Research on identification method of multiple cracks in a shaft by vibration characteristics

As the main transmission device in mechanical equipment, the shaft plays an important role in the function realization and stable operation of the machine, but it is particularly prone to failure due to the long-term alternating or random axial load, bending moment and torsion, so it is of great significance to find the crack on the shaft in its early state, to reduce economic losses and prevent catastrophic accidents. The vibration characteristics of the circular cross-section shaft with multiple cracks are studied, and a damage detection method is proposed. Based on the basic beam theory and the local compliance theory, the stress intensity factors(SIFs) for the cracked shaft subjected to axial force, shear force and bending moment are derived, and the evaluation of corresponding compliance coefficient is given. The differential equation of motion is discussed. Results indicate that the derived stress intensity factor is in good agreement with the experimental results. As the shaft has cracks, the mode shape will show discontinuous at the crack location. This method can identify the crack position, depth and the number of cracks. (paper)