Reliability Analysis On Circulating Water Pump Gearbox Considering Failure Mode Correlation

The high reliability design of the gearbox of the nuclear circulating water pump is the guarantee of the efficient,safe and stable operation of the nuclear power unit.However,the coupled physical field effects and time-dependent characteristics of the gearbox can lead to multiple failure modes with multiple locations,types,and certain correlations in the system,thereby affecting the confidence level of system reliability evaluation.The purpose of this thesis is to study the key failure modes and their failure causes that restrict the reliability of the gearbox of nuclear power circulating water pump,characterizing the correlation between key failure modes,and establish the reliability analysis method of the gearbox system considering the failure mode correlation based on the load characteristics of the gearbox transmission system,so as to improve the accuracy of the reliability evaluation results.To contribute to the improvement of the reliability design capability of domestic nuclear power circulating water pump gearbox,the main research contents include the following aspects:(1)By studying the working environment and structural composition of the nuclear power circulating water pump gearbox,using an improved fuzzy comprehensive evaluation method to allocate its reliability,and clarifying the fault criteria for the gearbox,determining various possible failure modes,analyzing the causes of failure and their impact on various levels of the system,summarize and develop FMECA report to identify key components and critical failure modes that restrict the reliability of the nuclear power circulating water pump gearbox,and establish their functional functions based on failure physics to lay the foundation for reliability analysis of the circulating water pump gearbox.(2)On the basis of the established key failure mode function,the correlation between failure modes was analyzed,and based on the theory and method of the Copula function,the static reliability of the nuclear power circulating water pump gearbox considering the correlation of failure modes is analyzed to evaluate the reliability level of the gearbox.(3)On the basis of the static reliability analysis method,considering the performance degradation and load randomness of the nuclear power circulating water pump gearbox during the life cycle,the time-dependent function functions of each key failure mode were established,and the time-dependent correlation between each failure mode was described.The time-dependent Copula function and mixed Copula function theory were combined.This thesis analyzes the time-dependent reliability of the gearbox of nuclear power circulating water pump considering the failure mode correlation,reveals the law of its reliability level changing with time during the life cycle.