Influence of Torsional Excitation on Dynamic Responses of Rotors with a Breathing Slant Crack

Abstract

Abstract. Focusing on a rotor-bearing system with a breathing slant crack in the power transmission machine, influence of torsional excitations on the coupled nonlinear responses of the system is studied in this work. The slant crack element stiffness matrix is derived based on energy principal and the crack breathing phenomenon is simulated by the Crack Closure Line Position (CCLP) model; and the timevarying coupled dynamic equation of a rotor with a slant breathing crack considering the eccentricity of static unbalance is established using the finite element method and is solved by the NEWMARK method; then the influences of static torque and periodic torsional excitations on rotor dynamic responses in transverse and torsional directions are discussed. Results show that with the increment of static torque, cracks will become open gradually and the nonlinearity degree of rotors will increase firstly and then decrease. For periodic torsional excitation, the torsional excitation frequency and its rotating frequency combination can be found in transverse vibration response, and the larger is the amplitude of excitation, the larger are the combinational frequency components. Then a crack monitoring method for power transmission machines can be suggested by monitoring the coupled response characteristics and their variation from transverse responses of rotors before and after the loads change.

Dynamic Characteristics of Rotor System with a Slant Crack Based on Fractional Damping

“…The results showed the shear stiffness of spatial slant-crack in the axial and vertical direction was very obvious. Lu et al [18] used the energy principle to derive the stiffness matrix of an element with a slant crack, and used the crack closure line method to simulate the breathing behaviour of slant crack, and used the finite element method to construct the coupled dynamic equations of rotor system with a breathing crack base on the static unbalance and eccentricity distance.…”