Material properties and residual stresses of cold-formed high strength steel hollow sections

• Cold-formed high strength steel hollow sections were examined.
• Material characterizations were conducted through 66 tensile coupon tests.
• Cold-forming effects were investigated on halves of the three hollow sections.
• A new material model for high strength steel was proposed.
• Residual stresses on three sections were measured and reported.

This paper presents the experimental investigation on the material properties and residual stress distributions of cold-formed high strength steel hollow sections. The nominal yield stresses (0.2% proof stresses) of the hollow sections were 700, 900 and 1100 MPa. The sections were composed of 9 square hollow sections, 2 rectangular hollow sections and 6 circular hollow sections. 66 tensile coupons were tested to determine the modulus of elasticity, 0.2% tensile proof stress, ultimate tensile strength and elongation at fracture of the material. The results were also compared with the American, Australian and European standards. Based on the Ramberg–Osgood expression, a new constitutive model for high strength steel material is proposed. On three of the hollow sections, strength variation and cold-forming effect were studied by testing coupons extracted from different locations of the cross-sections. Residual stresses were also investigated both in longitudinal and transverse directions on three hollow sections using wire-cutting method. A total number of 82 longitudinal strips and 3 transverse rings were cut from the original sections.