radical transformations.

This research attempts to lay the foundation of the optimal control and mathematical representation of discontinuous dynamical systems with impulsive impacts.

A large number of processes require infinite dimensional state space for their adequate descriptions. The application of regular finite- dimensional adaptive control algorithms to such processes might result in poor convergence properties and inadequate performance of adaptive controllers. The purpose of this research is to explore the methods of improving controller adaptation capabilities for systems described by partial differential and functional equations.

The project focuses on the development of robust controllers for time- varying systems with uncertainties. The specific application is the control of startup and shutdown and transient dynamics of a boiler.

This project aims at combining recently developed H predictive identification to synthesize robust controllers for several classes of MIMO uncertain nonlinear systems. The application is currently focused on the stream generation processes in industrial and utility boilers.

The broad objective of this project is to investigate the applicability of active control of acoustic emissions to air conditioning and refrigeration systems. The specific objectives of the proposed project are to: (1) identify the major sources and characteristics of acoustic emissions in air conditioning and refrigeration systems, (2) determine the techniques best suited for modeling and analysis of these emissions, and (3) determine which control strategies and sensor/acuator configurations are plausible for active noise control in these systems. Experimental work will be conducted to determine the noise sources and transmission paths in a typical air conditioning or refrigeration unit.

This research investigates the design, dynamic modeling, simulation, and control of energy-efficient, fast response, electrohydraulic actuators for camless engine valvetrain application. An accurate dynamic model of an experimental camless valvetrain system is developed and used for parametric and sensitivity studies and manufacturing tolerance analysis for dynamic performance variations. Also, the model is used to design control strategy for the engine valves operation, as well as to develop an engine-wide optimal control strategy incorporating this new actuation method. An experimental camless engine will be integrated using the electronically controlled hydraulic valvetrain to verify analytical results.

This research studies the shift dynamics and control of an automatic transmission. An experimental facility has been provided by the sponsor and is being integrated for data acquisition and control. The transient response and dynamics of transmission shift and clutch engagement will be modeled. Control algorithms will be designed for improved shift quality and implemented on the test facility.

High sampling rate, digital motion control algorithms and their implementation and application to dynamic variable depth of cut machining is investigated. The control algorithms in conjunction with fast response actuators can be used to compensate for dynamic errors occurring in machining processes such as oval piston turning and dynamic compensation of cutting-force-induced workpiece deformation. An experimental boring bar with embedded piezoelectric actuator has been developed and used in a boring experiment to reduce by six times the out-of-roundness error caused by bore deformation.

The objective is to develop dynamic control of direct-drive machining systems. Recent advances in tooling materials and spindle technology have the potential to dramatically increase metal removal rate. These have made machine tool performance the limiting factor in applying higher cutting speeds. To increase feed speed, use of direct drives is considered. Control of the drives is critical in the development of high-performance, direct-drive machine tools. This research will develop an integrated control methodology, presenting a synergy of inner loop robust feedback control, outer loop special-purpose repetitive control and contour tracking control, and optimal feedforward/preview control.

Fluid power systems exhibit nonlinear, time-varying, and infinite dimensional dynamics. The major nonlinearities are from the static friction and the pressure-flow relation. The time-varying dynamics are from the temperature changes, component wear, and fluid aging. The infinite dimensional dynamics come from transmission-line dynamics. A fixed linear controller cannot compensate for these nonlinearities, variations, and uncertainties. High sampling rate, digital adaptive control techniques with nonlinearity compensation and robust stability to high-frequency unmodeled dynamics are under development using digital signal processors for high-performance hydraulic servo- actuators.

This research studies the dynamics and control of a steel belt type of continuously variable transmission (CVT) for passenger vehicle application. Under development is a control-oriented model, which describes the dynamics of the speed ratio shifting and the torque transmission. A control system is then designed based on the particular model structure under actuator capacity and speed constraints.

The distortions in the receptance plots of forced nonlinear mechanical systems are examined. Weak nonlinearities of stiffness and damping are considered, and approximate harmonic steady-state responses are evaluated. The Nyquist plots of weakly nonlinear systems are then constructed and the nonlinear distortions are identified and analytically investigated. Based on the results of the analysis, a method for identifying and quantifying weak nonlinearities in the frequency responses of practical systems is suggested. The applicability of the proposed technique is then tested with theoretical and experimental data.

A new approach for studying traveling or stationary waves with spatially localized envelopes in nonlinear periodic particle chains is studied. The technique used is an extension of previously used nonlinear normal mode (NNM) methodologies for analyzing NNMs of discrete and (bounded, one-dimensional) continuous nonlinear oscillators. In the context of these methods, stationary wave solutions in the chains are regarded as localized NNMs of unbounded, continuous, 1-D systems. Propagating, weakly modulated waves are then computed by imposing Lorentz coordinate transformations to the stationary wave solutions.

A study of the dispersion of transient stress waves in the first layer of a weakly coupled semi-infinite bilayered system is performed. The analysis employs asymptotic Fourier transform inversions and makes use of the fact that the weakly coupled system possesses small propagation zones in frequency. The derived analytic expressions contain nonoscillating terms and convolution integrals with decaying oscillatory kernels. Depending on the frequency and amplitude of the convolution kernels, the dispersed waves overshoot or undershoot the applied impulsive excitation. This result is of significant practical importance in the design of layered systems as stress attenuators.

System identification and diagnostic methodologies for detecting defective bearings in rotating machinery are developed. This is of direct relevance to the utility industry, where vibrational-related failure in rotating machinery is a leading cause of forced outages in power plants. Modal analysis techniques and nonlinear system identification methodologies (higher-dimensional frequency response functions and Volterra series) are considered. A second problem studied is the computational investigation of transient heat conduction in laminated thermal barriers used for thermal protection of gas turbine components. A double integral transform methodology is used, and numerical inversions are performed by efficient computational algorithms.

An analytical/numerical study of nonlinear confinement of transient motions in a flexible truss structure is carried out. We investigate nonlinear motion confinement caused by clearance or geometric nonlinearities. We then develop passive or active techniques to enhance the motion confinement phenomenon.

We experimentally investigate transient and steady-state localized modes in periodic flexible systems with stiffness nonlinearities. The goal is to show that for sufficiently small coupling between substructures these systems possess passive nonlinear motion confinement properties, which can be used in new vibration and shock isolation designs.

The aim of this research is to develop new methodologies for suppressing noise disturbances in spacecraft. The fundamental issue is the maintenance of small levels of vibration on a spacecraft whose mission involves precision pointing. A new vibration isolation technique to effectively suppress high-frequency noise in the range 30 Hz to 300 Hz is studied. The technique relies on passively or actively inducing localized nonlinear normal modes in the spacecraft system using actively or passively induced stiffness nonlinearities. This design is new and innovative and relies on the efficient use of nonlinear forces to spatially confine the unwanted motion from sensitive parts of the spacecraft.

FLUID DYNAMICS

The vestibular semicircular canal system is a phylogenetically old sensory apparatus responsible for transducing angular motions of the head. Fluid-structure interactions in the semicircular canals that result from head rotation give rise to spike initiation in afferent nerve complexes which encode the vestibular nerve. The aim of this research is to study the response dynamics of the semicircular canals. A new mathematical model of canal mechanics is under development which couples an asymptotic theory of pulsatile flow in curved circular ducts to a biphasic theory of flow and deformation in and around important structures involved in the transduction process.

It has become increasingly evident in recent years that the presence of a macromolecular layer lining the luminal surface of capillary blood vessels is a fundamental determinant of the rheological behavior of blood in microvessels less than 50 mm in diameter. The aim of this research is to study the effect of this structure on microvascular resistance and red blood cell flux through capillaries. A new theoretical analysis is under development which utilizes mixture theory, lubrication theory, and the shell equations of equilibrium for hyperelastic solids to analyze the flow and deformation of red blood cells within capillaries.

