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The spring-back tendency of HSS and UHSS represents one of the most relevant bottlenecks to enlarge the use of these new generations of steel in BIW. The focus of the research project was to increase the knowledge about SPBK behaviour of UHSS and to develop reliable numerical and experimental tools useful for spring-back prediction and characterisation in the early tool and process design stages. The main subjects and results of the research project were as follows. 1. In deep spring-back characterisation of representative HSS, UHSS and stainless steels using specifically developed tests: the drawn cup ring test and the strip tensile test with deflection. They were able to quantitatively distinguish the specific SPBK tendency of materials and allowed a ranking of them. Large amounts of data were extracted contributing to increasing knowledge about steels. 2. A wide analysis of the numerical tools and their application to simple and complex shapes allowed the identification of the major limitations in SPBK prediction, the definition of rules for the correct use and of ways to improve them, including from the material model point of view. 3. Specific knowledge has been created about the nonlinear behaviour of the steel grades. 4. Reliable constitutive models were developed, implemented and validated on the basis of laboratory tests. 5. Data obtained from (3) were utilised to identify material parameters for (4). 6. The improved accuracy of the software has been demonstrated using also a semi-industrial case. 7. Three different spring-back quality functions were identified, implemented and validated. They will allow for estimating qualitatively the spring-back tendency at the end of the forming phase, using stress-strain field. One of them, MQF, was able also to give a qualitative estimation of the SPBK without explicit calculation. 8. Guidelines related to numerical aspects, materials, tests and use of new steel grades were also an output of the project.

Additional information

Authors: PLACIDI F, Centro Sviluppo Materiali (CSM), Roma (IT);LEMOINE X, Arcelor Research (IRSID), Maizières-lès-Metz (FR);TILL E, Voest-Alpine Stahl GmbH, Linz (AT);GEORGI H, FQZ Oderbrücke, Eisenhüttenstadt (DE)
Bibliographic Reference: EUR 22835 EN (2007), 363 pp. Euro: 45
Availability: Katalogue Number: KI-NA-22835-EN-S The paper version can be ordered online and the PDF version downloaded at:
ISBN: ISBN: 978-92-79-05513-3
Record Number: 200819636 / Last updated on: 2008-01-21
Original language: en
Available languages: en
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