Model-based identification of surface properties during the milling process of Ti-6Al-4V

该研究项目的主要目标是使用基于模型的方法控制铣削过程，以便同时在钛组件(Ti-6Al-4V)中产生定义的几何形状和残余应力。在项目的第一阶段，开发了一个实时的分析模型，描述了工艺参数和残余应力之间的关系。将未加工零件的刀具磨损和散布材料特性分别视为可观测扰动变量和隐藏扰动变量。控制策略依赖于对温度和切削力的过程测量，其中使用了典型的感官刀柄。为了解析地描述工艺参数和表层状态之间的复杂关系，选择了两步法。第一步是模拟加工区内的热输入和切削力。在第二步中，对加工零件内产生的残余应力和硬度分布进行建模。第一个项目阶段的工作提供了实时模型，可用于确定Ti-6Al-4V球磨过程中的热机械部件载荷。这为建立加工后零件边缘层的残余应力状态和硬度分布模型奠定了基础。在二期工程中，该模型用于残余应力状态的动态过程控制。这包括制定和实施适当的控制概念，并验证其对干扰的稳健性。此外，模型和控制系统可以通过附加的控制变量进行扩展。除了已经考虑的常规工艺参数之外，这还包括例如工具攻角的影响。

The primary objective of the research project is to control the milling process using a model-based approach in order to generate defined geometries and residual stresses in titanium components (Ti-6Al-4V) simultaneously. In the first phase of the project a real-time, analytical model, which describes the relationship between the process parameters and the residual stresses, is developed. The tool wear as well as scattering material properties of the unmachined parts are also considered as an observable disturbance variable and as a hidden disturbance variable, respectively. The control strategy relies on in-process measurements of temperatures and cutting forces for which a prototypical sensory toolholder is used. To analytically describe the complex relationship between the process parameters and the surface layer state, a two-step approach is selected. The first step is to model the heat input and cutting forces within the process zone. In a second step, the resulting residual stresses and the hardness profile within the machined part are modeled. The resulting sub models are then put together in an overall model.The work of the first project phase provides real-time models that can be used to determine the thermomechanical component loads during the milling process of Ti-6Al-4V. These form the basis for the modeling of the residual stress state and of the hardness profile of the component edge layer after machining. In the second phase of the project, the models are used for the dynamic process control of the residual stress state. This includes the development and implementation of a suitable control concept and the verification of its robustness against interferences. Furthermore, the models and the control system can be extended by additional control variables. In addition to the conventional process parameters already taken into account, this includes, for example, the influence of the tool angle of attack.