This project seeks to obtain nonintrusive, laser-based, diagnostic measurements to identify the important flow mechanisms in three- dimensional base flows that are representative of high-speed objects flying at the angle of attack. Important questions to be addressed include the steadiness of the overall flowfield, the interaction of the lee-side vortical flow with the base flow recirculation region, and the size and shape of the separated flow regions. Measurement methods used include Schlieren/shadowgraph photography, surface streakline visualizations, LDV, planar Rayleigh/Mie scattering, and PIV.

Planar visualizations and measurements of the large-scale turbulent structures in axisymmetric supersonic base flows are being obtained by means of Rayleigh/Mie scattering and planar laser-induced fluorescence (PLIF). We have obtained similar visualizations for planar, supersonic base flows, but the focus here is to investigate the extra rates of strain that occur in axisymmetric flows. In addition, the effects of afterbody boattailing and mass bleed into the separated region will be studied. Both of these flowfield manipulations are known to increase base pressure, but their effects on the detailed turbulent structure are currently unknown.

The objectives of this research are the development and application of a technique for quantitative measurements of the structure of high Reynolds number gaseous shear flows. The extent of mixing at the molecular as well as the macroscopic level in shear flows will be measured instantaneously by using two different lasers and two different cameras to excite and then detect LIF from NO and acetone simultaneously. Quantitative measurements of molecular mixing are of tremendous importance, particularly in chemically reacting systems, where mixing of the fuel and oxidant streams at the molecular level is required to initiate reactions.

Particle image velocimetry (PIV) is being used to obtain a more complete understanding of the behavior of large-scale structures in both incompressible and compressible mixing layers. These experiments will provide data on the characteristics of the large-scale structures, including their size, orientation, and shape, and instantaneous planar velocity and vorticity fields. The experiments will also provide insights into the mechanisms of mixing layer growth through both the entrainment of freestream fluid into the mixing layer by large-scale structures, and also by the interaction of two or more structures to form larger structures.

Mean velocity and turbulence measurements are being obtained by LDV in a plume-induced separated boundary layer embedded in a supersonic freestream. Because the separation process is unsteady, a conditional analysis technique is necessary. This technique is accomplished using high-speed pressure transducers installed in the wall near the mean separation location in order to detect the instantaneous separation shock wave position. The primary objectives of this study are to characterize the formation and development of the shock-separated shear layer and to determine the velocity field inside the separated flow region surrounding the base.

A nonintrusive, optical measurement technique is being developed to make spatially well-resolved pressure measurements on surfaces in aerodynamic flows. The method is based on applying a ruthenium-based compound to the surface of interest, illuminating the compound with the proper wavelength of light, and detecting the resulting luminescence intensity. This luminescence signal is known to be inversely proportional to static pressure resulting from quenching by oxygen. Development and use of the technique will allow measurement of the mean pressure distributions on various aerodynamic surfaces with excellent spatial resolution.

Isothermal flow tests have been conducted to determine parametric flow resistance characteristics of hypervapotron (i.e., building in single- sided ribbed flow channels) configurations using low-pressure water systems, with prototypic dimensions and flow rates. Experimental data indicate friction factors significantly lower than previously published correlations and are only slightly higher than smooth wall values. For very small flow channel heights, of the dimension of the tooth pitch or smaller, the tests show a modest friction factor increase, but this is very sensitive to channel height.

The objective of this research is the development of a new nonintrusive optical technique for spatially and temporally resolved measurements of pressure, temperature, and velocity in high-speed flows. A high-resolution coherent anti-Stokes Raman scattering (CARS) technique will be developed. Pure rotational and vibrational Raman resonances of the nitrogen molecule will be probed simultaneously using dual-pump CARS in a counterpropagating pump beam configuration. Velocity will be determined from the relative frequency shift between the vibrational and pure rotational lines and pressure and temperature from the resonance lineshapes and relative spectral intensities.

The objective of this research program is the development of new nonintrusive optical techniques for spatially and temporally resolved measurements of pressure, temperature, and density in high-speed separated flows. Two new coherent anti-Stokes Raman scattering (CARS) techniques are proposed: simultaneous detection of vibrational and pure rotational Raman signals using dual-pump CARS and high-resolution vibrational CARS. In the high-resolution vibrational CARS technique, the CARS signal from the overlapped transitions in the Q-branch head will be spectrally resolved using a high-finesse solid etalon.

A flow visualization loop using refrigerant R123 is being constructed. A novel optical measurement system is being developed for nonintrusive measurement of two-phase flow parameters.

Rapid and uniform deposition of copper on the inner surface of high aspect ratio "through-holes" of printed circuit boards is important in electronics manufacture. We are investigating a new approach using a rotating screw electrode (RSE) inside the hole. In addition to improving the electric field distribution, the RSE generates a 3-D flow that greatly enhances mass transfer. Experiments at UCLA show that plating uniformity is excellent. In the theoretical work (at Illinois), we consider the Navier-Stokes equations for the time-dependent flow between the RSE and the through-hole wall. For high aspect ratio holes, we have transformed the equations into a rotating helical coordinate system, rendering the computational problem 2-D and steady.

Many drugs, pesticides, and other biologically active compounds are chiral, existing in left- and right-handed mirror images called enantiomers. In most cases, the desired activity resides in one enantiomer. Thus, separation of enantiomers is of interest. Enantioselective complexation with a chiral carrier (e.g., vancomycin) gives rise to an effective electrophoretic mobility difference, which we will amplify using an axisymmetric annular swirl flow. Computational work will guide fabrication of an electrophoresis cell at NIST, and will focus on effects of diffusion, electric field strength, geometry, and swirl. Buoyant or electrohydrodynamic secondary flows will also be assessed.

Construction of low-dimensional, nonlinear, ordinary, differential equation models from measurements has been demonstrated for several incompressible flows. Although widely applicable in principle, this method has only been applied to fully developed statistically stationary channel flows, for which its massive data requirements are met by existing databases. We are developing a technique that uses M measured time series to construct an N > M-dimensional quadratically nonlinear (appropriate to Navier-Stokes) dynamical model. This procedure will be very attractive for free-surface flows, in which use of physically faithful models in real-time applications is precluded by complexity.

"Freckling" and other compositional nonuniformities in directionally solidified alloys are of concern in producing single- crystal turbine blades and other high-strength components and electro- optic materials (e.g., mercury cadmium telluride). These defects have been related to a morphological instability and buoyancy-driven convection in the melt adjacent to the growing interface. To date, we have shown that rotation (acting through the Coriolis acceleration) can suppress convection in a horizontally unbounded layer, and (through the Coriolis and centrifugal accelerations) can reduce the melt-solid interface curvature in a cylindrical ampoule.

At low Reynolds numbers (Re), flow past axisymmetric bodies is steady, axisymmetric, and attached. For bluff bodies (e.g., spheres, raindrops, torpedoes), the flow separates as Re increases; ultimately, transition to unsteady, nonaxisymmetric flow occurs. We have studied this transition computationally for a fixed sphere; the steady, axisymmetric flow becomes unstable with respect to an oscillatory helical instability at Re = 175.1. The critical Re and predicted Strouhal number (dimensionless frequency) agree well with previous experiment. We are extending this work to the case where the body falls or rises freely under the action of gravity. In that case, the rigid body motion can couple to the flow disturbances, leading to a lower critical Re.

High-temperature thermal treatment is a potentially promising approach to isolation of radioactive and otherwise hazardous metals from liquids. We are conducting computational and experimental investigations of the dynamics of liquid drops in high-temperature gas flows, with particular emphasis on how heat and mass transfer affect metal speciation. The computational work focuses on understanding how flow internal and external to drops affect transport and speciation, with particular emphasis on the drop's wake. This involves extending our previous work to higher density ratios, different viscosity ratios, accounting for thermal effects (e.g., variable surface tension), and ultimately, multicomponent mass transfer.

