A Finite Element Study Relating Load-Penetration Curves and Indentation Topography to Yield and Post-Yield Constitutive Behavior

Finite element simulations of ball and cone indentation tests were performed with systematic variations in the input constitutive laws. The ball indentation simulations were used to evaluate the assumptions and applicability of proposed analytical methods to extract the constitutive laws from instrumented load-penetration data. These methods were found to provide good approximations for a small, but useful, range of strain-hardening rates. However, significant differences were found for low (elastic-perfectly plastic) and high (hardening exponents > 0.2) strain-hardening laws and when significant hardening occurs at small plastic strains (< 0.02). The cone indentation simulations were used to investigate the corresponding effects of constitutive behavior on the pile-up geometry around the indentation. In agreement with previous work, the height-to-width aspect ratio of the pile-up increases with a decreasing strain-hardening exponent. However, the pile-up aspect ratio method is sensitive only to the average strain-hardening exponent, and not to details of the constitutive behavior at very high and low strains.