Main menu >> Materials Research Laboratory >> Theoretical and Applied Mechanics: Behavior of Engineering Materials

Materials Research Laboratory

Theoretical and Applied Mechanics: Behavior of Engineering Materials
^ Effects of Surface Microstructure on Strength and Durability of Adhesive Bonding
K. J. Hsia,* A. Pearlstein* (Mech. & Indus. Engr.), A. Scheeline* (Chemistry), J. K. Shang* (Mater. Sci. & Engr.)
U.S. Department of Energy, DE-FG02-91ER45607

(In cooperation with the Frederick Seitz Materials Research Laboratory)
kj-hsia@uiuc.edu

The program is supported by a U.S. Department of Energy initiative to develop scientific understanding of surface-preparation processes to enhance adhesive bond strength and durability for lightweight vehicles. Metal (such as aluminum) surfaces are usually chemically treated before being adhesively bonded together to form a structural component. The chemical treatment produces an oxide film with complicated microstructures. This project aims at providing a mechanistic understanding of the relationship between the microstructure of the oxide film and the interfacial failure strength of adhesive joints.

^ Interfacial Fracture due to Cavitation in a Ductile Adhesive Layer
K. J. Hsia,* S. Zhang
U.S. Department of Energy, DE-FG02-91ER45607

(In cooperation with the Frederick Seitz Materials Research Laboratory)
kj-hsia@uiuc.edu

As part of the program to understand the relationship between microstructure of pretreated surfaces and interfacial strength of an adhesively bonded component, this project studies one particular failure mechanism—cavitation within a ductile adhesive layer. A new method utilizing fluid mechanics solutions is developed. The plastic deformation field surrounding a growing cavity is approximated by a fluid flow field. Using the principle of virtual work, we obtain the fracture toughness due to failure by cavity growth in the ductile layer. The results of this study can provide guidelines for generating optimized surface microstructures to achieve excellent strength and durability of adhesive bonding.

^ Mechanics of Powder Densification
P. Sofronis,* R. S. Averback (Mater. Sci. & Engr.), S. Subramanian
U.S. Department of Energy, DE-FG02-91ER45439

(In cooperation with the Frederick Seitz Materials Research Laboratory)
sofronis@uiuc.edu

Powder densification is used to manufacture advanced structural materials and the promising class of nanocrystalline materials. The finite-element method is used to predict the deformation of a powder under general loading conditions. Scaling laws are detected for the macroscopic strain rate as a function of the macroscopic stress in the numerical results. The mechanisms considered include linear and nonlinear deformation effects, grain-boundary and surface diffusion, and grain-boundary slip. The coupling of these mechanisms is accounted for in the models, which are tested against experimental measurements from the densification of nanophase TiO2, porous alumina, and Ti-48Al powder compacts.

^ The Mechanics of Hydrogen Embrittlement
P. Sofronis,* H. K. Birnbaum (Mater. Sci. & Engr.), Y. Liang, N. Aravas (Univ. of Thessaly)
U.S. Department of Energy, DE-FG02-91ER45439

(In cooperation with the Frederick Seitz Materials Research Laboratory)
sofronis@uiuc.edu

Hydrogen embrittlement is a severe environmental type of failure and the mechanisms involved are not well understood. Recent numerical results on the effect of hydrogen on dislocation–defect interactions are used to study the hydrogen-induced localization of plastic deformation into bands of intense shear and the hydrogen effect on crack tip blunting. In hydride-forming systems, the finite-element method is used to predict the size of the hydrides accommodated by plastic deformation in the neighborhood of a crack tip. The results are used to establish criteria for the onset of crack propagation in engineering materials in the presence of hydrogen.


Summary of Engineering Research