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Licensed Unlicensed Requires Authentication Published by De Gruyter June 21, 2022

Improved Implementation of Material Behaviour Change due to Bake Hardening in the Simulation of the Process Chain

Verbesserte Berücksichtigung der Änderung des Materialverhaltens infolge des Bake-Hardenings in der Simulation der Prozesskette
M. Hofmann, A. Oeckerath, T. Wallmersperger and K. Wolf

Abstract

The steadily increasing demands on the crash safety of automobiles with simultaneous weight reduction also mean higher requirements for crash simulation. In addition to manufacturability, the focus in component dimensioning is increasingly on crash properties. In order to improve the predictive accuracy of crash simulation, the individual process steps must be coupled in the simulations. To increase the quality of the predictions, thermal treatments such as curing of the paint, which normally takes place at 170 °C for around 20 minutes, should also be taken into account. In many steels, the so-called bake-hardening effect occurs. This leads to an increase in the yield stress. In this publication, different transformation approaches for the hardening curves will be investigated in order to increase the prediction accuracy in the process chain. An example is used to demonstrate their easy applicability in the simulation of the process chain.

Kurzfassung

Die stetig steigenden Anforderungen an die Crash-Sicherheit von Automobilen bei gleichzeitiger Gewichtsreduktion bedeuten ebenfalls höhere Anforderungen an die Crash-Simulation. Dabei liegt bei der Bauteildimensionierung neben der Herstellbarkeit der Fokus auch immer stärker auf den Crash-Eigenschaften. Um die Vorhersagegenauigkeit der Crash-Simulation zu verbessern, müssen in den Simulationen die einzelnen Prozessschritte gekoppelt werden. Dabei sollen zur Erhöhung der Prognosegüte auch thermische Behandlungen, wie zum Beispiel zum Aushärten des Lackes, welches normalerweise bei 170 °C für circa 20 Minuten stattfindet, berücksichtigt werden. Dabei kommt es bei vielen Stählen zu dem sogenannten Bake-Hardening-Effekt. Dieser führt zu einer Zunahme der Fließspannung. Im Rahmen dieser Veröffentlichung sollen verschiedene Transformationsansätze für die Verfestigungskurven untersucht werden, um die Prognosegenauigkeit in der Prozesskette zu erhöhen. An einem Beispiel wird deren einfache Anwendbarkeit in der Simulation der Prozesskette demonstriert.

Acknowledgments

This publication was developed during work on the AiF-funded project 19868BG UmLaC – “Material Models and Characteristic Determination for Industrial Application of Forming and Crash Simulation Considering Thermal Treatments during In-Process Painting for High-Strength Materials”. The authors would also like to thank Ford Werke GmbH for conducting the indentor tests and providing the measurement data.

Danksagung

Diese Veröffentlichung entstand während der Arbeit an dem durch die AiF geförderten Projekt 19868BG UmLaC – „Werkstoffmodelle und Kennwertermittlung für die industrielle Anwendung der Umform- und Crash-Simulation unter Berücksichtigung der thermischen Behandlungen beim Lackieren im Prozess bei hochfesten Werkstoffen“. Die Autoren möchten sich außerdem bei der Ford Werke GmbH für die Durchführung der Indentorversuche und die Bereitstellung der Messdaten bedanken.

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Published Online: 2022-06-21
Published in Print: 2022-06-30

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