PVP2008-61404 STUDY ON STRESS-STRAIN RELATION FOR TYPE 316L STAINLESS STEEL USING MIXED HARDENING LAW

ABSTRACT To determine stress-strain diagrams for a pipe butt joint of type 316L stainless steel, stress-strain diagrams for pipe specimens subjected to monotonic uniaxial tensile load were measured. Tensile-test specimens were extracted from the deposited metal area, heat-affected zone, and parent-material area of the pipe butt joint. The specimens of the depositedmetal area and the heat-affected zone were extracted from positions at the pipe inner surface, mid-thickness, and the pipe outer surface. The measurement temperatures were 20, 300, 600, and 800 o C. The measured stress-strain diagrams show that measured stress at the same given strain increases from measurement point on the outer surfer of the pipe to that on the inner surface. This stress increase is thought to be related to the number of thermal-load cycles used for the weld. The number of cycles at the pipe inner surface was greater than that at the pipe outer surface. To use the measured stress-strain diagrams in a thermal elasto-plastic analysis of welding residual stress and distortion, the measured diagrams for the deposited-metalarea pipe specimen and the parent-material-area pipe specimen were fitted to calculated diagrams by using an isotropic/kinematic mixed hardening law. Material constants for approximating the stress-strain diagrams for the parentmaterial specimen and deposited-metal specimen were determined. The calculated stress-strain diagrams derived from the isotropic/kinematic mixed hardening law show good agreement with the measured stress-strain diagrams