Fatigue crack growth life prediction for butt-welded joints under block spectrum loading based on the modified strip-yield model

To achieve quantitative prediction of fatigue crack growth life in welded structures under block spectrum loading, this study develops a prediction model for fatigue crack growth life in butt- weld joints based on the weight function method and the modified strip-yield model, which takes into account residual stresses and load history effects. Fatigue crack growth tests were conducted on butt-welded joints with surface defects under various loading spectra using the commonly used 16MnDR steel for railway welded bogies, to verify the applicability of the prediction model. The results show that the model can accurately predict butt-welded joints' fatigue crack growth life. Compared to the traditional NASGRO equation, this model can effectively simulate the crack closure behavior introduced by load history, providing higher accuracy and reliability in predicting the fatigue life of butt-welded joints. The life prediction method developed in this study offers a theoretical guidance for the damage tolerance design and inspection interval optimization of welded structures.