Tribological impact of the finishing technology onto meso- and microforming processes

Abstract

Abstract. Tribological conditions between workpiece and tool have a major impact onto forming processes. Besides lubrication, temperature, and material, they are mainly influenced by the tool surface characteristics, especially by its topography, which is a result of finishing technology. Thereby formed lubricant pockets are of prime importance for the tribosystem due to its ability to separate the tribopartners by storing lubricant. The influence of four different tool finishing processes and their according surface topographies onto frictional behaviour have been investigated and quantified by the barrel compression test, in dry and lubricated tribosystems. The tool steel surfaces were stochastically microstructured by grinding and spark erosion as well as deterministic structured with micro calottes, applied by jet electrochemical machining and compared to a polished reference tool. The allocation of open and closed lubricant pockets over tool surfaces before and after the forming process was analysed by a self-made MATLAB tool.

Effects of nano-particle lubrication on micro deep drawing of Mg-Li alloy

“…Thus, surface roughness in microforming is a part of sample geometry while in macroscale merely it is surface characteristic [8]. In addition to the conventional models, including Hall-Petch model, inclusive models such as the modified surface layer and open and close lubricant pockets models have been proposed to explain flow stress reduction and surface characteristics in microscale [9][10][11]. Yet, the mentioned and modified models are not capable of clarifying size effects expansively.…”