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To reach safety, emissions, and cost objectives, manufacturers of automotive body structural and chassis components shape thin gauge, high strength steel tube with a bending, pre-forming and hydroforming process. Challenging grades and bend severity require a careful optimization of the bending procedure. A joint project between Ford and ArcelorMittal Tubular Products investigated suitable bending parameters for severe bends using commercially available thin-walled DP780 and HSLA350 tubes. This paper summarizes the measurement methods found to be capable of capturing small differences in bending formability and details the influence of bender variables such as boost, pressure die, center-line bend radius and bend angle on the wrinkling, thinning and springback of these tubes. As a result of this work, recommendations were made as to effective bender set-ups for these tubes.

To reach safety, emissions, and cost objectives, manufacturers of automotive body structural components shape thin gauge, high strength steel tube using a series of manufacturing steps that often include bending, preforming and hydroforming. Challenging grades and bend severity require a sensitive optimization of the tubular bending process. To this end, it is necessary to achieve an understanding of efficient measurement methods capable of capturing small differences in bending formability. In preparation for an optimization of a 90o bend using Dual Phase 780 (DP780) and High Strength Low Alloy (HSLA350) thin walled tube, the measurement techniques of three formability characteristics: thinning, strain, and final geometry were statistically evaluated. In addition, the difference in the bending behaviour of the two grades was evaluated.