Experimental and numerical study of cold-drawn duplex stainless steel square tube columns

ABSTRACT Cold-drawing is one of typical cold-forming techniques in producing stainless steel tubes. Compared with cold-rolling, cold-drawing can be used to manufacture large scale stainless steel tubes. In this study, material properties tests of 14 coupons taken from cold-drawn duplex stainless steel square tubes were reported, along with six stub and seven long column tests under axial compression. Stress-strain curves, ultimate loads and failure characteristics of stub and long columns were obtained. Test results indicate that cold-drawn duplex stainless steel tubes have pronounced cold-forming effect, the yield strength of the flat region reaches up to 750 MPa and the elongation at the fracture decreases significantly. And, all the stub columns show local buckling mode, while most of the long columns undergo overall flexural buckling mode. Finite element models were developed, validated using test data, and then used to generate more results over a wider range of cross-sectional and member slenderness. Both the results of test and numerical modeling were compared with the design strengths of the European, American, Australian/New Zealand and Chinese codes, the design method proposed by Afshan, and the deformation based continuous strength method (CSM). Comparisons show that: for stub columns, design strengths according to all the design codes are underestimated, while the continuous strength method provides reasonable predictions especially for both the stocky and slender cross-sections; for long columns, design strengths calculated using the European, Australian/New Zealand, Chinese codes and the method proposed by Afshan are conservative, while those calculated using the American code are unsafe.