Fatigue Life Prediction and Reliability Evaluation Method for Shear Impact Coupling Failure of Locking Screw

The locking screw in the drive mechanism bears the radial alternating impact load during the reciprocating motion of the control rod, which is prone to shear impact coupling fatigue failure. The existing fatigue reliability analysis methods can only deal with the single failure mode of shear fatigue or impact fatigue, In order to improve the reliability of reactor operation, a fatigue life prediction model and reliability evaluation method considering shear impact coupling failure mode are proposed. Firstly, the single transient impact simulation analysis of the screw is carried out, and the rain flow counting method is used to decompose the simulation output. Then, the shear fatigue life prediction model is used to calculate the life of the screw. Finally, considering the uncertainty of working condition, material and model parameters, Monte Carlo sampling method is used to calculate the reliability of the screw. The results show that the reliability of the locking screw will decrease rapidly after 2.82 million times of armature impact, and the locking screw is prone to fracture failure. This evaluation method can be used for fatigue life prediction and reliability evaluation of all kinds of screws under shear impact load, and can also help to determine the safety inspection cycle and inspection focus of reactor structure.