本文選題：KDP晶體　切入點(diǎn)：超精密飛切　出處：《哈爾濱工業(yè)大學(xué)》2013年博士論文　論文類型：學(xué)位論文

【摘要】：KH_2PO_4（KDP）晶體較低的激光損傷閾值是限制慣性約束核聚變（InertialConfinement Fusion，ICF）高功率激光器輸出能力提升的瓶頸環(huán)節(jié)。光學(xué)元件超精密加工表面中高頻形貌信息及各類瑕疵對其光學(xué)性能具有重要影響。但是，目前在KDP晶體超精密飛切微納形貌對其損傷閾值影響機(jī)制方面的研究工作尚未見相關(guān)報(bào)道。本課題首先研究了KDP飛切微納表面主要形貌要素的表征方法，并提取能夠反映晶體光學(xué)質(zhì)量的主要表征參數(shù)；然后建立了表面主要微納形貌特征與晶體損傷閾值之間的映射關(guān)系；最后以對晶體損傷閾值影響較大的形貌參數(shù)為優(yōu)化目標(biāo)，建立了飛切主軸振動(dòng)模型，并結(jié)合實(shí)驗(yàn)來指導(dǎo)飛切參數(shù)的選擇，為KDP晶體超精密加工提供了重要的參考意見。 為了對晶體飛切表面波紋度及粗糙度進(jìn)行分析，本文利用Motif方法、功率譜密度、小波及分形來對表面形貌進(jìn)行表征。分析發(fā)現(xiàn)：Motif方法所獲得的波紋度平均幅值能避免對單一成分求權(quán)重而直接對表面波紋進(jìn)行幅值評價(jià)；一維、二維PSD曲線以及角譜和半徑譜能夠?qū)︼w切表面進(jìn)行全波段以及紋理方向性評價(jià)；小波變換可以通過多尺度分解與重構(gòu)實(shí)現(xiàn)KDP晶體三維形貌的提取與分析；分形維數(shù)可以克服測量儀器的誤差而對表面粗糙度進(jìn)行最真實(shí)的評價(jià)。上述方法的結(jié)合使用對KDP晶體飛切表面微納形貌的全面表征具有重要意義。 為了研究中頻波紋對晶體損傷閾值的影響，本文綜合利用PSD與傅里葉模方法來分析波紋參數(shù)對入射波的調(diào)制特性，發(fā)現(xiàn)KDP飛切表面頻率構(gòu)成具有多樣性特征。對晶體損傷閾值影響較大的危險(xiǎn)波紋周期基本集中在80μm-180μm范圍內(nèi)，而該范圍內(nèi)波紋幅值是較周期更敏感的致傷參量。因此，提出使用波紋度Motif平均深度作為衡量飛切表面損傷閾值大小的一個(gè)近似度量參數(shù)。同時(shí)，基于諧波產(chǎn)生的耦合波方程，提出降低飛切波紋幅值是提高晶體倍頻效率并改善輸出波形的有效措施。 為了研究表面粗糙度與亞表層裂紋對光傷閾值的影響，本文利用傅里葉模法來對上述特征的調(diào)制屬性進(jìn)行分析，并引入分形理論來表征表面的抗熱損傷能力。分析發(fā)現(xiàn)：粗糙度增強(qiáng)了晶體表面對激光的熱吸收，，而圓周輪廓分形維數(shù)分布能夠很好地表征飛切表面抗激光熱破壞的能力；亞表層裂紋的調(diào)制增強(qiáng)是損傷晶體的又一重要機(jī)制，亞表層裂紋深度與損傷閾值呈相反的映射關(guān)系，而與波紋幅值具有同樣的變化規(guī)律；即抑制波紋的同時(shí)，亞表層裂紋將同時(shí)得到改善。綜合分析發(fā)現(xiàn)：波紋幅值是飛切表面必須抑制的制造誤差。 為了對引致飛切波紋特征的機(jī)床主軸振動(dòng)特性進(jìn)行分析，本文提出利用二自由度陀螺的技術(shù)方程來建立飛切機(jī)床空氣主軸的振動(dòng)模型，定性分析加工過程中切削參數(shù)對波紋頻率與幅值的影響規(guī)律。研究發(fā)現(xiàn)，頻率成分間存在明顯的倍頻與差頻關(guān)系。因此，提出通過對主軸轉(zhuǎn)速及轉(zhuǎn)動(dòng)慣量比的合理設(shè)定，實(shí)現(xiàn)頻率預(yù)測。波紋幅值基本隨進(jìn)給量與切深的增加而增大，進(jìn)給量的影響較切深稍大。極低轉(zhuǎn)速下雖然有利于小幅降低幅值但卻以增加表面破損從而增加熱損傷為代價(jià)。理論及實(shí)驗(yàn)結(jié)果顯示：轉(zhuǎn)速400r/min左右，進(jìn)給量10μm/r左右，切深10μm左右，刀具前角-45能夠得到較好的飛切表面。
[Abstract]:KH_2PO_4 (KDP) crystal laser damage threshold of lower limit of inertial confinement fusion (InertialConfinement Fusion ICF) to enhance the output capacity of the bottleneck of high power laser. The surface morphology of high frequency information and all kinds of defects of optical components in ultra precision machining has important effects on the optical properties. However, currently in the KDP crystal ultra precision fly micro nano cutting research of morphology and its influence mechanism of damage threshold has been reported. This paper studied the characterization methods of KDP micro nano fly cutting surface morphology of main elements, and extract the main parameters can reflect the crystal optical quality; and the establishment of the main surface micro nano mapping relationship between morphology and crystal damage threshold; finally to threshold on the crystal damage morphology parameters greatly as the optimization goal, established the fly cutting spindle vibration model, and combined with the experiment The selection of flying cutting parameters provides an important reference for the ultra precision machining of KDP crystal.
