Fundamentals of material-specific process damping on rounded and worn cutting edges

自激振动，即所谓的颤振振动，在提高加工生产率时往往是一个限制因素。然而，颤振振动可以通过增加侧面与材料的接触来抑制，因为进入材料的振荡运动被材料的回弹所抑制。这种效应被称为过程阻尼。避免颤振的另一种方法是模拟预测合适的工艺参数，从而避免颤振。然而，在模拟模型中考虑过程阻尼效应会带来很高的不准确性。这是由于现有的工艺阻尼模型不能充分反映翼面以下高度复杂的弹塑性变形过程。作用在侧面的阻尼力通常被建模为一个恒定的过程阻尼系数和侧面下方缩进的体积的乘积。一些初步的工作表明，过程阻尼系数取决于切削刃的圆角和间隙角。这可以归因于热效应和模型内塑性变形的忽视。然而，刀具几何形状、间隙以下的弹塑性材料性能和工艺阻尼力之间的确切关系尚不清楚。因此，该项目的目的是在侧面接触过程中，基于弹塑性材料的行为，获得对材料和几何相关过程阻尼的基本理解。为了实现这一目标，通过高速图像和力测量，分析了正交切削试验中不同切削刃磨圆和磨损条件下的切削刃接触情况。在实验结果的基础上，建立了一个新的过程阻尼模型，该模型将用于铣削过程的材料去除模拟，以预测刀具的动态行为。

Self-excited vibrations, so-called chatter vibrations, are often a limiting factor when the productivity of machining processes is increased. However, chatter vibrations can be suppressed by increasing the contact of the flank face with the material, since oscillation movements into the material are damped by the springback of the material. This effect is called process damping. A further method of avoiding chatter vibrations is the simulative prediction of suitable process parameters, in which chatter vibrations are avoided. However, taking the process damping effect into account within simulative models is associated with high inaccuracies. This is due to the fact that the existing process damping models do not adequately reflect the highly complex elastic-plastic deformation processes below the flank face. The damping force acting on the flank face is often modelled as the product of a constant process damping coefficient and the volume indented under the flank face. Some preliminary work shows that the process damping coefficient depends on the rounding of the cutting edge and the clearance angle. This can be attributed to thermal effects and the neglect of plastic deformations within the model. However, the exact relationship between tool geometry, the elastic-plastic material behaviour below the clearance and the process damping force is unknown. Therefore, the aim of the project is to obtain a fundamental understanding of the material- and geometry-dependent process damping on the basis of the elastic-plastic material behaviour during the flank-face contact. In order to achieve this goal, the contact conditions at the cutting edge for different cutting edge rounding and wear conditions are analysed in orthogonal cutting test by high-speed images and force measurements. Based on the experimental results a new process damping model will be developed, which will be implemented in a material removal simulation of the milling process to predict the dynamic tool behaviour.