Fatigue behavior investigation on dissimilar aluminum alloy ring welded joints in a new type sandwich high-pressure shell

Fatigue tests subjected to constant amplitude under the environments of dry air were performed on 5A06-O aluminum alloy, 7A05-T6 aluminum alloy and 5A06-O/7A05-T6 dissimilar aluminum alloy ring welded joints in a new type sandwich high-pressure shell. The fatigue behaviors were analyzed and compared based on the experimental data, and the mechanisms of welding defect impacts on fatigue properties of the welded joints were deduced from fractographic analysis. It is showed that welding defect has a detrimental influence on fatigue properties of the welded joints. The lower stress level can cause the more obvious decrease of fatigue life of the welded joints. Fatigue cracks of aluminum alloys base metal usually initiated at the surface defects such as two-phase particles and inclusions, and however, welding defect of welded joints are more likely to cause stress concentration and lead to the early initiation of fatigue cracks, which is dominated in decreasing of fatigue life of the welded joints.