The Study On Die Stress Of Cold Backward Extrusion For Aluminum Alloys

As an important and indispensable metal forming technology, cold extrusionpossesses a wide range of applications in industry departments. However, the strengthand life of mould limit cold extrusion for the further development as main resistancebecause of high deformation resistance. At present, it usually adopts punch stress asdie stress, and which distributes evenly along the height of die cavity when designingextrusion die. In fact, they are not equal, and don’t exist simply proportional relations,so it will be blind to use punch stress as a measurement of die stress and strengthcalculation. Therefore, it still need to study stress distribution of inner wall of die forfurther understanding of these questions.First of all, with blank as research object, radial stress of deformation blankapplying on inner wall of integral die was researched in cold backward extrusion basedon DEFORM-3D. The maximum die stress always existed in the stable extrusion stagethrough simulation of backward extrusion, and the value would be selected as a furtheranalysis; With the single factor and orthogonal experimental method, DEFORM-3Dwas used to simulate influence law and degree of blank deformation, ratio of height todiameter, friction, material performance and extrusion speed on radial stress ofbackward extrusion die; and with simulating different aluminum alloy in differentdeformation degree, the equation between the maximum die stress of inner wall withpunch stress had been deduced.Next, regarding maximum radial stress of inner wall of die as known internalpressure, integral die response was discussed based on ANSYS Workbench in thecondition of even-distributed load when loading length and location changed.Therefore, the general rules of stress distribution was found, which provided the basisfor die stress analysis with non-uniform load. Finally, taking1060aluminum alloy for instance, the distribution law of radial andshear strain were measured in the process of extrusion based on the resistance straingauge paste technology. Meanwhile, comparing numerical simulation results withexperiment results verified the accuracy of simulation, and it showed that experimentand simulation strain curve of the points changed consistently, the maximal relativeerror was13.6%and minimum was0.38%for the maximum strain of correspondingpoint between them.