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

在该项目的初始阶段，目的是说明一般的损伤建模，特别是高温和应变率下的损伤建模，以及在应变速率高达750 S-1和温度高达519°C时的流动行为的建模，对于力-位移曲线的数值确定以及数值过程的真实呈现是一个重要因素。在本项目第一阶段的过程中，实验测定了高达400℃的应变硬化行为的温度依赖性和高达80 S-1的应变速率依赖性。然而，失效与应变率和温度的相关性没有被考虑。利用实验测得的力位移曲线可以在数值识别的基础上对流动曲线的应变率依赖关系进行定标，但不可能对影响应变硬化行为的关键因素即温度和应变率进行基本的物理表示。这些方面将在项目的继续阶段解决，在该阶段将确定更高的温度和应变率下的流动和破坏行为。此外，还将针对不同的应力三轴度范围进行五种不同的试验，以实现损伤模型的参数化。所测损伤曲线的准确性取决于试验过程中应力三轴度的变化。使用特殊的试验程序和试件几何形状，可以实现几乎恒定应力三轴的破坏参数。在这方面，IFUM最近开发了一种新的试验方法来表征高强度钢板在几乎恒定应力三轴下的破坏行为。这种方法将有助于在该项目的第二阶段实现更好的故障表征。此外，利用该实验方法，有可能将负应力三轴性范围和破坏表征的基础扩展到与剪切有关的重要应力三轴性范围。此外，在延续阶段，将在三维空间中构建剪切剪切模型。此外，对于损伤建模，将实现Mohr Coulomb失效模型(MMC失效模型)，并以应变率和温度相关的形式使用该模型。MMC失效模型通过考虑切削角和应力三轴来描述剪切过程中的应力状态，从而可以进一步提高剪切切割过程的模拟质量，特别是对所产生的刃口几何形状的表示，并有助于更好地理解剪切切割过程中的物理过程。

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.