PSI - Issue 60

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A. Kumar et al. / Procedia Structural Integrity 60 (2024) 541–552 Akshay Kumar/ StructuralIntegrity Procedia 00 (2023) 000 – 000

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noded 3D brick type solid element. The element supports plasticity, hyper elasticity, creep, stress stiffening, large deflection, and large strain capabilities. An internal pressure of 4 MPa is applied on the inner surface of pressure tube. The longitudinal pressure is also an input to calculate the correct deformation in pressure tube. Temperature data obtained from thermal analysis is used as input to the structural analysis. Temperature is superimposed for a duration of 5 seconds and then changed with another set. A total of 21 set of temperature data has been used for calculation of deformation for 200 seconds. 3. Validation of model for PT ballooning The deterministic results of the model are compared with those from the experiment in order to validate the estimation model. This model is then further used for evaluating an uncertainty analysis. 3.1 Results from Thermal Analysis The temperature profile for the point in the FE model with highest temperature at the end of the analysis is given below in the Fig. 6 with time. At this stage, the time at which the PT-CT contact happens due to ballooning is not known. It can be concluded from thermal analysis that the effect of heat transfer is coming in the analysis and the equivalent length which is affected by this difference in heat transfer coefficient is around 250 mm. The variation along the radial direction of pressure tube is negligible. Variation along the axial direction of pressure tube which is enclosed by calandria tube is also negligible. 3.2 Results from Structural Analysis The temperature profile obtained from thermal analysis is used as input for structural analysis with material properties as discussed in the previous section. The radial deformation of the pressure tube is calculated in FE analysis by employing the creep model as discussed earlier. The variation of maximum deformation with respect to time is plotted in Fig. 7. The variation in the deformation in axial direction of the pressure tube is negligible. From the structural analysis it can be concluded that the deformation in first 70 seconds is negligible or less than 0.1 mm. The significant deformation starts occurring after a time period of 70 sec. The deformation increases with time and cross the gap of 8.9 mm between CT and PT after a time span of 190 seconds.

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Fig. 6: Temperature profile of pressure tube obtained from thermal analysis