本文選題：高功率激光焊接 + 光致等離子體��； 參考：《上海交通大學(xué)》2015年博士論文

【摘要】：在高功率激光焊接的過程中,光致等離子體-激光-材料三者之間有著復(fù)雜的相互制約與能量耦合關(guān)系。光致等離子體將會(huì)影響激光穿越等離子體的空間路徑以及最終到達(dá)工件表面的激光能量密度,從而極大地影響整個(gè)焊接過程以及焊縫成形。準(zhǔn)確測(cè)量激光焊接等離子體內(nèi)部的三維物理參數(shù)分布是研究等離子體行為特性以及激光傳輸過程的重要前提。由于高功率激光焊接過程中光致等離子體高能量密度、高速動(dòng)態(tài)變化的特性,以及不均勻非對(duì)稱分布的內(nèi)部特征,現(xiàn)階段針對(duì)高功率激光焊接等離子體物理參數(shù)的測(cè)量絕大部分是單點(diǎn)測(cè)量或二維分布測(cè)量,對(duì)等離子體內(nèi)部三維物理場(chǎng)測(cè)量的研究非常有限。由于對(duì)激光焊接等離子體的內(nèi)部結(jié)構(gòu)及物理特性缺乏準(zhǔn)確而可行的實(shí)驗(yàn)測(cè)量手段,直接限制了對(duì)激光焊接過程中發(fā)生的光致等離子體-激光能量交互作用的研究。因此,迫切需要研究適用于高功率激光焊接的光致等離子體三維重建方法,準(zhǔn)確測(cè)量等離子體內(nèi)部的三維物理參數(shù)場(chǎng),并基于等離子體的三維模型研究等離子體-激光能量交互機(jī)制。這對(duì)于認(rèn)識(shí)高功率激光焊接等離子體的物理特性,揭示激光焊接機(jī)理具有十分重要的意義。本文開發(fā)了一套多通道同步攝影系統(tǒng)來(lái)獲得激光焊接過程中光致等離子體在空間不同角度的投影數(shù)據(jù)。設(shè)計(jì)了由多角度投影光譜圖像進(jìn)行激光焊接等離子體三維重建的方法,準(zhǔn)確測(cè)量等離子體溫度場(chǎng)等三維物理參數(shù)場(chǎng)。并以此為手段計(jì)算了He+Ar混合氣體保護(hù)下鋁合金CO2激光焊接過程中Ar-He-Al三元等離子體的三維溫度場(chǎng)以及吸收系數(shù)與折射率的空間分布,并以三維物理模型為基礎(chǔ)研究了等離子體對(duì)激光的吸收與折射機(jī)制。深入研究了側(cè)吹氣體參數(shù)對(duì)等離子體的三維形態(tài)、物理特性以及激光能量傳輸?shù)挠绊�。本文的主要研究成果如�?針對(duì)等離子體圖像中存在的噪音污染、飛濺顆粒以及工件表面反光等嚴(yán)重影響重建精度的干擾因素,采用P-M擴(kuò)散法對(duì)等離子體圖像去噪處理,在去除噪聲的同時(shí)保留等離子體的邊緣;運(yùn)用灰度形態(tài)學(xué)開運(yùn)算濾除飛濺顆粒引起的孤立點(diǎn)集,減小飛濺物對(duì)等離子體投影光路的影響;采用改進(jìn)的snake算法,利用等離子體形狀的先驗(yàn)知識(shí)將等離子體本體與像的邊緣剝離,避免了將高亮度的等離子體像錯(cuò)誤地劃分進(jìn)重建區(qū)域。提出了一種基于質(zhì)心投影準(zhǔn)則的圖像校正方法,以等離子體圖像的質(zhì)心投影線在空間交于一點(diǎn)為約束條件,對(duì)圖像進(jìn)行平移微調(diào)。校正后等離子體圖像質(zhì)心配準(zhǔn)誤差由1mm左右減少到0.1mm以內(nèi),實(shí)現(xiàn)了校正攝像機(jī)標(biāo)定參數(shù)的優(yōu)化效果。根據(jù)幾何光學(xué)知識(shí)構(gòu)建了等離子體中心投影模型。在中心投影模型中,投影光線是由一系列經(jīng)過投影中心的幾何光線所組成的楔形光線束,此時(shí)投影權(quán)重計(jì)算變得復(fù)雜。對(duì)此提出了一種新的投影權(quán)重計(jì)算方法,將重建區(qū)域的格子投影到成像面后計(jì)算投影面積對(duì)像素點(diǎn)的貢獻(xiàn)。這樣可將計(jì)算空間從n維變換為n-1維,降低了計(jì)算量與計(jì)算復(fù)雜度。通過分析可知本文提出的投影權(quán)重計(jì)算方法與傳統(tǒng)的投影光線路徑法的計(jì)算結(jié)果等效。采用多目標(biāo)優(yōu)化的ART算法進(jìn)行等離子體三維重建,通過模擬計(jì)算分析了重建參數(shù)對(duì)重建過程的影響,獲得了一組優(yōu)化的重建參數(shù)。結(jié)合局部熱力學(xué)平衡態(tài)方程計(jì)算了鋁合金CO_2激光焊接等離子體三維溫度場(chǎng)。計(jì)算結(jié)果表明:等離子體最高溫度在8000K-12000K之間,最高溫度出現(xiàn)在工件上方約0.5mm處。等離子體中心區(qū)域溫度場(chǎng)的分布具有不連續(xù)性和不平滑性,由多個(gè)孤立高溫區(qū)域和相對(duì)低溫區(qū)域組成。采用本文方法計(jì)算得到的等離子體溫度略高于基于Abel逆變換重建算法的計(jì)算值。深入分析了球形分層模型和平行分層模型(或網(wǎng)格模型)對(duì)激光傳播軌跡的影響,揭示了平行分層模型(或網(wǎng)格模型)計(jì)算的激光軌跡與實(shí)際情況相悖的根本原因是:當(dāng)激光進(jìn)入分層界面時(shí),由于分層界面的法線位于光線右側(cè),激光趨向于更接近中心線,因此等離子體起到了正透鏡的作用,與實(shí)際情況不符。建立了可從網(wǎng)格模型轉(zhuǎn)化的等離子體二次曲面分層模型,可以解決網(wǎng)格分界面的法線方向無(wú)法反映宏觀尺度實(shí)際情況的問題。研究了He+Ar混合側(cè)吹氣體流量及組分對(duì)等離子體的形態(tài)特征、物理特性以及激光能量傳輸效率的影響。研究發(fā)現(xiàn):等離子體的溫度隨著氣體流量的增加而減小,在各個(gè)氣體流量下隨著Ar含量的增加呈線性增長(zhǎng)的趨勢(shì)。但是隨著氣體流量的增加,等離子體溫度的下降速度逐步減小。各組氣體參數(shù)下等離子體沿激光入射方向的溫度分布趨勢(shì)較為相似,最高溫度均出現(xiàn)在距離工件上方約0.5mm處,且最高溫度隨Ar含量的增加而上升。等離子體的折射作用造成的激光能量損失率在6%-22%范圍內(nèi),等離子體吸收造成的能量損失率在4%-15%范圍內(nèi)。在同樣的氣體參數(shù)下折射造成的能量損失略高于吸收。激光穿越等離子體后總的能量損失率隨著氣體流量增大而減小,隨Ar含量的增加而增加。從能量損失的角度來(lái)看,Ar在He+Ar混合保護(hù)氣體中的含量并沒有一個(gè)特定上限�？梢酝ㄟ^增大流量的方法將保護(hù)氣體中的He替換成Ar,而并不影響激光能量的傳輸效率。
[Abstract]:In the process of high power laser welding, there is a complex interaction and energy coupling relationship between the three light induced plasma laser materials. The light induced plasma will affect the space path of the laser through the plasma and the laser energy density that eventually reaches the surface of the workpiece, thus greatly affecting the whole welding process and welding. The accurate measurement of the distribution of the three-dimensional physical parameters inside the plasma of the laser welded plasma is an important prerequisite for the study of the characteristics of plasma behavior and the process of laser transmission. The characteristics of high energy density, high speed dynamic change and inhomogeneous asymmetric distribution in the