Lubricant-free Forming by Affecting Thermoelectric Currents

目前，大多数成形工艺只能通过使用润滑剂来实现。特别是在成型过程中，如压花或冲裁，在不使用润滑剂的情况下，可以在很短的时间内观察到磨损机制粘附。除温度外，热电现象对粘着磨损的发展也有重要影响。由于大部分成形功的耗散导致成形区温度升高，因此每个工具都会产生热电。热电和磨损之间的基本关系已经在这个项目中得到了发展。基于热电效应，建立了一个分析模型，为磨损最小化提供了具体的策略。当该项目完成时，所获得的结果能够预测发生的温度和热电性，从而可以选择基于工艺参数的磨损减少策略。该资助期的目的是证明该模型对任何成形工艺的普遍适用性，并将其扩展到任何工具-工件-材料组合，而无需通过实验确定塞贝克系数。在拟议的资助期内，将追求三个部分目标，以实现总体目标。首先，开发了一种用于材料特定的热电性能的一般估计的方法。为此，可根据化学成分对各种材料以及纯合金元素进行热电特性分析和比较。第二个分目标是，考虑到热电和温度的比例，提高对粘附力形成过程的认识。这是基于一个面向实践的模型实验的压花过程中，温度，电流强度和方向可以相互独立地变化。实验深冲试验最终验证了分析模型的可移植性方面所获得的结果，以其他成形工艺。

Currently, the majority of forming processes are only possible by the use of lubricants. Especially during forming processes, such as embossing or blanking, the wear mechanism adhesion can be observed after a very short time when no lubricants are applied. In addition to temperature, thermoelectric phenomena have a significant influence on the development of adhesive wear. Thermoelectricity is generated in every tool due to the temperature increase in the forming zone that is caused by the dissipation of a large proportion of forming work. Fundamental relationships between thermoelectricity and wear have already been developed within this project. On the basis of thermoelectricity, an analytical model providing specific strategies for wear minimization was developed. When this project is finished, the gained results enable both a prediction of the occurring temperature and thermoelectricity, whereby a strategy for wear reduction on the basis of process parameters can be chosen. The aim of this funding period is to proof the general applicability of the model to any forming process and its extension to any tool-workpiece-material combinations without an experimental determination of the Seebeck coefficient.Three partial targets are pursued in the proposed funding period to achieve the overall target. First of all, a method for the general estimation of material-specific thermoelectrical properties is developed. For this purpose, a broad spectrum of materials as well as pure alloy elements is thermoelectrically characterized and compared on the basis of the chemical composition. The second sub-goal is to improve the understanding of the adhesion development process, taking into account the proportions of thermoelectricity and temperature. This is based on a practice-oriented model experiment of an embossing process in which temperature, current strength and direction can be varied independently of each other. Experimental deep drawing tests finally verify the analytical model with regard to the transferability of the results obtained to other forming processes.