We are conducting computational investigations of the stability of the steady (asymmetric) 2-D flow past a rotating cylinder, as well as the time-periodic 2-D flow to which it loses its stability as the Reynolds number (Re) is increased. To date, we have shown that the critical Re at which the steady flow becomes unstable to 2-D disturbances depends nonmonotonically on the dimensionless rotation rate, and that the frequency of the critical mode that evolves from the Hopf bifurcation has several discontinuities along the stability boundary, corresponding to transitions from one mode to another.

Fully developed pipe flow of a dense suspension is characterized by low-frequency fluctuations in wavy stratified flow in a horizontal pipe. Upgrading synchronized measurements of laser Doppler velocimetry and phase Doppler particle analyzer gives components of fluctuating velocities and densities of particle suspensions where particle- particle interactions are significant when compared to particle-wall interactions. Data permit closure of the time-averaged equations for the predictions of stress components in a flowing suspension. Advances include optics and software for determining the local instantaneous density, velocity components, and diffusivities of particles clouds from their passage through the laser-measuring volume.

We are studying the three-dimensional structure of vortex shedding from a circular cylinder placed in a spanwise sheared free stream. Computations are being performed using a high-order accurate numerical scheme and high performance parallel computers.

Attempts are being made to develop a parallel, spectrally accurate, numerical method for conducting DNS of wakes of rectangular bluff bodies. A spectral domain decomposition technique has been developed and validated in simple geometries. The method has been implemented on the massively parallel computer, CM-5. Three-dimensional calculations are being performed for turbulent flow over a square cylinder.

Single crystals composed of alloys of two semiconductors are important for devices to interface between optical signals and electrical signals. During the growth of these crystals from a liquid, temperature gradients produce voltage gradients which drive circulations of electric current through the liquid because of the nonuniform thermoelectric properties of the alloy. Strong magnetic fields are often applied during crystal growth to stabilize the liquid motion, and these magnetic fields interact with the thermoelectric currents to drive additional melt motions. Models are being developed to predict the thermoelectric effects during crystal growth with a strong magnetic field.

During the crystal growth of an alloy of two semiconductors, one compound is rejected into the melt, producing variations in the composition of the melt. Because one compound has a much larger density than the other, the compositional variations drive a buoyant convection which may lead to unacceptable nonuniformities in the crystal. A strong magnetic field damps this convection, leading to much better crystals. Models are being developed to predict crystal properties as functions of magnetic field strength and of other parameters. Predictions will be compared to experimental results obtained at the NASA Marshall Space Flight Center.

Many optoelectronic devices require indium-phosphide crystals with small defect densities. Most crystal-growth processes involve large temperature gradients, and the associated thermal stresses produce large defect densities in the weak InP crystals. The liquid- encapsulated Kyropoulos process involves crystal growth with very small temperature gradients, so that the InP crystals have very small defect densities. A magnetic field is needed to stabilize the melt motion and to eliminate turbulent temperature fluctuations. Analytical and numerical models are being developed to guide process optimization. The purpose of the modeling effort is to complement an experimental program being conducted at an air force laboratory.

Any crystal growth experiment in an Earth-orbiting vehicle is subjected to chaotic accelerations called g-jitters. A magnetic field can be used to suppress the melt motions driven by g-jitters in order to achieve optimal crystal properties. Models are being developed for the magnetically damped melt motions and for the associated transport of dopants which determine the electrical properties of the crystal. Model predictions will be used to design the magnet damping furnace to fly on shuttle missions beginning in 1999.

In the floating zone process, there is a zone of molten semiconductor between a melting feed rod and a growing crystal. The thermocapillary convection is driven by the change of the temperature-dependent surface tension along the free surface of the floating zone. Floating zone crystal growth in space is very promising, but it is currently limited by an instability in the thermocapillary flow, leading to an oscillatory flow with adverse effects on the crystal. A magnetic field can be used to stabilize the flow and to eliminate the adverse effects of the oscillatory flow. Models are being developed to guide the selection of the optimal magnetic field.

HEAT TRANSFER AND ENERGY SYSTEMS

Radiation heat transfer in absorbing and scattering media including general multidimensional gaseous absorption is under consideration. The correlated-k approach is being developed and validated for thermal radiative transport in highly nonhomogeneous media containing water vapor and carbon dioxide. Simplified approaches are being used to model the entire infrared spectrum of water vapor and carbon dioxide for temperatures up to 2500 K.

This research program consists of a combined analytical and experimental investigation of the scattering and emission from realistic interfaces, including those with surface length scales on the order of the wavelength. The objectives are to rigorously quantify the scattering of thermal radiation from electromagnetic theory, to develop approximate yet accurate scattering models, and to experimentally determine reflection for such interfaces.

This project is motivated by the emergence of new technologies for stationary (unitary and split) air conditioning systems: (1) making heat exchangers more compact, (2) varying compressor and fan speeds, and (3) modulating refrigerant flow. The goal is to use models and experimental facilities to focus on these objectives: (1) quantify benefits of ultracompact heat exchangers on steady-state and transient performance; (2) explore energy efficiency and design implications of multi- or variable-speed compressor/fan control in combination with fixed and/or electronic throttling devices; (3) examine the effect of evaporator design on system performance and noise; and (4) expedite the capillary-tube/charge optimization process.

The goal of this project is to use our equipment, test facilities, and simulation model to investigate the implications of incorporating several technologies that could increase performance or reduce cost of domestic refrigerator freezers. The project objectives are to (1) quantify the performance tradeoffs associated with using dual evaporator systems as an alternative to mixing cabinet airstreams as a means of controlling compartment temperatures; (2) analyze strategies for minimizing charge inventory to reduce cycling losses while maintaining acceptable performance over a wide range of ambient temperatures; (3) identify system and component performance implications of designing for variable-speed compressors; and (4) identify the scope of performance improvements obtainable through capillary tube-suction line heat exchanger design.

Thermal processes generate irreversibilities, i.e., entropy. In many processes, the optimum performance on operating limits can be estimated by finding the minimum rate of irreversibility, i.e., entropy production. Such a technique is often considerably simpler than more conventional ones. The method has been successfully applied to cooled shields in insulations, to heat exchangers, and to heat exchanger networks.

Various aspects of the thermal behavior of biological materials, particularly the human body, are studied. The work ranges from the morphological studies of the blood vessels which affect heat transfer to computer modeling of various organs as well as the entire thermoregulatory system. One application is the prediction of the rise of the deep-body temperature in a hot bath.

Over the past few years, it has been demonstrated conclusively that chlorofluorocarbons, or CFCs, contribute to the depletion of the ozone layer. For this reason, new ozone-safe refrigerants are being developed to be used in air conditioning and other refrigeration systems. This conversion to new refrigerants will require the establishment of a reliable database for the identification of the various heat transfer regimes and for the design of heat transfer equipment. Currently, two experimental apparati are used to determine the condensation and evaporation heat transfer coefficient characteristics and pressure drops associated with these new refrigerants in various tubes. Analytical and numerical methods of modeling these phenomena are also under development.

Current standards and practices for establishing the maximum allowable surface temperatures for industrial and consumer use are very simplistic and probably too restrictive. The goal of this research project is to establish more realistic safe "touch" or "hold" temperatures for equipment which take into account the material properties as well as typical configurations.

This project is directed toward the design of a new generation of heat exchangers for residential refrigerators. In particular, research is being conducted to develop new condenser configurations and to exploit new air-side heat transfer enhancements. Heat transfer diagnostics, system simulation, and simple optimization methods are being used to identify promising new directions for heat exchanger development and to estimate the potential benefits of improved component performance in this application.

An investigation is being conducted of the thermal performance of the wire and tube condensers typically used in domestic refrigerators. Emphasis is on the air-side heat transfer characteristics. Both forced flow and the natural convection limit are being studied experimentally. Simultaneously, a computer model for predicting the thermal performance of wire and tube condensers for a variety of configurations is being developed.