process of high power laser welding are present. Most of the measurements of plasma physical parameters in high power laser welding are single point measurement or two-dimensional distribution measurement. The study of three-dimensional physical field measurement inside the plasma is very limited. Because of the lack of accurate and feasible experimental measurement methods for the internal structure and physical properties of the laser welded plasma, the direct limitation is limited. The interaction between photoinduced plasma and laser energy in laser welding is studied. Therefore, it is urgent to study the three-dimensional reconstruction method of photoinduced plasma for high power laser welding, accurately measure the three-dimensional physical parameter field inside the plasma, and study the plasma excitation based on the three-dimensional model of plasma. The interaction mechanism of light energy is of great significance for understanding the physical characteristics of high power laser welding plasma and revealing the mechanism of laser welding. In this paper, a multi channel synchronous photographic system is developed to obtain the projection data of the photoplasma at different angles in the process of laser welding. The multi angle projection is designed. The three-dimensional reconstruction of laser plasma by laser welding is used to accurately measure the three-dimensional physical parameters of plasma temperature field, and the three-dimensional temperature field of Ar-He-Al three element plasma and the spatial distribution of the absorption coefficient and refractive index of the Ar-He-Al three element plasma in the CO2 laser welding of aluminum alloy under the protection of the mixed gas are calculated. The absorption and refraction mechanism of plasma to laser is studied on the basis of a three-dimensional physical model. The effects of the parameters of the side blowing gas on the three-dimensional shape, physical properties and laser energy transmission are deeply studied. The main research results of this paper are as follows: noise pollution in the plasma images, spatter particles and The interference factors such as the surface reflection of the workpiece surface seriously affect the accuracy of the reconstruction, the P-M diffusion method is used to denoise plasma images, and the edges of the plasma are retained while the noise is removed; the outlier set caused by the spatter particles is filtered by the use of grayscale morphology, and the effect of the splash on the plasma projection optical path is reduced. The snake algorithm uses the prior knowledge of plasma shape to peel off the plasma and the edges of the image, avoiding the wrong partition of the high brightness plasma image into the reconstruction area. A image correction method based on the centroid projection criterion is proposed, which is constrained by the plasma image centroid projection line at a point. The image centroid registration error is reduced from about 1mm to less than 0.1mm, and the optimization effect of calibrating the camera calibration parameters is realized. The projection model of the plasma center is constructed according to the geometric optics knowledge. In the center projection model, the projection light is a series of projection centers. The calculation of the weight of the projection becomes complex at this time. A new method of calculating the weight of projection is proposed. The projection area of the reconstructed area is projected to the imaging surface to calculate the contribution of the projection area to the pixel. This can change the computing space from the n-dimension to the N-1 dimension, which reduces the complexity of calculation and calculation. The calculation method of projection