核电站控制棒驱动机构隔磁片应力分析

Stress Analysis for Magnetic Isolation Shims in CRDM of Nuclear Power Plants

考虑到磁极对隔磁片的弹性支撑,根据弹性力学板壳理论建立了隔磁片在衔铁冲击载荷作用下的基于弹性基础的薄壁圆盘轴对称弯曲的应力分析模型,利用幂级数和传递矩阵技术给出了相应的解析解,并将理论分析结果与有限元数值计算结果进行了比较.结果表明:理论分析结果与有限元数值计算结果完全吻合;在隔磁片磁极接触侧出现与冲击疲劳相关的弯曲拉应力;以径向拉应力为主体的最大疲劳等效应力发生在距离内径1/3的隔磁片径向宽度处,它是导致隔磁片经历一定次数步跃运动的衔铁冲击载荷作用后出现疲劳破损的主要原因.

Considering the elastic supports provided by lift poles, and based on the theory of plates and shells in elastic mechanics, a stress analysis model was set up for the magnetic isolation shim placed on e- lastic foundation with axisymmetrical bending and subjected to impact load from lift plunger in control rod drive mechanism （CRDM） of nuclear power plant, with which corresponding analytical solutions were ob- tained by means of power series and matrix transfer technology, and subsequently the anlaytical results were compared with numerical calculations. Results show that the analytical results agree well with those of finite element calculation. Bending tensile stress caused by impact fatigue occurs in the shim at the side contacting with lift pole. The maximum equivalent stress, which is mainly of the radial tensile kind, ap- pears in the one-third radial width from inner side of the shim. This is the main reason leading to fatigue carcking of the shim after the action of impact load from lift plunger for a certain period of operation.