PSEUDO-STEADY INDENTATION CREEP

Abstract

Theoretical analysis and computational modeling have been performed to carry out constant-indentation strain rate tests. Results show that both the indentation pressure and indentation strain rate become constant after a lapse of loading time. Moreover, the finite element simulation reveals that the contour-line patterns of equivalent stress and equivalent plastic stain rate underneath a conical indenter evolve with geometrical self-similarity corresponding to indenter displacement. This finding confirms that pseudo-steady indentation creep occurs in the region beneath the indenter. We define representative points in the underlying material as those with equivalent stress equal to the indentation pressure divided by a constraint coefficient of 3. During the pseudo-steady indentation creep of a power-law material, the equivalent plastic strain rate at these points is proportional to the indentation strain rate for compatibility. These results point out that a constitutive equation for the tensile creep of a power-law material can be predicted by constant-indentation strain rate tests.