Crack Identification in Plates Using Genetic Algorithm

Abstract

When a crack exists in a structural member, it leads to changes in natural frequencies. Therefore, cracks in structures can be detected by measuring the vibrations in the natural frequencies of appropriate vibration modes. In this paper a crack identification method for plates is presented using both a genetic algorithm (GA) and FEM. The FEM program is developed to calculate the natural frequencies of the cracked plates based on the BFM (Bogner, Fox and Schmidt) plate model since the accuracy of the forward solver is important. In the study, two types of cracks, i.e., internal and edge crack are considered. To identify the crack location and the depth from frequency measurements, the width and the position of the crack in a plate are coded into fixed-length binary digit string. By using GA, the square sum of residuals between the measured data and the dynamic response is minimized in the identification process and thus the crack is identified. To avoid a large number of calculation cost, Response Surface Method (RSM) is also adopted in the minimizing process. The combination of GA and RSM made the identification more effective ad robust. The availability of the proposed method is confirmed by -results of numerical simulation.