| Rub-impact fault is a common fault in rotating machinery.Acoustic emission detection technology has the characteristics of high response sensitivity,wide frequency response range and rich frequency components,and has unique detection advantages in rub-impact fault diagnosis.Phase-shifted fiber grating has the characteristics of anti-electromagnetic interference,light weight,high sensitivity and easy integration.In this paper,the fiber grating sensing technology and acoustic emission technology are combined to carry out the research on the rub-impact fault detection technology of rotating machinery.In this paper,the rub-impact mechanism and acoustic emission dispersion theory of rotating machinery are analyzed,and the magnetic suction fiber grating rub-impact acoustic emission sensor is designed.The strain wave propagation process of acoustic emission signal in shaft parts and the response characteristics of the sensor are simulated and studied.The nut screw rub-impact acoustic emission trigger device is designed,and the fiber grating demodulation experimental system based on tunable laser is built.The experimental study of fiber grating for rub-impact acoustic emission of rotating machinery is carried out.Firstly,the feasibility of fiber grating used in acoustic emission signal detection element is analyzed,and a magnetic fiber grating acoustic emission sensor is designed.Through the study of acoustic emission signal waveform effect,guided wave theory,pilot characteristics,draw the dispersion curve in the shaft parts.The finite element simulation was used to study the propagation process of ultrasonic signal in shaft parts,and the maximum stress on the sensor was found to determine the paste position of the fiber grating grating grating area.According to the sensing principle of fiber grating,the fiber grating is applied to the rub-impact acoustic emission signal detection of rotating machinery.A detection system based on tunable laser with fiber grating as the sensing element was built,and the optical intensity signals were detected by balanced photodetector and tunable gain photodetector,respectively.A nut screw-screw rub-impact device for generating acoustic emission signals of rub-impact of rotating machinery was designed.The rub-impact acoustic emission trigger device is used to simulate the rub-impact acoustic emission signal transmitted in the transmission chain when the machine is running.The static and dynamic rubbing signal experiments were carried out,and the time-frequency analysis and energy spectrum analysis were carried out using the short-time Fourier transform and the Hilbert-Huang transform.The fiber grating on the bearing seat and the fiber grating on the bearing get similar time domain signals and similar principal frequency components.The fiber grating on the bearing seat can be used for the detection of the acoustic emission signal of the rub impact on the bearing.The experimental study of dynamic rub-impact acoustic emission detection under the condition of rotating machinery operation was carried out.The sensing performance of fiber grating and traditional piezoelectric ceramic acoustic emission sensors on dynamic rub-impact acoustic emission signals was compared.Compared with piezoelectric ceramics,fiber grating can simultaneously sense the rotating speed and rub-impact acoustic emission signals of rotating machinery,and has more abundant signal characteristics.The strength of the detection signal meets the requirements of online monitoring.Finally,the experimental study of phase-shifted fiber grating for rub-impact acoustic emission signal is carried out.Compared with ordinary grating,phase-shifted fiber grating has better signal to noise ratio. |
