ANALYSIS OF RIDGING IN ALUMINUM AUTO BODY SHEET-METAL

A finite-element model is presented for the analysis of surface roughe ning of aluminum sheet metal. A hybrid finite-element model is develop ed which accounts for the elasto-viscoplastic constitutive response of a single crystallographic orientation. Initialization bf a finite-ele ment mesh representing several grains is performed using data gathered through automated collection of backscattered Kikuchi diffraction dat a. To handle a region that contains sufficient:variation (contains num erous distinct grains), the implementation is carried out using distri buted computation strategies. Application is made to 6111-T4 sheet met al intended for auto body applications. The numerical simulations are complemented with mechanical testing in plane strain and biaxial stret ch. Based on the simulation results, there are two conclusions that ca n be drawn concerning the action of surface grains deforming through c rystallographic slip. One is that grains can act collectively to form localized regions of thinning. The other is that grain interactions ca n lead to behavior which is different from that expected if grains def orm with the average (macroscale) strain. Neighbor interactions can al ter the deformation from that computed using the macroscale deformatio n rate.