Fundamental Investigations on the frictional contact in the working zone in machining processes

加工过程主要受刀具与工件接触区摩擦事件的影响。工作区具有高变形速率、高接触压力和高温度的特点。因此，切屑形成过程的摩擦条件与既定的摩擦测试有很大的不同。在这个项目中，摩擦分析应该是在机械加工条件下进行的，涉及机构及其相互作用，以及工艺参数的影响。调查中使用了一种特殊的测试装置，使测试条件与加工条件相似。在该试验中，工件相对于刀具移动，从而使工件发生塑性变形。这两个物体都是由机械加工过程中常用的材料制成的。滑动速度、表面拓扑和温度决定了摩擦接触，并在本项目中进行了研究。测试装置提供了以相同的滑动速度达到不同温度的能力。因此，这种方法优于销盘测试等方法。本项目的另一个目标是实现一个改进的、真实的摩擦模型来模拟切屑形成。在过去的十年里，切屑形成的有限元模拟取得了很大的进展。为了获得逼真的模拟结果，需要为材料和摩擦行为输入适当的数据。尤其是切削法向力取决于切屑与前刀面之间的摩擦力，在有限元模拟中经常会出现误算。因此，本项目应提供合适的摩擦模型，以完善过程力的模拟。

Machining processes are majorly influenced by frictional events in the contact area of the tool and the workpiece. The working zone is characterized by high deformation rates, contact pressures and temperatures. Therefore, the friction conditions of the chip formation process distinguish significantly from established friction tests. In this project the analysis of friction is supposed to be carried out under the terms of machining conditions with respect to mechanisms and their interactions as well as influences by process parameters. A special test setup that enables testing conditions similar to machining conditions is used for the investigation. In this test the workpiece is moved relatively to the tool so that the workpiece is plastically deformed. Both objects are made of materials commonly used for machining processes. The sliding velocity, the surface topology and the temperature determine the frictional contact and are investigated in this project. The test setup provides the ability to reach different temperatures at the same sliding velocity. Therefore, this setup superior to methods like the pin-on-disc-test.Another goal of this project is to achieve an improved and realistic friction model for the simulation of chip formation. Finite-Element-simulations of the chip formation made great progress over the last decade. In order to obtain realistic simulation results proper input data for the material and frictional behavior is needed. Especially the cutting normal force depends on the friction between the chip and the rake face and is often miscalculated in FE-simulations. Therefore, this project should provide a proper friction model to improve the simulation of process forces.