On friction in metal power compaction process
Abstract: The present work describes different ways of measuring and studying friction in a metal powder compaction process. Reducing friction during this process will allow an increase in the density of powder components and reduce variation in the density, which is a common problem in this process. This work contain three papers. In paper A two different techniques were used to evaluate their applicability for measuring friction between powder particles and die wall during compaction and ejection of metal powder. A comparison between the methods, a "High-pressure apparatus" and a "Jumping ball apparatus", showed that the results from both correlate well. In order to identify the wall friction coefficient an analytical approach and an optimisation approach using finite element method were used in paper B. Estimation of the wall friction coefficient from a pressing experiment is a problem of measuring local contact stress. In paper B an estimation of the die wall friction coefficient has been made with both constant k value, and also with variable k based on experimental results. The influence of different parameters on frictional behaviour during compaction and ejection were investigated in paper C. The results obtained offer a better understanding of friction behaviour during pressing and ejection of metal powder components and can also be used as input data for computer simulations of the compacting process.
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