With the assistance of heat exchanger manufacturers, this project involves fabrication of a breadboard system to explore the energy conservation benefits of an air conditioning system that employs ultracompact heat exchangers. It is also quantifying benefits of reducing transient losses by reducing charge inventory, as a potentially simple alternative to variable-speed fans and compressors as a means of increasing system efficiency.

Temperature-sensitive paint (TSP) and liquid crystal thermography (LCT) measurements will be obtained in a generic flat plate heat transfer geometry, such as a plate-vortex generator system. To further develop TSP, the following issues will be explored: optimal probe molecule formulation, reduction of noise signal, system calibration, and data reduction procedures. To make LCT more accessible to users, the effects of experimental procedures and color-data interpretation will be considered. The strengths and weaknesses of the two methods will be determined, and the use of both methods will be documented for application to AC/R systems.

This project is directed at obtaining a detailed understanding of the velocity, pressure, and acoustic fields surrounding a fan-and-coil unit that is typical of those found in AC/R systems. Mean, fluctuating, and spectral measurements of these quantities will be obtained in both the near- and far-fields. Using the flow and acoustical data, the role that the fan-coil unit plays in generating system noise will be determined. Furthermore, the flow features responsible for this noise will be identified, and methods will be recommended for managing the flow to avoid the generation of objectionable noise.

This is a fundamental investigation of complex systems characterized by two-phase media separated by a complicated interface. Currently, a study of wetting phenomena is undertaken with emphasis on the dynamics of contact lines. Ab initio mesoscopic numerical simulations are coupled to observation (via optical microscopy) of droplets spreading on substrates coated with monolayers.

The ability to model energy transport in highly irregular geometries has eluded complete characterization. Important applications include fixed porous beds with and without chemical reactions, moving beds, and dispersed phase flows. Lattice-Boltzmann methods (LBM) are a general and powerful approach to the calculation of energy transport in these geometrically complex flows. Schemes based on LBM have two distinct advantages over conventional numerical methods: (1) they do not require the generation of cumbersome boundary-conforming numerical grids, and (2) they are naturally parallelizable and easily executed in massively parallel computers. This project seeks to develop, implement, and validate general lattice-Boltzmann methodology for energy transport problems.

In applications with complex internal flows, it is the unpredictability of the tortuous fluid particle trajectories that produces enhanced heat and mass transfer beyond the level of simple molecular diffusion. The research program consists of a combination of noninvasive measurements with magnetic resonance imaging (MRI) and numerical simulation using lattice-Boltzmann methods (LBM) of such internal flows. The key objectives are: (1) to develop a non-invasive methodology to probe convective transport in complex flows using a combination of MRI and LBM and (2) to understand and quantify the mechanisms of heat/mass transport enhancement in stirring processes.

This research is directed at developing a fundamental understanding of frost formation and growth in air conditioning and refrigeration applications. This deeper understanding will be used to develop models of frost deposition that account for the microstructure. Detailed experiments to study frost initiation on conventional surfaces and on surfaces coated with hydrophilic and hydrophobic materials are complemented by careful measurements of mature frost growth on flat- plates and on surfaces with louvers and vortex generators. The data and resulting models will help guide the development of frost-tolerant design methods, frost mitigation techniques, and defrost strategies.

The objective of this project is to quantify the two stages of frost growth (early and mature) by using two new techniques: scanning confocal microscopy (SCM) and magnetic resonance imaging (MRI). The SCM technique will be used during the early stages of frost growth and the MRI technique during the mature growth phase. SCM provides video- rate imaging in terms of optical slices with near- or submicron spatial resolution.

The overall aim of this project is to investigate noise radiation and flow-induced force excitation in expansion devices, design and build devices to measure sound pressure inside the refrigeration tubes, and explore possibilities for noise reduction by varying orifice tube geometry or other parameters.

Several different air-side enhancements are investigated experimentally in a wind tunnel. The heat exchangers are the plate-fin type with microfinned tubes, operating as condensers in regimes similar to room air conditioners.

Orifice tubes are the most frequently used expansion devices in automotive A/C systems. Further understanding of two-phase choked flow phenomena is acquired in experimental testing as a part of this project. The influence of diameter, length, screens, and other factors is examined and models are developed.

The goal is to investigate maldistribution and fractination in brazed plate heat exchangers, especially when operating with lower mass velocities. Special attention will be focused on the stability of the superheat signal.

Supermarkets are second only to automotive A/C systems in polluting the atmosphere with refrigerants. A circulating liquid concept should increase energy efficiency, reduce inventory and leakage of expensive and environmentally damaging refrigerant, and utilize centralized units that are more reliable, efficient, and less expensive. The project will determine viable fluids, appropriate defrost technique, and experimentally verify models that will be developed.

The feasibility of using a heat pipe to augment the cabin heater in passenger vehicles is under study. The heat-pipe evaporator is located in the exhaust gas; energy from the hot exhaust gas evaporates the working medium within the heat pipe, driving vapor to the heat-pipe condenser. The condenser is located within the usual heater-core duct in the cabin. Upon condensation, the vapor rejects heat to the cabin air, condensates within the heat-pipe, and drains back to the evaporator. A mathematical model and computer simulation of the cabin and heater system is being developed to guide the design of such a system, and experiments to validate the model are underway.

When an oil is in solution with a liquid halocarbon refrigerant, the mixture has thermophysical properties different from those of the pure refrigerant. Changes in the saturation state and transport properties can have an important impact on heat transfer and thermal system performance. The thermophysical properties of conventional refrigerants with commonly used oils have been measured; however, environmental concerns have prompted the consideration of many new refrigerants and refrigerant/oil combinations--several of these candidates are blends of refrigerants. This research is directed at measuring and modeling the thermophysical properties of new refrigerants and refrigerant blends with synthetic and natural oils.

Basic flow and heat transfer mechanisms in louvered-fin and vortex- generator geometries will be studied to answer several unresolved questions. For louvered surfaces, research will address the effects of the approach turbulence intensity and velocity profile on vortex shedding, the ability of the flow to follow the louvers, and sources of acoustic noise in the flow. For vortex generators, the role of the approach turbulence and velocity distribution and the interaction of multiple generators will be studied. Full-scale heat exchanger studies will be conducted, and each surface will be examined using performance evaluation criteria for particular applications.

The objectives of this project are to develop a deeper understanding of evaporation and two-phase flow in the vertical channels, identify the source of pulsations in plate heat exchangers, explore methods for stabilizing super-heat signals and system operation, and characterize TXV performance.

Heat exchangers in air conditioning applications often operate below the dew point, and water condensing from the air onto the surface affects performance. At high Reynolds numbers, retained condensate enhances heat transfer by acting as a surface protuberance, generating local secondary flows or an early transition to turbulence. At low Reynolds numbers, condensate can accumulate and act as an added resistance to air flow and heat transfer. The overall thermal impact is dependent on geometry and operating conditions. The purpose of this project is to measure of water retention and shedding effects and to develop and validate a model for predicting these effects for a slit- fin heat exchanger.

In many applications, water retention and shedding affect heat exchanger performance. There are no general models available for predicting condensate retention and its effects on heat transfer. The purpose of this project is to develop and validate a model that can predict condensate retention in these applications and to provide design correlations for the wet performance of heat exchangers. This research will provide the first geometrically generalized model of condensate retention. Special attention will be directed at condensate management for enhanced surfaces.

This project addresses heat transfer in an unsteady, developing, channel flow. Controlling the unsteadiness of the flow may provide significant heat transfer enhancements. This research focuses on the application of this idea to the low Reynolds number flows associated with refrigeration and air conditioning applications. Experiments in rectangular and triangular channels will quantify the heat transfer enhancement as a function of the acoustic or mechanically induced pulse frequency and amplitude, and the boundary layer structure will be investigated in detail using laser diagnostics. The physical mechanisms for the enhancement will be determined with a focus on exploiting these effects.

