The densification of metal powders via automatic uniaxial die compaction in hydraulic or mechanical presses is a very important operation in standard P/M manufacturing procedures for sintered metal parts with complex shapes. Consequently, a knowledge of how the metal powders behave during cold compaction is very important for the development of new powdered materials andthe manufacturing optimisation of sintered parts. Recently, some computer models have been developed which enable the successful prediction and simulation of the dynamic behaviour of powders during their compaction and ejection from the die. The models are used to calculate a series of process parameters that are important for the optimum powder compaction into the complex compact, for the dimensioning of the dies and presses and for the prediction of the die life. The reasons for crack formation inside the compact can also be analysed. An instrumented die is used for the exact experimental determination of the parameters and the data needed for the determination of the appropriate constitutive law which describes the powder/compact behaviour during the compaction/ejection. Actuators and sensors are connected to a computer and adequate hardware/software is used for the continuous, fast and accurate acquisition, processing, and analysis of the measured data. The complete analysis and determination of all constitutive parameters requires a complex instrumented die (cell) in which the powder is subjected to a 3D stress field. Recently, it has been proved that it is possible to obtain enough experimental data with a simpler instrumented cylinder die in which the investigated powder is compressed uniaxially. The die must be incorporated into the press, which makes it possible to control the compaction of the powders up to high pressures (800-900 MPa) and relatively high green densities (above 95% of T.D.). This kind of equipment allows us to determine all the experimental data which describe the behaviour of a new or existing powder material during compaction, and allows the analysis and experimental validation of a certain model, or the starting points for the development of a new model. A new instrumented cell for the analtsis of metal and ceramic powders during uniaxial cold compaction was developed at the Institute of Metals and Technology, Ljubljana. The cell was incorporated into a universal 500 MPa Instron 1255 (UK) servo-hydraulic testing machine which serves as a uniaxial press. The complete system also allows us to analyse the behaviour of the compact during its ejection, as well as to determine the compacts' green strength. The developed software allows us to continuously collect and process all the measured values and calculate the basic relationships and present them graphically. In this article we present the new equipment and some experimental results obtained during the compaction of water-atomised steel powders. The system can also be used independently for the determination of the compaction true-stress-strain curves of conventional materials. Therefore, some experimental results from this area are also presented.
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