The above-mentioned linear relationship holds also for the block loading conditions based on total energy dissipated per block. For lower growth rates a power law relationship can be proposed between these two parameters. In particular, it is shown that there exists a linear relationship between the crack growth rate and the energy dissipated per cycle at high growth rates, which is valid for both the environments studied, and it corresponds to a crack growth mechanism characterized by striation formation during each cycle. It is shown that most of the effects usually attributed to closure can be successfully explained using energy concepts. The measured crack opening levels under constant-amplitude loading conditions are comparable to those predicted under plane strain conditions for moderate ΔK levels. After an overload, in the deceleration phase, the evolution of the crack opening load is not compatible with that of the crack growth rate.

Crack opening loads using the compliance technique permit the effect of load ratio to be taken into account. The different test conditions studied include load ratio and environmental effects, crack growth retardation following a single overload, and crack propagation under block load tests. The fatigue crack growth behavior of the aluminum alloy 2024 is analyzed using the crack closure and an energy-based concept. The knowledge gained in this study provides a reference to build a self-healing system on the ship. The system would predict the crack of shaft. The idea of constructing evaluation system is put forward. To simulate the crack propagation, the flow chart in MSC. 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. Then, the methods of crack propagation using finite element theory are studied. Secondly, crack initiation /strain life is investigated. In this study, firstly, fatigue and multiaxial fatigue are analyzed. As a result, the thrust shaft would crack and fracture. The thrust shaft is under cycle load and alternating stress.

Moreover, the working conditions are very rigorous because of frequent changes of navigation environment. Due to the long journey of ships, the thrust shaft keeps on running for a long time. Based on the power transferred by the thrust shaft, the ship is forward and backward. The transmission system on a ship is one of the most important parts of marine power equipment.

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