Computational mechanics of heterogeneous materials––influence of residual stresses

Abstract

In this contribution, a physically based micromechanical approach is applied in order to clarify the influence of residual stresses on local as well as global properties of metal matrix composites. Artificial microstructures as well as a representative microstructural cut-out of an Al/10%SiC-composite are meshed with finite elements in order to take phase boundaries into account. The latter mesovolume possesses all characteristic features of the material, such as volume fraction, distribution characteristics as well as shape of the particles. The deformation behaviour of this microstructure is analysed under large compressive external loading up to strains of about 10%. In addition, the failure behaviour is modelled using Rice & Tracey’s failure criterion which was recently shown to model microstructural failure to a good approximation. In order to illuminate the influence of particle shape and arrangement, artificial two-dimensional microstructures are analyzed first. It is found that although residual stresses do have some impact on failure initiation in the microstructure, strains due to external loading are much more of importance in this respect. It is also found that irregular particle shapes are much more prone to fracture in the matrix as compared to regular shapes and that particle alignments are not beneficial with respect to failure aspects. The distribution and maximum values of the damage parameter are shown. It is found that in all cases investigated, damage follows the pattern of plastic deformation and is much less influenced by hydrostatic stresses than expected. Nevertheless, damage nucleates between clusters of particles where shear deformation as well as hydrostatic tensile stresses are concentrated in the matrix.