Nano-indentation test of visco-elastic materials and the influence of contact geometry on indentation

Instrumented nano-indentation was performed on polyvinyl chloride (PVC) material and finite element method (FEM) calculation was used to simulate the nano-indentation experiment. The data of the FEM calculation and nano-indentation experiment were compared. It was concluded that the method of using FEM to simulate experiments of nano-indentation into visco-elastic materials is feasible. Four 2D axisymmetric FEM modules of conical-indenters with different tip radii were built to interact with PVC. The simulation results show that the measured hardness increases with the tip radius and decreases with the depth of indention in nano-indentation of visco-elastic materials. Indenter dimension index was employed to help establish two FEM modules classified by the difference between the indenter dimension index and surface roughness. The simulation results indicate that the measured hardness is under or over the proper value when the point of surface contact is at its maximum or minimum and that the deviation of hardness increases with that of roughness as well as the distance between the ripples.