Estimations of the True Stress and True Strain until Just before Fracture by the Stepwise Tensile Test and Bridgman Equation for Various Metals and Alloys

抄録

True stress (σ)–true strain (ε) relationships until just before fracture, i.e., the plastic deformation limit, were estimated by the stepwise tensile test and the Bridgman equation for various metals and alloys with different crystal structures. The estimated σ–ε relationships were different from the nominal stress–strain curves including the conventional tensile properties. In the relationships between the true stress (σ_pdl) and true strain (ε_pdl) at the plastic deformation limit, SUS304 and SUS329J4L indicated a better σ_pdl–ε_pdl balance. On the other hand, SUS329J4L, tempered martensite, and an ultrafine-grained steel showed superior results in the yield strength–ε_pdl balance. The estimated σ–ε relationship for the ultrafine-grained steel suggests that grain refinement strengthening can improve σ and ε up until the plastic deformation limit. The value of ε_pdl became larger with increasing the reduction in area and a decrease in the fracture stress. The products of σ_pdl and ε_pdl became larger with increasing work-hardening rate at the plastic deformation limit.