PNNL

Abstract

This paper presents the use of full-field kinematic measurements obtained using the digital image correlation (DIC) procedure and load-displacement data to determine constitutive material properties by solving an inverse finite element optimization problem. A key ingredient in the proposed approach is computing accurate sensitivities with respect to the unknown parameters. These sensitivities were used to solve the optimization problem using an accurate, efficient, gradient-based method, and were computed using the complex-variable finite element method, ZFEM. The use of ZFEM's gradients to inversely determine material properties is demonstrated with two examples. First, the elastic-plastic material properties of DP-590 steel are obtained using a tensile test specimen. Second, the cohesive material parameters of an adhesive are determined using a double cantilever beam test. A significant outcome of this paper is that the use of a weighted residual formulation of the interfacial strain fields and the load-displacement data within the optimization procedure provides better estimates of the constitutive properties than using only using the load-displacement data. This technique minimizes the relative error in both the strain fields and the load-displacement curve, which is important to obtain accurate interfacial properties.