Formability consideration during bead optimisation to stiffen deep drawn parts

Beads that alter the geometry of sheet parts can increase the stiffness of deep drawn sheet parts. The locations and geometry of the beads have a great influence on the stiffness of the parts. The design of beads is the result of numerous bead optimisations, developed without considering the manufacturability. Therefore, a bead optimisation algorithm should be developed to increase the efficiency of the bead design while simultaneously considering manufacturability. The trajectory generated along the principal direction of bending stress determines the locations of the beads that maximise the stiffness of the parts. Formability is chosen as a criterion that effectively suggests itself for the initial bead geometry during bead optimisation. The influences of the deep drawing depth, initial specimen geometry and bead height on formability are then investigated by means of a sensitivity analysis. The maximum formable bead height as function of pre-strains is derived from this sensitivity analysis using linear superposition and second order polynomial fitting. The initial bead height function will play a crucial role in supplying the initial values and the validity of the simulation model is experimentally confirmed by the chosen bead locations and geometry.