Indentation and imprint mapping method for identification of residual stresses

Abstract

Indentation tests are at present frequently employed for the identification of material parameters. A recently proposed technique combines the traditional indentation test with the mapping of residual deformations (imprint), thus providing experimental data which are used to identify isotropic and anisotropic material parameters in more accurate fashion and in larger number. In this paper, such new methodology is employed for the identification of bi-dimensional states of stress, in particular residual self-stresses. Axialsymmetric indenters are referred to. While the indentation curve is almost insensitive to the direction of pre-existing bi-dimensional stress states, the mapped imprint (which, generally, does not exhibit axialsymmetry because of the presence of the residual stress state) directly reflects all features of such stresses and turn out to be crucial for their identification. Three-dimensional finite element simulations are performed in finite-strain regime. Inverse analysis is carried out by a batch, deterministic approach, using conventional optimization algorithms for the minimization of a discrepancy norm between measured and computed quantities. Numerical examples are discussed apt to test the performance of the proposed methodology in terms of result accuracy and computing effort. The present method is validated also by means of applications to truly experimental data available in literature.