Residual stress testing and proposed residual stress model of hot-bent H-shaped steel

Abstract

Curved H-shaped steel is frequently processed by hot bending, and this high-temperature processing method alters its original residual stress pattern. In this study, residual stress in the H-shaped steel members was examined experimentally and through numerical simulations. Longitudinal residual stresses were measured using a cutting method. The residual stress distributions of the top and bottom flanges were symmetric, while the distribution in the web was asymmetric. The maximum tensile residual stress in the top flange appeared at both its tips, and the maximum compressive residual stress appeared at the web-to-flange junction; the stress distribution of the bottom flange was opposite that of the top flange. The maximum tensile and compressive residual stresses in the web appeared near the neutral axis in the top and bottom halves, respectively. A parametric analysis involving 45 numerical models was performed considering factors such as the bending ratio, height-to-width ratio, and yield strength. The results demonstrated that the magnitude of the residual stress closely correlated with the bending ratio. The height-to-width ratio had no distinct correlation with the residual stress. The magnitude of the residual stress was greater for higher yield strengths; therefore, in this study, the effect of the yield strength was simplified as the residual stress multiplied by fy/355. A simplified residual stress model using internal equilibrium conditions was proposed and verified to satisfactorily reproduce the distribution and magnitude of the residual stress of the hot-bent H-shaped steel members.