本文關(guān)鍵詞： 管道 超聲導(dǎo)波 非通透缺陷 時(shí)間反轉(zhuǎn)法 數(shù)值模擬　出處：《華東理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：管道經(jīng)過長期服役后,由于磨損、腐蝕和意外損傷等原因,對(duì)管道正常運(yùn)行產(chǎn)生危害。在實(shí)際工況中,小的腐蝕缺陷容易發(fā)展成腐蝕穿孔、淺層的小裂紋容易發(fā)展成穿透型裂紋,因此探究如何有效的檢測(cè)出管道非通透缺陷是很有必要的。本文采用ANSYS有限元分析軟件,對(duì)空管和充水管道中的非通透缺陷進(jìn)行模擬檢測(cè)。采用有限元方法,首先分別用L(0,2)模態(tài)和T(0,1)模態(tài)針對(duì)空管道中的周向和軸向裂紋進(jìn)行檢測(cè)模擬,得到反射系數(shù)與缺陷特征尺寸間的關(guān)系,利用縱向L(0,2)模態(tài)對(duì)位于管道內(nèi)側(cè)或外側(cè)的圓孔形減薄缺陷進(jìn)行檢測(cè)模擬,并將得到的檢測(cè)信號(hào)進(jìn)行對(duì)比,發(fā)現(xiàn)位于管道內(nèi)外兩側(cè)的圓孔形減薄缺陷的反射系數(shù)幾乎相同,然后針對(duì)相同橫截面積下不同徑向深度缺陷的檢測(cè)靈敏度差異,發(fā)現(xiàn)導(dǎo)波對(duì)窄深形缺陷更敏感;而后利用時(shí)間反轉(zhuǎn)法針對(duì)空管中小尺寸缺陷的信號(hào)放大和缺陷周向定位問題進(jìn)行了研究,結(jié)果說明利用時(shí)間反轉(zhuǎn)法可以有效放大缺陷回波的信號(hào),使缺陷回波容易被識(shí)別,還可以對(duì)斜裂紋缺陷進(jìn)行有效的周向定位與缺陷形狀判別;采用L(0,2)模態(tài)針對(duì)充水管道的單周向裂紋缺陷和多周向裂紋缺陷進(jìn)行了模擬檢測(cè),得到反射系數(shù)與缺陷周向長度間的關(guān)系,并將反射系數(shù)與空管時(shí)得到的反射系數(shù)進(jìn)行對(duì)比,發(fā)現(xiàn)當(dāng)被檢缺陷相同時(shí)充水管的缺陷反射系數(shù)始終小于空管缺陷反射系數(shù);利用時(shí)間反轉(zhuǎn)法,對(duì)充水管道中各種類型的單缺陷和多缺陷進(jìn)行了信號(hào)放大和缺陷定位研究,模擬結(jié)果表明,對(duì)信號(hào)進(jìn)行時(shí)反處理后并重新激勵(lì),可以對(duì)充水管道中多類型的單缺陷和多缺陷進(jìn)行有效的周向定位以及缺陷形狀判別,同時(shí)發(fā)現(xiàn)利用時(shí)間反轉(zhuǎn)法對(duì)軸向位置不同的兩個(gè)小尺寸圓孔形內(nèi)減薄缺陷進(jìn)行信號(hào)放大,可以有效的得到缺陷的個(gè)數(shù)及各個(gè)缺陷的軸向位置。
[Abstract]:After long service, due to wear, corrosion and accidental damage, the pipeline is harmful to the normal operation of the pipeline. In actual working conditions, small corrosion defects can easily develop into corrosion and perforation. Shallow small cracks are easy to develop into penetrating cracks, so it is necessary to explore how to detect pipeline non-permeable defects effectively. In this paper, ANSYS finite element analysis software is used. The non-permeable defects in empty pipe and water-filled pipeline are tested by simulation. Using the finite element method, the circumferential and axial cracks in the empty pipe are detected and simulated by using the L0 ~ (2)) mode and the T _ (0 ~ (1)) mode, respectively. The relationship between the reflection coefficient and the characteristic size of the defect is obtained. The circular hole thinning defect located inside or outside the pipeline is detected and simulated by using the longitudinal L0 / 2) mode, and the detected signals are compared. It is found that the reflection coefficient of the circular hole thinning defect located on both sides of the pipeline is almost the same, and then according to the difference of the detection sensitivity of different radial depth defects under the same cross-sectional area, it is found that the guided wave is more sensitive to the narrow and deep defect. Then the time reversal method is used to study the problem of signal amplification and defect circumferential localization for the small and medium size defects in the air tube. The results show that the time reversal method can effectively amplify the signal of the defect echo and make the defect echo be easily recognized. It is also possible to perform effective circumferential localization and defect shape discrimination for oblique crack defects, and to simulate the detection of one-cycle crack defects and multi-circumferential crack defects in water-filled pipes by using LZO _ (2) mode. The relationship between the reflection coefficient and the circumferential length of the defect is obtained, and the reflection coefficient is compared with the reflection coefficient obtained when the defect is the same. It is found that the reflection coefficient of the filled pipe is always smaller than that of the empty tube defect when the defect is the same. The signal amplification and defect localization of various types of single and multiple defects in water-filled pipeline are studied by using time reversal method. The simulation results show that the signal is re-excited after the signal is backprocessed. Many types of single and multiple defects in water-filled pipeline can be effectively located in the circumferential direction and the shape of the defects can be distinguished. At the same time, it is found that the time reversal method is used to amplify the signal of two small size circular hole thinning defects in different axial positions. The number of defects and the axial position of each defect can be obtained effectively.
【學(xué)位授予單位】：華東理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：U178

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