Degradation analysis methods are increasingly used in reliability assessment of long-life products. The small sample size problem is worthy of attention in the degradation analysis. Bayesian hierarchical method is employed for fusing multi-source degradation information to handle small sample problems. The competing relationship multiple degradation models have been widely researched and applied. However, there is the non-competing multiple degradation situation exist in mechanical products. In this paper, a Bayesian hierarchical model-based information fusion degradation method with gamma process model is introduced for describing the non-competing relationship multiple degradation process. Therefore, the Bayesian method and the MCMC method are employed for parameters estimation. A numerical example of spool valve of hydraulic system in exoskeleton robot is provided to demonstrate the proposed Bayesian hierarchical model-based information fusion degradation method.
Reliability assessments of long-life and high-reliability products often face the difficulty of lack of failure time data. Meanwhile, there existing individual differences in produces due to the uncertainties during their whole lifetime, such as manufacturing, assembly, work environment and work load. This paper develops a reliability modeling and assessment method considering individual differences based on performance degradation data. Firstly, the model selection method is employed into the analysis of degradation process. And according to the model selection results, the appropriate degradation model for the degradation process can be chosen. Then, the Bayesian method is applied to establish the parameter estimation method and reliability assessment framework based on the appropriate model. At last, a real engineer example is presented to illustrate the effectiveness of the proposed degradation analysis method with individual differences.
The magnetic jack type control rod drive mechanism (CRDM) is the key actuator in the nuclear power plant reactor. The latch assembly of the CRDM acts as the execution component to lift, insert, and release the control rod assembly to accomplish the reactor startup, power regulation, and shutdown, etc. The accuracy and the timeliness of CRDM latch assembly action will directly determine the safety operation of the reactor. Considering the time variation of the structural strength deterioration in the latch assembly, the time‐dependent reliability of CRDM's lift action is evaluated based on the Gamma degradation process. P‐S‐N curve is introduced to model the shape function and the scale parameter of the Gamma process. The stress subjected to the key structure of the latch assembly is calculated by a multi‐physics field coupling simulation scheme with utilization of MATLAB to transfer simulated results between the ANSYS and ADAMS software. Finally, the time‐dependent reliability is calculated based on the Monte Carlo simulation method. In this paper, the lift pole thread of the assembly is presented to demonstrate the effectiveness of the proposed method.
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