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Mechanical and Industrial Engineering

Design Methodology and Tribology
^ Evaluating Operator Visibility of Earth-moving Equipment
C. S. Larson,* R. Ingram,* B. Keenan
Caterpillar, Inc.

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 CAVETM. 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.

^ Optimal Path Planning for an Earth-moving Vehicle
C. S. Larson,* R. Ingram,* M. Vande Wiele
Caterpillar, Inc.

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.

^ Friction and Vibration Modeling for Ultralow Fly-Height Head Disk Interfaces
A. A. Polycarpou,* S. C. Lee
National Science Foundation; National Storage Industry Consortium

The objective of this research is to study the interaction between friction, adhesion, and vibration of ultra-low-flying head disk interfaces and their effect on the fly-height and off-track motions of the recording slider. The focus of the research is to characterize the contacting interface and develop appropriate quasi-dynamic friction and adhesion models; develop linear and nonlinear dynamic models for the head disk interface system; and combine the adhesion, friction, and vibration models to accurately predict the instantaneous adhesion and friction forces, normal (fly-height/bouncing) vibrations, and lateral (off-track) motions.

^ Friction and Wear Studies of Compressor Surfaces
A. A. Polycarpou*
Copeland Corporation

The main objective of this study is to experimentally investigate the friction and wear of tribomaterials used for compressor surfaces under mixed lubrication conditions in a controlled environment that simulates application conditions. A high-pressure tribometer will be used for the tests, which provides independent control of normal load, speed, temperature, pressure, and oil/refrigerant mixture supply rate at the interface.

^ Fundamental Investigation on the Tribological Failure Mechanisms of Compressor Surfaces: Scuffing
A. A. Polycarpou,* T. F. Conry* (Gen. Engr.), J. J. Patel, N. Yu
22 Company Consortium: Air Conditioning and Refrigeration Center, National Science Foundation

The purpose of this research is to investigate the cause of catastrophic failures, or scuffing for realistic compressor surfaces. The project has two major components. Researchers will make detailed characterization of the changes in surface topography and physical structure of mating surfaces from their initial (virgin) state up to the point of scuffing. After researchers understand the material properties and surface topography, a modeling effort will be initiated to describe the essential coupled processes of deformation and heat transfer and the resulting effects of stress and temperature at points in a contact interface.

^ Control of Nonlinear Dynamic Systems
D. A. Tortorelli*
University of Illinois

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, researchers seek to combine open- and closed-loop strategies in the overall control scheme.

^ Smart Meso Flaps for Aeroelastic Transpiration to Control Shock/Boundary-Layer Interactions
D. A. Tortorelli,* J. Y. Kim
Defense Advanced Research Projects Agency

The capability and performance of smart meso flaps for aeroelastic transpiration (SMAT) is investigated, which will provide mass and momentum transfer to control Shock/Boundary-Layer Interactions (SBLIs). Numerical and experimental investigations will be closely integrated in relevant SBLI flowfields. Numerical studies will employ an aeroelastic, finite element code to investigate the fluid physics between the supersonic turbulent boundary layer, the subsonic cavity flow, and the deforming meso flaps. This will be coupled to advanced shape- and topology-optimization techniques so that the numerical representation of the nonlinear adaptive controllers is such that meso flap design can be designed for a given flowfield.

^ Topology Optimization of Geometrically Nonlinear Structures and Compliant Mechanisms
D. A. Tortorelli,* J. Noratoes
University of Illinois

Topology optimization of structures has become an area of rapidly increasing interest to researchers during the past decade. Most structural topology optimization problems assume a linear elastic response. This assumption is not valid for systems undergoing large deformation. The structural analysis here accommodates geometric and material nonlinearities and its impact on the topology optimization is investigated. A well-posed, regularized topology optimization problem is developed by introducing a Gaussian-weighted density measure. Topology results based on the linear and nonlinear elastic formulations are compared. The formulation of the structural design problem is then extended to design compliant mechanisms undergoing large displacements.

^ Design of Fiber Brushes for Homopolar Machines
J. S. Walker,* M. N. Alexakis
Naval Surface Warfare Center, N65540-99-M-0121

In fiber brushes for homopolar motors and generators, electric current flows through thin copper fibers which have tips that slide over the surface of a rotating copper drum. Large electromagnetic forces on the fibers can dramatically increase or decrease the contact force between the tip of each fiber and the rotating drum. This contact force must be greater than a minimum value to maintain electrical contact and must be less than a maximum value to minimize wear. Models with large-deflection beam theory are being developed to achieve an optimal design.


Summary of Engineering Research