CRDM承压壳体多故障模式下的动态可靠性分析

Dynamic Reliability Analysis of CRDM Pressure Shell under Multiple Failure Modes

为研究控制棒驱动机构(CRDM)的结构可靠性规律,考虑CRDM承压壳体的多失效模式,根据应力强度干涉理论建立与CRDM步跃动作次数相关的结构动态可靠性模型。用顺序统计量描述强度失效模式下应力幅值的动态分布模型,基于Miner累积损伤理论和疲劳等效应力分布模型建立结构疲劳寿命和累积损伤分布与步跃冲击载荷作用次数的关系。研究结果表明,在步跃冲击载荷作用下,承压壳体前期的结构可靠度主要由强度失效模式的可靠度决定,当步跃动作达到一定次数时,疲劳失效模式的失效率开始显著增大;相对于疲劳失效模式,强度失效模式的可靠度对应力均值的变化更加敏感。该结果可对CRDM承压壳体的可靠性设计和维修管理提供参考。

To investigate the structural reliability of the control rod drive mechanism(CRDM),multiple failure modes of the CRDM pressure shell is considered,while the structural dynamic reliability model related to the CRDM step number is built by the stress-strength interference theory.The dynamic distribution model of the stress amplitude under the strength failure mode is represented by the order statistic.Based on Miner cumulative damage theory and fatigue equivalent stress distribution model,the relationship between fatigue life,cumulative damage distribution and the number of step impact loads is established.The results show that under the action of step impact load,the early structural reliability of pressure shell is mainly determined by the reliability of strength failure mode.When the step action reaches a certain number of times,the failure rate of fatigue failure mode starts to increase significantly;Compared with the fatigue failure mode,the reliability of the strength failure mode is more sensitive to the change of the mean stress.The results can provide reference for the reliability design and maintenance management of CRDM pressure shell.