Finite Element Simulation of Cyclic Ball Indentation on Zr 2.5 wt.% Nb Alloy and Assessment of the Residual Stress Produced

In-situ Property Measurement System based on ball indentation technique has been developed for estimation of mechanical properties of pressure tubes of Pressurised Heavy Water Reactors. Pressure tubes, made of Zr 2.5 wt% Nb material, operate under high pressure and high temperature and are susceptible to failure due to Delayed Hydride Cracking (DHC). Initiation of DHC from a location is possible under the presence of high tensile stress and hydrides. As the ball indentation process produces residual stress, it is necessary to quantify its magnitude and distribution to assess the fitness of the pressure tube for continued operation. The cyclic indentation process was simulated using a two dimensional axisymmetric finite element model and inelastic analysis was carried out to assess the effect of various parameters on the stress distribution. Th s paper describes the finite element simulation of the indentation process and results obtained from the parametric studies.