Detecting Method of Striation Region of Fatigue Fracture Surface Using Wavelet Transform
Kenta YAMAGIWA, Satoshi IZUMI and Shinsuke SAKAI
Abstract:A numerical analysis of a fracture surface is needed in the fractography. The method proposed in this paper identifies quantitatively the striation region observed in the fatigue fracture surface, and the striated surface ratio is calculated. The method proposed characterizes the striation region by using the wavelet transform, and the degree of striation is calculated from the wavelet coefficient. The Gabor function is applied as the mother wavelet function and it can be used to extract the striped pattern which is the feature of a striation. In order to evaluate the validity of the method, it is applied to the virtual fracture surface and the SEM picture of the fatigue fracture surface of 2.25Cr-1Mo steel. Matching of the striation region calculated from the degree of striation and the result obtained from the human observation is performed. Consequently, good agreement between the judgment result by human observation and the judgment result by the method is obtained, and it is shown that the proposed degree of striation is appropriate to the evaluation of a striation region. Therefore, it becomes possible to evaluate a striation region using the method proposed, and it supports for the decision-making of an analyst who is unfamiliar with the fractography. Key Words:Fractography, Fatigue fracture, Image analysis, Wavelet analysis