Alan Needleman, Ph.D.

April, 24, 2012

“Deformation of Plastically Compressible Hardening-Softening-Hardening Solids”

Calculations have shown that a phenomenological elastic-viscoplastic constitutive relation that allows for plastic compressibility can give rise to a progressive buckling-type mode of deformation as seen in experiments on vertically aligned carbon nanotube (VACNT) pillars although a more common response with such a constitutive relation is a propagating instability. This phenomenological constitutive model is used in 2D and 3D finite deformation, finite element analyses to model the response of compressible hardening-softening-hardening solids under various imposed loadings, including uniaxial compression, uniaxial tension and indentation. The effect of material parameter variations on the mechanical response and the type of instabilities that emerge is considered. The responses are compared with the corresponding responses of non-softening solids. This is joint work with Shelby Hutchens, Nisha Mohan and Professor Julia Greer of Caltech.