本文選題：小徑管焊縫　切入點：弱磁檢測　出處：《南昌航空大學》2016年碩士論文　論文類型：學位論文

【摘要】：小徑管被廣泛應用于電場設(shè)備中,焊接是其最普遍的連接方式。輸送介質(zhì)是小徑管最常見的功能,長期帶壓運行,工作環(huán)境惡劣,對其焊接質(zhì)量帶來了很大的挑戰(zhàn),無論是在焊接加工時,還是在長期運行過程中均需要質(zhì)量檢測。在傳統(tǒng)檢測條件下,對小徑管焊縫實施全覆蓋式檢測需要多種檢測方法的結(jié)合,效率很低。針對這一狀況,本文提出將弱磁檢測應用在小徑管焊縫檢測中,實現(xiàn)常見類型缺陷的快速檢測。本文首先分析了弱磁檢測的技術(shù)原理與小徑管焊縫的特征,指出了其檢測的難點,并利用仿真計算論證了小徑管焊縫弱磁檢測的可行性。根據(jù)小徑管焊縫的幾何形態(tài)及缺陷信號特點提出了三種檢測方案:旋管法向檢測、側(cè)向掃查檢測和法向掃查檢測。然后,采用便攜式弱磁檢測設(shè)備對兩個小徑管焊縫試件進行檢測,并對三種檢測方案的結(jié)果進行分析。前兩種檢測方案的結(jié)果曲線比較明顯,結(jié)合經(jīng)驗即可完成簡單的缺陷評判,利用小波分析消除了法向掃查檢測時的背景磁場干擾信號,成功的提取到了缺陷信號。與DR檢測結(jié)果進行了對比,驗證了各個檢測方案的有效性,并總結(jié)了各個方案的優(yōu)缺點。最后,針對缺陷定性的困難,提出了一種缺陷識別算法,能夠減少經(jīng)驗判斷帶來的誤差。將缺陷歸為裂紋類與氣孔類兩大類,利用小波包能量譜作為缺陷的特征參數(shù),根據(jù)距離判別分析法建立了缺陷的分類識別模型。應用小徑管焊縫缺陷樣本數(shù)據(jù)訓練模型,確定了缺陷分類的判別函數(shù),并對預留的20組缺陷樣本進行了識別,識別結(jié)果顯示:氣孔的識別準確率達到70%,裂紋的識別準確率達到90%,驗證了缺陷識別模型的有效性。弱磁檢測方案及缺陷識別技術(shù)的研究為小徑管焊縫的快速檢測提供了新的方法與思路。
[Abstract]:Small diameter tube is widely used in electric field equipment, welding is the most common connection mode, conveying medium is the most common function of small diameter tube, it has long run with pressure and bad working environment, which brings great challenge to its welding quality. Both in welding process and in long-term operation, quality testing is required. Under the condition of traditional inspection, it is necessary to combine many kinds of testing methods for the weld seam of small diameter tube, and the efficiency is very low. In view of this situation, In this paper, the application of weak magnetic field detection in weld detection of small diameter tube is proposed to realize the rapid detection of common types of defects. Firstly, the technical principle of weak magnetic field detection and the characteristics of weld seam of small diameter tube are analyzed in this paper, and the difficulties in detection are pointed out. The feasibility of detecting the weak magnetic field of weld seam of small diameter tube is demonstrated by simulation calculation. According to the geometric shape of weld seam of small diameter tube and the characteristics of defect signal, three detection schemes are put forward: normal inspection, lateral scan inspection and normal sweep inspection. The portable weak magnetic testing equipment was used to detect the weld specimens of two small diameter tubes, and the results of the three kinds of test schemes were analyzed. The result curves of the first two kinds of test schemes were obvious, and the simple defect evaluation could be completed by combining experience. The background magnetic field interference signal is eliminated by wavelet analysis, and the defect signal is extracted successfully. Compared with Dr detection results, the validity of each detection scheme is verified. The advantages and disadvantages of each scheme are summarized. Finally, a defect identification algorithm is proposed, which can reduce the error caused by empirical judgment, and classifies the defect into two categories: crack class and pore class. By using wavelet packet energy spectrum as the characteristic parameter of defects, the classification and identification model of defects is established according to distance discriminant analysis, and the discriminant function of defect classification is determined by using the training model of sample data of weld defects in small diameter tubes. And 20 groups of defect samples were identified. The recognition results show that the accuracy of gas hole identification is 70 and that of crack recognition is 90. The validity of the defect identification model is verified. The research of weak magnetic field detection scheme and defect identification technology is the fast detection of weld seam of small diameter tube. New methods and ideas are provided.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TG441.7

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