本文選題：激光超聲　切入點(diǎn)：數(shù)值模擬　出處：《哈爾濱工業(yè)大學(xué)》2016年碩士論文

【摘要】：飛秒激光與物質(zhì)相互作用的機(jī)理性的研究對(duì)認(rèn)識(shí)物質(zhì)各項(xiàng)彈性參數(shù)對(duì)激發(fā)出的超聲波的影響有著非常重要的意義。人們還可以根據(jù)對(duì)超聲表面波的檢測(cè)表征材料表面的缺陷。在許多理論機(jī)制的研究中,學(xué)者們首先考慮激光使得材料表面具有一定的溫度場(chǎng),然后溫度場(chǎng)產(chǎn)生熱應(yīng)力,最后熱應(yīng)力又引起形變。在溫度場(chǎng)模型的選擇上許多學(xué)者還是傾向于拋物線型的熱傳導(dǎo)方程,但是對(duì)于超短脈沖激光,雙溫模型才能比較好的描述溫度場(chǎng)。針對(duì)超短脈沖激光與金屬膜相互作用時(shí)間短的特點(diǎn),基于電子及晶格的雙溫模型,構(gòu)建了激光加熱金屬膜的熱沉積模型,并給出了熱場(chǎng)的時(shí)間演化數(shù)值解,得到了電子和晶格熱平衡的時(shí)間�；跓釓椥�(yīng),構(gòu)建了應(yīng)力場(chǎng)的時(shí)空演化方程,并給出了應(yīng)力場(chǎng)的時(shí)空演化數(shù)值解,得到了激光驅(qū)動(dòng)應(yīng)力波在金屬銅膜中的傳播速度。基于應(yīng)力與形變的轉(zhuǎn)換關(guān)系,數(shù)值模擬了飛秒激光作用下銅膜中位移場(chǎng)的分布情況,分析了超聲縱波在銅膜中的產(chǎn)生和傳播情況。在實(shí)驗(yàn)部分本文設(shè)計(jì)并且搭建了泵浦探測(cè)超快攝影平臺(tái),利用應(yīng)力波在材料中傳播時(shí)會(huì)產(chǎn)生雙折射效應(yīng),在銅膜樣品前后加了一組消光的偏振片作為超快快門(mén),以圖像的形式研究了飛秒激光在銅膜表層激發(fā)出的超聲波的傳播過(guò)程,給出超聲波在銅膜表層中傳播的速度。
[Abstract]:The study of the mechanism of femtosecond laser interaction with matter is of great significance in understanding the effect of various elastic parameters of matter on the excited ultrasonic wave.The defects on the surface of the material can also be characterized by ultrasonic surface wave detection.In the study of many theoretical mechanisms, the researchers first consider that the laser makes the surface of the material have a certain temperature field, then the temperature field produces thermal stress, and finally the thermal stress causes deformation.In the choice of temperature field model, many scholars still prefer parabola heat conduction equation, but for ultrashort pulse laser, the double temperature model can describe the temperature field better.In view of the short interaction time between ultrashort pulse laser and metal film, the thermal deposition model of metal film heated by laser is constructed based on the double temperature model of electron and lattice, and the numerical solution of time evolution of thermal field is given.The time of thermal equilibrium of electron and lattice is obtained.Based on the thermoelastic effect, the space-time evolution equation of the stress field is established, and the numerical solution of the space-time evolution of the stress field is given, and the propagation velocity of the laser-driven stress wave in the copper film is obtained.Based on the relationship between stress and deformation, the distribution of displacement field in copper film subjected to femtosecond laser is numerically simulated, and the generation and propagation of ultrasonic longitudinal wave in copper film are analyzed.In the experiment part, we designed and built the pump detection ultra-fast photography platform. Using the stress wave propagating in the material will produce birefringence effect, adding a group of extinction polarizers before and after the copper film sample as the ultrafast shutter.The propagation process of ultrasonic wave excited by femtosecond laser on the surface of copper film is studied in the form of image, and the velocity of ultrasonic wave propagating in the surface layer of copper film is given.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TN249;O426.2
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本文編號(hào)：1712713