In order to fly cutting crystal surface waviness and roughness were analyzed by using Motif method, the power spectral density, wavelet and fractal to characterize the surface morphology. Analysis shows that the Motif method which can avoid waviness of the average amplitude of single component weights obtained directly on the surface ripple amplitude of one-dimensional, two-dimensional evaluation; the PSD curve and the angular spectrum and the spectral radius can be full band and texture direction of evaluation on the fly cutting surface; wavelet transform can realize extraction and reconstruction and analysis of KDP crystal morphology of 3D multiscale decomposition; fractal dimension can overcome the error of measuring instrument of surface roughness evaluation has important significance to the most real. According to the above method using the comprehensive characterization of the KDP crystal surface micro nano fly cutting.
In order to study the effect of frequency ripple on the laser damage threshold, this paper analyzes the modulation characteristics of wave parameters of incident wave by using PSD and Fourier modal method, KDP fly cutting surface has the characteristics of diversity. The frequency composition of crystal damage threshold risk larger ripple period is concentrated in the 80 m-180 m range, and this range is more sensitive than the ripple amplitude cycle of the injury parameters. Therefore, the average depth of the ripple of the Motif as an approximate measure parameter to measure the fly cutting surface damage threshold size. At the same time, the coupled wave equation based on the harmonic generation, put forward to reduce the fly cutting ripple amplitude is to improve the efficiency and effective measures to improve the frequency doubling crystal the output waveform.
In order to study the surface roughness and subsurface cracks on the laser damage threshold effects, the modulation property of the characteristics were analyzed by using Fourier modal method and fractal theory is introduced to characterize the surface thermal damage. Analysis shows that the roughness of the crystal surface enhanced laser heat absorption, and the fractal dimension of circular distribution to characterize well fly cutting surface anti laser damage; modulation of subsurface crack is an important mechanism to enhance the damage of crystal, subsurface crack depth is contrary to the mapping relationship between the damage threshold, and has the same change with the ripple amplitude; i.e. suppressing ripples and subsurface crack at improved. Comprehensive analysis shows that the ripple amplitude is the fly cutting manufacturing error surface must be suppressed.
In order to cause the spindle vibration characteristics of corrugated fly cutting are analyzed. The vibration model is proposed in this paper to establish air utilization technology of fly cutting machine tool spindle equation of two degree of freedom gyroscope, a qualitative analysis of the effects of cutting parameters in the process of wave frequency and amplitude. The study found that there is obvious relationship between frequency doubling and frequency difference between components. Therefore, put forward by the spindle speed and inertia setting ratio, frequency prediction. Increase the ripple amplitude with the feed rate and cutting depth increases, the influence of feeding amount is slightly larger. The cutting depth at very low speed is helpful to reduce the amplitude slightly but to increase the surface damage to increase the cost of heating damage. Theoretical and experimental results show that the speed of about 400r/min, the amount of feed about 10 m/r, cutting depth of about 10 m, the rake angle of -45 can get good fly cutting surface.

【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：TN241;TH161

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