In this paper, an experimental investigation of fatigue crack growth behavior and fatigue life of Coach Peel (CP) specimens is reported. In this investigation, the CP specimens with 1 and 1.5 mm thickness and from mild steel are used. Specimens are tested by a 25 kN capacity INSTRON 8802 servo-hydraulic fatigue test machine under constant amplitude but various level loadings. During loading, the crack length and cycle numbers are measured accurately by a 100X light microscope. Initiation and propagation of spot weld specimens are measured by drawing vertical displacement of the specimen’s vs cycle’s curves. Results show that initiation and propagation of cracks often occur in the plate with less thickness. Also in low level loadings, cracks propagate longtitudinaly, but in high level loadings, usually nugget pull out and joints, fail catastrophically. The crack lengths during propagation, are nearly unique in both plates with the same thickness.

Keywords: Spot Weld, Nugget, Crack, Fatigue Life, Crack Initiation, Coach Peel Specimen.

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