weight proposed in this paper is equivalent to the result of the traditional projection ray path method. The ART algorithm of multi-objective optimization is used to reconstruct the plasma. The effect of the reconstruction parameters on the reconstruction process is analyzed by the simulation calculation, and a set of optimized reconstruction parameters is obtained. The equilibrium state equation is used to calculate the three-dimensional temperature field of the CO_2 laser welding of aluminum alloy. The calculation results show that the highest temperature of the plasma is between 8000K-12000K, the highest temperature is about 0.5mm above the workpiece. The distribution of the temperature field in the center of the plasma is discontinuous and unsmooth, and the temperature field of the plasma center is from a number of isolated high temperature regions and phases. The plasma temperature degree calculated by this method is slightly higher than the calculated values based on the Abel inversion reconstruction algorithm. The influence of the spherical stratification model and the parallel layered model (or mesh model) on the laser propagation trajectory is deeply analyzed, and the laser trajectories and the reality of the parallel stratified model (or grid model) are revealed. The fundamental reason for the contrary is that when the laser enters the layered interface, the laser tends to be closer to the center line because the normal line of the layered interface is located on the right side of the light, so the plasma plays the role of the positive lens and does not correspond with the actual situation. The two layer surface layer model of the plasma which can be transformed from the grid model can be solved. The normal direction of the grid interface can not reflect the actual situation in the macro scale. The influence of the flow and composition of He+Ar mixed side blowing gas on the morphological characteristics, physical properties and laser energy transmission efficiency of the plasma is studied. The study shows that the temperature of the plasma decreases with the increase of the volume flow of the gas. With the increase of Ar content, the decreasing speed of plasma temperature decreases gradually with the increase of gas flow. The temperature distribution trend of plasma body along the laser incident direction is similar, the highest temperature appears at about 0.5mm above the workpiece, and the highest temperature is with the Ar content. The energy loss rate of the laser energy caused by the plasma refraction is within the range of 6%-22%. The energy loss rate caused by the plasma absorption is within the range of 4%-15%. The energy loss caused by the refraction of the same gas parameters is slightly higher than that of absorption. The total energy loss rate of the laser through the plasma increases with the gas flow rate. The decrease is increased with the increase of Ar content. From the point of view of energy loss, there is no specific upper limit for the content of Ar in the He+Ar mixed protection gas. By increasing the flow rate, the He in the protective gas is replaced with Ar without affecting the transmission efficiency of the laser energy.
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG456.7

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5 劉道明;利用“中國(guó)虛擬人”的三維重建構(gòu)建外科三維診療平臺(tái)[D];中國(guó)人民解放軍第一軍醫(yī)大學(xué);2003年

6 高劍;三維重建應(yīng)用系統(tǒng)研究[D];山東大學(xué);2009年

7 劉勇;基于非定標(biāo)圖象的三維重建方法研究[D];西安電子科技大學(xué);2001年

8 楊宇;水下多通道真彩色三維重建與顏色還原方法研究[D];中國(guó)海洋大學(xué);2014年

9 吳恩啟;微細(xì)管道內(nèi)表面檢測(cè)及三維重建關(guān)鍵技術(shù)研究[D];浙江大學(xué);2005年

10 朱新勇;肝臟及其內(nèi)部血管64排螺旋CT掃描數(shù)據(jù)三維重建及虛擬手術(shù)研究[D];第一軍醫(yī)大學(xué);2007年

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