Research On Laser Ultrasound Technology For Detection Of Surface Defects In Additive Manufacturing

Additive manufacturing technology has developed rapidly in recent years and has been widely used in industry.At present,the research on quality control of additive manufacturing technology at home and abroad mainly focuses on the mechanical properties of processed materials,and there are relatively few studies on defect detection of additive manufacturing components.The defects of the additive manufacturing component directly affect the characteristics and performance of the material,causing huge losses to the equipment.Therefore,it is important to realize the surface defect detection of the additive manufacturing component.As a new type of detection method,laser ultrasonic technology is increasingly used in complex industrial inspection.This paper systematically carried out research on laser ultrasonic surface defect detection technology in additive manufacturing.Based on the laser ultrasonic technology,this paper analyzes the ultrasonic pulse characteristics and propagation characteristics of the excitation light excited on the additive manufacturing components.On the basis of theoretical analysis and research,the experimental system of laser ultrasonic deflection detection using pulsed laser excitation and continuous laser detection is determined.A laser ultrasonic experimental system was set up to test the surface defects of the samples of the simulated additive,and the detection accuracy reached 0.2 mm.In this context,it is defined that the defects within a thermal diffusion length from the surface are surface defects.The influence of the excitation laser parameters on the ultrasonic waves is analyzed.When the excitation optical power density increases,the amplitude of the excited acoustic waves increases,and the corresponding spectral center frequency shifts to the high frequency.The ultrasonic signal is analyzed based on various methods of time domain,frequency domain and time frequency of the photoacoustic signal to determine the defect position.The average signal and wavelet are used to increase the signal to noise ratio of the ultrasound signal.The influence of the defect size parameter on the ultrasonic wave is verified.As the defect size decreases,the center frequency of the ultrasonic signal moves toward the high frequency as the defect becomes smaller.