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Keywords: plasticity, TRIP, parameter identification, homogenization.

Summary

In order to augment the functionality and the lifetime of engineering structures a new hybrid transforming process is described in [1]. During the combination of mechanical shaping and heat treatment the material experiences phase changes of a different kind. In our work we concentrate on the austenite to martensite phase change.

To calibrate a set of macroscopic constitutive equations the experimental database [2] is used, thus taking into account the effects of uniaxial stress on the kinetics of phase transformation at different temperatures. However, for the case of temperatures below the martensite start temperature with simultaneous stresses above the yield limit, it is difficult to obtain experimental data. Therefore, as a remedy we employ a homogenization technique by using a representative volume element. In this way the flow behavior of the macroscopic mixed material is characterized by use of a cubic finite-element-model. Here the macroscopic material within each element represents one grain which is able to change its material properties from austenite to martensite and vice versa. The resulting data basis - for stresses above and below the yield stress, above and below the martensitic start temperature - is used for parameter identification of a macroscopic constitutive model by least squares minimization.

References

1: Steinhoff K., Weidig U., Scholtes B., Zinn W., "Innovative Flexible Metal Forming Processes based on Hybrid Thermo-Mechanical Interaction", Steel Research Int., 76, 154-159, 2005.
2: Ahrens U., "Beanspruchungsabhängiges Umwandlungsverhalten und Umwandlungsplastizität niedrig legierter Stähle mit unterschiedlich hohen Kohlenstoffgehalten", Dissertation, University of Paderborn, 2003.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 88 PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping and M. Papadrakakis Paper 257 Macro Modeling and Homogenization for Identification of Material Parameters to Simulate Phase Transformations R. Mahnken¹, A. Schneidt¹ and T. Andretter² ¹Chair of Engineering Mechanics, University of Paderborn, Germany ²Institute of Mechanics, Montanuniversität Leoben, Austria doi:10.4203/ccp.88.257 purchase the full-text of this paper Full Bibliographic Reference for this paper R. Mahnken, A. Schneidt, T. Andretter, "Macro Modeling and Homogenization for Identification of Material Parameters to Simulate Phase Transformations", in B.H.V. Topping, M. Papadrakakis, (Editors), "Proceedings of the Ninth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 257, 2008. doi:10.4203/ccp.88.257 Keywords: plasticity, TRIP, parameter identification, homogenization. Summary In order to augment the functionality and the lifetime of engineering structures a new hybrid transforming process is described in [1]. During the combination of mechanical shaping and heat treatment the material experiences phase changes of a different kind. In our work we concentrate on the austenite to martensite phase change. To calibrate a set of macroscopic constitutive equations the experimental database [2] is used, thus taking into account the effects of uniaxial stress on the kinetics of phase transformation at different temperatures. However, for the case of temperatures below the martensite start temperature with simultaneous stresses above the yield limit, it is difficult to obtain experimental data. Therefore, as a remedy we employ a homogenization technique by using a representative volume element. In this way the flow behavior of the macroscopic mixed material is characterized by use of a cubic finite-element-model. Here the macroscopic material within each element represents one grain which is able to change its material properties from austenite to martensite and vice versa. The resulting data basis - for stresses above and below the yield stress, above and below the martensitic start temperature - is used for parameter identification of a macroscopic constitutive model by least squares minimization. References 1 Steinhoff K., Weidig U., Scholtes B., Zinn W., "Innovative Flexible Metal Forming Processes based on Hybrid Thermo-Mechanical Interaction", Steel Research Int., 76, 154-159, 2005. 2 Ahrens U., "Beanspruchungsabhängiges Umwandlungsverhalten und Umwandlungsplastizität niedrig legierter Stähle mit unterschiedlich hohen Kohlenstoffgehalten", Dissertation, University of Paderborn, 2003. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £145 +P&P)
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