Seminar Series - 1996-1997

Dynamic Strength and Inelastic Deformation of Shocked Polycrystalline Silicon Carbide

Dr. R. Feng
Shock Dynamics Center and Department of Physics
Washington State University
Pullman, WA   99164-2418

Sponsored by the Dept. of Engineering Mechanics

Date:  Thursday, February 6, 1997
Time:  3:30 p.m.
Place:  306 Bancroft Hall


A good understanding of the strength and inelastic deformation of ceramics under rapid impulsive loading is central to predicting and optimizing the armor performance of these materials.  The scientific challenge is how to probe the strength properties and identify the inelastic deformation mechanisms in these brittle solids under well characterized high rate loading conditions.  In this talk, an in-depth study on a high density, polycrystalline silicon carbide using plane shock wave experiments and detailed computational analysis will be presented.  To experimentally determine the material strength in the shocked state, two independent methods were used:  1) in-material, piezoresistance gauge measurements, and 2) combined compression and shear wave experiments.  The experimental measurements in combination with rigorous one and two-dimensional wave propagation calculations have provided a complete characterization of the stress state in shock compressed SiC.  The results show that the material sustains an extremely high strength in the shocked state.  The strength evolution in the inelastic state resembles neither catastrophic failure due to massive cracking nor classical plasticity response.  An inhomogeneous deformation mechanism combining both partial brittle-ductile transition and highly confined microdamage at various stages of shock compression will be discussed along with some supporting evidence from a very recent series of shock unloading experiments.


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