Research On Detection Technology Using Ultrasonic Surface Waves

The flaw and residual stress can affect the the comprehensive performance of mechanical components,especially mechanical properties and fatigue life.It is a focus in the industry and academia at home and abroad that how to detect the flaw and residual stress of components quickly and nondestructively.The paper studies two types of ultrasonic waves which are the Rayleigh wave and the critical refraction longitudinal wave(LCR wave)to solve flaw and residual stress detection problems.The technology of air-coupled testing flaw by the surface wave is studied based on the Rayleigh wave propagation theory.Based on LCR wave theory the ultrasonic residual stress measurement technology of composites is studied.In this paper,the research background and significance of the flaw and residual stress are firstly introduced.And the research status of detection technology by the surface wave,air-coupled ultrasonic testing technology,LCR wave testing technology and composites stress detection technology are summarized.It is known that flaw and residual stress detection technology researches are necessary.Then the theoretical formula of the Rayleigh wave vibration and propagation is deduced.The generation and features of the Rayleigh wave are introduced.The attenuation and impedance characteristics of the ultrasonic wave in the air are studied and the difficulty of air-coupling is presented.These are the basis of the construction of air-coupled detection system using the surface wave.Based on acoustoelasticity theory,the relationship between ultrasonic velocity and stress wave is researched.The excitation mode of LCR wave is introduced and the theoretical formula of LCR wave detection method is deduced,which lay the theoretical foundation for the construction of detection system using LCR wave.Based on the theoretical basis,air-coupled detection system using the surface wave and ultrasonic testing system of the composite material residual stress using LCR wave are built.The paper introduces the main hardware components of air-coupled detection system.The excitation and reception of the Rayleigh wave are achieved though the detection system.Further the feasibility to detect surface flaw by the surface wave air-coupled method is studied.The hardware and software components of the residual stress ultrasonic testing system are introduced.The calculation algorithm of the software is analyzed.The feasibility to employ the LCR wave to measure residual stress of composites is studied by tensile test for two typical composites.The detection technologies of air-coupled ultrasonic surface wave and composites residual stress have a good prospect.It is of great practical significance to carry out theoretic and experimental research,explore their detection laws and perfect these detection techniques.