Instability in bending-under-tension of aged steel sheet

Abstract In combined bending and stretching of aged steel sheet, an instability of an unusual kind is identified. Analysis of the behaviour of a sheet using a simplified material model shows that under certain conditions the maximum tension is less than the fully yielding tension and springback in the opposite direction to that normally observed could occur. Some of the sheet used industrially for panels of small curvature may age and there is considerable current interest in the prediction of springback in panels formed by combined bending and stretching.