【摘要】：金屬管道廣泛應用于各行各業(yè),在長期的服役過程中,由于管材老化、所處環(huán)境苛刻或工況惡劣等原因,其壁面上會產生裂紋、腐蝕、凹坑等損傷。特別是管道彎頭部位,因內部介質沖刷和撞擊而造成的腐蝕失效更易發(fā)生,成為整體管道的薄弱環(huán)節(jié)。管道損傷的積累最終會引發(fā)泄漏或爆炸事故,給安全生產帶來隱患。因此,對在役管道進行定期的無損檢測,以便及時發(fā)現(xiàn)問題并進行維護,顯得尤為必要。遠場渦流檢測技術對內外壁缺陷有相同的靈敏度,而且對傳感器的提離不敏感,在金屬管道的無損檢測中備受重視。但是,常規(guī)的遠場渦流傳感器為內通過式,在實際應用時往往需要設備停機,以便將傳感器放入管內。為滿足壓力管道在役檢測的需求,本學位論文針對其易腐蝕的管道彎頭部位,設計了一種在管外放置的遠場渦流傳感器。主要研究如下:1.基于有限元仿真,以實現(xiàn)激勵磁場兩次穿透管壁的遠場渦流現(xiàn)象作為目標,研究了激勵線圈放置方式、磁屏蔽、激勵單元個數(shù)等因素對激勵磁場穿透效果的影響,確定了以矩形線圈為激勵線圈、外加磁屏蔽罩、夾角為120度的雙激勵單元作為外置式遠場渦流傳感器的結構形式,仿真表明采用這種傳感器不僅可縮短遠場區(qū)的周向距離,還能增強遠場區(qū)的磁場信號。2.利用有限元軟件建立了彎頭缺陷外置式遠場渦流檢測仿真模型,研究了傳感器信號的幅值和相位與內、外壁缺陷深度的定量關系,以及傳感器對不同取向外壁缺陷的檢測性能。結果表明傳感器信號的相位隨缺陷深度線性變化,可用于彎頭缺陷深度的定量,但由于傳感器對內、外壁缺陷檢測靈敏度不同,尚不能對內、外壁缺陷都存在時的缺陷深度進行定量;周向缺陷引起的傳感器響應比軸向缺陷響應顯著減弱,但兩者引起的相位變化相差較小。3.根據仿真設計結果,研制了外置式遠場渦流傳感器,搭建了遠場渦流檢測系統(tǒng)硬件平臺;并基于LabVIEW設計了鎖相放大器,實現(xiàn)檢測信號相位和幅值的提取;利用該系統(tǒng)在Q235管道彎頭、45鋼階梯管等試件上進行了試驗。試驗信號特征的變化規(guī)律與仿真結果一致,驗證了所設計探頭的有效性和實用性。與常規(guī)遠場渦流傳感器相比,本文所提出的外置式傳感器具有結構緊湊、無需設備停機等優(yōu)勢。因此,研究結果可為壓力管道在役檢測提供可借鑒的新思路和方法。
[Abstract]:Metal pipes are widely used in various industries. In the long service process, due to the aging of pipes, harsh environment or harsh working conditions, cracks, corrosion, pits and other damage will occur on the wall. Especially, the corrosion failure caused by internal media scour and impact is more likely to occur in the bend of pipeline, which becomes the weak link of the whole pipeline. The accumulation of pipeline damage will eventually lead to leakage or explosion accident, and bring hidden danger to safety production. Therefore, it is necessary to carry out regular nondestructive testing to detect problems and maintain them in time. The far field eddy current testing technology has the same sensitivity to the inner and outer wall defects, and is not sensitive to the lifting of the sensor, so it has attracted much attention in the nondestructive testing of metal pipes. However, the conventional far field eddy current sensor is an internal passage type, which often requires the equipment to stop in order to put the sensor into the pipe. In order to meet the need of in-service inspection of pressure pipes, a far-field eddy current sensor is designed for the corrosion prone pipe elbows. The main research is as follows: 1. Based on finite element simulation, the effect of excitation coil placement, magnetic shielding and the number of excitation units on the penetration effect of excitation magnetic field is studied. The rectangular coil is used as the exciting coil, the magnetic shield is applied and the double excitation element with an angle of 120 degrees is used as the structure of the external far-field eddy current sensor. The simulation results show that this kind of sensor can not only shorten the circumferential distance in the far field. Can also enhance the far-field magnetic field signal. 2. The simulation model of the far field eddy current detection of elbow defects is established by using the finite element software. The quantitative relationship between the amplitude and phase of the sensor signal and the depth of the inner and outer wall defects, as well as the detection performance of the sensor for the outer wall defects with different orientations are studied. The results show that the phase of the sensor signal varies linearly with the depth of the defect, and can be used to quantify the depth of the defect in the elbow. The depth of defects in the outer wall is quantified when there are defects in the outer wall. The response of the sensor caused by circumferential defect is much weaker than that of axial defect, but the phase change caused by them is smaller than that caused by axial defect. According to the simulation design results, the external far-field eddy current sensor is developed, the hardware platform of the far-field eddy current detection system is built, and the phase-locked amplifier is designed based on LabVIEW, which can extract the phase and amplitude of the detection signal. The system was used to test the Q235 pipe elbows and 45 steel ladder pipes. The characteristics of the test signal are consistent with the simulation results, and the validity and practicability of the designed probe are verified. Compared with the conventional far field eddy current sensor, the external sensor presented in this paper has the advantages of compact structure and no equipment shutdown. Therefore, the results of the study can provide a new idea and method for the in-service inspection of pressure pipelines.
【學位授予單位】：湘潭大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG115.28

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