基于非线性振子的结构微裂纹振动声调制检测技术研究

发布时间：2019-04-12 09:42

【摘要】：结构接触式微裂纹会导致不规则的高水平非线性,而且在内部传播的超声波因接触声非线性会产生如弹性波畸变的非线性声响应。本文研究了结构微裂纹的振动声调制检测技术,基于非线性振子模型研究了振动声调制的增强作用,重点做了实验分析研究。首先,本文分析了非线性振子的研究非线性动力学,探讨了具有两个以上振动稳态的结构系统原理,结合外加磁场分析了非线性作用力的实现,建立非线性结构系统的模型并分析了其动力学规律。我们设计了双稳和三稳悬臂梁非线性振子系统,实验探讨了非线性双稳态系统在参数d取不同值时,悬臂梁振子末端位移的不同表现。然后,本文构造了三稳结构微缺陷检测系统模型,该模型能够依据非线性动力原理扩展非共振区振动声调制的振动激励带。此非线性检测模型可以有效利用不同来源的环境振动,能有效增强固体材料中不同类型微裂纹的检测。调制指数值与增加信号输入幅值的动力学机制相吻合。非线性振动系统在相当小的阈值电压都可以达到振动声调制效果。另外,本文搭建了双稳结构系统试验模型,利用宽带随机振动激励验证其随机共振效应,实验分析了该模型的随机共振规律。双稳微裂纹悬臂振子利用随机共振机理拓展了线性压电振子的共振频宽、增强了低频振动激励下的振动响应,我们从中发现频移振动声调制效应。通过将调制频率向悬臂振子的共振频率转换,低频宽带激励能够产生振动声调制效果。这种固有机制与非线性变化的自然频率有关。通过周围振动激励的振动声调制效应能够有效检测固体材料的微裂纹。
[Abstract]:The contact micro-crack of the structure can cause irregular high-level nonlinearity, and the ultrasonic wave propagated in the interior will produce a nonlinear sound response such as elastic wave distortion due to the contact acoustic nonlinearity. In this paper, the vibration acoustic modulation detection technology for structural micro-cracks is studied. Based on the nonlinear oscillator model, the enhancement of vibration acoustic modulation is studied, and the emphasis is placed on the experimental analysis. Firstly, this paper analyzes the nonlinear dynamics of the nonlinear oscillator, discusses the principle of structural system with more than two vibrational steady states, and analyzes the realization of the nonlinear force combined with the external magnetic field. The model of nonlinear structural system is established and its dynamic law is analyzed. The bistable and tristable cantilever beam nonlinear oscillator systems are designed. The different behavior of the end displacement of the cantilever beam oscillator when the parameter d is different is discussed experimentally. Then, a tristable structure micro-defect detection system model is constructed, which can extend the vibration excitation band of vibration and acoustic modulation in the non-resonant region according to the nonlinear dynamic principle. This nonlinear detection model can effectively utilize environmental vibration from different sources and can effectively enhance the detection of different types of micro-cracks in solid materials. The modulation exponent value is consistent with the dynamic mechanism of increasing the input amplitude of the signal. The nonlinear vibration system can achieve the vibration and sound modulation effect at a very small threshold voltage. In addition, the experimental model of bistable structure system is set up in this paper. The random resonance effect is verified by wide-band random vibration excitation, and the stochastic resonance rule of the model is analyzed experimentally. By means of stochastic resonance mechanism, a bistable micro-crack cantilever oscillator extends the resonant frequency width of a linear piezoelectric oscillator and enhances the vibration response under low frequency vibration excitation. We find that the acoustic modulation effect of frequency-shifted vibration is found in this paper. By converting the modulation frequency to the resonant frequency of the cantilever oscillator, the low-frequency broadband excitation can produce the vibration-sound modulation effect. This inherent mechanism is related to the natural frequency of nonlinear variation. The vibration acoustic modulation effect of the surrounding vibration excitation can effectively detect the micro-cracks of solid materials.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB302.5

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