Crack Tip Fields in Plastically Compressible Hardening Softening Hardening Solids under Cyclic Loading

Abstract

It appears that there is a need to investigate more about the behavior of such materials under a wide range of loadings. Even though the effect of plastic dilatancy is neglected in classical plasticity theory, the above materials exhibit plastic volume changes and/or pressure-sensitive flow strength. In a recent study, it has been observed that the deformation of the entangled arrays of carbon nanotubes or VACNTs follow elastic- viscoplastic constitutive relation which incorporates plastic compressibility, plastic non- normality and a hardening-softening-hardening type hardness function. These VACNTs have prospective uses in a variety of applications like viscoelastic energy absorption, compliant thermal interfaces, biomimetic dry adhesives etc and hence it is useful to develop a predictive framework for the mechanical behavior of VACNTs under a wide range of loadings. In this thesis work, finite element finite deformation quasistatic mode I plane strain small scale yielding analysis of crack tip blunting and near crack tip fields was carried out for plastically compressible solids exhibiting a variety of uniaxial stress strain responses. In particular solids with hardening-softening-hardening responses as can occur for foams and VACNTs have been considered. The novelty of this model includes unique characteristics as mentioned earlier like the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Numerical results obtained from the quasistatic mode I plane strain analysis demonstrate that plastic compressibility is found to give an increased crack opening displacement for a given value of the applied loading. The plastic zone shape and size are found to dependon the plastic compressibility newline