Research On Key Techniques Of Automatic Phased Array Ultrasonic Imaging Inspection For Steel Pipes

Steel pipes,as the main material of the pipe,have huge impact on national economy and people's lives,and the quality directly determines the operating performance and service life of related equipment,so the demand for non-destructive testing(NDT)has always been very strong.In a variety of non-destructive testing methods,ultrasonic NDT,with its high safety,rich acoustic information and various combination to information technology,has become an effective means of quality control for steel pipes,and is moving towards the direction of phased array ultrasonic technology.Especially,besides the common advantages of ultrasonic NDT,phased array ultrasonic NDT also has a flexible synthetic beam and adaptive control capability,and can effectively reduce the blind zone,thus,it is of obvious technological advantage in steel pipe inspections.However,with the increased production capacity and strict quality control of steel pipes,traditional manual testing method has been increasingly difficult to meet the modernization needs,thus the demand for automatic ultrasonic testing technology is increasing strong.According to the background above,supported by the National Science Foundation Project "Research on theory and practice of automatic online ultrasonic nondestructive testing with high performance based on rotating acoustic field(NO.51175465)",the research on key techniques of automatic phased array ultrasonic imaging inspection for steel pipes was put forward in this dissertation.Based on analysis of related theory and inspection methods,phased array acoustic field model in steel pipes was established to solve the problem of real-time high resolution imaging and result friendly representation.What's more,combined with mechatronic technique,an online phased array acoustic imaging and experiment inspection system for steel pipes was developed,and related experiments was carried out,laying a theoretical and applied foundation for automatic acoustic imaging inspection for steel pipes.The detailed contents of this dissertation were presented as follows:In chapter one,the important position of steel pipes in national economy and people's lives,together with research significance of phased array ultrasonic NDT for steel pipes were introduced,and the research status and development trends of phased array ultrasonic NDT technique was systematically summarized.The problems on technology of phased array ultrasonic imaging inspection for steel pipes are pointed out to clarify the main research of this paper and indicate the direction for the following chapters.In chapter two,based on principle of beam forming and control,phased array acoustic field model in fluid was established using Rayleigh integral,and common phased array ultrasonic imaging inspection techniques for steel pipes were introduced.Meanwhile,the functional goals and the diagram of the automatic phased array imaging inspection system for steel pipes were pointed out,which lay a theoretical and applied foundation for the following chapters.In chapter three,research on phased array acoustic field modeling based on DPSM was carried out.By using DPSM theory the acoustic filed in fluid and solid medium were numerically simulated.Meanwhile,according to characters of applications of phased array ultrasonic nondestructive testing for steel pipes,the theoretical calculation on phased acoustic field for wedge-steel interface was established.Furthermore,by analyzing the influence of different transducer parameters on the phased array acoustic field using the established model,the goal of inspection parameter optimization and focusing of acoustic beam in the region of interest of steel pipe are reached.In chapter four,research on phased array ultrasonic imaging for steel pipes and friendly representation of results were carried out.According to the characters of spiral scan imaging and pitch inconsistency in practical application,after dynamic extraction of A scan inspection data,the extracted data was dynamically resampled using bilinear interpolation,relationship between the spatial coordinates and the detection data was established,and phased array ultrasonic C scan imaging of steel pipes under the spiral scanning mode was realized.Meanwhile,by using partition RGB color mapping strategy,the imaging data was transformed with high contrast resolution,and the phased array imaging results for steel pipe was finally friendly represented.In chapter five,adopting the distributed architecture and modular design strategy,with our own research and development of the phased array ultrasonic testing instrument as the core component,after processes of hardware design and software development,an automatic online phased array acoustic imaging inspection system for steel pipes was successfully developed.Meanwhile,the practical experiment of seamless steel pipe is performed on this system to verify the feasibility and effectiveness of relevant theory and techniques proposed in this dissertation.In chapter six,the research achievements and the innovative points of this dissertation were summarized,and the future research works were also forecasted.