Material properties of cold-formed lean duplex stainless steel sections

This paper presents the behaviour of cold-formed lean duplex stainless steel for six different sections, among which two are square hollow sections and four are rectangular hollow sections. The test specimens were cold-rolled from flat strips of lean duplex stainless steel. The material properties of high strength cold-formed lean duplex stainless steel square and rectangular hollow sections were determined. Tensile coupons in the flat portions and corners of each section were tested. Hence, the Youngʹs moduli, 0.2% proof stresses, 1.0% proof stresses, tensile strengths, elongation at fracture and the Ramberg–Osgood parameter (n) of lean duplex material for each section were measured. The material properties of the complete cross-sections in the cold-worked state were also obtained from stub column tests. The initial local geometric imperfections of the six sections were measured, and the profiles of the local imperfections along cross-section were plotted for each section. Residual stresses were measured for section 150×50×2.5 using the method of sectioning. The membrane and bending residual stress distributions in the cross-section were obtained and plotted. Furthermore, finite element model of stub columns was developed and compared well with the test results. The stub column test strengths were also compared with the design strengths predicted by the American Specification, Australian/New Zealand Standard and European Code for stainless steel structures. Generally, the three specifications conservatively predicted the column strengths. The European Code provides the most conservative prediction.