Research On Ultrasonic Phased Array Detection For Sector Scanning Imaging

Ultrasonic phased array technique makes the beam-forming which can be sent and received by array transducer flexibly controlled through exciting the phase of each element accurately,so as to achieve the omnidirectional and multi-angle beam scanning of mechanical structure or parts,and then the internal characteristics of the detected objects are visually displayed in the form of images.Aiming at the actual situation of industrial ultrasonic testing,the thesis the algorithm of sector scan delay calculation and imaging correlation of phased array is studied in the thesis.The scheme uses B-type phased array test block to test and verity the algorith is designed.At the same time,the related factors affecting the image quality of sector formation are analyzed.Based on the principle of ultrasonic phased array detection,the realization process of deflection,focusing and deflection focusing of synthetic beams is studied,and the delay time rule is obtained by combining the geometric acoustic principle.The calculation formula and algorithm flow chart of sector scan delay time of ultrasonic phased array are given,the program of equal-path focusing is compiled,xwhile the delay curxve is given with an example.The image formation algorithm of ultrasonic phased array detection sector scan is studied.In this paper,the A-scan data matrix is obtained by controlling the delay of transmitting and receiving the signal.Then the sector scan image is obtained after coordinate correction.The flow chart and the specific algorithm steps are given,as well as the sector-scan schematic diagram of the imaging area.Four commonly used image interpolation algorithms are compared.Bicubic interpolation algorithm has the best effect in terms of image quality and running time.A good sector scanned ima.e is obtained by combining the interpolation algorithm with mathematical morphology filling method.The test scheme is designed using the existing Verasonic Vantage 64 hardware system in the laboratory,two different types of cross-hole areas in the B-type phased array test block are selected to carry out the experiment,and two sector scan images of the areas are both obtained.The imaging results are similar to the actual defect information,nearly without missing detection,and the location information is accurate.The validity and reliability of the sector scan and imaging algorithm of phased array are proved,and the causes of errors are analyzed in many aspects.Based on the basic principle of ultrasonic phased array technology,the focusing depth,the deflection angle and the time compensation gain as the main parameters that involved in phased array ultrasonic sector scan detection are analyzed,and the effects of these three parameters on sector scan detection and imaging quality are studied by using control variable method.