Abstract:With applied dislocation theory, the effects of shear and normal stresses on the slide and climb motions at the same section of a crystal were analyzed. And, based on the synergetic effect of both normal and shear strain specific energies, the concept of the total equivalent strain specific energy (TESSE) at an oblique section and a new strength theory named as limiting strain energy strength theory (LSEST) were proposed. As for isotropic materials, the plastic yielding or brittle fracture of under uniaxial stress state would occur when the maximum TESSE reached the strain specific energy, also the expressions on the equivalent stresses and a function of failure of the LSEST under different principal stress states were obtained. Relationship formulas among the tensile, compressive and shear yield strengths for plastic metals were derived. These theoretical predictions, according to the LSEST, were consistent very well with experiment results of tensile, compressive and torsion tests of three plastic metals and other experiment results from open literatures. This novel LSEST might also help for strength calculation of other ma, terials.

Key words: equivalent stress; total equivalent strain specific energy; limiting strain energy; failure function; strength theory