Influence of gliding speed and contact pressure on the wear of forming tools

Abstract

The usage of high-strength instead of mild sheet metals leads to increased wear of forming tools. Especially deep-drawing tools are of high economic relevance. Due to their good corrosion resistance zinc-coated sheet metals are often used in deep drawing operations. In order to enable the design of a sufficiently wear resistant tool which is not unnecessarily overdesigned a prediction of tool wear is desirable. So far, the usage of Archard's law is state of the art. This law does not imply any influence of the contact pressure or the gliding speed on the wear coefficient. The subject of this paper is the influence of different process parameters on the wear of forming tools when zinc-coated sheet metals are processed. Strip drawing tests are used for experimental investigations. In the strip drawing test, the practical conditions of the deep-drawing process can be reproduced while process parameters such as gliding speed, surface pressure and load history can be varied individually. A gray cast iron tool, which is prevalent in automotive industries for forming processes, is used in the tests. For the ascertainment of the impact of the parameter variations on the amount of wear, single parameters are altered under the condition that the cumulative work of friction is kept constant for all tests. The worn surfaces of the tools are analyzed by a confocal white light microscope in order to quantify the wear progress at fixed intervals during the tests. Additionally, EDX-analyses showed the chemical composition of the surface layers. The derived experimental data are used to proof and improve Archard's law. This paper focuses on the influence of gliding speed and contact pressure on the abrasive and adhesive wear of forming tools. It will be shown that the prediction of tool wear under different geometrical and process conditions is possible when finite element simulations and a modified Archard's law are combined.