The implications for public safety, down time, repair costs, and product loss make hydraulic shock a crucial issue for the refrigeration industry. Dangerous pressure excursion incidents have been attributed to the initiating mechanisms of condensation-induced shock and vapor-propelled liquid slugging. The objectives of this study are to identify the critical flow regimes in refrigeration piping and to analyze and model the initiating mechanisms of hydraulic shock within these regimes. Along with advancing our understanding of two-phase transients, knowledge of the generic causes of these transients will allow engineers to avoid them through proper system design.

The multilouver heat exchanger surface is primarily used in automotive refrigerant-to-air applications, where air-side face velocities are above 8 m/s. However, recent demands for compactness and effectiveness in domestic air conditioning systems have motivated the adaptation of louvered fins to systems with face velocities from 0.5 to 2 m/s. The current generation of louvered fins, developed for high face velocities, is not optimal for residential air conditioning systems. Our objective is to develop and validate a numerical tool that can evaluate louvered-fin performance for residential air conditioning systems.

When a liquid film falls from one horizontal tube to another below it, the flow may take the form of discrete droplets, jets, or a continuous sheet. This flow mode plays an important role in the wetting, heat transfer, and mass transfer characteristics of the falling-film heat exchanger, but there have been no reliable methods for predicting the mode behavior. This research is directed toward generalizing our earlier work on this topic in order to understand how a flow in the surrounding vapor affects the liquid falling-film mode.

A numerical model of boiling heat transfer in heterogeneous porous layers with and without chimneys has been conducted. Experimental observations have provided qualitative modeling information and model refinements. 1-D and 2-D models have been evaluated numerically with nonlinear coupling between mass, momentum, energy, capillary pressure, and evaporation rate. Good agreement with published data has been obtained. Examination of artificially created layer performance suggests broad potential applications for controlled boiling heat transfer, such as computer chip cooling via freon or other CFCs, with heat fluxes in excess of 100 W/cm2, and in steam generator tube performance.

The effect of interfacial mixing and contact area between two liquids of differing densities and temperatures that result from a high- density, high-temperature liquid passing through a lower density, low- temperature liquid has been studied. Heat transfer effects, including the effects of vapor generation, break-up, and solidification, were modeled. Analytical modeling was carried out at UIUC, while experimental studies using simulant materials of both single and multiple injected columns were conducted at Argonne National Laboratory. Good agreement between model predictions and experimental data is found.

This project attempts to identify the source of acoustic emissions from plate-type air conditioning evaporators. It is hoped that improved heat exchangers can be developed as a result of this work.

This project is developing diagnostic methods for identifying faults in air conditioners and refrigerators during normal cycling operation. Preliminary calculations suggest that many faults can be detected using only a small number of sensors. The objectives are to (1) apply model-based fault detection and diagnosis methods to extract as much information as possible from a small set of inexpensive sensors; (2) demonstrate that these diagnostic methods can accurately identify "simulated faults"; (3) modify existing well-instrumented refrigerators and air conditioners to simulate these same faults; and (4) demonstrate experimentally the viability of these methods. The approach involves first using numerical simulations, followed by laboratory experiments to verify the numerical results.

This work integrates thermal design principles with modern control techniques to provide the basis for developing optimal systems for transient operation and varying environmental conditions. An experimental facility has been constructed to develop and evaluate alternative control techniques and hardware for mobile air conditioning systems. Alternative control methods that involve the use of advanced electronic devices and novel types of actuators and control inputs are being investigated. The project will determine which combinations of sensors, actuators, and control devices work best.

The objectives of this project are to separate the modes of acoustic signal propagation and radiation through tubes and through stream of fluid, investigate the production of the pressure spectrum at the inlet and outlet of expansion devices, and study methods for reducing its intensity and/or modifying its frequency content.

Investigation of void fraction in smooth and microfinned, horizontal tubes. R134a and R410A refrigerants are being tested.

A half-acre solar pond has been constructed in the agriculture section of campus. Continuing research investigates the feasibility of solar ponds for low-temperature heating processes.

Heat transfer and pressure drop models are being formulated for refrigerant mixtures. A unique method for liquid film thickness has been developed.

The U.S. government has supported the development and maintenance of two general-purpose energy analysis programs during the past two decades or longer. The Department of Defense sponsored the BLAST program and its successor IBLAST, while the Department of Energy supported the DOE-2 program. While both programs provide an hourly simulation of a building, its HVAC systems, and the associated central energy plants, they have fundamentally different approaches in the area of building simulation. The goal of this project is to provide a technical plan and some insight into the mechanics required to effect the merger of the programs.

This project initiates combining the best parts of DOE-2 and BLAST. The combined program will be called EnergyBase. The heat balance engine of the IBLAST program (a version of the BLAST program which has integrated building, system, and plant simulation) with a generalized HVAC engine which includes the systems from BLAST and DOE-2. The heat balance engine will also be restructured to accommodate the daylighting program and WINDOW-4 based fenestration program from DOE-2 as well as new ground heat transfer and zone air flow models. All legacy code will undergo significant reengineering and will be converted to standard Fortran90.

The objective of this project is to determine the effect of surface characteristics on low-temperature radiant panel performance. The impact of the project as a whole may be evaluated in the larger context of developing efficiency standards that accurately portray radiant heating and cooling systems.

The goal of this project is to develop energy-related agents that will work with the USACERL Agent Collaborative Environment to allow multidiscipline collaboration in the design of buildings.

Mechanical structures with dimensions as small as a few microns are being used in conjunction with electronic circuits to create micro- electro-mechanical systems. These devices offer low weight and batch production methods, which are advantageous for many applications. The small size and mass of these devices is particularly suited for space applications. The reliability of these devices in space depends on their ability to remain functional while exposed to radiation. Additionally, laser processing of microstructures can supplement other fabrication methods. A method of recovering stiction-failed microcantilevers has been developed. This project examines the effect of radiation on microstructures.

MEMS, micro-electro-mechanical systems, are a rapidly developing technology with applications in the automotive, health care, aerospace, environmental sensing, and consumer products industries. MEMS devices have been used to extend thermal measurement capabilities to greater sensitivities and smaller spatial resolutions than those achieved by traditional methods. Additionally, some MEMS devices are thermally actuated. For example, bimaterial cantilevers deform when heated because of mismatches in the thermal expansion coefficients and have been used to actuate MEMS devices. This project investigates measuring thermal properties with and thermal means of actuating MEMS devices.

During short-pulse, high-power laser irradiation of solids, electrons are ejected from the surface in large numbers and with high energy, which creates very high transient electromagnetic fields near the surface. Radiant thermal emission from the surface may change nonlinearly because of the presence of this induced field. The purpose of this project is to measure the distribution of thermal radiation with wavelength under applied electric fields to determine the relative importance of electromagnetic fields on thermal emission at different temperatures.

The goal of this project is to improve control strategy in plate heat exchangers when used as evaporators by exploiting potential advantages of micro-electro-mechanical systems.

Thermal energy storage for building and process cooling in the form of chilled water has been demonstrated to be an economical system. Diffusers have been used to achieve natural stratification by taking advantage of the buoyancy forces. It was observed that natural stratification involves the formation of a thermocline by introducing chilled water at suitable inlet condition and geometry. A computer model will be developed for the optimization of design to minimize the volume and optimize the storage capacity, mixing and heat transfer between the warm and cold water, as well as the operating procedures.

This project is a study of the air-side heat transfer and pressure drop impact of wavy passages on heat exchanger performance. It has been observed that unsteadiness, either forced or self-exciting, significantly increases heat transfer. Self-induced unsteadiness is generally well understood as the enhancement mechanism for wavy channels; however, the very large design parameter space has made it difficult for engineers to exploit this mechanism. This study will provide a fundamental understanding of the flow of the potential and proper application of wavy fin enhancements.

