Molecular Dynamics Simulation of Nanoindentation on Folded Chain Crystal of Polyethylene

Nanoindentation tests on a folded chain crystal of polyethylene are implemented with the molecular dynamics simulation. The orthorhombic crystal is made of the planar zig-zag chains and has the thickness of about 10nm. The ideal Berkovich indenter is plunged into upper surface of the crystal down to 2nm with the constant loading rate of 200m/s or 2000m/s. After the holding time of 1000fs at the maximum depth, the indenter is then pulled up with the same speed. The results are summarized as follows; a) The indentation of 2000m/s remains the residual depression while that of 200m/s recovers the hollow, b) No elastic component is found in the deformation under the both rate of 200m/s and 2000m/s, c) The crystal deforms statically under the indentation of 200m/s while that of 2000m/s shows delayed response.