Stress-strain model for mild steel considering cold-forming effect-A consistent approach

Cold-forming is currently the mainstream manufacturing technology for steel structural products, which produces a multitude of shapes to meet various requirements in engineering design. It is necessary to recognize the influence of cold-forming effect on the performance of full section. Benefiting from abundant existing experimental data, this paper investigated the material properties development characteristics of cold-formed sections in three regions: corner, flat, and side areas, and focuses on the material yield strength, ductility, and stress-strain curves. Research has found that among the three influencing factors of the ratio of fsu,v/fsy,v, thickness t, and inner radius ri, the fsu,v/fsy,v exhibited a strong correlation in the cold-forming effect and the material properties of flat area can be approximated as the virgin material. Subsequently, new formulas of material parameters were determined through the sensitivity and regression analysis and a unified stress-strain model for the full section of steel was established. Finally, the comparison indicates that the proposed stress-strain model not only has satisfactory adaptability in fitting nonlinearity, but also can be used to evaluate yield strength and ductility after cold-forming.