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.
References
1 Elsen, P.; Hougardy, H. P.: On the Mechanism of Bake-hardening. Steel Res. 64 (1993) 8–9, pp. 431–436, DOI:10.1002/srin.19930104910.1002/srin.199301049Search in Google Scholar
2 Bleck, W.; Brühl, S.; Gerber, T.; Katsamas, A.; Ottaviani, R.; Samek, L.; Traint, S.: Control and exploitation of the bakehardening effect in multi-phase high-strength steels. Office for Official Pub. of the EC, Luxembourg, 2007, pp. 1–169. – ISBN: 978-9-2790-4608-7Search in Google Scholar
3 DIN EN 10325 : 2006: Bestimmung der Streckgrenzenerhöhung durch Wärmebehandlung (Bake-Hardening-Index). Beuth Verlag, Berlin, 2006Search in Google Scholar
4 Palkowski, H.; Anke, T.: Bake hardening of hot rolled multiphase steels under biaxial pre-strained conditions. Steel Res. Int. 77 (2006) 9–10, pp. 675–679, DOI:10.1002/srin.200606446,OA10.1002/srin.200606446,OASearch in Google Scholar
5 De, A. K.; Vandeputte, S.; Cooman, B. C. D.: Static strain aging behavior of ultra low carbon bake hardening steel. Scr. Mater. 41 (1999) 8, pp. 831–837, DOI: 10.1016/S1359-6462(99)00232-810.1016/S1359-6462(99)00232-8Search in Google Scholar
6 Liu, T.; Hou, H.; Zhang, X.; Liu, H.; Zhou, Q.; Zhang, J.; Gao, R.; Liu, X.; Lv, Z.: Effects of prestrain and grain boundary segregation of impurity atoms on bake hardening behaviors of Ti+V-bearing ultra-low carbon bake hardening steel. Mater. Sci. Eng. A 726 (2018), pp. 160–16810.1016/j.msea.2018.04.060Search in Google Scholar
7 Ji, D.; Zhang, M.; Zhu, D.; Luo, S.; Li, L.: Influence of microstructure and pre-straining on the bake hardening response for ferrite-martensite dual-phase steels of different grades. Mater. Sci. Eng. A 708 (2017), pp. 129–141, DOI:10.1016/ j.msea.2017.09.127,OA10.1016/ j.msea.2017.09.127,OASearch in Google Scholar
8 Durrenberger, L.; Lemoine, X.; Molinari, A.: Effects of pre-strain and bake-hardening on the crash properties of a top-hat section. J. Mater. Process. Technol. 211 (2011) 12, pp. 1937–1947, DOI:10.1016/j.jmatprotec.2011.06.015,OA10.1016/j.jmatprotec.2011.06.015,OASearch in Google Scholar
9 Cottrell, A. H.; Bilby, B. A.: Dislocation Theory of Yielding and Strain Ageing of Iron. Proc. of the Phys. Soc. A, Inst. of Phys. 62 (1949) 49, pp. 49–62, DOI:10.1088/0370-1298/62/1/308,OA10.1088/0370-1298/62/1/308,OASearch in Google Scholar
10 Elsen, P.; Houghardy, H. P.: Bake-hardening – A Possibility of Increasing the Yield Strength of Steel Sheet. Stahl und Eisen 113 (1993), pp. 101–106Search in Google Scholar
11 Das, S.; Mohanty, O. N.; Singh, S. B.: A phenomenological model for bake hardening in minimal carbon steels. Philos. Mag. 94 (2014) 18, pp. 2046–2061, DOI:10.1080/14786435.2014.906754,OA10.1080/14786435.2014.906754,OASearch in Google Scholar
12 Berbenni, S.; Favier, V.; Lemoine, X.; Berveiller, M.: A micromechanical approach to model the bake hardening effect for low carbon steels. Scr. Mater. 51 (2004) 4, pp. 303–308, DOI:10.1016/j.scriptamat.2004.04.03110.1016/j.scriptamat.2004.04.031Search in Google Scholar
13 Ballarin, V.; Soler, V.; Perlade, A.; Lemoine, X.; Forest, S.: Mechanisms and Modeling of Bake-Hardening Steels: Part I. Uniaxial Tension. Metall. Mater. Trans. A 40 (2009) 6, pp. 1367–1374, DOI:10.1007/s11661-009-9813-5,OA10.1007/s11661-009-9813-5,OASearch in Google Scholar
14 Ballarin, V.; Perlade, A.; Lemoine, X.; Bouaziz, V.; Forest, S.: Mechanisms and Modeling of Bake-Hardening Steels: Part II. Complex Loading Paths. Metall. Mater. Trans. A 40 (2009) 6, pp. 1375–1382, DOI:10.1007/s11661-009-9812-6,OA10.1007/s11661-009-9812-6,OASearch in Google Scholar
15 Hofmann, M.; Wallmersperger, T.: Bake hardening of three high strength steel grades. Metall. Mater. Trans. A, eingereichtSearch in Google Scholar
16 Wolfram Mathematica R 11.3.0: Copyright 1988-2018 Wolfram Research, Champaign, Illinois, USASearch in Google Scholar
17 Barlat, F.; Brem, J. C.; Yoon, J. W.; Chung, K.; Dick, R. E.; Lege, D. J.; Pourboghrat, F.; Choi, S.-H.; Chu, E.: Plane stress yield function for aluminum alloy sheets – part 1: theory. Int. J. Plast. 19 (2003) 9, pp. 1297–1319, DOI:10.1016/S0749-6419(02) 00019-0,OA10.1016/S0749-6419(02) 00019-0,OASearch in Google Scholar
18 Chaboche, J. L.; Rousselier, G.: On the Plastic and Viscoplastic Constitutive Equations: Part I: Rules Developed With Internal Variable Concept. J. Press. Vessel Technol. 105 (1983), pp. 153–158, DOI:10.1115/1.326425710.1115/1.3264257Search in Google Scholar
19 Livermore Software Technology, LS-Dyna R12 FEM-Software, 2011-2020Search in Google Scholar
20 Fraunhofer SCAI, „MpCCI Mapper,“ Fraunhofer SCAI: https://www.mpcci.de/en/mpcci-software/mapper.html 09. 02. 2022, onlineSearch in Google Scholar
© 2022 Walter de Gruyter GmbH, Berlin/Boston, Germany
