Research On Damage Identification Technology Of Pipes Based On Strain Modal Analysis

Pipelines are important transportation carriers in the transportation industry,which serve as a special means of transporting oil,gas and water resources.With the gradual improvement of the establishment of the national industrial layout,many pipelines for domestic and industrial use have been in service for a long time and have formed various forms of damage,such as cracking,perforation and rusting,due to natural or man-made influences.Unstable pipeline conditions in operation can cause serious economic losses and safety incidents.Therefore,how to prevent pipeline damage and detect the location of the damaged pipeline in time is an important subject of research.Based on the above research background needs,this thesis is dedicated to the research of a monitoring system that can be used to identify the location of pipe damage and its damage magnitude.This thesis uses Fiber Bragg Grating(FBG)sensing technology as the hardware base and structural strain mode vibration as the damage identification parameter to carry out the research.Based on the strain transfer theory,two types of encapsulated FBG sensors for pipeline structural deformation testing were designed for pipeline overall and local range monitoring,and their dynamic sensing performance was experimentally demonstrated and analyzed.Then,in order to verify the reliability of the designed FBG sensor devices for practical engineering monitoring and the feasibility of the strain power spectral density transfer ratio method for practical application,this thesis designs a sine sweep vibration and pulse sweep vibration experiment of the pipeline,and the strain modal parameters of the pipeline were obtained by post-processing the output data of the packaged FBG sensing element using the strain power spectral density transfer ratio method.Finally,this thesis establishes a set of pipeline damage identification algorithm,using ANSYS to simulate the working conditions of eight different damage states of the pipeline,and establishes the Structural Damage Indicator(SDI)and damage determination thresholds based on ANSYS calculation data,which can identify the location of pipeline damage in the pipe axis and can estimate the damage degree of the damaged location under specific working conditions.It can be concluded from the research of this thesis that the damage identification system based on FBG monitoring information and strain power spectral density transfer ratio method has better stability and damage identification accuracy,which can identify the damaged location of the pipeline and estimate the magnitude of damage.