No abstract

In this paper, An-Non destructive test procedure was used to study the effect of depth and Location of circumferential cracks on the vibration characteristics of the rotating shafts. The first procedure was to measure the natural frequencies of rotating shaft before renewing circumferential cracks with different dimensions and depths from the bearing of the rotating shaft using (vibration analyzer B & K type 2515) apparatus to analyze the vibrational characteristics during the rotation and comparing it with mathematical analysis using the method of mounting the rotating shaft. Secondly, a crack of certain depth and dimension away from the rotating shaft bearing was made. The measurements of the natural free vibration due to the presence of the crack were carried out. The study took into consideration the diameter and the length of the rotating shaft, beside the measurement of the natural free vibration of the shaft. The practical results showed a decrease in the natural frequencies of rotating shaft when the crack prested. This decrease was more when the crack located in areas near the bearing than was located away from the bearing.

In this study, a qualitative analysis of a transverse vibration of a rotor system with a crack that grows at an angle of 45 degrees toward the axis of the shaft is presented. Based on the assumption that the bending stiffness of the shaft changes synchronously with the opening / closing behavior of the crack caused by the torsional vibration of the shaft, the equation of motion of a simple rotor system with a shaft having a slant crack is represented by a differential equation with parametric excitation in fixed coordinate system rotating at the operation speed of the rotor. Finally, it is shown by the solution that the steady-state response of the rotor system with a slant crack on its shaft induced by imbalance contains the frequencies represented by ,.... 2 , 1 , 0 ,...., 3 , 2 , 1 , 2 n m n m T n