Rate-Dependent Homogenization Based Continuum Plasticity Damage Model for Dendritic Cast Aluminum Alloys

摘要

The objective of this dissertation is to develop a computationally efficient rate-dependent homogenization based continuum plasticity damage model for macroscopic analysis of ductile failure in porous ductile materials containing brittle inclusions. The macroscopic model developed in this dissertation is an extension of the model proposed by Ghosh et al. S. Ghosh, J. Bai, and D. Paquet. Homogenization-based continuum plasticity damage model for ductile failure of materials containing heterogeneities. (J Mech Phys Solids, 57:10171044, 2009). The overall framework of this rate-dependent HCPD model follows the structure of the anisotropic Gursen-Tvergaard-Needleman(GTN) type elasto-plasticity model for porous ductile materials. This model is assumed to be orthotropic in an evolving material principal coordinate system throughout deformation history. The viscoplastic behavior is modeled through an over- stress viscoplastic model. Anisotropy and viscoplastic parameters in the rate- dependent HCPD model are calibrated from homogenization of evolving micro- variables in representative volume element (RVE) of the microstructure. These parameters are dependent on microstructural features such as morphology and distribution of different phases. Micromechanical analyses for this purpose are performed by locally enhanced Voronoi cell finite element model (LE-VCFEM) Hu, C., Ghosh, S., 2008. Locally enhanced Voronoi cell finite element model for simulating evolving fracture in ductile microstructures containing inclusions. Int. J. Numer. Methods Eng. 76(12),(1955-1992). This work also introduces a novel rate-dependent void nucleation criterion for the macroscopic damage evolution due to the combined inclusion and matrix cracking happening in the underlying microstrucure of the RVE. The results of the rate-dependent HCPD model are compared with the homogenized micromechanics (LE-VCFEM) results and show excellent agreement.