Modify your axisymmetric model of a thick walled cylinder subjected to an internal pressure so that the cylinder has an inner radius of 120 mm and an outer radius of 220 mm. The length of the model should be 400 mm. Ensure that you mesh this geometry with a 10 by 10 mesh of quadratic elements which use full, rather than reduced, integration. Specify a boundary condition on one end of the cylinder to enforce axial symmetry. The elastic material model should specify a Young's modulus of 200 kN/mm2 and a Poisson's ratio of 0.3. Specify a perfectly plastic material model with a yield stress of 215 N/mm2. Apply an autofrettage pressure of 101 N/mm2 and then, a final working pressure of 51 N/mm2 to the model. Plot a graph of the circumferential stress, on the plane of symmetry, at the autofrettage pressure. Using this graph, determine the radial position of the elastic plastic interface. Give your answer in mm.