UIUC Air Conditioning and Refrigeration Center; American Society of Heating, Refrigerating, UIUC Air Conditioning and Refrigeration Center; American Society of Heating, Refrigerating, American Society of Heating, Refrigerating, Illinois Department of Energy and Natural Resources, STILENRAE25SLRPND129; International Salt Co.; American Society of Heating, Refrigerating, MANUFACTURING SYSTEMS

The objectives of this research are to (1) develop the relationships between the metrics of quality, cost, lead time, and innovation and the traditional bottom line functions of return on investment and market share; (2) to generate a fundamental and encompassing definition of quality that includes considerations of value and cost and apply it to the entire product realization process; and (3) to explore the role of organization structure and corporate culture on manufacturing effectiveness. Initial results, based upon a market model that incorporates value as well as the more traditional elements of cost and price, show that a single universal metric governs manufacturing effectiveness. The new quality function being developed yields the traditional Taguchi formalism as a limiting case.

The purpose of this research is to develop strategies for simultaneous turning of complex workpieces with high material removal rates under stable machining conditions while maintaining a good surface finish. The model developed for the simultaneous turning project involves a mechanistic approach, whereby the dynamic responses of given machining system elements are measured through impact tests and serve as the input to models for generating stability lobe diagrams for the process. The stability lobe diagrams will reveal the allowable depths of cut for selecting speeds that assure chatter-free machining processes.

Critical problems in automotive machining applications are the rapid setup of new or changing processes and troubleshooting problems during production machining that result in unreliable productivity and pool quality. A machining diagnostic system is proposed that will combine the elements of sensor data collection, mechanistic process modeling to predict the characteristics of typical process maladies, and fault diagnosis strategies including genetic algorithm and neural network methods to suggest rational process changes. It is envisioned that the commercial realization of this system will be a portable diagnostic system that can be used in the factory as a troubleshooting aid for the process engineer.

Turning simulation models considered in the past were suitable for uniform cross-section along the length of cut/axis of the part. However, while machining a hemispherical geometry, these models fail to consider the variation of cutting parameters along the length of cut. The purpose of this project is to create a turning process simulator that can capture the effects on cutting performance of part geometries that can include hemispherical features and surface interruptions and that can be calibrated to predict cutting performance for both standard-metals cutting and the machining of a specific group of defense-related materials.

Accurate and reliable fixture design and fabrication is crucial to successful machining and assembly operations. Traditional fixture design is often performed using trial-and-error methods to obtain a feasible, but not necessarily optimal, design. This stands as an obstacle to the development of a truly flexible manufacturing system. One of the key issues in the fixture-workpiece system is the handling of the contact problems at the interface of workpiece and clamp locators. The objective of this work is to develop an accurate model of the contact interface and to study the mechanical behavior of both workpiece and fixture components.

This research--an NSF TIE project between the University of Illinois and the Georgia Institute of Technology--addresses the tribological aspects of fixturing for machining applications, finite-element models of the fixture workpiece system, and experimental verification of contact mechanics in fixturing. It is expected that the results will lead to the development of computer-aided simulation tools and procedures for machining fixture design and analysis based on workpiece quality considerations.

A hardware testbed is a physical location for an experiment, a unique piece of equipment or production facility that can be monitored through video cameras and through sensors in real time over the Internet. Until now, dedicated data/phone lines have been used for such transfer, which are very prohibitive in cost and provide only point-to-point solutions. Potential applications for the MTAMRI hardware testbeds include: (1) supporting cross-university, collaborative research, (2) enabling access to a unique facility/test set-up; (3) supporting the Internet-based MTAMRI education program; and (4) industrial applications, including customer/vendor quality assurance.

It is well known that all bulk materials possess some level of inhomogeneity in their material properties and microstructure. It is not surprising that variations in machinability are observed within workpieces and from workpiece to workpiece. In many cases this variation of machinability can result in tool breakage, rapid tool wear, poor surface finish, and a host of other problems which in turn mean higher machining costs, poorer product quality, higher rejection rates, and so on. This study proposes to decrease these process problems by quantifying the impact if material property variability on machining performance, namely, the machining forces, tool wear, and product quality.

In conventional machining operations where a continuous chip is being produced, the process must be interrupted because of inadequate control of the chip. The most common method of exerting control over the chip is to direct the chip flow away from the workpiece and then impose or induce some curvature to the chip using either an obstruction or groove type of chip-forming device. This research will investigate the effect of individual groove parameters on the cutting forces and will develop a mechanistic force model that can predict the cutting forces for an arbitrary shape of the groove.

The scope of this research is to develop ultrafiltration technology that will alleviate or eliminate liabilities (environmental, health, performance, financial) by cleaning and reusing the cutting fluid. As a pollution prevention project, this ultrafiltration research aims to drastically reduce pollution emissions to the environment from cutting fluid waste while eliminating risk factors for occupational airway disease and allergic contact dermatitis. At the same time, the ultrafiltration technology will maintain a constant and, therefore, improved process performance while greatly reducing disposal and acquisition costs.

Twist drill hole making is a commonly used manufacturing process. The most important aspects in this process are the hole quality measures, and these are especially significant for the case of long drills where the effects of radial forces and, hence, the resulting drill deflections, are more pronounced. The overall research objective of this project is to develop an enhanced mechanistic model to study the effects of the forces of cutting and drill deflections on the hole quality parameters such as hole cylindricity, locations errors, over size, and straightness.

Fixturing, a critical and expensive process of holding a component during the machining process, is performed today with dedicated fixtures in all high-volume manufacturing systems. Automotive experts consider the dedicated nature of fixturing as the main barrier to the implementation of a flexible, agile manufacturing system. Because of the limits of current fixturing, this project proposes that an intelligent fixturing system for high-volume production be produced. The project tasks include: a flexible clamping system, a part location system, a part micropositioner, a fixture configuration station prototype, and a fixture-process model.

Tapping is one of the most common but perhaps one of the least analyzed machining processes. The purpose of this research is to establish a comprehensive mechanistic torque and thrust model for the tapping process. This objective will be accomplished by systematically and analytically formulating elemental cutting torques. The basic concept involved in this model is that elemental cutting and thrust forces acting on each land of flutes are proportional to the uncut chip area. In the modeling of tapping torque, the effects of tool geometry, material characteristics, machining configurations, tap- workpiece interactions, and process parameters will be quantitatively and explicitly presented.

In this project we have designed and built a machine tool based on a novel parallel-link mechanism called the tetrahedral tripod. To do so, we have developed a number of analysis and synthesis tools to aid in the design process of such machine tools. For example, we have developed analytical procedures for producing bounds on the stiffness of parallel-link machine tools across the workspace. Currently, we are developing a second high-speed, high-stiffness, 3-axis, parallel-link machine to serve as a universal tooling system (i.e., either for workholding or for cutting tool positioning).

In this project we attempt to design and fabricate a novel X-Y translation system. In contrast to conventional "stacked axes" configurations, this design is such that both (x and y) acuators are simultaneously grounded (so the table is the only moving member in the mechanism), and there is no asymmetry in the inertial loads carried by the actuators. This allows for uniform behavior across the workspace and low inertial loads, making this design particularly useful in high-speed, high-accuracy applications.

In this project we have developed an experimental machine tool for conventional and rotary ultrasonic machining of structural ceramics. One of the challenges in developing a machine-tool for machining of ceramics is that it must be capable of producing very fine (of the order of a few) engagements between the tool and the ceramic workpiece and not deflecting during the machining process. We have integrated the tetrahedral tripod mechanism into a stiff, NC machine tool for machining such materials.

The manufacturing execution system (MES) is the information and control layer of a manufacturing system. When dealing with flexibly automated systems, the MES plays a role similar to that of an operating system in a computing environment. Borrowing from operating systems architecture and adding the elements of deadlock avoidance and efficient resource allocation, we are constructing a configurable and distributed execution system for control of large flexibly automated systems.

