PSI - Issue 60

352 Nagaraja Bhat Y V et al. / Procedia Structural Integrity 60 (2024) 345–354 Y V N Bhat, M A Davinci, A Kumar, N L Parthasarathi, S I S Raj, D Samataray, B.K. Sreedhar / StructuralIntegrity Procedia 00 (2019) 000– 000

predictions is shown in fig. 9. From the Fig. 9 it is observed that trend of the theoretical prediction for all the three cases of theoretical estimation in the initial sliding distance i.e. during running in condition are not matching with experimental result. However, prediction using Sarkar model is comparatively closer to the experimental results in the running in region as compared to the prediction done by Archard wear equation using two different values of specific wear coefficients. Towards the end of the testing, trend of theoretical curves for different wear equations and K H values become similar to experimental curve. At the end, values predicted from both Archard wear equation with K H value 2.68×10 -14 m 3 /N-m and Sarkar wear model are closer to the experimental value. Even though trend is somewhat matching, value obtained from prediction using Archard wear equation with K H value 2×10 -14 m 3 /N-m is deviating from the experimental results. Not matching of theoretical prediction trend with experimental trend in the initial running in condition might be due to consideration of average contact stress in GIWM as compared actual case of varying contact stress across the contact area. Based on above mentioned observations, it is decided to carry out prediction only in the steady state region i.e. from 200 m to 800 m, where the contact stress is mostly flattened as compared to initial sliding distance, which matches with the main approximation of GIWM. For the initial conditions of GIWM, like wear depth is taken from case-3 experimental value at the sliding distance of 200 m and contact radius is estimated using wear depth and cap formulae. From the theoretical prediction, it is seen that there is a good agreement between the theoretical and experimental values, as shown in Fig. 10. The matching of results also validates the K H value estimated from the experimental results for given load condition in the steady state region.

Fig. 10. Comparison of experimental data with theoretical data

5. Conclusion

In PFBR, for fuel handling system, Colmonoy-5 is one of the main tribological materials used for the rubbing surfaces of relatively moving components to minimise friction and wear. However, 440C material considered as an alternate material to Colmonoy-5, due to the manufacturing difficulties associated with it. Hence, it is very important to know friction and wear behaviour of 440C material under the conditions as in the reactor. As part of that, tribological testing of 440C material was carried out in ambient condition using pin on disc tribometer. Testing was done for normal loads varying from 10N to 20N and sliding velocity of 5 mm/s to 30 mm/s. For all cases of the tests, sliding distance of 800 m is considered. From the test results, following important conclusions are made. • For all cases of tests, the coefficient of friction gradually increases from 0.1 and stabilizes at 0.8 within a sliding distance of 120 m. This region is known as the running in region. For the remaining sliding distance, coefficient of friction remains 0.8, which is the steady state region. • Specific wear coefficient for pin is estimated using Archard wear equation and cap formulae based on weight