Defect Data Based On Full Focus Ultrasound Detection Imaging Method Research

Phased array ultrasonic testing technology,as one of the new ultrasonic testing technologies,makes up for the shortcomings of traditional ultrasonic testing,and is widely used in industrial nondestructive testing.Then,in order to ensure the real-time imaging,the number of acoustic beams emitted by phased array ultrasound and the number of focusing points are limited,resulting in the detection accuracy and defect characterization ability can not be fully played.Fully focused ultrasonic phased array testing is a post-processing based phased array ultrasonic testing technology,which has higher defect imaging capability than the current conventional phased array ultrasonic testing technology.However,full focused ultrasonic phased array detection technology still has many shortcomings.For example,the angle of conventional signal processing is to directly de-noise the received echo signal data.The analysis angle is single,the cost of experimental equipment is high,and the defect identification of different characteristics needs to be combined with new signal characteristics to complete the defect identification;The attenuation of ultrasonic beam leads to some errors in the received signal itself;In addition,after the completion of defect imaging,based on the traditional full-focusing delay stacking algorithm,the algorithm itself will produce a primitive error due to the diffusion of the isoacoustic path,which has an impact on the enhancement of the defect image.In order to solve the above problems,this paper,based on the full-focus imaging algorithm,takes defect signal processing and image enhancement as the anchor point to carry out the research of full-focus ultrasonic phased array defect imaging method.The main work completed in this paper includes:(1)In view of the problems of expensive ultrasonic testing equipment,high entry threshold and single received signal characteristics.Abaqus software was used to complete the full focus ultrasonic detection simulation analysis of crack defects distributed in different angles,and the characteristics of weld defects were analyzed by obtaining the echo sensitive frequencies of different defects in the software,which provided a certain theoretical basis for the detection and identification of weld crack defects.(2)When the full-focusing imaging algorithm is oriented towards multi-layer media,the energy of the acoustic beam in the wedge coupling model decreases,resulting in the decrease of detection energy and the decrease of the reliability of defect imaging.In this paper,a new improved full-focus imaging algorithm model suitable for wedge coupling detection is proposed.The attenuation coefficients of different transmitting and receiving acoustic beams in the coupling model are measured by plexiglass reflection method,which can be used to correct ultrasonic beam propagation data and improve the energy uniformity and accuracy of the overall defect image.(3)In order to eliminate the original noise and make full use of the collected echo signal data,a phase coherence factor weighted full-focus imaging method based on threshold fusion is proposed.The effective and invalid pixel information is distinguished by the reasonable threshold,which avoids the problem of model selection redundancy and image distortion,reduces the complexity of the algorithm model and improves the imaging resolution.