A STABILIZED P1-NONCONFORMING IMMERSED FINITE ELEMENT METHOD FOR THE INTERFACE ELASTICITY PROBLEMS

We develop a new finite element method for solving planar elasticity problems involving heterogeneous materials with a mesh not necessarily aligning with the interface of the materials. This method is based on the 'broken' Crouzeix-Raviart P-1-nonconforming finite element method for elliptic interface problems [D.Y. Kwak, K.T. Wee and K.S. Chang, SIAM J. Numer. Anal. 48 (2010) 2117-2134]. To ensure the coercivity of the bilinear form arising from using the nonconforming finite elements, we add stabilizing terms as in the discontinuous Galerkin (DG) method [D.N. Arnold, SIAM J. Numer. Anal. 19 (1982) 742-760, D.N. Arnold and F. Brezzi, in Discontinuous Galerkin Methods. Theory, Computation and Applications, edited by B. Cockburn, G.E. Karniadakis, and C.-W. Shu. Vol. 11 of Lecture Notes in Comput. Sci. Engrg. Springer-Verlag, NewYork (2000) 89-101, M.F. Wheeler, SIAM J. Numer. Anal. 15 (1978) 152-161.]. The novelty of our method is that we use meshes independent of the interface, so that the interface may cut through the elements. Instead, we modify the basis functions so that they satisfy the Laplace-Young condition along the interface of each element. We prove optimal H-1 and divergence norm error estimates. Numerical experiments are carried out to demonstrate that our method is optimal for various Lame parameters mu and lambda and locking free as lambda -> infinity.