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

自激振动，即所谓的颤振，在提高加工过程的生产率时通常是一个限制因素。然而，通过增加后刀面与材料的接触可以抑制颤振，因为进入材料的振荡运动通过材料的回弹而被阻尼。这种效应称为过程阻尼。避免颤振的另一种方法是模拟预测合适的过程参数，其中避免颤振。然而，在模拟模型中考虑过程阻尼效应与高不准确性相关联。这是由于现有的过程阻尼模型不能充分反映后刀面以下高度复杂的弹塑性变形过程。作用在后刀面上的阻尼力通常被建模为恒定的过程阻尼系数和后刀面下压入的体积的乘积。一些初步的工作表明，过程阻尼系数取决于倒圆的切削刃和后角。这可以归因于热效应和忽略模型内的塑性变形。然而，刀具几何形状、间隙下方的弹塑性材料行为和过程阻尼力之间的确切关系是未知的。因此，该项目的目的是获得材料和几何形状依赖的过程阻尼的基础上的弹塑性材料行为在侧面接触的基本理解。为了实现这一目标，在正交切削试验中，通过高速图像和力测量，分析了不同的切削刃倒圆和磨损条件下的切削刃接触状况。基于实验结果，将开发一种新的过程阻尼模型，该模型将在铣削过程的材料去除模拟中实施，以预测动态刀具行为。

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.