Abstract:This paper discusses the yielding and strength characteristic of friction materials. A new method is proposed to expand 2-D yield curve in p-q plane into 3-D yield surface. When applying this method on Mohr-Coulomb yield surface, a generalized yield surface is obtained. Characteristic of this generalized surface is depicted. The yield surface is applied on isotropic and anisotropic friction materials, and the result shows its ability of fitting the yielding characteristic of such materials reasonably. Finally,this yield surface is compared with four classical yield surfaces and other researchers` result. Comparison shows that it covers the scope of these classical yield surfaces thus more comprehensive.