Research On Detection Technology For Corrosion Fatigue Damage By Nonlinear Surface Wave

Metal materials are widely used in the sea,and their applications are commonly seen in industries such as ships and offshore oil extraction.In the process of long-term service,metal materials are subjected to corrosion of complicated corrosion environment and the impact of strong winds and waves.Corrosion fatigue damage is one of the main forms of damage,which seriously affects the durability and safety of metal components and equipment.However,the traditional ultrasonic testing technology can not achieve the detection of corrosion fatigue damage of metal materials,and the nonlinear Rayleigh surface wave can detect the change of nonlinear characteristic parameters in the corrosion fatigue damage of metal materials.Therefore,using non-linear Rayleigh surface wave detection technology to study the degree of corrosion damage of metal materials has important theoretical value and engineering application value.This paper introduces the basic principles of nonlinear ultrasonic testing,formulates the experimental scheme of metal materials samples corrosion damage and nonlinear ultrasonic testing system for,studies the Rayleigh surface wave detection method,analyzes the influence of the experimental system,the number of the excitation electrical signal,the propagation distance of the Rayleigh surface wave and the spectral characteristics of the transducer on the experimental results.Based on the Rayleigh surface wave detection method,the fundamental amplitude and second harmonic amplitude of the Rayleigh surface wave are detected,the acoustic nonlinear coefficient is calculated,and the changes of acoustic nonlinear coefficient under different cyclic tensile fatigue cycles is obtained,and so as to achieve the nonlinear ultrasonic testing of corrosion damage of metal materials samples.The main contents include:(1)Studying the effects of different corrosive environments on corrosion fatigue damage of metal materials;(2)Studying the effects of different loadingfrequencies on corrosion fatigue damage of metal materials;(3)Studying the effects of different stress ratios on corrosion fatigue damage of metal materials;(4)analyzing the micro-structure of metal materials.The experimental results show that the different corrosive environments have a greater influence on the corrosion fatigue damage of metal materials;the different loading frequencies have little effect on the corrosion fatigue damage of metal materials;the different stress ratios have a greater impact on the corrosion fatigue damage of metal materials;There is a certain relationship between the ultrasonic nonlinear coefficient,the micro-structures observation of the metal material and the macro-properties,the ultrasonic nonlinear coefficient can be used as the middle of the micro-structures observation and macro-properties of the metal materials to characterize the process of corrosion fatigue damage of metal materials,and provide a certain basis for the detection of corrosion fatigue damage of metal materials by nonlinear ultrasonic.