Research On Damage Detection Techniques For Pipeline Based On Guided Ultrasonic Waves

As indispensable weaponry in modern war,safety and reliability of artillery are widely concerned.According to statistics,barrel damage is one important cause of artillery accident,so it is of significance that barrel damage is timely detection and measures are taken to avoid disastrous accident.Currently barrel detection technology is mainly confined to surface damage with low detecting efficiency and accuracy.Recently,guided ultrasonic wave detection technology has received more and more attention for its advantage of high detection efficiency,wide detection range and the ability to detect inner damage.The method detects and evaluates damage according to reflection and scattering occurring while ultrasonic wave propagates in the structure.The principle of guided ultrasonic wave detection is relatively simple,but many problems still needs to be further researched if it is applied to artillery barrel which is complex pipe-like structure.The study includes mechanism of interaction between damage and guided ultrasonic wave,damage feature extraction method,damage localization method.Aiming at the abovementioned problems,this dissertation carries out the research on theory,simulation and experiment of propagation characteristics of guided ultrasonic wave in the pipe-like structures,signal processing algorithms,damage detection and localization and the application of nonlinear ultrasonic in micro-crack damage detection.1.The propagation characteristics of guided ultrasonic wave in pipe and interaction law of guided ultrasonic wave and damage are discussed.The fluctuation equation of guided wave in pipe is derived from Navier equation.Dispersion characteristics and wave structural properties of guided ultrasonic wave in pipe are analyzed by numerical calculation.The finite element model of interaction between guided ultrasonic wave and damage is established using ANSYS.Interaction law between damage and guided wave is acquired from simulation results.All the work above provides a theoretical basis for construction of experiment system and selection of experimental parameters.2.The experimental research of pipe structure damage detection based on guided ultrasonic wave is carried out and guided wave signal processing algorithms are studied.In the basis of theoretical analysis,experimental system is set up and pipe structure damage detection experiment is carried out.Guided wave signal is non-stationary and of multi-component.Hilbert-Huang transform is selected as guided ultrasonic wave processing method.The damage characteristic parameters are extracted and the axial localization of damage is realized.Error cause and influencing factors are analyzed.3.Guided ultrasonic wave enhance detection method based on time-reversal is studied.Aiming at the problem of inaccurate localization due to dispersion and multi-mode effect,time-reversal is applied to ultrasonic guided wave detection.Time-reversal field expression is theoretically derived,demonstrating the time-space focus effect.Time-reversal guided ultrasonic wave detection experiment is carried out.The experimental result shows that time-reversal can suppress dispersion and multi-mode effect and make energy adaptively focus.Time-reversal can also increase the amplitude of damage echo and enhance axial localization accuracy of damage.4.The application of nonlinear modulated ultrasonic guided wave to pipe structure micro-crack detection is explored.Aiming at the problem of non-sensitivity of linear guided ultrasonic wave to micro-crack and closed-crack,the application of nonlinear modulated guided ultrasonic wave to pipe structures micro-crack and closed-crack detection is explored.The experimental result shows that nonlinear modulated guided ultrasonic wave is more sensitive to micro-crack and closed-crack compared with linear guided ultrasonic wave.