Development of a model to predict the machining forces in the rolling process of powder metallurgical parts using the example of gears

粉末冶金齿轮是多孔的，因此，实现较低的承载能力比全密度，锻造钢齿轮。外横轧增加了齿侧和齿根的密度，从而提高了它们的强度。本课题的目标是建立一个预测轧制过程中加工力的模型。由于齿轮轧制过程的高度复杂性，现有的模型，如薄板轧制，无法计算轧制力。这种复杂性源于两侧牙齿的接触、接触比和不断变化的接触几何形状。此外，由于致密化和加工硬化，材料性能不断变化。在机床发展的早期阶段，了解加工力对机床的尺寸确定和工艺设计至关重要。已知的加工力可以缩短加工过程和机床本身的开发时间。这是至关重要的，因为工艺链压制-烧结-轧制明显短于传统的齿轮切削工艺链。因此，机械加工力的预测模型的基本发展是必要的，以促进这一过程链为行业的长期发展。为了开发pm -零件轧制过程中加工力预测模型，需要实现以下子目标：1。建立了考虑轧制过程中密度变化的本构材料模型。2. 根据刀具和工件的几何形状以及工艺运动学对刀具-工件的穿透进行的数学描述。3. 模拟试验的概念和执行，以产生考虑不同接触条件和记录发生力的数据库。基于模拟试验数据库的轧制力模型的建立。5. 将齿轮轧制的接触条件转化为轧制力模型，并对结果进行验证。轧制力模型的发展使人们对齿轮的轧制过程有了更好的理解，并使工艺设计符合机器、工艺和工具的要求。

Powder metallurgical gears are porous and, therefore, achieve lower load-carrying capacities than full-dense, wrought steel gears. External transverse rolling increases the density of both the flank and the tooth root to increase their strength. The goal of this project is the development of a model which predicts the machining forces in the rolling process. Existing model, e.g. for sheet rolling, can not calculate the rolling forces due to the high complexity of the gear rolling process. This complexity originates out of the two-flanked tooth contact, the contact ratio and the continuously changing contact geometries. Additionally, the material properties are continuously changing because of the densification and work hardening. The knowing of the machining forces is crucial for the dimensioning of the tool machines and the process design in a very early state of the development. Known machining forces lead to shortened development time for both process and the tool machine itself. This is crucial since the process chain pressing - sintering - rolling is significantly shorter than the convectional, gear cutting process chain. Therefore, a fundamental development of a prediction model of the machining forces is necessary to facilitate this process chain for the industry on the long term. For the development of the model for the prediction of the machining forces in the rolling process of PM-parts the following sub goals need to be achieved: 1. Development of a constitutive material model which considers the changes in density in the rolling process. 2. A mathematical description of the penetration of tool-workpiece depending on the tool- and workpiece geometry and the process kinematics. 3. Conception and execution of analogy-tests to generate a database considering different contact conditions and recording the occurring forces 4. Development of a rolling force model bases upon the database of the analogy-tests. 5. Transferring the contact conditions of gear rolling onto the rolling force model and verification of the results. The development of a rolling force model leads to an improved understanding of the rolling process of gears and enables for a process design which meets the requirements of the machine, the process and the tools.