Abstract：Although the Hosford yield function is more suitable for describing both the yielding and the plastic deformation of orthorhombic material than the Hill quadratic yield function, it suffers from the restriction that the three principal stresses have to be coaxial with the pressing direction (RD),transversal direction (TD) and?vertical direction (ND) for metal sheet. Hence, this article derives the Hosford yield function for orthorhombic materials included direction of principle stress from the six-order plastic tensors, expanded of the introduced orientation-dependent functions in its Taylor. And when n=2, this yield function can be reduced to the Hill quadratic yield function. Finally, it shows?that q-value, R-value and the yield stress， obtained from the Hosford yield function for orthorhombic materials included direction of principle stress, agree well with the results of?experiment. And there are many merits on this yield function, such as only including 11 material parameters, simple form, generality, and so on. And this yield function will lay a theoretical foundation for analyzing mechanical properties of metal materials.
2016, Vol. 37 
