to determine the density and the strain components. The sample diameter can be obtained incrementally by removing An instrumented die has been developed to measure the compact from the equipment to measure its dimensions, friction and constitutive data on powders during combut preferably, a diameter gauge can be used to measure paction. Such data is useful for quality assurance and the diameter continuously.5 as input data for computer models of die compaction.Simple compaction in a circular die is a specific case in The measurement system consists of a die with radial which radial strain is constrained to be zero. Stress stress sensors, punch force measurement, and a measurements can be made accurately and the strain displacement transducer to measure punch disconditions are very well defined. Yield surfaces can be placement. The outputs of these sensors enable simuldeduced from such data provided that certain assumptions taneous measurement of density, die wall friction are made concerning their shape. In this paper the yield coefficient, and the triaxial stresses acting on the surfaces in deviatoric hydrostatic stress space are assumed powder during the course of compaction.to be elliptical, as in the cam-clay model. The die system has been tested at three industrial Die wall friction coefficients can be determined by sites on automated and manual presses measuring measurement of loads on top and bottom punches during ferrous, ceramic, and tungsten carbide powders at compaction.6-9 The difference between these loads is the applied stresses of up to 650 MPa and speeds of up to friction force on the die wall. This enables a friction 26 mm s−1. Sensor outputs were sufficiently noise free coefficient to be determined at each stage of compaction, to permit the recording of useful data down to stresses as a function of density. less than 1 MPa. Typically the run to run reproduc-In order to determine constitutive data and friction ibility of friction coefficients was better than ±0•005, coefficients it is necessary to measure the radial stress depending on the type of powder and the applied acting on the die bore. In the equipment described in this stress. Variations in constitutive data were usually paper, this is sensed by strain gauged pins, housed in better than ±4%, again depending on material and recesses in the die casing. These pins sense the displacement the stress. Die wall friction coefficients are found genof the die liner under load and are calibrated by applying erally to decrease with increasing density and stress.a measured hydrostatic pressure to the bore of the die by It has been possible to discriminate between differcompressing an elastomer plug in the die. The elastomeric ent grades and batches of the same material using the material behaves essentially as a fluid in the die and the frictional and constitutive data. Constitutive data for developed pressure is isostatic. all types of powder can be accurately represented by A Pentium II PC with a data acquisition card and an analytical relationship...

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