A New Yield Function on Isotropic Metals Included One to Six-Order Plastic Tensors

The yield function is very important in establishing the plastic constitutive relation and analyzing the plastic deformation. Hence this article derives the yield function on isotropic metals included one to six-order plastic tensor, expanded of the general yield function in its Taylor. As well, the plastic tensors are analyzed by traceless, totally symmetric and objectivity in this article. And the yield function for isotropic metals can be degenerated to the one for identical and different property on tension-compression yield. Finally, by means of the results of Lode test, it is proved that this yield function is very suitable in the metal materials, which had the identical and different property for tension- compression yield. And there are 2 material parameters in this yield function, hence, the form is simple and had higher value in engineering.