Efficient and accurate determination of mode I type 3-D surface crack by measuring strain around the crack on the idea of the body force method

Abstract

In this study, the location and the size of a three-dimensional semi-elliptical surface crack in a semiinfinite body are detected from data of strains measured around a region of the crack. Also the loading stress at infinity is treated as an unknown parameter. The crack location, size and the loading stress are determined through the condition which minimizes the square sum of residuals between measured strain distributions and computed ones for an assumed crack. The body force method is used to calculate the strain field around the crack. In order to obtain the solution with short CPU time, the crack is represented by a set of force doublets, and the database of the magnitudes of force doublets for various aspect ratios of the crack is utilized. The method of gradient search is employed to find out an optimal set of parameters. The fact that the strain field around the surface crack is mainly dominated by the crack area is utilized in detecting the crack. Several inversion schemes are examined to obtain accurate results. Numerical simulations are carded out and the results show that crack location, shape and loading stress are determined efficiently with good accuracy.

Detection of Plural Cracks in an Infinite Plate by PSO Algorithm

“…Recently, a crack-detection is regarded as one of the inverse problems. Then, a quantitative measurement of a crack based on an application of inverse analysis has attracted a lot of researchers' attention [1][2][3][4].…”

“…Therefore, the identification of the crack, which causes the change of strains, may be possible from measuring the strain field around the crack. In the previous papers [1][2][3][4], based on the data of strains measured around the crack, the efficient and accurate inversion method to determine the location and the size of the surface crack has been proposed. In this study, the identification problem for plural cracks in an infinite plate is treated.…”