A validated finite element model for designing a multistage forming process to enhance annealing-induced shape change in AISI 420 sheet
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Modern manufacturing demands high-precision metallic parts for miniaturization and net shaping, which is not easily accessible. For example, sheet metals like AISI 420 stainless steel require post-forming heat treatment to meet stringent performance standards. However, the heat treatment causes changes in shape, with the annealing step accounting for most of the shape change, which is critical to maintaining precise dimensions and challenging to measure [1, 2]. This research introduces an optimized demonstrator of a multistep forming process, which intentionally enhances shape changes during heat treatment to facilitate measurements. The demonstrator enables the study of the influences of material properties and deformation on shape change during heat treatment. Utilizing 0.2 mm thick AISI 420 sheet metal, the research focuses on the annealing process as the primary cause of the shape changes [2]. We used MSC Marc solver, and the following outlines the research procedure. (1) Acquiring and implementing the material’s properties, including flow curve, anisotropy, variations of elastic modulus and yield strength with temperature, and creep law. (2) Validation of the implemented material models by an existing demonstrator. (3) Design of a new multistage forming process. (4) Measurement of the shape change caused by the annealing process. The key findings are summarized. (1) The detailed finite element model can estimate the shape change of an existing demonstrator during the annealing process. (2) The designed process exhibits more shape change compared to prior research [2]. (3) The underlying reasons for the shape changes were explained. REFERENCES [1] G. Zijlstra, M. Groen, J. Post, V. Ocelík, J.T.M. De Hosson, On the role of the residual stress state in product manufacturing, Mater. Des. 105 (2016) 375-380. https://doi.org/10.1016/j.matdes.2016.05.085 [2] M. Groen, G. Zijlstra, D. San-Martin, J. Post, J.T.M. De Hosson, Product shape change by internal stresses, Mater. Des. 157 (2018) 492-500. https://doi.org/10.1016/j.matdes.2018.08.013
