Free vibration analysis of cracked cylindrical shell by numerical and experimental methods

Cylindrical shell structures are exposed to various types of defects and damages such as cracking, which may destroy their structural safety. The effects of cracks in the design of cylindrical shell structures are significant due to their impact on vibration and safety characteristics. In this article, the free vibration analysis of cracked cylindrical shell has been investigated by numerical and experimental methods. In order to investigate the actual vibration behavior, modal analysis was used in the laboratory method and commercial finite element software was used in the numerical method. In order to verify the results, by creating a crack in the laboratory model, the frequencies of the cracked cylindrical shell are measured and compared with the numerical solution. The effect of various parameters such as crack length, crack angle, crack depth, crack location, shell thickness, shell length under boundary conditions of two free ends has been investigated on vibration frequencies. To determine the influence of each parameter on the vibration frequencies, a test design has been done using RSM-CCD. The obtained results show that with a 67% increase in the ratio of crack length to diameter, the natural frequency decreases to 32.7% and also with a 50% decrease in the crack angle, the frequency decreases to 24.5%. As a result, the natural frequency created by the crack changes in a certain number of modes--condition, depending on the location of the crack.