Objectives  This paper aims to study the influence of welding defects on fatigue life of aluminum alloy plate frame.

  Methods  Firstly, use X-ray to detect the welds of the test aluminum alloy plate frames with two gusset joints, and then select two plate frames with and without welding defects respectively. Then obtain main types of the welding defects through the analysis on the X-ray images. Then, carry out fatigue tests for these two plate frames with and without welding defects under different loads, so as to obtain the fatigue life of the plate frames. Finally, establish local FE models for the test plate frames with three types of welding defects by using ABAQUS software, and analyze and reveal the failure mechanism of the plate frames with welding defects.

  Results  The test results show that, the failure of the test plate frame with welding defects is caused by the fracture on the longitudinal web due to the extension of the crack in the welding defect at the end of the weld; the failure of the test plate frame without welding defects, which is related to the gusset joint, is caused by the fracture on the longitudinal web due to the extension of the fatigue crack generated under the cyclic loads on the longitudinal web.

  Conclusions  This study results can provide a reference for the assessment of the fatigue life and for the influence of the welding defects on the fatigue life.