窄板结构中超声导波传播特性研究
发布时间：2019-06-06 10:23
【摘要】：窄板在工程中有着广泛的应用，从飞机机翼桁架到变电站接地网，这些工程结构都由大量的窄板组合而成。窄板结合处的漏焊、虚焊，以及长期暴露在空气中或深埋于土壤中而引起的腐蚀和氧化等因素的影响，经常会因窄板结构损伤而导致整个结构的失效，从而引发严重的事故。因此，对这些窄板进行无损检测就显得极为至关重要。 针对窄板超声导波无损检测需要，本论文进行窄板中超声导波传播特性研究，主要研究内容包括： (1)基于特征频率法进行窄板结构中超声导波频散特性数值分析。基于振动模态理论，采用特征频率法计算窄板中频散关系，重点研究窄板宽度方向边界对A0、S0和SH0模态导波频散特性的影响； (2)优化换能器结构，，在原有固定波长电磁声换能器基础上，设计并制作出一种可变波长低频剪切波的EMAT换能器，并对其进行了性能测试。结果表明，研制的电磁声换能器可在一定波长范围内激励出单一模态的SH0波； (3)针对超声回波达到时间准确、自动提取问题，提出一种利用动态小波指纹技术提取超声回波到达时间的方法，并研究了动态小波指纹分析中参数选择对回波时间提取的影响； (4)通过数值仿真和检测试验，研究了窄板宽度对A0、S0和SH0模态导波在窄板中传播的影响。重点分析了窄板边界对各模态超声导波的群速度的影响。
[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.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB553
[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.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB553
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