Prediction and evaluation of cracks on thrust shaft

The transmission system on a ship is one of the most important parts of marine power equipment. Based on the power transferred by the thrust shaft, the ship is forward and backward. Due to the long journey of ships, the thrust shaft keeps on running for a long time. Moreover, the working conditions are very rigorous because of frequent changes of navigation environment. The thrust shaft is under cycle load and alternating stress. As a result, the thrust shaft would crack and fracture. In this study, firstly, fatigue and multiaxial fatigue are analyzed. Secondly, crack initiation /strain life is investigated. Then, the methods of crack propagation using finite element theory are studied. Moreover, considering Paris´s formula about propagation life of fatigue, the relationship between crack propagation and the rotating speed of the shaft is deduced as well as the relationship between crack propagation and power of the shaft. To simulate the crack propagation, the flow chart in MSC. Fatigue is given. The idea of constructing evaluation system is put forward. The system would predict the crack of shaft. The knowledge gained in this study provides a reference to build a self-healing system on the ship.