Plastic Properties of Metal-Metal Composites : A Numerical Investigation

Abstract

A two-dimensional finite element model of an elastic-plastic solid(aluminum) is used to predict the plastic properties including stress-strain behaviour of aluminum composites containing up to 40 volume percent particulate reinforcements under combined loading up to 0.2 in equivalent logarithmic strain. The effects of reinforcement size, shape, contents, orientation, elastic properties and loading conditions on the overall behavior of the composite are investigated. The elastic modulus of the composites is isotropic, almost independent of the type of reinforcement, and controlled solely by the volume percentage of reinforcement present. The work hardening exponent of the composites(one of the plastic properties) is surprisingly influenced by the ratio (γ) of the elastic constants of the reinforcement and the matrix in an inverse manner. It is also affected by the volume fraction, size, shape, orientation and distribution of the reinforcement. The variation in flow stress is controlled primarily by volume fraction, type, distribution and γ. For various loading conditions, the parameters, namely, the work hardening exponent, elastic modulus and flow stress of the composites for all kinds of reinforcements, remain almost constant for a particular value of γ and volume fraction with a slight change in the values for plane strain tension. For porous solids, these parameters are affected slightly by the loading conditions. Furthermore, the degree of constitutive softening of porous solids is strongly dependent on the volume fraction and shape of voids. A comparison of properties with conventional aluminum shows that an improvement in the plastic properety of a metal by combination with other metals could become an interesting subject, especially in the field of metal forming processes. For such research, the FEM model used here is a powerful tool.