Stress Relaxation of Residual Metalworking Stresses
SourceThe stress relaxation behavior of 1010 and 1020 steels was evaluated for an application involving the relaxation of mandrel-drawn, roller-straightened tubes. The distortions observed in full-sized tubes after annealing at 260 and 482°C are reported, as well as measurements of the actual residual stress levels in such tubes. Bending stress relaxation experiments were performed on strip specimens removed from full-sized tubes at temperatures of 23, 149, and 260°C for up to 2000 h. The relaxation of metalworking stresses was modeled using small beams plastically deformed in four-point bending. The curvature relaxation of the beams after annealing at 260 and 482°C was measured. The results of this work indicate that less than 10 percent of the initial stresses due to metal forming should relax in tubes in service at room temperature.