| Summary: | In this thesis, experimental investigations into powder-die friction and powder yielding measurement techniques, and numerical modelling work on powder-die friction mechanisms are presented. The experimental friction work explores the use of a shear-plate technique to measure the frictional characteristics between a compacted powder and a target surface. The study confirms that the shear-plate technique is valid to measure these frictional characteristics. Surface roughness and hardness was explored fully for both Iron and an Alumina power. This confirmed the major impacts of surface hardness, roughness and roughness orientation on the friction coefficient. With regard to static friction, benefit may be obtained by using a very smooth surface finish, however, the minimum level of dynamic friction coefficient is not always associated with the smoothest surface. Comparisons between different experimental techniques for characterising the yielding of powders are presented. Three techniques were compared using an iron powder: triaxial testing, instrumented die testing and shear-box testing. The techniques were compared with a particular view to measuring the applicability of the less well recognised experiments with the more established triaxial experiment. Predicted yield surfaces from a single instrument die test compared very well with the yield surfaces obtained triaxial tests. Results from shear-box experiments show that it defines the region in which it is appropriate to use the yield surfaces obtained from the instrumented die, for modelling purposes. Beyond this limit yielding of the powder is achieved by a shearing mechanism.
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