Development Of Phased Array Ultrasonic Zone Discrimination System For Pipeline Girth Welding

Pipeline is widely used in various fields,and weld is the basic craft for the application of pipeline.So,it is bound to exist a lot of weld in the pipeline.However,weld has the poorest performance in the pipeline system,and the quality of girth weld has a significant impact on the safe operation of pipeline.So,quality testing and evaluation must be made.Although,there are many non-destructive testing methods,ultrasonic non-destructive testing has became the major method for the detection of girth weld with the advantages of ability to carry abundant information,strong penetrating power,high resolution,harmless to human beings and various combination to information technology.But with the growing of pipeline’s applications,especially for the applications in the sky and underground,traditional manual ultrasonic testing is difficult to meet the development needs of the pipeline in the respects of efficiency and accessibility.On the other hand,weld has a strong demand for the method of quantitative ultrasonic NDT with the development of ultrasonic non-destructive evaluation.Zone discrimination is an effective way for the quantitative ultrasonic NDT of weld,taking the features of weld into account.The traditional zone discrimination which using multi-probes is facing challenges in adaptability and testing performances.According to the background above,the development of zone discrimination system for pipeline girth welding based on phased array ultrasonic is carried out in this dissertation with the support of National Natural Science Foundation of China(No.51675480).On the basis of learning the zone discrimination of girth weld,phased array ultrasonic imaging,the research status and development tendency of related technology,the theoretical foundation of phased array ultrasonic imaging is established and the functional goals of zone discrimination system for pipeline girth weld based on phased array ultrasonic is pointed out.Meanwhile,by accomplishing the research on key techniques of beam forming and control for phased array acoustic,compound ultrasonic imaging system and the expression of testing result for high resolution of girth weld,a zone discrimination system for pipeline girth weld based on phased array ultrasonic is developed,laying applied foundation for the quantitative ultrasonic NDT of girth weld defects.The main research contents and innovation points are as follows:In chapter one,illuminated the significance of the material transportation with pipeline and the importance of research on girth weld NDT.On the basic of summarizing the research status and development tendency of pipeline non-destructive testing systematically,the challenge that pipeline girth weld NDT facing was analyzed and the zone discrimination system for pipeline girth welding based on phased array ultrasonic was clarified as the main research of this paper.Meanwhile,the research direction of quantification and automation was advanced and the direction of the following chapters was indicated.In chapter two,according to the wave equation and the distribution of point source acoustic field,on the basic of inferring the distribution of single rectangular piston source by using Rayleigh Integral,the beam forming and control of phased array piston acoustic transducer was realized.At the same time,overall implementation plans of the zone discrimination system for pipeline girth welding based on phased array ultrasonic was designed,the modules of function were divided and the key techniques to be solved was explicated.In chapter three,theoretical research on the phased array zone discrimination acoustic field was carried out.The theoretical calculation of focusing acoustic field for uniform medium and layered medium were accomplished,and the influence of different transducer parameters on the phased array focusing acoustic field were analyzed.Meanwhile,selecting the focusing position for each zone discrimination area in weld as the start point,according to the thickness of the pipeline and the relative locations of phased array transducers,the indexes of the transducer elements those participate in the process of transmit and reception were calculated by using Fermat Theory and focal law for zone discrimination of weld was established resulting in the forming and controlling of the testing beam.In chapter four,research on the phased array zone discrimination imaging techniques was carried out.On the basic of realizing the control of mechanical scanning movement and coupling water for probes,compound ultrasound imaging for weld was realized by combining strip map of double-gates,B-Scan imaging and TOFD imaging which strip map of double-gates represents the time and amplitude in zones,B-Scan imaging represents the distribution of transverse defects in weld,and TOFD imaging represents the tiny defects in the center area of weld.Representing the defects of weld roundly,accurately and quantitatively can be realized in this way.In chapter five,aided with distributed architecture and modular design strategy,making multimodal communication bus as an information transmission bridge,on the basic of developing scanning machine,the module of movement based on CAN bus,testing board for array phased ultrasonic based on PXI bus and the module of software,the phased array ultrasonic zone discrimination system for pipeline girth welding was developed.At the same time,an experimental study to test the artificial block was carried out to demonstrate the feasibility and effectiveness of the techniques in this paper.In chapter six,research contents of this paper were summarized,and the future research works were also forecast.