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Abstract

The present sensor is, as reported previously, a brass sheet having a ridged surface which is inserted into the tool-workpiece interfaces to measure the width of flattened plateau of the ridges as the index of the pressure exerted during forging. In order to examine the reliability of the response of the sensor to non-uniform pressure distribution, pressure distributions over some tool surfaces were determined in several plane-strain extrusion processes of fully work-hardened aluminium specimens and the results were compared with the theoretical results obtained from the slip-line field analysis. The discrepancies were found to be within 5 to 10 per cent.The sensers were then applied to determine pressure distributions in some plane-strain and axisymmetric cold forging processes of work-hardened and annealed specimens. Generally the pressure distribution of hardened aluminium over a tool surface showed a more marked non-uniformity than did that of the annealed. A simple law that correlates the container pressure with the extrusion pressure was obtained. Thus, for a given extrusion geometry, the non-deforming portion of annealed specimen exerted a higher pressure over the container surface than did that of the hardened, while the latter required a higher extrusion pressure.