本文選題：變徑厚壁管 + 周向蘭姆波�。� 參考：《南昌航空大學(xué)》2017年碩士論文

【摘要】：變徑厚壁管在核電、石油化工、軍工等特種設(shè)備領(lǐng)域應(yīng)用的越來越廣泛。傳統(tǒng)上變徑管損傷的分析方法,一是化學(xué)成分;二是通過模擬實(shí)驗(yàn),對變徑管在某些環(huán)境中容易產(chǎn)生裂紋、腐蝕等缺陷進(jìn)行剖析;三是采用數(shù)值計(jì)算或?qū)嶒?yàn)的方法,直接分析變徑管的應(yīng)力、強(qiáng)度等材料特性。以上方法雖然能夠分析變徑管的強(qiáng)度及材料性能是否合格以避免由變徑管損傷引起的相關(guān)事故,但對變徑管的質(zhì)量狀況不能進(jìn)行快速檢測。研究變徑管的有效無損檢測技術(shù),實(shí)現(xiàn)變徑管缺陷的快速檢測具有重要意義。與軸向?qū)Рㄏ啾?超聲周向?qū)Рǜm合用于厚壁管道的檢測,沿著管道軸向移動(dòng)超聲導(dǎo)波換能器,可實(shí)現(xiàn)變徑厚壁管的全面掃查。本文研究了變徑厚壁管的檢測方法,為有關(guān)變徑厚壁管檢測技術(shù)標(biāo)準(zhǔn)的制定,提供基礎(chǔ)性實(shí)驗(yàn)數(shù)據(jù)和可行性方法。本文首先對變徑厚壁管中周向蘭姆波的頻散特性進(jìn)行了分析,給出了周向蘭姆波的頻散方程的推導(dǎo)過程,運(yùn)用等效替代法,把變徑厚壁管等效成不同徑厚比等徑厚壁管,通過求解頻散方程和波結(jié)構(gòu),得到壁厚不變、不同徑厚比管道所對應(yīng)群速度曲線以及波結(jié)構(gòu)。對比在0~1MHz頻率范圍內(nèi)的頻散曲線可知,隨著變徑厚壁管外徑減小,各個(gè)模態(tài)在處于較優(yōu)頻散特性時(shí)的群速度也都依次減小,且模態(tài)階數(shù)越高,整個(gè)變徑厚壁管全部外徑所對應(yīng)群速度曲線都處于較優(yōu)頻散特性所需要的激勵(lì)頻率越大;在激勵(lì)中心頻率不變的情況下,隨著變徑厚壁管外徑不斷減小,能夠檢測整個(gè)壁厚所需要的導(dǎo)波模態(tài)階數(shù)越高;根據(jù)頻率與入角度的關(guān)系,選擇合適的激勵(lì)角度,有望激勵(lì)出較少模態(tài)的周向蘭姆波。其次,開展了變徑厚壁管周向蘭姆波傳播特性及在缺陷上反射的數(shù)值模擬研究,利用有限差分方法模擬了周向蘭姆波在壁厚30mm、大管徑250mm、小管徑100mm、軸向長度600mm的變徑厚壁管上的傳播特性和散射特性。研究了采用壓電晶片30°、45°和60°斜入射時(shí),變徑厚壁管中聲場的分布規(guī)律,并檢測了不同尺寸的位于外壁、中壁和內(nèi)壁的缺陷。此外,還進(jìn)一步研究了周向蘭姆波在不同傾斜度變徑厚壁管中的傳播特性。研究結(jié)果表明:對于周向蘭姆波,不同入射角會影響變徑厚壁管中聲場的覆蓋范圍,角度過大會使得內(nèi)壁聲場較弱,角度過小時(shí)頻散現(xiàn)象嚴(yán)重;周向蘭姆波在變徑厚壁管中不同大小的缺陷反射時(shí)會產(chǎn)生不同效果,缺陷尺寸太小,效果很弱,當(dāng)內(nèi)壁圓孔缺陷半徑大于3mm時(shí),效果變化顯著;通過對比周向蘭姆波在等徑厚壁管、變徑厚壁管、45°變徑厚壁管、60°變徑厚壁管上的傳播特性可知,變徑厚壁管傾斜角度越大,周向蘭姆波越難以在其中傳播。再其次,基于數(shù)值模擬的結(jié)果,選取中心頻率為500KHz的壓電晶片,設(shè)計(jì)了楔塊角度為37°、45°、55°的有機(jī)玻璃楔塊,制作了中心頻率為500KHz的角束斜探頭以激發(fā)周向蘭姆波。確定了周向蘭姆波在變徑厚壁管中傳播時(shí),形成穩(wěn)定幅值的周向蘭姆波的周向距離是300mm。在此基礎(chǔ)上,利用連續(xù)小波時(shí)頻分析得到周向蘭姆波在這三種角度斜入射時(shí),群速度與頻率的關(guān)系曲線,分析了主要的傳播模態(tài)。最后,開展了變徑厚壁管缺陷周向蘭姆波檢測實(shí)驗(yàn)研究,針對壁厚30mm、大管徑250mm、小管徑100mm、軸向長度600mm的變徑厚壁管,在外壁、中壁、內(nèi)壁不同位置加工了一系列缺陷,研究了不同角度探頭對不同位置、不同大小、不同類型缺陷的檢測,以及變徑厚壁管不同徑厚比周向蘭姆波的反射波能量問題。實(shí)驗(yàn)檢測結(jié)果表明:變徑厚壁管周向蘭姆波的檢測靈敏度為長1mm、寬1mm、高1mm的缺陷;當(dāng)檢測變徑厚壁管中、外壁缺陷時(shí),楔塊角度55°的周向蘭姆探頭所激勵(lì)的導(dǎo)波檢測效果最好,當(dāng)檢測內(nèi)壁缺陷時(shí),選擇楔塊角度45°的探頭更適合;周向蘭姆波在變徑厚壁管中的傳播具有較強(qiáng)的指向性,了解周向蘭姆波在變徑厚壁管中反射波能量有利于對缺陷進(jìn)行定位分析。
[Abstract]:The variable diameter thick wall tube is becoming more and more widely used in the fields of nuclear power, petrochemical, military and other special equipment. The traditional analysis method of the variable diameter tube damage is chemical composition. Two through the simulation experiment, the defects of the variable diameter tube are easily analyzed in some environment, such as crack and corrosion, and the three is the method of numerical calculation or experiment. The above method can analyze the strength of the variable diameter tube and whether the material performance is qualified to avoid the related accidents caused by the variable diameter tube damage, but the quality condition of the variable diameter tube can not be detected quickly. The effective nondestructive testing technology of the variable diameter tube is studied and the fast tube defect is realized quickly. The speed detection is of great significance. Compared with the axial guided wave, the ultrasonic circumferential wave guide wave is more suitable for the detection of the thick wall pipe. The ultrasonic guided wave transducer is moved along the axial direction of the pipe to realize the comprehensive scanning of the variable diameter thick wall tube. This paper studies the detection method of the variable diameter thick wall tube, which provides the basis for the formulation of the technical standards for the variable diameter thick wall tube detection. The basic experimental data and the feasibility method. Firstly, this paper analyzes the frequency dispersion characteristic of the circumferential Lamb wave in the variable diameter thick wall tube, gives the derivation process of the frequency dispersion equation of the circumferential Lamb wave, and uses the equivalent substitution method to equip the variable diameter thick wall tube into a thick wall tube with different diameter and thickness ratio, and obtains the wall by solving the dispersion equation and the wave structure. The group velocity curve and wave structure corresponding to the diameter thickness of the pipe are not constant, and the frequency dispersion curve in the 0~1MHz frequency range shows that with the decrease of the diameter of the variable diameter thick wall tube, the group velocity of each mode in the better dispersion