Efficient utilization of high-strength steel is crucial in various industrial applications, including offshore structures, ships, and bridges. To achieve this, advanced manufacturing and analytical tools are required to consider the fatigue strength of high-performing surfaces and welded joints. In high-performing structures, the reduction in imperfection size results in higher fatigue strength than conventional ones, especially when high-strength steel is used. Therefore, fatigue modelling of the initiation and propagation of short cracks is essential for evaluating high-performing structures. In this context, non-local continuum damage mechanics-based modelling of crack initiation and growth has gained attention lately. This model relies on local stress and strain fields and the accumulation of fatigue damage within representative volume element depending on grain size statistics for arbitrary shaped imperfections and various crack sizes. Thus, the method enables explicitly considering the effects of surface roughness, material mechanical properties, and residual stress. As a result, this model estimates fatigue life for all short crack initiation and short and long crack propagation, extending beyond fracture mechanics-based methods that require the assumption of initial crack size. This paper aims to present a methodology of continuum damage mechanics-based modelling and its application to the analysis of short crack initiation and growth in high-performing structures. The methodology provides a detailed description of the modelling concept, the procedures for calculating the fatigue life, and simulation tools using finite- element methods. The application cases include high-quality cut-edge plates and welded joints with superior fatigue strength. The results of estimated fatigue life are compared to experimental data. After that, this study discusses the fatigue damage mechanism of high-performing structures by focusing on the change of local fatigue response during short crack growth.

This study describes a non-local continuum damage mechanics-based model for crack initiation and growth modelling. The focus is on its application in high-performing welded structures, where crack initiation and short crack growth play an important role. The introduced model uses local stress-strain field and microstructure-dependent material units together with continuum damage analysis, allowing the same modelling principle used for initial geometry and following crack growth analysis, i.e. whole fatigue damage process from crack initiation to final failure. This modelling enables an explicit consideration of micro-scale geometry, residual stress conditions, and material mechanical properties to estimate fatigue life accurately. An application case using a mild notch geometry illustrates the evolution of local fatigue response during crack initiation and growth, offering insights into surface integrity effects on fatigue behavior. Also, examples of welded joints are also given to demonstrate the model’s capability in estimating total fatigue life and S-N curves.