Twin shear stress yield criterion

A twin shear stress yield criterion is described. This criterion was proposed by the author in 1961[1]. It assumes that yielding begins when the sum of the two larger principal shear stresses reaches a magnitude C. Thus the initial yield function is f = τ13 + τ12 = σ1 − 12(σ2 + σ3) = c[(τ13 + τ12) ± c][τ23 + τ21) ± c][τ31 + τ32) ± c] = 0.