Simulation analysis of the deformation behavior of nanoindentation based on elasto-plastic constitutive model

The yield criterion of pressure-sensitive materials based on the elliptic model is obtained, and an elasto-plastic constitutive model in generalized plastic mechanics has been proposed by combining the associated flow rule and linear hardening model. This criterion is validated with the basic tension, compression, and combined compression-shear experimental results for the material PMMA. The elasto-plastic model is implemented into the Finite Element Method software using a properly conceived UMAT subroutine in an implicit fashion. The nanoindentation behavior of PMMA is investigated via numerical simulation, and simulation results are validated with the nanoindentation experimental results. Then, the distribution law of the plastic deformation gradient under the indenter is obtained based on the numerical simulation results.