Plastic Deformation

· The hydrostatic component of the principal stress tensor has equal stress values on the diagonal.
· The reduced stresses acting on a material element are the difference between the hydrostatic and the principal stresses.
· Plastic deformation (yielding) begins when the resolved shear stress on a particular plane becomes larger than some critical value, τ_cr .
· In a continuum the plane of maximum shear stress is at 45 degrees to the 1,3 axes. The maximum resolved shear stress is then: τ_res = (σ₁- σ₃)/2.
· Slip (plastic deformation) will occur on this plane if: τ_res > τ_cr