| This thesis focuses on the theoretical analysis of ACFM and the prototype development, including simulation analysis of magnetic-circuit couple, design and optimization for intelligent recognition and visualization probe, electromagnetic signals processing based on hardware and software, development and industrial application of ACFM prototype and so on, which is sponsored by Scientific and Technological Development Projects in shandong province (No.2007GG10005004). The main research progress is summarized as follows:(1) Theoretical research and numerical simulation analysis of ACFMCombined with principle of ACFM and theory of numerical calculation, mathematical model of ACFM defect recognition and calculation method of crack depth are presented. In order to analyze the distribution of electromagnetic field and the impact of various parameters on the results, simulation analysis of two-dimensional electromagnetic–circuit coupled is introduced and the common circuit elements that can be used for linear circuit simulation provided by ANSYS are introduced. All of this can provide theoretical basis for the future experimental research.(2) Series design of probeThe induced simulation model of inducer with different parameters is built based on ANSYS, and then discussed the relationship between parameters of the inducer and the induced electromagnetic field distribution. This provides the theoretical foundation to design and optimize the probe. To achieve better effect, overall structure of every kinds of sensor is designed including standard single probe, surface detection probe, pen probe and array probe that with reasonable size and shape of inducer coil. The application situation and environment of every kinds of probe are different. Standard single probe has high sensitivity which can be used in any situation, and surface inspection probe is mainly used for surface detection and pen probe can be used in the narrow zone. The array probe can increase the detection area and improve the detection rate. The results show that the probes have a high sensitivity when they are used to detect the workpiece.(3) Study on prototype for ACFMACFM system is set up for the purpose of industrial application, including design of hardware and software parts. Firstly, the primary signal process is realized by designing signal producing and processing circuits. Then, the analog signal is acquired by data acquisition card, which processed by digital signal acquisition and processing software modules compiled by Labview language. Considering the methods of combining hardware and software, system can amplify weak signals and suppress noise, this method simplifies hardware circuit and economizes the cost of system development. This system can achieve the visualization of the defect intelligent and visual recognition, which provides the foundation for industrial application and industrial test.(4) Industrial application of ACFM prototypeSome important industrial parameters that affect the technical index of ACFM prototype are tested, the results show that the system has a high detection speed and lift-off height without distortionless, and influence of cable length to Bx is small but greater than Bz in certain extent. Moreover, in-line equipment having crack-free, axial cracks, radial cracks and sub-surface cracks can also be detected by this system, the results show that system have a high detection accuracy, they can achieve real-time discrimination and intelligent quantifying recognition. In addition, the system can be more accurate in discription of defect shape. |
