Adiabatic Shear Bands in Thermoviscoplastic Materials

Professor Romesh C. Batra
Engineering Science and Mechanics
Virginia Polytechnic Institute and State University

Sponsored by the Dept. of Engineering Mechanics

Date:  Monday, November 24, 1997
Time:  3:30 p.m.
Place:  306 Bancroft Hall


An adiabatic shear band is a narrow region, usually a few microns (micrometers) wide of intense plastic deformation that forms in high strain-rate deformations of most metals, some polymers and several other materials.  Because of very little time available for the heat to be conducted out of these thin regions, they are called adiabatic.  The predominant mode of deformation in these regions is shearing.  These bands usually precede shear fractures in ductile materials.  Nucleation, coalescence and growth of voids have been observed in these severely sheared regions which eventually cause fracture of the material.  This talk will review some of the experimental evidence and then discuss numerical simulations of dynamic processes involving the initiation and development of shear bands.  Even though our model includes the nucleation and growth of voids, no fracture criterion has been incorporated in it.  Some of the challenging issues include the numerical integration of stiff nonlinear coupled ordinary differential equations, refining finite element meshes adaptively to follow the band, and modeling the fracture phenomenon.