Investigation on fatigue behaviour of load-carrying fillet welded joints based on mix-mode crack propagation analysis

The fatigue behaviour of the load-carrying fillet welded joints was investigated by experimental and numerical approach in this paper. 26 load-carrying cruciform fillet welded joints involving 8 stress levels were tested and the S-N curves of 95% survival probability in terms of toe failure and root failure were established separately. The test results also demonstrate that the design curves of Eurocode3 are not suitable for this batch of specimens. In the following numerical simulations, three types of initial crack assumption were analysed by 3D mix-mode fatigue crack propagation analysis according to experimental observation. All the possible crack growth routes were simulated well. However, the single crack assumptions cannot form satisfactory simulations on fatigue lives with enough safety stock. Therefore, multi-crack analysis was conducted based on the combined data in terms of both toe failure and root failure. It is found that multi-crack analysis with 0.5 mm weld toe initial line crack and 0.1 mm weld root initial line crack can provide appropriate prediction. The findings can be beneficial for the fatigue assessment of load-carrying fillet welded joints fabricated by the normal welding technique in China and offer some references for the fatigue assessment of structural details with different possible failure modes.