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Dominant inelastic deformation processes of polycrystalline metals in the infinitesimal strain regime are different than those at larger strains. Within the infinitesimal strain regime, dislocation/dislocation interactions and the nucleation and evolution of small-scale dislocation structures such as dislocation cells dominate the strain-hardening character of a face-centered cubic (fcc) material. As the strain transcends the infinitesimal regime, the dominant dislocation substructures become larger macroscopically oriented structures such as dense dislocation walls and microbands. These structures have a profound effect on the mechanical response of the material. The nonrandom crystallographic textures that form at large strain also affect the stress-strain response. With this in mind, interesting and technically significant questions arise concerning the effects of multiaxial nonproportional loading at large strain as well as the effect of a large prestrain on subsequent small-strain multiaxial cyclic deformation behavior. In an attempt to address this question, a matrix of multiaxial large- and small-strain experiments were conducted on Type 304L stainless steel. The large-strain tests consisted of compression, torsion, compression followed by torsion, and torsion followed by tension experiments. A non-proportional small-strain axial-torsional cyclic history was then imposed on material in an annealed state as well as material subjected to an effective torsional plastic prestrain on the order of ¯εp= 100%. Experimental details as well as modeling implications are presented.
polycrystalline metals, multiaxial loading, nonproportional straining, torsion testing, compression testing, sequence tests, large strain, prestrain effects, strain hardening, axial-torsional loading, fatigue (materials), fracture (materials), testing, deformation (materials), multiaxial fatigue
Assistant professor, The Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY
Professor, The George Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA