Failure-mode Dependent Reliability Analysis For The Thrust Bearing Positioning Mechanism Of Nuclear Main Pump

The thrust bearing of the nuclear main pump is a key component to bear the axial load,and the complex environment in which it is located has high requirements for reliability.The impact fatigue failure and wear failure of the positioning mechanism are the main reasons for the failure of the thrust bearing.If the reliability of the positioning mechanism system is studied,if the correlation between the failure modes is not considered,the error of the calculated reliability results will be too large.In this paper,the impact fatigue and wear performance experiments of the WC-10 Ni coating positioning mechanism prepared by spraying are carried out,based on the Bootstrap method to fit the random variable distribution,and the reliability analysis of the second-order moment method and Monte Carlo method is used,and based on considerations The reliability calculation method related to the failure mode is used to analyze the reliability of the positioning mechanism system.The impact fatigue reliability analysis of the positioning mechanism is carried out.According to the allowable number of impacts of the positioning mechanism in 60 years,6000 times,based on the Paris formula and the linear cumulative damage criterion,the functional function of the relationship between the impact fatigue failure of the positioning mechanism and the load and the initial crack length is established.The combined load and the distribution parameters of the initial crack length.According to the wear reliability analysis,according to the allowable wear depth of 50 μm,the functional function of the relationship between the wear failure of the positioning mechanism and the load,the initial crack length and the wear distance is established,and the distribution parameters of the fitted load,the initial crack length and the wear distance are used.The firstorder second-moment method Monte Carlo method is used to analyze the fatigue reliability and wear reliability of the positioning mechanism.The fatigue reliability of the positioning mechanism is about 0.9930,and the wear reliability is about 0.9849.Both fatigue reliability sensitivity and wear reliability sensitivity are positive values,and the random variable that has the greatest impact on reliability is the initial crack length.Calculating the reliability of the positioning mechanism under different process conditions shows that an increase in the spraying angle will increase the fatigue and wear reliability of the positioning mechanism.Considering the correlation of random variables,fatigue reliability and wear reliability both decrease as the correlation coefficient between variables increases.For wear reliability,the degree of influence of the correlation between random variables on the reliability index is the correlation between the wear distance and the initial crack,the correlation between the load and the initial crack length,and the correlation between the wear distance and the load.The failure tree of the positioning mechanism system is established,and the system reliability of the thrust bearing positioning mechanism is calculated using the given method considering the failure mode.The calculation result is 0.9309.Compared with the reliability calculation result of0.8914 without considering the failure correlation,the calculation error is smaller.In addition,the system reliability of the thrust bearing positioning mechanism system that considers the action of the balance weight decreases slowly when the thrust pad has a dimensional error.The system reliability of the nuclear main pump positioning mechanism affects the performance of the nuclear main pump.Considering the reliability calculation method related to the failure mode,the calculated result has a smaller error and provides a more accurate basis for the performance evaluation of the nuclear main pump.