Experimental and numerical residual stress evaluation for press-braked cold-formed advanced high-strength dual-phase steel angles

In this study, a series of experimental and numerical residual stress measurements of various corner radii lipped angles press-braked from a piece of advanced high-strength dual-phase steel sheet was conducted. The 1.8 mm thick sheet had a nominal yield strength of 580 MPa and a nominal ultimate strength of 980 MPa. Both destructive method sectioning and semi-destructive method hole-drilling were adopted. Longitudinal surface strains at the corners, legs, and lips of the cross-section were measured by linear strain gauges using sectioning, and both longitudinal and transverse outer surface strains at cross-section legs and lips were measured by strain gauge rosettes using hole-drilling. The residual stresses calculated from the measured strains were compared between the two methods and with relevant existing studies. The maximum residual stress on angle surface was observed at the cross-section corners, which was about 20% of the yield strength. Notably, specimens taken from the edge and center of the same member showed minimal variation, suggesting that discarding end portions in future tests may be unnecessary. In addition, corresponding computational models simulating the forming process of the angles were developed to investigate the induced residual stresses on surface and through thickness, in which a step-wise dynamic implicit analysis strategy was proposed and adopted. Good agreement between the results of the experiments and the simulation was observed.