Manufacturing Simulation of an Automotive Hood Assembly

This paper presents the results of applying the finite element method to calculating the spring back of an automotive hood assembly, and its application to the functional build method. The assembly was comprised of six individual panels: an inner panel, an outer panel, a major reinforcement, a latch reinforcement, and two hinge reinforcements. Finite element simulations were conducted for forming each of the six components. Each component was formed, trimmed, and positioned in car position. The outer panel required several secondary forming operations including a re-meshing, remapping, trim, and flanging operation. Once in car position, the components were moved so that they just contacted each other, and were “spot welded” together through the application of nodal constraints. Mastic between components was simulated with tied contact. Contact between components was simulated with contact interfaces. Finally, a spring back analysis was conducted. The models clearly illustrate that it is possible to predict spring back of large automotive assemblies, and that the assembly process yields different final shapes than those obtained from spring back of individual components. With this newly developed tool it is possible to predict whether or not the assembly process can correct out-of-spec components, a key factor in utilizing the functional build method.