Structural control refers to the shaping of the structure of the state space of a discrete-event system. The state space is a directed graph and one of the most important structural properties required of this graph is that the component containing the initial state be strongly connected. This guarantees that the system is free of deadlocks under normal operation. In this project, we devise control policies (which are essentially cuts on this directed graph) that are polynomially computable and guarantee strong conductivity while ensuring that the size of the strongly connected component is large. Special system structures under which these cuts are "optimal" are also explored.

Contact plays an important part in a number of manufacturing planning problems: automated fixturing, robotic grasping, assembly planning, NC code generation. In this project we study problems in feasibility, synthesis, and analysis of contact. For example, the kinds of questions we seek answers to are: Given n bodies with m contact relations defined on them, is it possible to produce a spatial configuration of the bodies to simultaneously satisfy all stated contact constraints? If such a configuration exists, what is the dimension of the solution space (or, does the specification produce a structure or a mechanism)?

Modern NC machine tools have different configurations and capabilities and produce vastly different results when executing the same NC program to produce the same workpiece geometries. This causes problems, both in process planning and in capability analysis. In this project, we are developing an integrated environment for storing and updating machine capability and performance data.

We are developing a software environment that allows users to rapidly configure virtual reality simulations of manufacturing plants, machines, and processes. The intent is to provide an integrated environment for various levels of facilities and process planning. The environment integrates continuous real-time simulations of automated devices with the discrete-event control of manufacturing systems allowing users to walk through a manufacturing facility, observe the behavior of such facilities under different discrete-event control logic, and interact with devices. Current research focus is on developing detailed models of machine tools and both tactile and visual interfaces to them.

Process development for machining of structural ceramics is a challenging balance between avoiding subsurface damage to the machined ceramic workpiece and obtaining reasonable machining rates to make the process economically viable. We have been studying the rotary ultrasonic machining process that combines high material removal rates with reduced subsurface damage. Currently we are modeling the indentation and abrasion that occur during this process to understand how they are related to process parameters. We are also extending the process capabilities to different machining feature geometries.

The spindle speed variation (SSV) method compared the conventional constant speed machining (CSM) results in an augmentation of the machining stability and improvement in the surface quality. The University of Illinois and the University of Michigan are collaborating on this project to develop a chatter-avoidance technology based on the SSV method. The primary process application of interest at UIUC is the face milling process and at Michigan, it is the turning process. A special spindle/motor/drive system is being designed and constructed, and a testbed is being developed at the UIUC to validate the theory developed for automotive industry powertrain applications.

This project is an in-depth study of tool wear aimed at developing a wear-force relationship and modifying existing mechanistic modeling approaches to incorporate that relationship. The focus is on flank wear and the prediction of cutting forces given a specific geometry of work tool flank. The reverse problem also being considered in which the current flank geometry is estimated given the measured force signal. The model will initially be developed for orthogonal cutting and then the approach will be extended to traditional 3-D processes.

It is well known that machining processes create residual stresses in the surface of machined components. Depending upon their nature, these residual stresses can have significant effects upon component life by influencing fatigue, creep, and stress corrosion cracking behavior. In addition, machining-induced residual stresses can have detrimental effects on component geometry and result in parts that do not meet specified tolerances. The purpose of this study is to develop a thorough understanding of the mechanisms that give rise to machining- induced residual stresses through detailed experimentation and modeling with the ultimate goal being the prediction of machining- induced residual stresses resulting from conventional machining operations.

The overall research objective of this project is to develop a mechanistic machining process model that incorporates the effects of tool geometry and workpiece material properties. Tools with varying chip breakers and edge preparations will be used. The specific research objectives include: experimental calibration of mechanistic turning, face milling, and drilling models; validation of the models with cutting tests; and an enhanced mechanistic force modeling procedure to incorporate the effects of tool geometry and workpiece material properties.

An exercise machine employing rate controlled hydraulics for sports- specific training and rehabilitation is being developed. Current exercise equipment designs do not provide an ideal muscle flex rate to applied force relationship. It is proposed that a design employing a combination of rate control and force monitoring/control would provide a superior system for sports-specific training and that this approach may also have some important rehabilitation applications. The objective of this project is to research, design, develop, and fabricate a prototype machine for the development of sports-specific training and rehabilitation methodologies.

A fractional factorial design methodology is being developed for identifying key cost drivers of a process and for developing empirical manufacturing cost models. Access to manufacturing cost data is particularly important during the early nonlinear and cyclic development of a design. It is during this time that the overall product structure is cast and a large percentage of the cost is effectively committed. The empirical cost models are used to make rapid ballpark cost estimates of both recurring and nonrecurring manufacturing costs during the initial design phases, as an integral part of the iterative DFM process.

Front wheel drive cars require constant velocity (CV) joints between the drive axle and each wheel. CV joints are prone to wear and often need to be replaced. In the CV driveline industry, there is no "standard" for wear measurement and serviceability evaluation. The first phase of this project has resulted in the design and development of a patented metrology device for quantifying wear profiles. Current research focuses on correlating performance parameters with these wear profiles. The CV joint rebuilder will then be able to measure serviceability against a supplied "standard."

The overall objective of this project is the development of systems design and application tools for shunt-type, bolted joint, force transducers for retrofitting with minimal downtime to a wide variety of machine tools. The emphasis is on cost-effective and industrially rugged systems solutions that do not compromise the integrity of the machine or limit the quality and performance of subsequent production due to reduced machine stiffness, recalibration needs, or spurious interference with the machine controller. An analytical model is being developed for shunt-type force transducer configurations.

This project researches contemporary tools for competitive product realization in the biomedical product development arena. Key tools and methodologies include quality function deployment, design-to-cost, and computer integrated design for manufacture and assembly. Parametric feature-base solid modeling is used to comprehensively model and analyze, for function and manufacturability, the new product as it evolves. The research explores how functional prototype iterations may be rapidly completed using in-house rapid prototyping methods including stereolithography, RTV molding, and spray-metal molding.

By combining new layered mesoscopic fabrication techniques with a scale-efficient vapor-compression cycle, a system of light-weight microcoolers is being developed. A network of compliant electrically powered devices approximately 120 mm (4.7 in.) square and 3 mm (<1/8 in.) thick are meshed together to form an active cooling fabric. The mesoscopic processes under development combine polyimide/thin-film layering technologies with silicon-based electro- mechanical device fabrication. An important potential application is the cooling of military personnel on active duty in hot climates. Other potential applications include cooling of microelectronics and infrared sensors, and weapon systems that can benefit from robust distributed cooling.

Applications for micro-electrical-mechanical systems (MEMS) that are being developed include low-cost microoptical mechanical switches for telecommunications, mechanical devices for microsurgery, and masks for biological molecule deposition. This project is aimed at high force and displacement devices, as well as using dissimilar materials and creating 3-D utility from planar elements. One approach is to combine wafer-scale and laser-material processing to join elements that cannot be fabricated in the same process as silicon. Research in silicon and laser-material processing is currently being developed to solve fundamental issues of MEMS.

The objective of this research is to develop a common hardware and software platform for implementing sensor-based precision machining control. Focus is on the processes of grinding and single-point turning, as they offer the most potential for improvement in light of present usage in industry. The project addresses basic research in sensors and control to improve the performance of existing machine tools as well as to provide the basis for improvements in design for the next generation of machine tools.

The purpose of this project is to develop a breakthrough technology that will revolutionize the manufacturing of camshafts. The technology is based on the use of variable-depth-of-cut machining in a single- point turning environment to produce noncircular shapes using a combination of rapid actuation of the tool slide and high-speed, real- time, digital signal processing and precision motion-control schemes. This technology enables the generation of a wide variety of cam profiles in software, creating an agile manufacturing process that will meet evolving trends and competitive needs for U.S. camshaft manufacturing in the years to come.

