The forming limit curves are important aids in determining the extent of deformation a material can be subjected to during a forming process. In this paper a forming limit criterion for bulk metalworking processes, based on the magnitude of the hydrostatic component and the effective stress of the state of stress, is proposed. The determination of the forming limit curve by means of three simple tests, namely, tension, compression, and torsion tests, is presented.

The stress analysis in the deformation zone in upsetting of a workhardening material by half-cylindrical die is presented. The load and average pressure as a function of die stroke were determined and compared to those obtained from experiments. The effect of friction and die radius were examined. Stress distributions for ideal-plastic material were also obtained and the results were compared to those for workhardening material.

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Two solutions for the detailed mechanics of tube extrusion are presented. One is based on the theoretical velocity field, and the other on the flow field observed experimentally. The theoretical solution makes use of admissible velocity fields containing no velocity discontinuities. Experimental flow patterns are obtained for commercially pure lead and a superplastic alloy of the eutectic of lead and tin. The two solutions are compared in terms of velocity components, grid distortions, and strain and stress distributions, and very good agreement between the two solutions is revealed.

Procedures for using a computer for the complete solution to plane strain as well as axisymmetric deformation problems have been developed. The velocity, strain rate, total effective strain, and stress distributions were obtained for two commercially pure lead specimens extruded in a forward extrusion process using white lead in oil as a lubricant. The axisymmetric extrusion was carried out at a speed of 1/8 ipm through a conical die having a 45 deg half-cone angle with a 2:1 extrusion ratio, and the plane-strain extrusion through a tapered die having a 45 deg half-taper angle with a 1.66:1 extrusion ratio.