Welded joints are usually the weakest link for welded structures due to the existence of stress concentration caused from welding. Fracture mechanics-based approach is a main method used to predict fatigue life for welded joints structures. In engineering, there are two main problems in fatigue life prediction, one is whether crack initiation life can be ignored or not, and the other one is to determine the crack size starting to propagate. Based on this research, a practical procedure is proposed to predict fatigue life of welded joints structures using an initial crack life model and Paris law. Emphasis is put on the discussion about crack initiation life and how to choose an appropriate method to determine the initial crack size. Noted that the proposed method in this paper does not need any tests to determine crack initiation life when crack size reaches a specified value, which depends on experience and is considered as crack size starting to propagate, thus human factors and uncertainty can be minished. Through comparison analysis, fatigue life predictions based on the proposed method are in a good agreement with experimental data.

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