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Book Chapter10.1520/stp24170s

Electric-Potential-Drop Studies of Fatigue Crack Development in Tensile-Shear Spot Welds

M. H. Swellam,Peter Kurath,FV Lawrence-1992-01-01
44

TL;DRAbstract

The development of fatigue cracks in galvanized low carbon and high-strength-low-alloy steel, tensile-shear-spot weldments was investigated using a d-c electrical-potential-drop technique which sensed the depth of fatigue cracks as they propagated through the thickness of the specimens. These resistivity changes were correlated with the actual crack depths measured on sectioned specimens. This correlation was used to identify lives at which certain crack depths were achieved: the duration of Stage I (initiation) corresponded to a crack depth of about 18% of the sheet thickness (≈0.16 to 0.48 mm), and the duration of Stage II (through-thickness propagation) corresponded to a crack depth equal to the sheet thickness (0.89 to 2.72 mm). The final failure of the specimen determined the conclusion of Stage III (cross-width crack propagation). The effects of sheet thickness, specimen width, and nugget diameter were studied. Sheet thickness was found to have the largest effect on fatigue life,

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The development of fatigue cracks in galvanized low carbon and high-strength-low-alloy steel, tensile-shear-spot weldments was investigated using a d-c electrical-potential-drop technique which sensed the depth of fatigue cracks as they propagated through the thickness of the specimens. These resistivity changes were correlated with the actual crack depths measured on sectioned specimens. This correlation was used to identify lives at which certain crack depths were achieved: the duration of Stage I (initiation) corresponded to a crack depth of about 18% of the sheet thickness (≈0.16 to 0.48 mm), and the duration of Stage II (through-thickness propagation) corresponded to a crack depth equal to the sheet thickness (0.89 to 2.72 mm). The final failure of the specimen determined the conclusion of Stage III (cross-width crack propagation). The effects of sheet thickness, specimen width, and nugget diameter were studied. Sheet thickness was found to have the largest effect on fatigue life,

Keywords

Materials scienceGalvanizationUltimate tensile strengthComposite materialAlloyDrop (telecommunication)Shear (geology)Crack closure

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