【作者】 王俊；

【导师】 杨晓庆；

【作者基本信息】 四川大学 ， 电子科学与技术， 2022， 硕士

【摘要】 微波无损检测是对待测物的结构、状态、以及缺陷的位置和尺寸进行监测的技术手段,与传统无损检测技术相比具有成本低、灵敏度高、操作简单、检测速度快等优点,目前,该技术已经在多个领域广泛使用。由于传统无损检测技术测量磁性材料厚度的设备复杂,精度偏低,适用范围受到严重限制。本文基于人工局域表面等离激元对材料介电常数和磁导率变化敏感的特性,提出了一种用于测量磁性吸波涂层厚度的新型微波传感器。该传感器具有精度高,成本低,结构简单的特点。此外,由于目前的微波无损检测技术在测量材料应变时使用灵活性低,适用范围窄,对待测物的表面具有一定程度的损坏。本文在人工局域表面等离激元传感器的基础上,提出了一种可灵活用于测量金属和非金属材料应变的传感器,该应变传感器分辨率高,可对材料应变进行无污染、无损伤测量。采用微带环给金属螺旋环耦合馈电,成功地在微波频段激励起人工局域表面等离激元。通过软件对人工局域表面等离激元传感器的结构和尺寸进行仿真优化,使传感器的设计更加合理。在软件中建立传感器测量金属表面磁性吸波涂层的模型,通过测量原理分析和数值仿真分析可知,传感器的反射系数的幅值对涂层厚度的变化很敏感。通过仿真测试了传感器的灵敏度和分辨率,仿真结果显示该传感器还可以区分厚度相同而损耗不同的两种材料。传感器加工后,在实验室对传感器的实际测量能力进行验证,对测量数据进行曲线拟合,得到传感器的反射系数幅值与涂层厚度满足双曲正切函数关系。实验结果表明该传感器测量磁性吸波薄膜的最高分辨率可达0.05mm,测量误差在6%以内,可测量范围为0.05mm-1.03mm。应变传感器在人工局域表面等离激元传感器的基础上,增加了一块耦合金属板。首先从电路的角度出发,提出了人工局域表面等离激元传感器的等效集总电路,利用软件对电路进行仿真,并提取元件的相关参数,等效电路的频率响应曲线与实验测量结果具有一致性。利用等效电路法分析了应变传感器的工作原理,从电路的角度揭示了应变传感器谐振频率变化的本质,并通过仿真发现传感器的谐振频率与材料的应变之间存在线性关系。然后加工应变传感器,在实验室中对应变传感器的实际测量能力进行验证。实验中的待测物为一块铝板,实验结果显示该传感器检测的最小应变约为0.01mm,谐振频率偏移了37MHz,最大测到的应变约为1.3mm,谐振频率偏移了613MHz。本文基于人工局域表面等离激元的特性,提出了一种用于微波无损测量的新型传感器,仿真和实验表明该传感器在测量磁性吸波涂层的厚度以及在测量材料应变方面具有可行性和可靠性,为了提高传感器的实际测量性能,文末提出了一些具体的改进方案。本文设计的人工局域表面等离激元传感器为微波无损检测领域提供了新的思路。更多还原

【Abstract】 Microwave nondestructive testing(NDT)is a technical means to monitor the structure,state,and the position and size of defects of the material under test(MUT).Compared with traditional NDT,it has the advantages of low cost,high sensitivity,simple operation and fast detection.Due to the complex equipment and low accuracy of traditional NDT technology to measure the thickness of magnetic materials,the scope of application of traditional NDT technology is severely limited.In this paper,a novel microwave sensor for measuring the thickness of magnetic absorbing coating is proposed based on the fact that localized spoof surface plasmons(LSSPs)are extremely sensitive to changes of permitivity and permeability of materials.The LSSPs sensor has the characteristics of high precision,low cost and simple structure.In addition,the current microwave NDT technology has low flexibility in measuring material strain,narrow application range,and damage to the surface of the material to a certain extent.Based on the LSSPs sensor,in this paper,a sensor that can be flexibly used to measure the strain of metallic and non-metallic materials is proposed.The strain sensor has high resolution and can measure material strain without pollution and damage.A microstrip ring is used to feed the metallic spiral structure,and the LSSPs is successfully excited in the microwave frequency band.The structure and size of the LSSPs sensor are simulated and optimized by software to make the design of the sensor more reasonable.A model of the sensor to measure the magnetic wave absorbing coating on a metal surface is established in the software.Through the measurement principle analysis and numerical simulation analysis,the magnitude of the reflection coefficient is sensitive to the thickness variation of the coating.The sensitivity and resolution of the sensor are tested by simulation,and the simulation results show that the LSSPs sensor can also distinguish two materials with the same thickness but different losses.After the sensor is fabricated by standard PCB technology,the actual measurement performance of the sensor is verified in the laboratory.The measurement data is fitted to obtain that magnitude of the reflection coefficient of the sensor meets the hyperbolic tangent function with the thickness of the coating.Taking a kind of magnetic absorbing film A4000 as an example,the function relationship between thickness of the film and magnitude of the reflection coefficient is established by two fitting methods.The experimental results showed that the highest resolution of the LSSPs sensor can reach 0.05 mm,the measurement error is within 6%,and the measurement range is 0.05mm-1.03 mm.The strain sensor adds a stand-off metal plate to the LSSPs sensor.Firstly,from the perspective of circuit,the equivalent lumped circuit model of the LSSPs sensor is proposed.The circuit is simulated by software,and the relevant parameters of the components are extracted.The frequency response curve of the equivalent circuit is consistent with the experimental measurement results.The measurement principle of the strain sensor is analyzed by using the equivalent circuit method,and the essence of the resonant frequency shift of the strain sensor is revealed from the perspective of the circuit.Finally,the sensor is processed and the actual measuring ability of the strain sensor is verified in the laboratory.The MUT in the experimrnt is an aluminium plate,and the experimental results show that the minimum strain measured by the strain sensor is 0.005% with a resonance frequency shifting by 37 MHz,and the maximum strain measured is 0.65% with a resonance frequency shifting by 613 MHz.Based on the characteristics of LSSPs,a novel sensor for microwave nondestructive measurement is proposed.Simulation and experiments show that the sensor is feasible in measuring the thickness of magnetic absorbing coatings and measuring material strain.In order to improve the actual measurement performance of the sensor,some specific improvement schemes are proposed at the end of the paper.The LSSPs sensor designed in this paper provides a new idea for the field of microwave nondestructive testing.更多还原