An XFEM based uncertainty study on crack growth in welded joints with defects

Decades of study on the fatigue of welded joints have shown that fatigue depends on many parameters such as initial defects, residual stresses and random loads, which are difficult for experiments to cover comprehensively, thus leading to scattered test results. Therefore, studies on uncertainties in the process of fatigue crack growth are required, especially for large-scale structures like orthotropic steel decks (OSDs). This paper presents an attempt to use the eXtended Finite Element Method (XFEM) to study the uncertainties induced by random defects, and the application on realistic projects with respect to uncertainties induced by random loads. Based on the concept of equivalent crack growth length, a homogenization process for simulating crack growth is proposed, showing that the uncertainties lie in the defect-related parameters, such as number, size and location of the defects. Finally, a case study based on on-site test data of an OSD is presented. By taking the uncertainties induced by vehicle loads as well as the defects into account, the macro-crack initiation life (MCIL) of OSDs is calculated. The results show that the method is applicable and effective to obtain the variation of the MCIL. However, to predict the MCIL accurately, careful attention should be paid when choosing the appropriate form of the Paris law and the values of the constants in it. The potential of this study is to evaluate the fatigue performance of all welded joints based on experiments on limited samples. (C) 2016 Elsevier Ltd. All rights reserved.