An Experimental Investigation of Initiation, Propagation and the Fatigue Life of Modified Coach Peel -MCP- Spot Weld Specimens

Abstract

In this paper, an experimental investigation on the fatigue crack growth<br>behavior and the fatigue life of Modified Coach Peel -MCP- specimens are<br>carried out. The MCP specimens with 1 and 1.5 mm thickness and from<br>milled steel are used. The specimens are tested by a 25 kN capacity<br>INSTRON 8802 servo-hydraulic fatigue test machine under the various level<br>loadings with constant amplitudes. During the loading, the crack length and<br>the cycle numbers are measured accurately. The initiation and the<br>propagation of the spot weld specimens are approximately determined by<br>plotting the vertical position of the specimen versus the cycle’s curve. The<br>results show that, the initiation and the propagation of the cracks often<br>occurred for thinner plates. The results also indicate that the crack\\\\\\'s length<br>for thinner specimens is longer than that of the thicker specimens. It is also<br>found that the crack growth gradually in low level loadings while it is<br>usually growth around the nugget and eventually pull out the nugget for high<br>level loadings.