Deviatoric Strength of Nanoporous Materials: A Limit Analysis Approach

In this paper, deviatoric strength properties of nanoporous materials are investigated by addressing the limit state of a hollow sphere undergoing axisymmetric deviatoric strain-rate based loading conditions. The hollow sphere is assumed to be comprised of a rigid ideal-plastic matrix obeying to a von Mises strength criterion. Void-size effects are consistently described by introducing a coherent-imperfect homogeneous interface at the cavity boundary. In the framework of a kinematic approach, the limit-analysis problem on the hollow sphere is solved by referring to a particular trial velocity field, expressed in terms of some free model parameters, chosen as a result of an optimization strategy. A closed-form expression for estimating the macroscopic deviatoric strength is obtained and successfully compared with available benchmarking data.