PSI - Issue 60

A. Syed et al. / Procedia Structural Integrity 60 (2024) 195–202 A. Syed/ Structural Integrity Procedia 00 (2023) 000 – 000

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Fig. 2 : Displacement (mm) contour for the clad tube with internal pressure of 2.1 MPa and burst temperature of 828 ˚C.

5. Computation of critical material damage parameter Rice and Tracey’s model (Rice and Tracey 1969) and Beremin material hardening model (Beremin (1981)) has been used to evaluate the critical value of material damage parameter that can predict the burst of the fuel clad using the stress field developed under different conditions of pressure and temperature. Equation (2) is used for computing the critical void growth ratio( ( 0 ) . Dc = ln ( 0 ) = ∫ 0.283 0 =0 .exp ( 3 ) (2) where R is the actual mean void radius, R 0 is its initial mean void radius, the ratio σ m /σ eq represents state of stress triaxiality, and is the equivalent plastic strain increment. Dc is the critical damage parameter obtained by integrating the incremental strain increment upto the burst of the tube. For obtaining the critical damage parameter where the clad tube will burst, value of the von-Mises stress and hydrostatic stresses are obtained at intern al pressure of 2.1 MPa and temperature of 828 ˚C. Ratio of the hydrostatic to von-Mises stresses are obtained to compute the stress triaxiality values prevailing under a particular operating condition. The maximum von-Mises creep strain is computed on the clad tube. Using these values, incremental increase in creep strain is computed at every interval of time. The obtained values are then numerically integrated with time to determine the variation of damage parameter as a function of time. The variation of damage parameter (D) with time is shown in Fig. 3. It can be observed that the damage parameter increases with time indicating the increase in deformation of the tube with time. As the value of damage parameter reaches a critical value, the unstable propagation of the voids generated due to combination of high temperature and internal pressure leading to the burst of the clad tube occurs. This critical damage parameter is found to be around 0.12. Most of the clad tube burst within few second after this critical parameter is reached. The failure of clad tube occurs at 45 sec under 2.1 MPa internal pressure and 828 ˚C temperature. This value is compared with the experimental value and the values are in agreement with each other.