Research On Corrosion Damage Detection Based On Laser Ultrasonic Lamb Wave

Corrosion occurs extensively in the industries of national defense,environmental protection,medical and health care,etc.,and the corrosion of steel and iron materials is particularly more serious.According to statistics,the economic losses caused by corrosion damage in China is as high as 520 billion yuan every year.In addition to economic losses,corrosion often induces catastrophic accidents,such as rusting and crashing of aircraft,destruction of oil rotors,and holes in ships' bottoms.Therefore,it is of great academic significance to study the failure mechanism and evaluate mechanical properties of metals after corrosion.Compared with the traditional physical and chemical detection methods,the ultrasonic Lamb wave detection method is of lower cost,which can detect a larger detection area more accurately and rapidly,so it is often used as the main method in industrial fields.In recent years,laser ultrasonic technology has been developed rapidly,and laser ultrasonic Lamb waves are also widely used for corrosion damage detection of structures.Compared with the traditional ultrasonic Lamb detection method,laser ultrasonic Lamb wave detection is faster and has higher resolution,and can eliminate the influence of contact between wave exciting transducers and inspected materials.This paper introduces the research background of ultrasonic detection technology,and analyzes the development of Lamb wave,laser Lamb wave and ultrasonic tomography at home and abroad.Based on the propagation mechanism of Lamb wave,the dispersion equation of Lamb wave and the energy equation of Lamb wave were derived.According to the basic theory of laser ultrasound,a set of automatic laser scanner detection experimental system is designed and developed.The laser experiment system has been used in testing a corroded aluminum plate,in order to study the relationship between Lamb wave energy,amplitude and corrosion,and visualize the damage area with the maximum amplitude.Then,in order to study the mechanism of visualization of corrosion damage further,carry out the experiment of Young's modulus measurement.Finally,we propose the amplitude integral ratio method,which can be used to evaluate the degree of corrosion damage,and demonstrate the effectiveness of the method with an experiment.The successful realization of laser ultrasonic visualization technology has made major changes and breakthroughs in ultrasonic non-destructive testing technology.This technology has changed the way that ultrasonic non-destructive testing results are presented,making the testing results intuitive and visual,and has a wide range of application prospects...