Influence of superimposed normal stress on the shear strength in perfect fcc metals

The influence of a stress applied perpendicularly to slip planes during the shear deformation of fcc crystals on the theoretical shear strength was studied for 〈 1 1 2 〉 { 1 1 1 } slip system using first principles methods. A special relaxation procedure guaranteed that all stresses acting on the system were zero with the exception of the normal stress and the resolved shear stress. The theoretical shear strength was found to be a decreasing function of the applied tensile normal stress. The results were compared with similar calculations for rigid atomic planes and the role of relaxation of atomic positions within the planes was found to be important for correct description of the studied deformation process.