Lubricant-free Forming by Affecting Thermoelectric Currents

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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.