Evaluation of friction conditions in powder compaction for admired and diewall lubrication

For the purpose of modelling powder compaction, a quantitative evaluation o f the friction conditions at the die wall interface is required. Using an i nstrumented compaction die, the friction at the interface between powder co mpact and die wall was evaluated through an empirical parameter called the slide coefficient, obtained from the applied pressure/transmitted pressure ratio. For powder compaction modelling, knowledge of the friction coefficie nt at the interface, however, is much more useful but its measurement is di fficult in real experimental conditions. A procedure based on the evaluatio n of the radial stress/axial stress ratio leads to the quantitative determi nation of the friction coefficient in admired zinc stearate added to iron p owder with and without die wall lubrication The resulting decreasing fricti on coefficient at the end of compaction gives a more uniform density charac terised by low loss of pressure through the compact and lower ejection ener gy per unit volume of the compact.