【摘要】：窄板在工程中有著廣泛的應(yīng)用，從飛機(jī)機(jī)翼桁架到變電站接地網(wǎng)，這些工程結(jié)構(gòu)都由大量的窄板組合而成。窄板結(jié)合處的漏焊、虛焊，以及長期暴露在空氣中或深埋于土壤中而引起的腐蝕和氧化等因素的影響，經(jīng)常會因窄板結(jié)構(gòu)損傷而導(dǎo)致整個結(jié)構(gòu)的失效，從而引發(fā)嚴(yán)重的事故。因此，對這些窄板進(jìn)行無損檢測就顯得極為至關(guān)重要。 針對窄板超聲導(dǎo)波無損檢測需要，本論文進(jìn)行窄板中超聲導(dǎo)波傳播特性研究，主要研究內(nèi)容包括： (1)基于特征頻率法進(jìn)行窄板結(jié)構(gòu)中超聲導(dǎo)波頻散特性數(shù)值分析。基于振動模態(tài)理論，采用特征頻率法計算窄板中頻散關(guān)系，重點研究窄板寬度方向邊界對A0、S0和SH0模態(tài)導(dǎo)波頻散特性的影響； (2)優(yōu)化換能器結(jié)構(gòu)，，在原有固定波長電磁聲換能器基礎(chǔ)上，設(shè)計并制作出一種可變波長低頻剪切波的EMAT換能器，并對其進(jìn)行了性能測試。結(jié)果表明，研制的電磁聲換能器可在一定波長范圍內(nèi)激勵出單一模態(tài)的SH0波； (3)針對超聲回波達(dá)到時間準(zhǔn)確、自動提取問題，提出一種利用動態(tài)小波指紋技術(shù)提取超聲回波到達(dá)時間的方法，并研究了動態(tài)小波指紋分析中參數(shù)選擇對回波時間提取的影響； (4)通過數(shù)值仿真和檢測試驗，研究了窄板寬度對A0、S0和SH0模態(tài)導(dǎo)波在窄板中傳播的影響。重點分析了窄板邊界對各模態(tài)超聲導(dǎo)波的群速度的影響。
[Abstract]:The narrow plate has a wide range of applications in the project, from the aircraft wing to the substation ground network, all of which consist of a large number of narrow plates. The effects of leakage welding, false welding, and long-term exposure to the air or deeply buried in the soil, such as corrosion and oxidation caused by long-term exposure to the soil, often result in failure of the whole structure due to the damage of the narrow plate structure, thus causing serious accidents. The non-destructive testing of these narrow plates is therefore of great importance. In view of the need of non-destructive testing of narrow plate ultrasonic guided wave, this paper studies the characteristics of ultrasonic guided wave propagation in the narrow plate, and mainly focuses on the content package. (1) The number of ultrasonic guided wave dispersion characteristics in a narrow plate structure based on the characteristic frequency method Based on the theory of the vibration mode, the characteristic frequency method is adopted to calculate the frequency dispersion relation in the narrow plate, and the characteristics of the narrow plate width direction boundary pair A0, S0 and SH0 mode guided wave dispersion are mainly studied. and (2) optimizing the structure of the transducer, The EMAT transducer with a variable-wavelength low-frequency shear wave is designed and fabricated on the basis of the energy absorber, The results show that the developed electromagnetic acoustic transducer can excite a single mode in a certain wavelength range and (3) extracting the ultrasonic echo by using the dynamic wavelet fingerprint technology, aiming at the problem of accurate time and automatic extraction of the ultrasonic echo, The time-of-arrival method is studied and the parameters of the dynamic wavelet fingerprint analysis are studied. The influence of time extraction is studied. (4) Through the numerical simulation and the test, the width of the narrow plate is studied in the mode of A0, S0 and SH0 mode. The influence of the propagation of the narrow plate in the narrow plate is analyzed.
【學(xué)位授予單位】：北京工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TB553

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