Research On Guided Wave Defect Detection For Pipeline Structure

Nowadays,pipeline structures are widely used.Such as watercourse drainage pipes,waterworks water pipelines,natural gas pipelines and so on.These pipes,applied in every corner of every field,connect the whole human society,and their importance is self-evident.If these pipes are damaged,and can not be timely and accurately detected,it will cause great losses to the society and national economy.Under this background,it is of great significance to detect the damage of pipeline structure.Ultrasonic guided wave nondestructive testing technology has the advantages of high efficiency and low cost in the current structural health testing technology.The damage detection within a certain range has been realized on the pipeline structure,which verifies the feasibility of ultrasonic guided wave nondestructive testing technology for pipeline structure damage detection,and also proves that this method has a broad application prospect.The main work of this paper is as follows:(1)The basic theory of ultrasonic guided wave propagation in pipeline structure is discussed.The dispersion characteristics of ultrasonic guided wave are described,and the principle of damage detection and the selection of excitation signal in pipeline structure are analyzed.Finally,the principle of finite element analysis and the choice of software are described.(2)The propagation mechanism and damage effect of guided waves in pipelines are analyzed.Guided wave propagation mechanism in pipeline structure is modeled and analyzed by finite element method,and ultrasonic guided wave modal calculation is carried out.Finally,the echo characteristics of different types of defects in the pipeline are analyzed.(3)An improved phased array monitoring method for pipeline structure is proposed.The basic principle of phased array is described and the experimental system is introduced.Then an improved experimental scheme based on the traditional phased array is proposed to monitor the phased array damage by placing the sensor group on the tilted pipe.The specific placement rules of sensor array are given to enhance the damage signal and locate the damage.(4)Proposed ultrasonic guided wave detection method in complex pipeline structure,namely two-point method.The simulation analysis of ultrasonic guided wave propagation in pipeline joints is carried out by ABAQUS,and the advantages of two-point method for multi-sensor layout are obtained through comparative tests.Finally,the amplitude and wave packet information of echo signal under two-point method are selected to distinguish damage by quantitative analysis.By calculating the wave packet area,it is concluded that when the difference of the wave packet area between the output data and the health data is greater than the threshold value,it can be judged that there is damage in the pipe joint specimen.