B.S. 1983 (Brown)
M.S. 1984 (California Institute of Technology)
Ph.D. 1989 (California Institute of Technology)
Rosakis joined the Cornell faculty in 1988, after completing his doctoral work in applied mechanics at Caltech. He returned there as a visiting professor during a leave in 1994-95. His professional affiliations are with the American Academy of Mechanics and the Society for Natural Philosophy.
Much of the current research in modern solid mechanics pertains to materials that-although initially homogeneous-partially transform to a new solid phase by changing their crystal structure. This can occur under the action of suitable mechanical, thermal, or even electromagnetic loads. Examples include twinning in single crystals and austenite-martensite transformations in various alloys. These are important deformation mechanisms that are responsible for the shape-memory effect in certain alloys.
My research concentrates on the study of solid-phase transformations using nonlinear continuum mechanics. A central issue is the modeling of constitutive behavior in such solids, which involves concepts of material instability and crystalline anisotropy. Starting from the geometric symmetry of the crystal lattice, I have formulated constitutive laws for the deformation of transforming crystals at the macroscopic level. These models account for the ability of crystals to undergo a change of lattice symmetry and a consequent change of phase, and have made it possible to study various interesting microstructures that are caused when different phases coexist in a solid. The different phases represent stable regimes of deformation that are separated by regimes of instability. In order to be compatible, these phases occupy different regions of complicated shapes, separated by sharp interfaces. These theoretical predictions of microstructural shape agree well with physical observations from materials science.
A substantial portion of my work is in the dynamics of phase transformation under applied stress. An important issue here concerns the kinetics governing the propagation of phase interfaces. Some of the results of this analysis predict that certain transformations may occur at supersonic speeds. This is confirmed by experimental observation. An ultimate goal of this project is to relate the microscopic behavior of transforming solids to the dynamics of microstructure evolution.
Other topics of interest include the application of nonlinear elasticity theory to the modeling of crystal defects, such as dislocations, and the modeling of electromechanical transitions, such as domain formation in ferroelectric materials.
