Detection of fatigue crack initiation and growth behavior in a double notched specimen based on strain information

If fatigue crack initiation and growth behavior in structures and materials can be detected based on strain information on the surface, the detecting method becomes a practical one for evaluating the fatigue damage and the residual life. From this standpoint, the strain interference method of detecting crack initiation and crack growth becavior was proposed by one of authors and the effectiveness of the method has been shown mainly through the fatigue tests using center-cracked specimens. In this paper, the applicability of the strain interference method to double V-notched specimens is investigated. First, the finite element analyses are carried out for double V-notched specimens, which are subjected to the tension-compression axial loading. The locations of strain measurement for detecting crack initiation and crack tip opening and closing points are discussed. After that, the exial loading fatigue tests of the specimen are carried out referring to the result obtained in finite element analyses. As a result of the experiment, it is shown that the crack initiation and crack growth behavior can also be detected by the strain interference method.