Improved FE simulation of the shear cutting process using a temperature and strain rate-dependent extension of the MMC model

• Applicant: Professor Dr.-Ing. Bernd-Arno Behrens
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2011 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 199808648

In the initial phase of this project, the aim was to show that the damage modeling in general and in particular the damage modeling at high temperatures and strain rates as well as the modeling of flow behavior at strain rates of up to 750 s-1 and temperatures up to 519 ° C is a significant factor for the numerical determination of force-displacement curves as well as a realistic representation of the numerical process. During the course of the first phase of this project, temperature dependence of the strain hardening behavior up to a temperature of 400 °C and strain rate dependence up to 80 s-1 were experimentally determined. However, dependence of failure on the strain rate and temperature were not considered. A scaling of strain rate dependence for flow curves can be made on basis of numeric identification using the experimentally determined force displacement curves, yet a basic physical representation of the vital factors influencing strain hardening behavior i.e. temperature and strain rate is not possible. These aspects are to be addressed in the continuation phase of the project where the flow and damage behavior will be determined for higher temperatures and strain rates as well. Furthermore, five different tests for different stress triaxiality ranges will be carried out for the parameterization of the damage models. The accuracy of the determined damage curves depends on the variation of stress triaxiality during the experiment. A failure parameterization at nearly constant stress triaxiality can be achieved using special test procedures and specimen geometry. In this regard, a new test method to characterize the failure behavior of high-strength steel sheet metals at nearly constant stress triaxiality was recently developed at the IFUM. This method will help to attain improved failure characterization during the second phase of this project. Furthermore, using the said experimental method, it is possible to extend the negative stress triaxiality range as well as the bases of failure characterization to the important stress triaxiality ranges related to shear cutting. Moreover, during the continuation phase, the shear cutting model will be constructed in three dimensional spaces. Besides, for the damage modeling, Mohr Coulomb failure model (MMC failure model) will be implemented and used in a strain rate and temperature dependent form. The MMC failure model describes the stress state by considering the lode angle along with the stress triaxiality.Thus, it is expected that the simulation quality of the shear cutting process, in particular the representation of the resulting cutting edge geometry can be further improved and help in a better understanding of the physical processes during the shear cutting process.

• DFG Programme: Research Grants