Seminars

Over the past five decades there has been an intense effort to understand and control the thermomechanical response of materials in extreme environments. A number of technologies critical to our safety and well-being stand to benefit from such understanding including next-generation fission and fusion reactors, defense systems, and spacecraft shielding. Materials in such extreme environments often exhibit complex, somewhat non-intuitive behavior that is difficult to predict with empirical or phenomenological models. Here we discuss our development of a number of multiscale mechanism-based models that help unravel this inherent complexity.

One of the main themes brought to light is that the time-dependent failure of materials in extreme environments is governed, in part, by the kinetics of a hierarchy of microscopic material defects. Furthermore, the kinetics of one particular defect are often governed by lower length-scale defects. Examples of this are provided for twin boundary propagation at high loading rates, dynamic void growth in ductile materials, and thermal fatigue crack growth in quasi-brittle asteroidal materials.

A second theme is that simple mechanism-based models are powerful and instructive, particularly when it comes to building an intuition for nonequilibrium failure processes. We make use of such simple scaling laws to help explain some perplexing experimental observations associated with dynamic ductile failure of metals. In addition to building intuition, these scaling laws are helpful in guiding the microstructural design of advanced armor and shielding materials.