Generally modelling of material behavior and surface modifications for FEM analysis of die forging of carbon steels

对于热机械模拟，主要的焦点应该是真实的氧化物结垢动力学，因为这对成型区的过程有影响。在第一个资助期内，在没有损害标准的情况下对成型过程中的氧化皮进行了模拟。然而，在实际成形过程中，临界应力会导致鳞片层出现裂纹或滑动。为了更详细地描述对成形过程有重要影响的局部材料温度和摩擦条件，必须在数值模拟中考虑成形过程中氧化膜的损伤行为。为了获得工艺链的全面视图，加热单元中氧化物的形成必须已经被数值考虑，并作为后续热成形模拟的输入数据。母材材料性能的变化以及氧化层的变化必须在商业有限元程序Simuface.Form中实现，使用Fortran子程序形成。因此，可以实现热锻耦合过程链模拟的输入，考虑了氧化膜的形成以及作为相关参数和合金化元素的函数的氧化物损伤行为、组织演变和摩擦学系统。

For the thermomechanical simulation, the main focus should be on the real oxide scale kinetic, because this has an influence on the processes in the forming zone. During the first funding period, the modelling of the oxide scale layer during forming was carried out without a damage criterion. However, in real forming processes critical stresses cause cracks or sliding in the scale layer. For a detailed representation of the local material temperature and friction conditions, which significantly influence the forming process, the damage behaviour of the oxide scale during forming must be considered in the numerical simulation. To achieve a comprehensive view of the process chain, the formation of oxide in the heating unit must already be considered numerically and as input data for the following hot forming simulation. The changes of the material properties of the base material as well as the oxide scale layer have to be implemented into the commercial FE-program Simufact.Forming by using Fortran-subroutines. Therefore, an input for the coupled process chain simulation in hot forging can be realised, taking into account the oxide scale formation as well as the oxide damage behaviour, the microstructure evolution and the tribological system as a function of the relevant parameters and alloying elements.