Modeling of pressure-sensitive materials using a cap plasticity theory in extended finite element method

In this paper, a new computational technique based on the extended finite element method (X-FEM) is presented in elasto-plastic behavior of pressure-sensitive material. The cap plasticity model is employed within the X-FEM framework in numerical simulation of powder die pressing. The double-surface plasticity model includes a failure surface and an elliptical yield cap, which closes the open space between the failure surface and hydrostatic axis. The yield cap expands in the stress space according to a specified hardening rule. Application of the X-FEM in simulation of two phase plasticity continuums is presented in an incremental manner and the role of sub-elements in the partition of unity method is demonstrated. Finally, three numerical examples, including: a plate with hole subjected to compression, a double-layer foundation and the compaction simulation of metal powder are analyzed numerically.