Research On The Method And Application Of Fluid Pipe Strain Measurement Based On Fiber Bragg Grating Sensing

The hydraulic system is widely used in modern industry due to the advantages of large power density,high reliability,etc.Pipelines are important component of the hydraulic system,and work in the environment of high temperature,high pressure and strong vibration.Vibration induced by multiple excitation coupling usually cause system failures.Therefore,the study of vibration and strain is an important part of the health monitoring and fault diagnosis of the pipeline system.In this dissertation,strain detection system based on fiber grating sensors was built aiming at the problem of strain detection of hydraulic pipelines.Firstly,the experimental system of hydraulic pipeline was established and the vibration characteristics of the pipeline were analyzed.Secondly,the pipeline strain detection method of fiber grating was studied and the detection system was established.Thirdly,the strain pipeline was tested and analyzed under different loads by the system.The accuracy of fiber grating strain detection was verified.Finally,the strain detection system was applied to the identification of the looseness of the clamp.The main tasks of this dissertation are:1.The current status of pipeline strain detection and fiber grating sensing at home and abroad is analyzed.Based on the existing strain detection problems and the advantages of fiber grating sensors,the application of fiber grating sensors in distributed detection of pipeline strains is proposed.2.The strain measuring method based on fiber grating was studied in pipelines according to the strain detection principle of fiber grating.The data processing method was analyzed on the basis of the vibration state and strain characteristics of hydraulic pipelines.The sensor layout problem is discussed and the pipeline strain detection system was established based on the FBG sensors.3.The applications of fiber grating strain detection system in dynamic characteristics experiment and pipeline strain detection under different simulation conditions were studied.In the modal experiment,the obtained natural frequency is the same as the accelerometer test result,and the strain mode is the same as theoretical results.The vibration mode is consistent with the theoretical analysis result.Under the constant pressure load,the axial strain of pipeline is proportional to the internal pressure,under the pulsating pressure,the strain signal can accurately reflect the pressure pulsation frequency.Under the effect of basic motivation,the strain detection system can detect the strain distribution state of pipelines.4.The application of distributed fiber grating strain sensing system in the detection of clamp looseness was studied.Under the action of hammering excitation and fluid excitation,the strain response of the pipe before and after the clamp looseness was measured;by analyzing the changes of strain mode and energy distribution,to achieve of clamp looseness fault was identified.