發(fā)布時間：2018-11-24 18:39

【摘要】：損傷檢測是重要工業(yè)技術(shù)之一,對社會經(jīng)濟(jì)的發(fā)展和對人身財(cái)產(chǎn)安全都具有重要意義。目前正朝向多傳感技術(shù)相融合的方向發(fā)展,而將光纖布拉格光柵(FBG)和聲波技術(shù)相結(jié)合,進(jìn)行損傷檢測,是當(dāng)前損傷檢測技術(shù)的熱點(diǎn)之一。本文研究應(yīng)用超聲波激勵待測結(jié)構(gòu),通過FBG測量攜帶損傷信息的超聲信號,構(gòu)建光聲結(jié)合的檢測系統(tǒng)以檢測損傷。論文的主要工作如下:(1)分析了超聲技術(shù)和FBG在損傷檢測技術(shù)中研究進(jìn)展和FBG解調(diào)技術(shù)的研究現(xiàn)狀。(2)分析了超聲波聲場分布的特點(diǎn),確定了FBG應(yīng)軸向布設(shè);分析了FBG傳感原理和超聲激勵下FBG光柵長度對反射譜的影響,獲得了用于檢測超聲波的FBG的光柵長度與超聲波長的關(guān)系。(3)為解決FBG檢測高頻聲波信號的波長解調(diào)問題,本文首先研究了基于長周期光纖光柵的高頻解調(diào)系統(tǒng)。該系統(tǒng)將FBG反射光利用長周期光纖光柵進(jìn)行光強(qiáng)調(diào)制,通過檢測系統(tǒng)輸出的光強(qiáng)的變化檢測超聲信號,該系統(tǒng)可以檢測高幅值的超聲信號,但靈敏度較低,無法獲取較低幅值的蘭姆波信號。(4)為獲得高靈敏度的波長解調(diào)系統(tǒng),本文設(shè)計(jì)了一種基于窄帶FBG的高頻解調(diào)系統(tǒng)。該系統(tǒng)將寬帶光源利用窄帶FBG調(diào)制為窄帶光源,利用傳感FBG對窄帶光源進(jìn)行光強(qiáng)調(diào)制,通過檢測傳感FBG的反射光強(qiáng)變化獲取超聲信號。實(shí)驗(yàn)表明改進(jìn)后的系統(tǒng)解調(diào)頻率達(dá)到了100KHz,并能獲取較低幅值的蘭姆波信號。該系統(tǒng)對某一固定傳感FBG的解調(diào)范圍較小,但蘭姆波激勵下傳感FBG中心波長偏移很小,可以滿足要求;通過分別設(shè)計(jì)對應(yīng)的窄帶FBG可解調(diào)多個傳感FBG。此外,該系統(tǒng)中窄帶光源由寬帶光源調(diào)制而得,降低了成本。(5)構(gòu)建了基于FBG和聲波技術(shù)的損傷檢測系統(tǒng),以復(fù)合材料板作為研究對象,采用分布式損傷檢測系統(tǒng)并利用幅值法對損傷進(jìn)行了識別和定位,實(shí)驗(yàn)結(jié)果表明該系統(tǒng)成功識別和定位了損傷。
[Abstract]:Damage detection is one of the important industrial technologies, which is of great significance to the development of social economy and the safety of personal and property. At present, the multi-sensor technology is developing, and the combination of fiber Bragg grating (FBG) (FBG) and acoustic wave technology to detect damage is one of the hot spots of damage detection technology. In this paper, ultrasonic excitation structure is used to measure the ultrasonic signal with damage information by FBG, and a photoacoustic detection system is constructed to detect the damage. The main work of this paper is as follows: (1) the research progress of ultrasonic technology and FBG in damage detection technology and the research status of FBG demodulation technology are analyzed. (2) the characteristics of ultrasonic sound field distribution are analyzed and the axial layout of FBG is determined. The principle of FBG sensing and the influence of the length of FBG grating under ultrasonic excitation on the reflection spectrum are analyzed. The relationship between the length of FBG grating and the length of ultrasonic wave is obtained. (3) in order to solve the problem of wavelength demodulation of high frequency acoustic signal detected by FBG, the relationship between the length of the grating and the length of ultrasonic wave is obtained. In this paper, the high-frequency demodulation system based on long-period fiber grating is studied. The system modulates the light intensity of FBG by long period fiber grating, and detects the ultrasonic signal by detecting the variation of the light intensity. The system can detect the high amplitude ultrasonic signal, but the sensitivity is low. Low amplitude Lamb wave signal can not be obtained. (4) in order to obtain high sensitivity wavelength demodulation system, a high frequency demodulation system based on narrowband FBG is designed in this paper. The system modulates wide band light source into narrow band light source by narrow band FBG modulation, uses sensing FBG to modulate the light intensity of narrow band light source, and obtains ultrasonic signal by detecting the change of reflected light intensity of sensing FBG. The experimental results show that the demodulation frequency of the improved system is 100 kHz and the low amplitude Lamb wave signal can be obtained. The demodulation range of a fixed sensing FBG is small, but the center wavelength shift of the sensor FBG excited by Lamb wave is very small, which can meet the requirements. Several sensing FBG. can be demodulated by designing the corresponding narrow band FBG. In addition, the narrow band light source is modulated by broadband light source, which reduces the cost. (5) the damage detection system based on FBG and acoustic wave technology is constructed, and the composite material plate is taken as the research object. The distributed damage detection system and amplitude method are used to identify and locate the damage. The experimental results show that the system can identify and locate the damage successfully.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB559

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本文編號：2354617