PSI - Issue 82

Andreas Taucher et al. / Procedia Structural Integrity 82 (2026) 295–301 A. Taucher et al. / Structural Integrity Procedia 00 (2026) 000–000

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3. Results 3.1. Simulation software

The interviews showed that all companies use the commercial AutoForm (AutoForm Engineering GmbH, Pfäffikon SZ, Switzerland) FE software and that three companies additionally use the commercial Pam-Stamp (Engineering System International ESI, Bagneux, France) FE software for simulating sheet metal forming (deep drawing) processes. The interview partners claimed that AutoForm is user-friendly, time-efficient and offers the possibility to standardize the modelling and simulation procedure. Moreover, the simulation results are reliable and the prediction quality of the software is high. The commercial LS-Dyna (Ansys, Inc., Canonsburg, Pennsylvania, USA) FE software is commonly used by experts on crash management for simulating the vehicle and component behavior in accident situations. This software provides a non-restrictive and detailed toolkit for modelling, solving and post-processing, and it offers more individual flexibility in terms of different applications. 3.2. Tribology models The geometrical specifications of the tools and the material model, but also the tribological model are important in the simulation of sheet metal forming (Hol et al., 2016). Therefore, the OEM interview partners use the TriboForm (TriboForm Engineering, Enschede, Netherland) software to generate tribological models that improve the prediction quality of sheet metal forming simulations in AutoForm, as recommended by the developer of the software. However, if default data are not available, generating tribological models requires higher experimental efforts for determining contact pressure- and sliding velocity-dependent coefficients of friction (Dom itner et. al., 2021, Hodži ć et al., 2023a, Shafiee Sabet et al., 2021). Although natural aging (Hodži ć et al., 2023b) and surface temperature (Hodži ć et al., 2023c, Shafiee Sabet et al., 2023) may also influence the formability of the sheets and the tribological conditions between the sheet and the tools at room temperature, the interview partners do not consider any of both phenomena. The non-OEM interview partners simplify the tribological conditions just by using Coulomb’s constant coefficient of friction (Wang et al., 2017). However, they claimed that they would replace the simplified constant friction model with an advanced multi-factor friction model (MFFM), if the direct failure costs due to the less precise model would exceed the licensing costs of the TriboForm software. 3.3. Flow curve criteria The interviews revealed that material model creators merge the true stress-true strain curves obtained from uniaxial tensile tests and bulge tests, and they extrapolate these curves as exemplarily illustrated in Figure 4a by using one of the flow criteria presented in Figure 1a. Results obtained from uniaxial tensile tests are reliable for lower strains, whereas results from bulge tests provide a good description for medium strains. The interview partner of the simulation software developer suggested using the hybrid Swift/Hockett-Sherby criterion for modelling the flow behavior of aluminum alloys, but the material model creators prefer using the criteria that best-fits the results of the material tests.

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Fig. 4. (a) Flow curve based on data from uniaxial tensile testing, bulge testing and extrapolation; (b) comparison of different yield criteria in the biaxial tensile area.