Study Of LabVIEW And ANSYS Based Rotor Monitoring And Fault Simulation

Rotating machinery is very commonly used in modern industrial enterprises andaerospace fileds. It has significant influence on the national economy and key fieldsof national defense. Once failure happens, it often leads to catastrophic accidents,and causes serious casualties and property losses. Fatigue crack is one of the mostcommon failures in rotating machinery, therefore it is necessary to make anintensive study of the generating and propagating process of the crack fault, predictthe remaining useful life of the crack rotor, and take corresponding measures formaintenance to reduce the incidence of accidents, which guarantees the systemworks with high efficiency, safety and low cost.This dissertation presents the research on dynamics modeling for a Jeffcott rotorwith a transverse breathing crack. It studies the influence of the existence of thefatigue crack on the rotor dynamics behavior, and an experiment is carried out toverify the accuracy of the theoretical model. Then the residual life prediction isperformed based on the fracture mechanics theory and the finite element analysis ofthe cracked rotor. The main content of this paper are as follows:Firstly, based on neutral axis theory, the breathing process of a cracked rotor isrepresented by closed and independent mathematical functions. By adopting thesefunctions, the governing equation for the cracked Jeffcott rotor can be built. Bytime-frequency analysis method, the influences of the rotor speed and the crackdepth on the rotor dynamics behavior are analyzed. Besides, the vibrationamplitudes and whirling orbits around the1/2and1/3sub-critical rotating speedsare studied, which is not only helpful to understand the variation law of the crack,but also can be used as the typical features of the crack fault. All these studiesprovide necessary foundations for the crack fault identification.Secondly, based on PXI bus technology, a rotor vibration signal data acquisition(DAQ) system is built in the virtual development environment LabVIEW. The DAQsystem adopts the idea of modular design, achieving the functions of vibrationsignal acquisition, data analysis and real-time data storage. By using this DAQsystem, an experiment is set up in a rotor test bed to verify the theoretical analysis.The whirling orbits and the variations of high-order frequency components duringthe passage through the sub-critical rotating speeds show highly agreement with thetheoretical results, which indicates that the modeling of breathing functions arecorrect.Thirdly, a finite element model (FEM) is constructed by the ANSYS software for the breathing cracked rotor in consideration of contact problem when crack breaths.In a spin cycle,8special status are studied and the vibration displacements obtainedfrom the dynamics model is used as the input of the FEM, then the dynamic stressintensity factor (SIF) at the crack front can be calculated. All these studies arehelpful to understand the breathing crack's mechanical characteristics and providenecessary foundations for fatigue life prediction of a crack rotor.Finally, based on fracture mechanics theory, the Paris law is used to estimate theresidual life of the cracked rotor at given crack depths, and how the depth of thefatigue crack effects its propagation rate is analyzed, which provides the basis forthe rotor performance estimation and the establishment of maintenance decision.