Ultrasonic Rayleigh Wave-based Surface Defect Detection And Device Development Of Additive Manufacturing Components

With the widespread use of additive manufacturing technology in various fields,the quality of the metal components formed by it has attracted much attention.Surface integrity of materials,especially damage defects such as surface cracks,limits the popularization and application of key metal additive manufacturing components under specific service conditions,so how to detect and evaluate surface defects in a timely manner is an effective way to reduce the occurrence of industrial accidents.Non-destructive testing technology is favored for its advantages of fast detection speed,high accuracy,low cost,green health,etc.Especially the ultrasonic Rayleigh wave is characterized by its long distance propagation on the surface of the material,and its waveform signal can contain a large amount of material surface information,is an important means of non-destructive evaluation of the material surface mechanical properties.Based on Rayleigh wave detection,this paper quantitatively characterizes the groove defects of different depths on the surface of the additive manufacturing specimens by the minimum reflection method,and develops an ultrasonic scanning platform that can detect additive manufacturing components,which provides a surface defect detection new means of representation.The testing instrument independently developed in this paper is a multi-functional and high-precision ultrasonic scanning platform,which is mainly composed of mechanical structure,hardware configuration and control software.The main testing components used are water-immersed flat probes,DPR300 transmitter and receiver,and6 motors.Control,can realize the automatic component surface defect detection function of ultrasonic front-end methods such as single/dual probe C scanning,Rayleigh wave,Lamb wave and so on.According to the actual mechanical properties of stainless steel specimens formed by additive manufacturing technology,a"liquid-solid coupling"finite element simulation model was established.According to the actual material mechanical parameters formed by the material manufacturing technology,the elastic modulus is165GPa,the Poisson's ratio is 0.3,the density is 7980kg/m~3,and the longitudinal wave velocity is 4683m/s,the shear wave velocity is 2503m/s.The Rayleigh wave velocity is 2318m/s,and the first and second critical angles and Rayleigh angles are 18.46°,36.33°and 39.8°,respectively.The designed"liquid-solid coupling"finite element simulation model uses the minimum reflection angle as a characterization method.When the incidence angle changes from 36.5°to 41°,the relationship between the reflection coefficient of each defect depth and the incidence angle is explored.The relationship between the minimum reflection angle and the depth of the defect.The analysis of the simulation results shows that the position of the minimum reflection coefficient without defects at a incidence angle of 40°is in good agreement with the theoretically calculated 39.8°Rayleigh angle;The incidence angle of the defects of different depths studied in this paper There is a certain deviation from the change curve of the reflection coefficient relative to the case of no defect,and the position of the minimum reflection coefficient of the defect is less than the Rayleigh angle;For defects of different depths,as the depth of the defect increases,the position of the minimum reflection coefficient occurs the minimum reflection angle gradually increases;Near the Rayleigh angle(40°?40.3°),the reflection coefficient is linearly related to the depth of the defect,and as the depth of the defect increases,the reflection coefficient becomes smaller.The above linear relationship can be used to characterize the depth of different defects on the surface of the component,which shows that Rayleigh wave is an effective means to characterize the depth of surface defects.