C. J. Wicall Gauthier Professorship; University of Illinois; Ford Motor Co.; NSF I/UCRC Center for Machine Tool Caterpillar, Inc.; NSF I/UCRC Center for Machine Tool National Institute of Standards and Technology, NSF Machine-Tool Agile Manufacturing Research Institute; Machine Tool Agile Manufacturing Research Institute, MATERIALS BEHAVIOR AND PROCESSING

Constitutive relations appropriate for high-temperature deformation will be fit to experimental data. The resulting equations will be introduced into finite-element codes for the study of problems have nonuniform deformations. Through the constitutive description, spatial gradients in properties will be related to features of the microstructure, such as grain size.

In this project, models for cast iron solidification are used to predict the behavior of casting processes. Casting residual stresses are computed, and a design optimization approach is used to improve product design.

Phase field models offer the potential to examine new theories of dendrite growth. However, previous work has been limited by computational limits imposed by the conflicting needs for spatial resolution and domain size. We apply adaptive grid methods to permit these calculations to be performed with acceptable computational resources.

The MHD-DC casting process is the first commercially viable route to produce metal with suitable microstructure for semisolid forming. In this project, we model the process to assess the role of electromagnetic, casting, and material parameters.

In this project, models and experiments are co-developed to describe residual stress in the heat treatment of aluminum alloys. Constitutive models for materials behavior are developed and applied to industrial process.

Fatigue characterization of thin foil materials at elevated temperatures has implications with regard to efficiency and reliability of cooling systems. Due to buckling considerations, fully reversed cantilever bending is utilized to determine the fatigue properties of the thin material. Data are compared to traditional, thicker stock durability data.

Pressing and sintering of powder-based alloys is often an alternative to casting processing. Closer tolerances than can be achieved with casting result in reduced final machining costs. A more uniform microstructure and alloying heat treatment to achieve high hardness (for wear resistance applications) are additional advantages of powder metal alloys. Currently, full theoretical density cannot be achieved. The program addresses the penalty incurred with regard to fatigue life and fracture toughness caused by a lack of theoretical density.

Baseline fatigue testing is often conducted on smooth polished hourglass specimens. However, service applications often use the as- cast condition. Unlike wrought metals, there is a significant microstructural variation within the thickness of many cast components. A program has been initiated to ascertain the effect of the as-cast surface on fatigue life. Additionally, differences between uniaxial fatigue and bending fatigue will be addressed.

Most testing of induction-hardened materials is conducted on uniaxial samples that have a uniform strain field, and often failure originates from the "core" material. Most structural applications involve either bending or torsion, both of which have nonuniform strain fields. Typically with a nonuniform strain field, the core material is subject to smaller strains than the hardened material, and uniaxial tests may underestimate the service durability of actual components. Incorporation of residual stresses into an elastic plastic deformation/fatigue damage model is also anticipated.

During routine operation, many engine components can experience nonuniform or localized temperature changes. These temperature differences in conjunction with structural constraint can cause stresses to develop in addition to those caused by normal operating loads. The effects of these additional stresses and possible acceleration of fatigue damage from oxidation at extreme temperatures are being investigated. Extending the experimental observations from uniaxial testing into a multidimensional model applicable to actual components is also being investigated.

The use of high-temperature CMCs requires holes, notches, attachments, and various joining procedures, all of which lead to stress concentration. Consequently, these stress concentrators are the most likely locations of failure in the material. Fortunately, fiber reinforcements impart a degree of ductility to CMCs that mitigates the stress concentration. Various CMCs are being investigated to determine their performance and notch sensitivities. Thermoelastic stress analysis (TSA) is being used to quantify damage progression; the results are used in the development of materials models and the subsequent development of new materials.

The advent of relatively small, high-powered computers is creating new opportunities for real-time processing of experimental data. Video and photographic images of test specimens are captured during loading. Key features on the specimens are identified and tracked throughout the loading history, enabling full-field displacement measurements as a function of applied load. The displacement fields are converted into strains, followed by constitutive transformation into stresses. This procedure provides a new, noncontacting tool for experimental stress analysis.

A composite paradigm is being used to develop a new generation of puncture-resistant polymer membranes. These membranes have a variety of applications in packaging automotive and commercial products industry. New models are being developed to determine laminate properties based upon the constituent properties.

A detailed investigation of composite constituent properties as related to stress redistribution, notch sensitivity, and damage evolution. Model ceramic, polymer, and cement matrix composites are fabricated with a range of constituent properties. These properties are measured using standard tensile tests as well as fiber pushout tests. The micromechanical mechanisms are then related to the macromechanical response. Damage evolution is quantified using infrared imaging and Moire interferometry.

Recent research indicates that electric fields can alter the threshold stress intensity factors in various glasses. The details of these effects as well as the mechanisms are not known. This project represents a basic investigation into this phenomenon.

Surface preparation of aluminum alloys for adhesive bonding is an important step in developing processes to use aluminum and other lightweight materials in automotive structural applications. Proper choice of acid, oxidant, temperature, contact time, and other processing conditions is critical in forming a porous oxide film on the alloy that simultaneously provides good corrosion protection and high bond strength. Our goal is to understand how processing affects oxide film microstructure and to use that information to develop a better process. We are currently developing a laminar-flow rotating cylinder electrode reactor for rapid evaluation of contact time and potential effects.

The objective is to investigate in situ at an atomic scale the fundamental mechanisms of failure in microelectronic components and micromechanical systems. Microinstruments, developed from micromechanical systems, as well as macroanalytical devices such as transmission electron microscopes are employed for the study. The study is initially directed to experimentally investigate the micromechanisms of failure of interfaces formed by a metal (aluminum) and a ceramic (silicon dioxide). The effects of environment, such as humidity, pressure, and temperature, on the mechanisms of failure are also studied.

A new novel class of micromechanical sensors is being developed based on buckling of a long slender beam to sense a wide variety of physical parameters such as temperature, humidity, acceleration, and electromagnetic fields. The sensors have two stable equilibrium states. They change state when the physical excitation exceeds a threshold value. They consume power during state change only, not while maintaining the state. The nonlinear dynamical behavior of the sensors is studied, e.g., the response of the bi-stable system subjected to a white noise excitation (thermal noise)

A single living embryo is mechanically probed using microactuators and sensors to study its internal fluid pressure, viscosity, mechanical stiffness, and dynamic response. The objective is to investigate whether these parameters change during cell division within the embryo. The study will reveal fundamental understanding of the biological processes during the initial stages of life. The parameters will also allow to distinguish between a healthy and a pathological embryo.

The thermomechanical fatigue resistance of a material often limits the lifetime of a component such as the cylinder head in engines. Isothermal tests performed at various temperatures, mechanical strain ranges, and strain rates may not capture many of the important damage micromechanisms under varying temperature and strain (i.e., TMF), and experiments and modeling of thermomechanical damage processes are needed. The study is developing a physically based life prediction method for the Al 319 and Al 356 alloys. The overall program considers the effect of the following process parameters on mechanical behavior: secondary dendrite arm spacing, effect of aging heat treatment, effect of porosity, and compositional effects.

The basic information obtained from the work will generate improved understanding of transformation under stress, stress-strain behavior as a function of temperature, and fatigue conditions. Single crystals of different orientations (in solution treated and precipitated microstructures) of Nitinol are studied. Several unique experiments under combined shear stress-hydrostatic pressure are conducted. Based on these experiments, the work will set the background to evaluate the theories proposed, and lay the foundation for new ones with particular emphasis on complex changes in transformation strains.

Based on a stress invariant hypothesis and a stress/strain relaxation procedure, an analytical approach is forwarded for approximate determination of residual stresses and strain accumulation in rolling contact. For line rolling contact problems, the proposed method produces residual stress distributions in favorable agreement with the existing finite-element findings. We study ratchetting behavior of 1070 steel under uniaxial tension-compression and axial-shear loadings experimentally. Strain ratchetting direction exhibits a complex dependence on the previous loading history, including nonconsistence with the mean stress direction. Different models to predict this phenomenon are proposed and compared to experiments.

With unique experiment