Material Effects and Tubular Steel Strut Capacity

Abstract

The type of mild steel, strain hardening, strain aging, and the Bauschinger effect due to strain reversal are shown to have a significant effect on the load capacity of tubular struts. Material and strut tests have been performed on circular tubular sections of 60–65 mm outside diameter and wall thickness 2.5–3 mm. The strut tests have been effectively pin‐ended and have slenderness ratios ranging from 20–150. Struts made from material which has been prestrained in tension have significantly lower load capacities than those made from as‐received material; this reduction is caused by Bauschinger strain (the rounding of the reverse loading stress‐strain curve) and the resulting reduced tangent modulus. The reduction occurs despite increases in material strength owing to strain hardening under the applied tensile prestrain and strain aging with time or temperature since application of the tensile prestrain. Strain aging has a more significant effect than strain hardening in minimizing the strut “load” capacity reductions due to prior tensile prestrain.