Flat crimping for automobile bodywork: Digital simulation

Faced with ever-increasing competition in the global automotive market, reducing design costs and lead times has become a major development focus for automakers. In order to maintain a high level of quality and robustness, while ensuring improvements through innovation in styling and technology, the automotive industry regularly introduces new means of production and new grades of sheet metal to achieve the required feasibility and productivity targets. The desire to reduce vehicle mass has become not only a major competitive challenge, but also an environmental constraint.

To meet these needs, digital simulation of forming processes has become an essential tool. It saves a considerable amount of time in the upstream phase of a project, guaranteeing the feasibility of parts or the development of an innovative forming process. Indeed, the aim of simulation is to reduce the number of experimental campaigns on prototypes or test specimens, deemed too long and too costly. Manufacturers began to show an interest in simulation in the 1980s. During the 1990s, finite element simulations evolved considerably in the field of sheet metal forming. Simulation models are constantly being improved in response to growing demands from automakers to reap the rewards of their investment in this field. They are demanding ever more accurate predictions.

Numerical simulation of the flat crimping process is a good example. Interest in finite element simulation of this process began around 1986, with the aim of improving the final quality of parts [1] . The crimping process is described in the article "Flat crimping for automotive bodywork: process" [BM 7 865] . The improvement of crimping calculation models is then part of a quality policy to predict the exact dimensioning of parts.

This article provides an introduction to flat crimping through numerical modeling. The first section deals with the physical modeling of sheet metal behavior and friction with crimping tools, with a view to integrating these laws into the numerical simulation of the process. The second section presents the finite-element simulation models used in conventional models. It illustrates the robustness of the numerical models used: finite element models, behavior laws and friction models.