| Welding structure is the key part of many large workpiece,which has a great impact on industrial production and daily life.Among the numerous detection methods,the ultrasonic guided wave detection method has become the best among the welding joint detection methods because it can detect the internal and external defects of long distance parts by a single scan.An efficient and stable guided wave weld inspection system is valuable.However,the existing system is usually composed of single piezoelectric sensors.In the practical detection of such sensors,due to the irregularities of the weld surface,the sensors are in linear contact or point contact with the weld surface,and the ultrasonic input efficiency is low.In order to improve the detection ability of guided wave in welding joint,this paper designs a welding joint detection system based on array sensor,and proposes an array sensor excitation method based on phased array technology,so that the array piezoelectric chip can produce a cluster of ultrasonic signal with good coupling effect.This paper focuses on the theoretical basis,numerical simulation,hardware design and experimental verification of characteristic guided waves of welding joints.The main research contents and results are as follows:1)Theoretical exploration and simulation verification of phased array technology to achieve array sensor signal focusing.In depth analysis of the existing features and design principle of weld detection system,based on the combination of array sensor characteristics and its mechanism of weld detection is put forward by phased array technology for sensor array more signal focusing method,and respectively from the axial and circumferential and the overall incentive way to verify the correctness of the proposed theory and effectiveness.The simulation results show that the phased array technology can realize the phase non-aliasing and amplitude linear superposition of multiple signals.2)Hardware design of welding joint detection system based on phased array technology is realized.The signal excitation channel with different delay excitation time and phase is set up.The analog amplifying circuit and filtering circuit of the signal excitation portion and the receiving portion are designed,which makes the signals of the signal excitation portion and the receiving portion all meet the application requirements.At the receiving portion,the FPGA is used to design the signal storage,display and communication modules,the whole hardware system is designed.3)The multi-signal focusing function of the array sensor is realized,and the weld detection capability of the phase control system is verified.The experimental platform was built and the designed welding joint detection system was used to test the welding joint.The amplitude superposition and signal coupling of the system were verified respectively.The amplitude of the signal increases linearly with the number of excitation points,and the phase coupling of the signal is good.The positioning accuracy and echo reflectance experiment for four different defects and the leakage wave detection experiment were carried out.It was found that the average positioning accuracy of weld defects was 1.58% higher than the traditional sensor by 3.66%,and the echo reflectance of the end surface and defects was 52.8% and 22.4%,24.1% and 8.2% higher than the traditional sensor respectively.The results of theoretical research,numerical simulation and experimental analysis show that,the array sensor can generate focused signals for weld detection with the application of phase control system,and the effect is favorable,which can provide the necessary foundation for the market development and application of the detection system to improve the efficiency and accuracy of nondestructive testing of weld defects... |
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