Abstract: A method is disclosed for constructing a complex tool surface for use in an age forming process. In one embodiment, the method comprises eight steps. Those steps are (1) modeling a flat panel as a set of finite elements, (2) modeling a rigid tool having a complex tool surface, (3) assigning material characteristics expressed as creep strain to each of the finite elements of the flat panel, (4) modeling the flat panel constrained to the rigid tool in an age forming process to produce a simulated age formed panel, (5) comparing the simulated age formed panel to an actual component and determining the differences, (6) modifying the rigid tool model to eliminate the differences determined in the comparison step, (7) repeating steps 4 and 5 with the modified rigid model until the differences fall within acceptable tolerances; and (8) constructing a tool for use in an age forming process in accordance with the modified rigid model.

Abstract: A method is disclosed for developing the contours of forming tools for fabricating metal members of complex shape such as wing skin and fuselage panels for aircraft. A computer simulation is performed of the age forming process on a geometrical representation of a member having the material properties of a desired metal member. The age forming process includes the steps of: a) overforming an unformed member in a tool having a contour of smaller curvature than the contour of the desired member; b) constraining the unformed member in the overformed condition; c) applying a thermal aging cycle to the member; d) cooling the constrained member following the thermal aging cycle; and e) releasing the constrained member from the condition imparted by step (b) and allowing it to spring back to a dimensionally stable condition which defines the desired member having a surface contour of complex shape.

Abstract: A method is disclosed for developing the contour of tools employed for forming aluminum alloy members exhibiting complex shapes. The members are precipitation, heat-treatable, aluminum alloys which are age formed. The resulting member is formed to the desired contour and, simultaneously, is heat treated to reduce residual stresses while improving its strength characteristics. The invention is particularly concerned with a new tool contour prediction method which is based upon the relationship, for a particular aluminum alloy, of the strain retained in a part after it has been subjected to an applied strain while constrained to a desired shape, then released after being heat treated in an autoclave or furnace.