EXPERIMENTAL INVESTIGATION ON STRESS AND DIE-WALL FRICTIONAL CHARACTERISTICS OF METAL POWDER DURING HIGH-VELOCITY COMPACTION

In this study, to evaluate the change in the stress and die-wall frictional characteristics during high-velocity compaction (HVC), a metal powder was subjected to HVC with a heavy hammer based on the stress-testing technology and Janssen-Walker model. The changes in the green density, stress characteristics and coefficients of friction at different impact heights were investigated. The density of green compacts increased with the increase in the impact height. The stress in the upper and lower punches and the die wall showed repeated loading and unloading. The coefficient of friction of the die wall underwent three stages and was related to powder densification. As the height position along the side wall was increased, the coefficient of friction increased gradually. With an increased impact height, the coefficient of friction increased significantly in the incomplete-molding stage but remained constant in the complete-molding stage. This work expands the theoretical basis of densification processing of a metal powder during HVC.