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Ph.D., Northwestern University (1977),
M.S., Northwestern University (1974), B.E., SUNY
Stony Brook (1972) My research is a practical blend of materials science and solid mechanics. A central theme for several of the new and ongoing projects is the Mechanics and Materials Science of Joining. Solder Mechanics addresses the joining of electrical components in electronic packaging. We build specialized equipment and develop new testing methods, one of which is currently under consideration by ASTM for standardization. Mechanics of Adhesive Bonding examines the stress intensities driving fractures as a function of the properties of the adherents and the adhesives. Excellent agreement between simple analytic models and finite element models to calculate stress intensities have been obtained. Stress intensities determined experimentally by compliance methods fall below those obtained analytically. Further work to explain these results and to better characterize the quality of adhesively bonded joints is under way. Characterizing welded joints is a third area we are exploring using chevron notched bend bar specimens. This sample uses a relatively small volume of material making it possible to probe the spatial dependence of fracture toughness within welded joints. Welds, clearly inhomogeneous in their properties, sometimes fail through the weld metal and at other times through the heat affected zone. Our work in this area should improve the way weld joints are tested and analyzed by providing information as to the spatial distribution of mechanical properties. Molecular Mechanics, Mechanics of Adhesion and Micromechanics of Fracture are also emphasized. Molecular Mechanics, that is keeping track of atoms and integrating their equations of motion based on assumed forces between them, is becoming a viable technique to explore mechanics of materials issues. We haves calculated the bulk single crystal elastic constants of materials as a function of the testing temperature, setting to rest the controversy about the Poisson's ratio for central force systems that has existed since 1828. We are examining the effects of small sizes on the apparent properties of solids. This leads us quite naturally into using molecular mechanics to study the mechanics of adhesion and the micromechanics of fracture. Our finding have caused us to reevaluate fundamental tenents of solid mechanics such as the definition of the Cauchy stress and the concept of stress at a point, both of which lose validity in the limit of small size. Further information and a set of recent reprints can be obtained by contacting me directly. Representative Publications
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