Abstract: An one-step inverse approach based on decoupled formulation in nodal tangent plane is proposed to improve the method based on traditional formulation in the global coordinate system. In this algorithm, considering the coordinate independency of principle of virtual work (PVW), stiffness equations are decoupled in nodal normal direction and nodal tangent plane by establishing the PVW equation in the nodal local coordinate system. Compared with traditional formulation, decoupled formulation avoids the numerical problems caused by projected stiffness matrix of vertical element, thus it improves the accuracy and convergence of iteractive solution. By flattening analysis of bending thin plate, quantitative analysis of the error of decoupled formulation shows that the algorithm meets the required precision. Finally, the decoupled formulation is integrated into King mesh analysis system (KMAS) software. By numerical simulation on square box, and comparisons among traditional formulation, decoupled formulation and incremental algorithm with LS-DYNA solver, the effectiveness of the decoupled formulation is verified.

Key words: Decoupled formulation, Nodal tangent plane, One-step inverse approach, Plastic deformation theory