Prediction and assessment of springback in typical creep age forming tools

Creep age forming is often carried out under vacuum or autoclave loading conditions, where a sufficiently high, uniform pressure is required to force the workpiece into close contact with the tool surface. However, many creep age forming tests are performed to evaluate springback by clamping the workpiece to both ends of a cylindrical tool and forcing it to the tool surface, which is different from reality. In this study, a set of mechanistically based unified creep ageing constitutive equations have been incorporated into the commercial finite element code ABAQUS and used to analyse a common creep age forming tester, which employs a cylindrical tool shape. Two loading conditions are investigated: (1) end clamp and (2) uniform pressure. The amount of springback has been predicted, compared and analysed for both loading cases. A method has been introduced to assess the local curvature and springback variations. Good contact was achieved between the workpiece and tool surfaces for the uniform pressure condition (except at the plate end), providing that sufficient pressure was applied. However, for the end clamp condition, contact was limited to the vicinity of the clamps.