基于非線性振子的結構微裂紋振動聲調制檢測技術研究
發(fā)布時間：2019-04-12 09:42
【摘要】：結構接觸式微裂紋會導致不規(guī)則的高水平非線性,而且在內部傳播的超聲波因接觸聲非線性會產生如彈性波畸變的非線性聲響應。本文研究了結構微裂紋的振動聲調制檢測技術,基于非線性振子模型研究了振動聲調制的增強作用,重點做了實驗分析研究。 首先,本文分析了非線性振子的研究非線性動力學,探討了具有兩個以上振動穩(wěn)態(tài)的結構系統(tǒng)原理,結合外加磁場分析了非線性作用力的實現,建立非線性結構系統(tǒng)的模型并分析了其動力學規(guī)律。我們設計了雙穩(wěn)和三穩(wěn)懸臂梁非線性振子系統(tǒng),實驗探討了非線性雙穩(wěn)態(tài)系統(tǒng)在參數d取不同值時,懸臂梁振子末端位移的不同表現。 然后,本文構造了三穩(wěn)結構微缺陷檢測系統(tǒng)模型,該模型能夠依據非線性動力原理擴展非共振區(qū)振動聲調制的振動激勵帶。此非線性檢測模型可以有效利用不同來源的環(huán)境振動,能有效增強固體材料中不同類型微裂紋的檢測。調制指數值與增加信號輸入幅值的動力學機制相吻合。非線性振動系統(tǒng)在相當小的閾值電壓都可以達到振動聲調制效果。 另外,本文搭建了雙穩(wěn)結構系統(tǒng)試驗模型,利用寬帶隨機振動激勵驗證其隨機共振效應,實驗分析了該模型的隨機共振規(guī)律。雙穩(wěn)微裂紋懸臂振子利用隨機共振機理拓展了線性壓電振子的共振頻寬、增強了低頻振動激勵下的振動響應,我們從中發(fā)現頻移振動聲調制效應。通過將調制頻率向懸臂振子的共振頻率轉換,低頻寬帶激勵能夠產生振動聲調制效果。這種固有機制與非線性變化的自然頻率有關。通過周圍振動激勵的振動聲調制效應能夠有效檢測固體材料的微裂紋。
[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.
【學位授予單位】：中國科學技術大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB302.5
本文編號：2456909
[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.
【學位授予單位】：中國科學技術大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB302.5
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