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Investigation of heat transfer in the press hardening process
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
2009 (English)In: Hot sheet metal forming of high-performance steel, CHS2: 2nd international conference, June 15-17 2009, Luleå, Sweden. Proceedings / [ed] Mats Oldenburg; Kurt Steinhoff; Braham Parkash, Auerbach: Verlag Wissenschaftliche Scripten , 2009, 239-246 p.Conference paper (Refereed)
Abstract [en]

The use of thin ultra high strength steel automotive passive safety components manufactured with the press hardening process has increased drastically the last two decades. The application and complexity in design has increased and thermo mechanical forming simulation is an important tool to optimize the final component properties early in the product development process. The transfer of heat is a key process that affects formability and the evolution of the mechanical properties in the product. Therefore it is essential that the thermal contact conditions between the blank and tool are properly described in the forming simulation code. In this study, an experimental setup and inverse simulation approach is used to predict the interfacial heat transfer coefficient (IHTC) in the press hardening process. Different process conditions such as contact pressure, air gaps in the contact and blank material (22MnB5 and Usibor 1500P) are investigated. In the inverse simulation approach, the improved-advance-retreat and golden section method is used to solve the ill-posed inverse heat conduction problem (IHCP). In the finite element analysis, a thermo-mechanical coupled simulation model is used including effects from changes in the microstructure during quenching. The results from simulations give the variations of the heat transfer coefficient in time for best match to experimental results. It is found that the heat transfer coefficient is dependent of the contact pressure and air gap and varies in time. The variation in time is assumed to be the temperature dependence. When heat transfer is under mechanical contact, the variation of the heat transfer coefficient is higher for higher contact pressures compared to lower. If there is heat transfer over a thin gap of air, the heat transfer coefficient also varies but tend to be close to constant for bigger air gaps. The present work will be used as a base in a future model of the heat transfer coefficient influence at different contact conditions in press hardening process.

Place, publisher, year, edition, pages
Auerbach: Verlag Wissenschaftliche Scripten , 2009. 239-246 p.
Research subject
Solid Mechanics
URN: urn:nbn:se:ltu:diva-34827Local ID: 922537a0-5f18-11de-9f57-000ea68e967bISBN: 978-3-937524-84-9OAI: diva2:1008078
International Conference on Hot Sheet Metal Forming of High-Performance Steel : 15/06/2009 - 17/06/2009
Godkänd; 2009; 20090622 (ysko)Available from: 2016-09-30 Created: 2016-09-30Bibliographically approved

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