Triaxial plastic stress-strain relations for an aluminum alloy 14S-T4

Abstract

This paper gives the results of an investigation on the plastic stress-strain relations of an aluminum alloy 14S-T4 subjected to triaxial stresses. In addition to providing information on the triaxial plastic stress-strain relations, this study serves to provide a further check on the validity of the theories of plasticity used to predict plastic stress-strain relations for combined stresses. The triaxial stresses considered consisted of two equal compressive principal stresses and a third tensile principal stress. The stresses were produced by subjecting a solid cylindrical specimen to radial hydraulic pressure in addition to axial tension. Two types of triaxial stress tests were made. In one type of test the loads were applied so that the ratio of the principal stresses remained essentially constant during the test. For these constant stress-ratio tests, the influence of the stress ratio on the plastic stress-strain relations was investigated. In a second type of test the ratio of the principal stresses was varied during the test. The variable stress-ratio type test was conducted in order to provide a further check on the validity of the simple flow theory. The constant stress ratio tests for various principal stress ratio showed good agreement between the test results and the predictions of the simple flow theory of plasticity. However, the variable stress-ratio test results did not agree with the predictions of the theory.