A review of equations applicable to general states of stress in forming problems is presented. Theoretical solutions for the particular case of cold-extruding 2S-O aluminum in an inverted extrusion process with negligible external friction are compared with experimental results. It is shown that the solution obtained by the work-of-deformation method yields good estimates of extrusion pressures if a constant flow stress for the equivalent uniform strain in a compression test is used in the calculations, but that the solution gives an incorrect estimate of distribution of stress and metal movement. The slip-line method of solution for plane strain, on the other hand, yields good agreement for the specific case investigated for both extrusion pressure and stress distribution, if the flow stress for an equivalent uniform deformation in a compression or tension test is chosen. The solutions available using the latter method do not, however, fully account for the observed metal movement.

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