characteristic decreases in turn, and the higher the modal order, the whole diameter of the whole variable diameter thick wall tube corresponds to the group. The faster the velocity curve is in the better frequency dispersion characteristic, the greater the frequency of the exciting frequency, and the higher the number of the guided waves needed to detect the thickness of the whole wall with the constant decrease of the diameter of the variable diameter thick wall tube, and the less modes are expected to be encouraged according to the relationship between the frequency and the angle of entry and the choice of the appropriate excitation angle. Secondly, the propagation characteristics of the circumferential rimbo wave and the numerical simulation of the reflection on the defect are carried out. The propagation and scattering characteristics of the circumferential Lamb wave on the wall thickness 30mm, the diameter of the tube 250mm, the diameter of the tube 100mm and the axial length 600mm are simulated by the finite difference method. The distribution of sound field in a variable diameter thick wall tube at 30, 45 and 60 degrees, and the defects in the outer wall, the middle wall and the inner wall of different sizes are detected. Furthermore, the propagation characteristics of the circumferential Lamb wave in different inclined variable diameter thick wall tubes are further studied. The results show that the different incidence angles are different for the circumferential Lamb waves. It will affect the coverage of the sound field in the variable diameter thick wall tube, and the angle over the assembly makes the inner wall sound field weak and the angle over hourly dispersion phenomenon serious; the circumferential Lamb wave can produce different effects when reflecting the defects of different sizes in the variable diameter thick wall tube. The defect size is too small and the effect is very weak. When the radius of the inner hole defect is larger than 3mm, the effect changes obviously. By comparing circumferential Lamb waves in equal diameter thick wall tube, variable diameter thick wall tube, 45 degree variable diameter thick wall tube and 60 degree variable diameter thick wall tube, it is known that the larger the inclined angle of the variable diameter thick wall tube is, the more difficult the circumferential Lamb wave is to propagate in it. Secondly, based on the numerical simulation results, a piezoelectric chip with the center frequency of 500KHz is selected and the wedge is designed. The angle of the block angle is 37, 45 and 55 degrees. The angle beam probe with the center frequency of 500KHz is made to stimulate the circumferential Lamb wave. The circumferential distance of the circumferential Lamb wave, which forms the stable amplitude, is 300mm. on this basis, and the continuous wavelet time frequency analysis is used to obtain Zhou Xianglan. When these three angles are oblique incidence, the relationship curves of group velocity and frequency are analyzed, and the main propagation modes are analyzed. Finally, an experimental study on the circumferential Lamb wave detection of variable diameter thick wall tube defects is carried out. The wall thickness 30mm, the diameter of the tube 250mm, the diameter of the tube 100mm, the axial length 600mm of the thick wall tube, are processed in different positions in the outer wall, the middle wall and the inner wall. A series of defects are studied, and the detection of different positions, sizes and types of defects and the reflection wave energy of different diameter thickness ratio circumferential ram wave are studied. The experimental results show that the detection sensitivity of the circumferential Lamb wave of the variable diameter thick wall tube is 1mm, wide 1mm, and high 1mm. In a thick wall tube, when the outer wall is defective, the guide wave excited by the circumference of the wedge angle of 55 degrees is the best. When the inner wall defect is detected, the probe which selects the wedge angle of 45 degrees is more suitable. The propagation of the circumferential Lamb wave in the variable diameter thick wall tube has strong directivity, and the reflected wave energy of the circumferential Lamb wave in the variable diameter thick wall tube is understood. It is beneficial to the location and analysis of the defects.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG115.285

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本文編號：2013134