Process design for the forming of organically coated sheet metal

In this research work, the process design for forming of organic coated sheet metal has been investigated. The project aims firstly at the investigation of the forming behavior of the OCSM, focusing on changes of the optical properties i. e. gloss degree depending on process parameters. Consequently, the application of Finite Element Method (FEM) to simulate the forming process of the OCSM and to predict the change of the surface properties is discussed. The FE modeling allows, finally, a material-based process design and optimization of forming process. The experimental results indicate that the gloss reduction of the coated surface is basically caused by the strain states and strain level imposed on both steel substrate and the coating layer. In order to predict exactly the coating failures the forming limit diagram of coating (FLDC) should be used instead of the forming limit diagram (FLD) of steel substrate. By using FLDC, the formability concerning the optical property of the coating layer is considered in the process design of OCSM. Furthermore, the dependence of the gloss reduction on the strain states can also be taken into account. The obtained results are finally validated by hydro-mechanical deep drawing (HDD) for forming of complex practice-oriented geometry. The influences of process parameters on the surface property of OCSM products in HDD process are also investigated. For this purpose, an analytical model is first investigated in order to evaluate the influences of geometrical and process parameters on the strain states and strain distributions over the forming part. Based on the conclusions obtained by the analytical results, the process design for the HDD process using OCSM can be optimized with regard to the best surface characteristics of organically coated layers.