Numerical study on the dynamic characteristics of the drive shaft system with diaphragm crack

The diaphragm coupling is widely used in the drive shaft system, which suffer from the crack at the waist of the diaphragm in long-term and high-speed working environments. However, the effect of the diaphragm crack (DC) on the dynamic characteristics of the drive shaft system. To solve the above issues, this paper researched the effect of the DC on the dynamic characteristics of the drive shaft system. The time-varying stiffness of the diaphragm group (DG) with crack was calculated considering friction. The calculation results indicated that the DC causes a decrease in the stiffness of the DG and introduces multiple higher-order harmonic components into the stiffness of the DG. The effect of the DC on the dynamic characteristics of the system was conducted. The accuracy of the system model is verified by comparing the critical speed results of the software and theory. The DC caused 2×, 4× super-harmonic resonance phenomenon. Meanwhile, the frequency-domain response of the system included a significant 2× super-harmonic component and also a significant 4× super-harmonic component at low speed. The super-harmonic components in the system response are introduced by the higher-order harmonic components in the time-varying stiffness of the DG, then leading to the super-harmonic resonance and irregular axis trajectory. The effect of the DC is significantly different from that of the open and breathing cracks in the rotor system. In engineering, it is possible to comprehensively observe the axis trajectory, super-harmonic resonance phenomenon, 2× and 4×super-harmonic components, and the 180° flip of the axis trajectory through the 1/2 first critical speed is used to determine whether the diaphragm has a crack.