Relationship of Tensile Specimen Size and Geometry Effects to Unique Constitutive Parameters for Ductile Materials

摘要

Straightforward reduction of tensile specimen load-displacement data to uniaxial true stress-true strain data valid at large deformations is not possible for ductile material specimens which exhibit necking. For applications such as fracture mechanics and metal forming processes, valid uniaxial true stress-true strain data is essential for the accurate analysis and prediction of deformations beyond those encountered at incipient necking. This investigation reports on the use of tensile speciment size and geometry effects to accurately and uniquely assess the uniaxial true stress-true strain curve. This is done for a ductile steel in the context of an incremental elastic plastic constitutive theory employing isotropic hardening and a von Mises yield function. Experimental load-displacement data, experimental full field deformation data and the corresponding finite element computational geometries and applied loads for tensile specimen length diameter ratios are known quantities. The uniaxial true stress-true strain curve parameters and treated as unknown quantities. Successive iteration on the solution curve resulted in successful correlation between the experimental data and computational predictions for all four specimens considered. Keywords: Constitutive, True stress true strain, Tensile specimen, Tensile necking, Fracture toughness, Energy density.