Extraction of Material Properties from 3-D Deformation Measurements
Andrew Gross (University of Texas, Austin), K Ravi-Chandar (University of Texas at Austin)
Instability in Solids and Structures
Mon 4:20 - 5:40
Barus-Holley 190
Modeling and characterization of material response is one of the most important goals in the mechanics of materials. Ideally, this involves the imposition of homogeneous deformation along different loading paths and extracting intrinsic response from a uniform state. However, localization of deformation prevents the extraction of the complete intrinsic response. This leads, by necessity, to an iterative process in which measured structural response is used to “calibrate” presumed material response functions, a process that brings with it issues related to uniqueness, completeness, etc. This process has led to the development of many models that have been proposed, calibrated, and used for specific materials. Even so, there remains a challenge in providing predictive ability to these models as demonstrated by recent challenges on blind prediction in ductile flow and failure problems posed by Sandia National Laboratories. Here, a technique for determining the constitutive behavior of ductile metals beyond their necking strains in uniaxial tension is developed. A tensile specimen with square cross section is observed with a 3D imaging system until rupture. Displacements are tracked on two adjoining faces of the specimen within the necked region at sufficiently high resolution to form reasonable, yet conservative strain estimates. A set of iterative finite element simulations of this tensile test with assumed constitutive properties are then compared to experimental data. This method allows for accurate calibration of all relevant constitutive parameters in the simulation to high strain levels. For the material studied here, a J2 flow theory model with isotropic hardening and Hill’s coefficients describing plastic anisotropy in the principal directions are determined.