Transfer of a friction model for cold bulk metal forming in industrial practice

在先前的DFG项目中，开发了具有确定性结构工件表面的冷挤压摩擦模型。通过压缩滑动试验（CST），确定了摩擦模型的参数。利用这些参数可以很好地描述正挤压过程中的摩擦行为，并具有精确的质量。除了优化摩擦公式外，新的摩擦模型还具有在有限元模拟中将表面参数作为场变量的优点。在上一个项目中，选择表面值Sq对模型进行验证和确认，上一个项目的结果似乎满足工业实践中传递的要求。因此，本项目的目的是将摩擦模型转移到工业实践中使用的工件表面。除了在有限元模拟中使用表面参数作为场变量外，通过划分过程中不同的接触条件来扩展摩擦模型也是该项目的重点，该项目的方法是确定选定的块体金属成形过程中的应力和应变，然后评估不同的摩擦模型参数。为了评估表面平整度和粗糙度，必须在每个成型步骤之后和之前测量形貌。在进一步的工作包中，摩擦模型将扩展到工件和刀具之间的不同接触条件。这种扩展是必要的，以获得一个普遍有效的块体金属成形过程中的摩擦公式。在项目结果的基础上，可以提高有限元模拟的模拟质量。

In the preceding DFG project, a friction model for cold extrusion with deterministic structured workpiece surfaces was developed. With the compression sliding test (CST), a model test for bulk metal forming, the parameters for the friction model were developed. With these parameters the friction behavior in a forward extrusion process can be represented very well and with accurate quality.Besides optimized friction formulation the new friction model has the advantage to consider surface parameters as field variable in finite-element-simulations. In the previous project the surface value Sq was chosen for validation and verification of the model.The results of the previous project seem to fulfill the requirement for the transfer in industrial practice. Therefore, the aims of this project are the transfer of the friction model to workpiece surfaces used in industrial practice. As well as the usage of surface parameters as field variable in finite-element-simulation the expansion of the friction model by dividing different contact conditions during the process are in focus of the project.The approach of the project is to determine the stresses and strains in chosen bulk metal forming processes followed by the evaluation of the varied friction model parameters. To evaluate the surface flattening and roughening, the topographies must be measured after and before each forming step. In a further work package the friction model will be expanded to different contact conditions between workpiece and tool. This expansion is necessary to obtain an universally valid friction formulation for bulk metal forming processes. On the basis of the project results the simulation quality of finite-element-simulations can be enhanced.