Revised Some Questions On Twin-shear Strength Theory

Orthogonal octahedron element body is founded by intercepted a cube one used three groups shear failure planes under true triaxial stress states, which is also a foundation of generalized octahedron theory system(Yang Jianhui, 2007) and analytical element body of twin shear theory. The stress on the element body is intituled to twin shear stress, which has clear physical and inherent plenty meanings and embodies mean principal stress and hydrostatic stress by being transformed of twin-shear and stress Lode parameter(including strain Lode parameter), and being proved in the universal adjustability of strength models.However twin-shear strength models existed some uncertainty by mathematical theory according to the model construction namely multinomial strength models, which is certainty by twin-shear stress characteristic, boundary condition, nonsingular or not of rank of system of equation, and practical problem, etc., but also a few, so which is be easily studied and applied. Some characteristic strength value can be inversion by some three-parameter twin-shear strength models by different boundary condition, which can also be predigested the third strength theory and Mohr-coulomb theory and unknown theorys, and being given condition of compatibility of each predigested model. On the other hand, correlation equations of characteristic strength parameters are set by uncertain solutions of four- and six-parameter twin-shear strength models, that is rank is no nonsingular, which is uni- and bi-axial characteristic strength parameters, bi- and tri-axial ones, and all of ones. Mutuality equations of multiaxial characteristic strength parameters and multiaxial ultimate strength models are founded based on twin-shear strength theory and multiaxial characteristic strength and multiaxial ultimate strength under proportional and un- loading can be forecasted by given multiaxial strength computation flow under only known axial tensile and compressive strengths.Orthogonal octahedron constitutive equation of strain is founded based on analyzing the stress and the strain on the diagonal section. The constitutive relation of orthogonal octahedron strength and deformation founded is just for isotropic and linear elastic element. Because of the symmetry and what any one diagonal section of orthogonal octahedron element body is parallel to a Cartesian axis of coordinates in space, the simple space problems could be transformed into the plane problems based on strength-deformation constitutive relation.The special strength models were deduced and generalized by the plenty characteristic of deduction that the twin-shear strength model has, which has a universal adjustability by deduction of multi-ultimate lines inπplane.At last, the models purposed have been verified by the data of experiments on the published literatures, so they are reliable.