FEM-analysis on graded meshes for turning point problems exhibiting an interior layer

We consider singularly perturbed boundary value problems with a simple interior turning point whose solutions exhibit an interior layer. These problems are discretised using higher order finite elements on layer-adapted graded meshes proposed by Liseikin. We prove $ϵ$-uniform error estimates in the energy norm. Furthermore, for linear elements we are able to prove optimal order $ϵ$-uniform convergence in the $L^2$-norm on these graded meshes.