Call number: LD2668 .T4 1963 R93 / Master of Science

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: leaves 120-126. / by John Edward Blendell. / Sc.D.

Abstract not available

Abstract not available

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Sciences, Systems Science and Industrial Engineering Department, 2006. / Includes bibliographical references.

Thesis (M.S.)--State University of New York at Binghamton, Mechanical Engineering Department, 2006. / Includes bibliographical references.

The finite element stress analysis method was utilized to determine the effects of thermal expansion in small scale crystal deformation with the entire study conducted within the elastic limits of failure. A 5 by 25 km model was simulated, with accepted physical properties of rock and heated to an average geothermal gradient 30° C/km. Parameters independently examined included 1) variance of the coefficient of thermal expansion; 2) variance of temperature magnitude; and 3) variance of temperature geometry.The variations in coefficient of thermal expansion, studied here produced slight alterations in stress patterns produced by body weight and the normal geothermal gradient. It was suggested that general ranges of coefficients were sufficient to predict the behavior of the body. Temperature magnitudes have also resulted in small changes in displacements and stress patterns.Displacements due to thermal expansion were of minimal geologic significance. However, the stress could alter stress patterns generated by other tectonic forces. This may dictate the time and location of the initial failure of the body; in turn controling any subsequent tectonic activity.Ball State UniversityMuncie, IN 47306

Thermally induced interfacial stress states between fiber and matrix at cryogenic temperature were studied using three-dimensional finite element based micromechanics. Mismatch of the coefficient of thermal expansion between fiber and matrix, and mismatch of coefficient of thermal expansion between plies with different fiber orientation were considered. In order to approximate irregular fiber distributions and to model irregular fiber arrangements, various types of unit cells, which can represent nonuniformity, were constructed and from the results the worst case of fiber distributions that can have serious stress states were suggested. Since it is difficult to measure the fiber transverse coefficient of thermal expansion at the micro scale, there is an uncertainty problem for stress analysis. In order to investigate the effect of error in assumed fiber transverse coefficient of thermal expansion on thermally induced interfacial stresses, systematic studies were carried out. In this paper, the effect of measurement errors on the local stress states will be studied. Also, in order to determine fiber transverse CTE values from lamina properties, a back calculation method is used for various composite systems.

Stress induced void formation in Cu interconnects, due to thermal stresses generated during the processing of semiconductors, is an increasing reliability issue in the semiconductor industry as Cu interconnects are being downscaled to follow the demand for faster chip speed. In this work, 1.8 micron and 180 nm wide Cu interconnects, fabricated by Freescale Semiconductors, were subjected to thermal cycles, in-situ in the TEM, to investigate the stress relaxation mechanisms as a function of interconnect linewidth. The experiments show that the 1.8 micron Cu interconnect lines relax the thermal stresses through dislocation nucleation and motion while the Cu interconnect 180 nm lines exhibit void formation. Void formation in 180 nm lines occurs predominantly at triple junctions where the Ta diffusion barrier meets a Cu grain boundary. In order to understand void formation in 180 nm lines, the grain orientation and local stresses are determined. In particular, Nanobeam Diffraction (NBD) in the TEM is used to obtain the diffraction pattern of each grain, from which the crystal orientation is evaluated by the ACT (Automated Crystallography for TEM) software. In addition, 2D Finite Element Method (FEM) simulations are performed using the Object Oriented Finite Modeling (OOF2) software to correlate grain orientation with local stresses, and consequently void formation. According to the experimental and simulation results obtained, void formation in 180nm Cu interconnects does not seem to be solely dependent on local stresses, but a combination of diffusion paths available, stress gradients and possibly the presence of defects. In addition, based on the in-situ TEM observations, void growth seems to occur through grain boundary and/or interfacial diffusion. However, in-situ STEM observations of fully opened voids post-failure show pileup of material at the Cu grain surfaces. This means that surface or interface diffusion is also very active during void growth in the presence of thermal stresses.

No description available.