The study of fatigue crack behavior in welded structures using AE technique during crack initiation and propagation is discussed in this paper. This was achieved both theoretically and experimentally using four point bending testing. A new averaging index known as AE intensity was used to analyze the fatigue crack initiation conditions in the specimen. A theoretical model based on acoustic emission energy rate was developed to determine the critical fatigue level and crack extension. The results were compared with fatigue crack growth using a non-contact non-destructive testing method known as the digital imaging correlation. It was realized that, AE technique was able to detect the unset of a crack at a length of 8 μm in welded connection and 10 μm in the base metal, this proved that, crack initiates faster in welded connection than base metal.
Key words: Acoustic emission, fatigue, initiation, propagation, digital imaging correlation.
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