Improved numerical manifold method (iNMM)-An extra-DOF free and interpolating NMM with continuous nodal stress

As a partition of unity method (PUM), the numerical manifold method (NMM) is capable of constructing global approximation by simply multiplying PU function with local approximation. In order to enhance accuracy, high order polynomials can be specified as local approximation. This, however, will hinder the engineering application of NMM by its ill conditioning of the global stiffness matrix. In this study, an improved NMM (iNMM) without extra degree of freedoms (DOFs) is developed. Without the extra DOFs, the resulting global stiffness becomes linear independent. In addition, the stresses are continuous at all nodes. Numerical studies show the iNMM's excellent accuracy.