發(fā)布時(shí)間：2018-12-17 17:26

【摘要】：由于激光超聲具有波長(zhǎng)短，方向性強(qiáng)，遇障礙物產(chǎn)生衍射和散射等特點(diǎn)，日益成為無(wú)損檢測(cè)領(lǐng)域重要研究?jī)?nèi)容。本文主要通過仿真與實(shí)驗(yàn)的方法，從激光超聲激勵(lì)與檢測(cè)系統(tǒng)構(gòu)成與原理出發(fā)，重點(diǎn)研究了激光超聲激勵(lì)與檢測(cè)技術(shù)。 以激光超聲激發(fā)機(jī)理為基礎(chǔ)，對(duì)激光超聲激勵(lì)關(guān)鍵技術(shù)進(jìn)行了分析，設(shè)計(jì)了激光點(diǎn)源聚焦和激光一維擴(kuò)束線源兩種激勵(lì)源空間調(diào)制模塊，設(shè)計(jì)過程中充分考慮激勵(lì)源高功率、不連續(xù)、不可見的特點(diǎn)。點(diǎn)源聚焦模塊采用倒立望遠(yuǎn)鏡系統(tǒng)改善光束質(zhì)量后再進(jìn)行聚焦，輸出光斑可實(shí)現(xiàn)100m-1000m連續(xù)可調(diào)。針對(duì)一維擴(kuò)束線源模塊提出了基于單一柱透鏡和基于鮑威爾棱鏡與菲涅爾透鏡相結(jié)合的兩種設(shè)計(jì)方案，柱透鏡方案設(shè)計(jì)過程中利用光學(xué)仿真軟件分析了柱透鏡成像規(guī)律，根據(jù)其輸出線源呈線型高斯分布的特點(diǎn)，提出了用精密光闌截取能量集中部分用于實(shí)驗(yàn)的解決方案。依據(jù)鮑威爾棱鏡線型公式利用Solidworks軟件建立了模型，并導(dǎo)入光學(xué)分析軟件進(jìn)行仿真，結(jié)果顯示輸出線源達(dá)到了良好的均勻性。 對(duì)常用的激光超聲光學(xué)檢測(cè)法相關(guān)理論及可行技術(shù)方案進(jìn)行研究，提出新型激光超聲檢測(cè)系統(tǒng)設(shè)計(jì)方案。該設(shè)計(jì)利用聲光調(diào)制器在信號(hào)中引入一個(gè)載波頻率，利用高頻調(diào)制手段提高信號(hào)的穩(wěn)定性和系統(tǒng)的抗干擾能力；通過雙光路差分原理消除了環(huán)境噪聲對(duì)干涉信號(hào)的影響；利用偏振特性，，使相同偏振態(tài)的光進(jìn)行干涉，大幅提高干涉信號(hào)幅值；通過增加聚焦透鏡組，進(jìn)一步提高系統(tǒng)靈敏度。針對(duì)激光外差信號(hào)的特點(diǎn)，設(shè)計(jì)了以AD8302為核心的相位解調(diào)模塊。該模塊利用AD8302良好高頻測(cè)相能力以及外圍相關(guān)電路的設(shè)計(jì)，解決了現(xiàn)有電路系統(tǒng)的諸多問題。其理論分辨率可以達(dá)到0.1nm，從而實(shí)現(xiàn)更高精度的激光外差干涉信號(hào)處理，并且該芯片能檢測(cè)兩干涉信號(hào)幅值比，實(shí)時(shí)監(jiān)控激光外差光路干涉質(zhì)量。 最后搭建了激光超聲激勵(lì)與檢測(cè)系統(tǒng)，對(duì)各模塊功能進(jìn)行了實(shí)驗(yàn)驗(yàn)證，實(shí)現(xiàn)了對(duì)超聲信號(hào)的激勵(lì)與檢測(cè)。結(jié)果表明本設(shè)計(jì)可提高激光超聲激發(fā)效率，超聲檢測(cè)系統(tǒng)信噪比高，有利于高頻微弱激光超聲信號(hào)檢測(cè)。
[Abstract]:Because of the characteristics of short wavelength, strong directionality, diffraction and scattering due to obstacles, laser ultrasound has become an important research field in the field of nondestructive testing (NDT). In this paper, by means of simulation and experiment, the laser ultrasonic excitation and detection technology is studied based on the structure and principle of laser ultrasonic excitation and detection system. Based on the principle of laser ultrasonic excitation, the key technology of laser ultrasonic excitation is analyzed. Two kinds of spatial modulation modules of laser point source focusing and laser one-dimensional beam spreading source are designed. The high power of excitation source is fully considered in the design process. The quality of being discontinuous or invisible. The point source focusing module uses the inverted telescope system to improve the beam quality before focusing, and the output spot can be continuously adjustable by 100m-1000m. Two design schemes based on single cylindrical lens and Powell prism and Fresnel lens are proposed for one-dimensional beam spreading source module. The imaging law of cylindrical lens is analyzed by optical simulation software in the design process of cylindrical lens. According to the linear Gao Si distribution of the output line source, the solution of using precision aperture to intercept the energy concentration part for experiment is put forward. According to Powell's prism linear formula, the model is established by Solidworks software, and the optical analysis software is introduced to simulate the model. The results show that the output line source has achieved good uniformity. The relevant theory and feasible technical scheme of laser ultrasonic optical detection method are studied, and a new design scheme of laser ultrasonic detection system is put forward. In this design, an acousto-optic modulator is used to introduce a carrier frequency into the signal, the high frequency modulation is used to improve the stability of the signal and the anti-interference ability of the system is improved, and the influence of environmental noise on the interference signal is eliminated by the principle of double optical path difference. By using the polarization characteristic, the interference of the same polarization state light can be carried out, and the amplitude of the interference signal will be greatly increased, and the sensitivity of the system can be further improved by increasing the focusing lens group. According to the characteristics of laser heterodyne signal, a phase demodulation module based on AD8302 is designed. This module solves many problems of the current circuit system by using the good high frequency phase measurement ability of AD8302 and the design of peripheral related circuits. The theoretical resolution can reach 0.1 nm, which can achieve higher precision processing of laser heterodyne interference signal, and the chip can detect the amplitude-value ratio of two interference signals and monitor the interference quality of laser heterodyne optical path in real time. Finally, a laser ultrasonic excitation and detection system is set up, and the function of each module is verified experimentally, and the excitation and detection of ultrasonic signal is realized. The results show that this design can improve the efficiency of laser ultrasonic excitation, and the signal-to-noise ratio of ultrasonic detection system is high, which is beneficial to the detection of high frequency weak laser ultrasonic signals.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN247

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