Patent ID: 7260972

Claim:
A method of stamping an article from an aluminum alloy sheet material, said sheet material having a thickness and a straining limit, where the shape of said article cannot be stamped into said sheet in a single stamping operation without exceeding the straining limit of the sheet at a location in said article, said sheet material being strain hardenable and having known stress/strain forming properties and being initially in a softened condition for forming by stamping, said method comprising: predetermining, from said stress/strain forming properties and the thickness of said sheet, a preform shape that is a deformation precursor of said article shape and includes at least one region in the preform shape that is to be strained up to, but not exceeding, the straining limit of the sheet material and the strain is higher than in adjacent portions of the preform shape, and an annealing practice for re-softening the at least one region of said preform shape, said preform shape and said annealing practice enabling one step stamping of said article shape from said preform shape without exceeding the straining limit of the sheet; and thereafter stamping a blank of said sheet material into said preform shape using a punch and a forming surface tool where the at least one region is strained and formed by stretching the sheet in contact with the punch and forming tool; annealing at least said strain-hardened region of said preform by said annealing practice; and stamping said annealed preform to the shape of said article using a punch and a forming surface tool, the duration of said annealing step being no greater than twice the duration of either of said stamping steps.