Thermomechanical analysis of the shear zone during fine blanking of quenched and tempered steel F. Schweinshaupt1,∗, T. Stoel1, M. Müller1, T. Herrig1, T. Bergs1,2 1 Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University, 52074 Aachen, Germany 2 Fraunhofer Institute for Production Technology IPT, 52074 Aachen, Germany ∗ f.schweinshaupt@wzl.rwth-aachen.de Keywords: Fine blanking, Thermoviscoplastic modeling, Thermographic measurement. In order to design deformation mechanism-based sheet materials as well as tribologically stressed tool elements, knowledge of the thermal load is required for fine blanking. The characteristic of fine blanking leads to a thermomechanically induced heat dissipation in the shear zone, which is influenced by the process parameters. Depending on the load spectrum, the dissipated heat accumulates in the shear zone and causes heating along the sheared path. The shear zone heating has an influence on the activation of the deformation mechanisms during fine blanking of high manganese steel and thus on the realization of a high sheared surface hardening [1]. In addition, the thermomechanically induced heating influences the wear behavior of the tool elements actively involved in fine blanking. Numerical modeling of plastic flow for analyzing the temperature in the die edge area and its influence on the shear zone requires a thermoviscoplastic material model [2], temperature-dependent physical parameters as well as consideration of the stress- and temperature-dependent contact heat transfer [3]. Therefore, this paper deals with the development of a methodology for numerical analysis of the thermomechanical influence of the process parameters on the shear zone heating. The methodology was derived by means of an experimental investigation of the sheared surface temperature based on thermographic measurements during fine blanking of quenched and tempered steel 42CrMo4 (AISI 4140). For this purpose, a thermomechanically coupled finite element (FE) model was designed, taking into account thermoviscoplasticity, temperature-dependent physical parameters as well as a steadystate calibrated contact heat transfer and validated by means of experimental fine blanking tests. The validation was carried out using force, die roll and thermography measurements based on varied blanking velocity and blank holder force. The thermomechanically coupled FE modeling showed a sufficiently accurate correspondence regarding the experimentally determined blanking force, die roll as well as sheared surface temperature. An increasing blanking velocity resulted in a reduction of blanking work. Numerical analysis in terms of reduced blanking work revealed a significant heat accumulation in the shear zone, indicating thermal softening at higher blanking velocity. References [1] Schweinshaupt, F., Herrig, T., Bergs, T. (2023). Fine blanking of pre-hardened high manganese steel to investigate the sheared surface hardening and part quality. Materials Research Forum LLC, pp. 2101-2113. [2] Joun M.-S. et al. (2022). A Review of Flow Characterization of Metallic Materials in the Cold Forming Temperature Range and Its Major Issues. Materials, 15. 85
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