Charpy V-notch impact toughness of cold-formed rectangular hollow sections

• CVN difference due to uneven degree of cold-forming explained.
• CVN differences between “direct” and “continuous” cold-formed RHS revealed.
• Transition temperature shift from flat to corners for “continuous-formed” RHS.
• Transition temperature shift from flat to corners for “direct-formed” RHS.

The notch toughness of cold-formed rectangular hollow sections (RHS), at low temperatures or in dynamic loading applications, has been a concern in North America for some time. For the assessment of notch toughness of RHS, steel product standards normally require testing of Charpy V-notch (CVN) coupons taken longitudinally from one of the flat faces not containing the weld. This tends to lead to the most optimistic notch toughness result for the cross-section. Thus, serious consideration must be given to the notch toughness of the corner and weld seam regions when low temperature or dynamic loading is a design criterion. In this study, a total of 378 CVN coupons were tested and complete CVN toughness-temperature curves were generated for the flat face, corner and weld seam regions of six North American RHS, to study the effects of cold-forming, heat treatment, cross-sectional geometry and welding on the CVN toughness around the cross-section of RHS. In particular, the CVN toughness properties of RHS cold-formed by different methods (direct-forming versus continuous-forming) were directly compared for the first time.