本文關(guān)鍵詞： 磁導體環(huán)形結(jié)構(gòu) 小徑管 脈沖渦流 周向裂紋 有限元仿真　出處：《南昌航空大學》2017年碩士論文　論文類型：學位論文

【摘要】：小直徑金屬管在電力、航空航天、石油能源等行業(yè)應用廣泛。管道的周向裂紋缺陷是一種易導致斷裂的缺陷。常規(guī)的渦流檢測其渦流走向平行于周向裂紋,因而對周向裂紋容易漏檢,其他無損檢測方法由于管徑小管壁薄也不易檢測,而陣列渦流、旋轉(zhuǎn)磁場掃描技術(shù)等先進的無損檢測技術(shù)由于成本高、機械裝置復雜等缺點,在實際檢測中難以大范圍推廣應用。本論文旨在探索一種低成本的對于周向裂紋的檢測技術(shù)。本課題根據(jù)磁場與電場的正交對稱性設(shè)計了磁導體環(huán)形結(jié)構(gòu)傳感器,形成垂直于周向裂紋的電場,利用近年發(fā)展的脈沖渦流檢測技術(shù),對小徑管周向裂紋缺陷檢測進行了研究。首先建立了檢測平臺,然后以實驗研究結(jié)合ANSYS有限元仿真的方式,從探頭結(jié)構(gòu)、激勵電壓以及激勵頻率等方面對小徑管周向裂紋脈沖渦流檢測方法及機理進行了深入研究。項目制作了單層單片式雙激勵、單層雙片式雙激勵以及單層分散式雙激勵三種探頭,通過實驗對探頭結(jié)構(gòu)對檢測效果的影響進行了研究,并進行了仿真分析。實驗結(jié)果表明單片式探頭對小徑管周向裂紋的檢測效果最好,檢測信號的信噪比最好,對0.5mm深以下小尺寸裂紋的檢測能力最強;雙片式探頭對0.7mm深以上大尺寸裂紋具有較好的檢測效果,對小尺寸裂紋的檢測易受到背景噪聲的干擾;分散式探頭檢測效果最差。仿真結(jié)果與實驗結(jié)果相一致。研究了不同幅值的激勵電壓對檢測的影響。實驗設(shè)置了激勵電壓為1V、2V、3V和5V,分別對小徑管試件上三組裂紋缺陷進行檢測。提取管道法向方向磁場數(shù)據(jù)結(jié)果發(fā)現(xiàn):隨著激勵電壓的增大,在檢測較深裂紋時效果逐漸增強;但在檢測淺裂紋時,3V、5V激勵的檢測效果差異不明顯。就信號的信噪比而言,激勵電壓越大,信噪比越高。隨后進行了仿真研究,通過仿真結(jié)果的接收電壓歸一化曲線可以看出,不同激勵電壓下接收信號歸一化值在小裂紋缺陷處區(qū)分并不明顯,與實驗結(jié)果一致。激勵頻率主要影響了脈沖渦流檢測的滲透深度。在50Hz、100Hz、200Hz、300Hz、400Hz、500Hz激勵頻率下進行實驗及仿真分析發(fā)現(xiàn),增大激勵頻率后雖然管道法向方向磁場信號的幅值略有減小,但是信號的信噪比明顯提高,檢測靈敏度增強。
[Abstract]:Small-diameter metal pipes are widely used in power, aerospace, petroleum and energy industries. The circumferential crack defects of pipelines are a kind of defects that lead to fracture. The conventional eddy current detection of the eddy current direction is parallel to the circumferential cracks. Therefore, the circumferential crack is easy to be detected, other nondestructive testing methods are difficult to detect because of the thin tube wall with small diameter, and the advanced nondestructive testing technology such as array eddy current, rotating magnetic field scanning technology, etc., due to the high cost. The mechanical device is complex and so on. The purpose of this paper is to explore a low-cost detection technique for circumferential cracks. Based on the orthogonal symmetry of magnetic field and electric field, a magnetic conductor ring structure sensor is designed. . In order to form an electric field perpendicular to the circumferential crack, the detection of the circumferential crack defects in the small diameter tube is studied by using the pulse eddy current testing technique developed in recent years. Firstly, the detection platform is established. Then with the experimental study combined with the ANSYS finite element simulation method, from the probe structure. The method and mechanism of pulse eddy current detection for circumferential crack of small diameter tube are studied in detail from the aspects of excitation voltage and excitation frequency. Single layer single chip double excitation is made in the project. The influence of the structure of the probe on the detection effect was studied by experiments. The experimental results show that the single-chip probe has the best detection effect on circumferential crack of small diameter tube and the best signal-to-noise ratio (SNR) of detection signal, and the best detection ability for small size crack below 0.5 mm depth. The double-chip probe has a good effect on the detection of large size crack over 0.7 mm depth, and the detection of small size crack is easily disturbed by background noise. The effect of the distributed probe is the worst. The simulation results are consistent with the experimental results. The effects of different amplitudes of excitation voltage on the detection are studied. The excitation voltage is set to be 1V / 2V ~ (3V) and 5V in the experiment. Three groups of crack defects on the specimen of small diameter tube were detected respectively. The results of extracting the normal magnetic field data of the pipe show that the effect of detecting the deep crack increases gradually with the increase of the excitation voltage. However, there is no significant difference in the detection effect of 3V / 5V excitation when detecting shallow cracks. As far as the signal to noise ratio is concerned, the greater the excitation voltage, the higher the signal-to-noise ratio (SNR). Then the simulation study is carried out. Through the simulation results of the received voltage normalization curve, it can be seen that under different excitation voltage, the difference of the received signal normalization value in the small crack defects is not obvious. The results are in agreement with the experimental results. The exciting frequency mainly affects the penetration depth of the pulsed eddy current detection. The experiment and simulation at 500Hz excitation frequency show that the signal-to-noise ratio (SNR) and detection sensitivity of the signal to noise ratio (SNR) of the normal magnetic field signal decrease slightly after increasing the excitation frequency.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG115.28

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