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可调谐二极管吸收光谱技术(tunable diode laser absorption spectroscopy,TDLAS)已成为超声速燃烧的重要测量手段之一. 为提高其空间分辨能力,需发展基于TDLAS,结合层析成像术的二维断层成像术(tunablediode laser absorption tomography, TDLAT). 设计了一套基于6 平行光束-旋转测量的新型TDLAT 系统,吸收波长为7 185.6 cm-1 和7 444.3 cm-1 双线,采用分时-直接吸收探测策略. 重建中,使用代数重建算法,先分别反演计算两吸收线的吸收率和吸收比分布,再获得温度和浓度分布. 利用该系统,在CH4/Air 预混平面燃烧炉上开展初步验证试验. 结果表明,TDLAT 系统可以反演出温度和浓度分布特征,反演的温度分布结果与热电偶测量值吻合较好. 进一步改进该系统,可用于超燃直连台中,测量燃烧室出口气流的温度和组分浓度分布. 相似文献
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沿润滑油膜厚度方向的剪切流速分布是影响机械部件润滑性能的重要因素.为此,搭建了基于荧光漂白成像的微间隙油膜剪切流速分布测量平台.通过对漂白区域形状演化过程进行图像分析,获得了微米量级间隙中的PB450和PAO6润滑油膜的剪切速度分布.结果表明:在设定测试条件下,厚度为8.5μm的PB450油膜沿膜厚方向的剪切流速近似为典型的线性分布,而相同厚度下的PAO6油膜流速分布表现为非线性塞流,界面附近油膜黏度较中层显著下降.研究还发现,同一滑动速度下,PAO6剪切流速偏离线性分布的程度随膜厚的降低而增加.经过比对分析,试验结果与流体动压润滑条件下的相关数据吻合. 相似文献
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激光散斑位移测量法是一种重要的现代光学位移测量方法,由于受到图像传感器元件感光性能限制,难以在强干扰光条件下获得有效散斑场信息,进而无法获取位移场数据,因此,基于单像素成像技术,本文提出一种新的激光散斑位移测量方法:对散斑信息进行图案编码调制,并使用单像素探测器采集调制后的光强信息;利用Walsh-Hadamard Transformation(WHT)成像算法对散斑场图像进行重建;最后结合自相关算法确定物体的位移场信息。分别利用商业相机和单像素成像技术对散射介质的单轴微小位移进行测量,结果表明基于单像素成像技术的激光散斑位移测量技术可以获得较好的测量结果。相比于传统测量方法,基于单像素成像技术的激光散斑位移测量方法在复杂环境中具有一定的优势,可实现强光干扰下的位移场测量。 相似文献
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根据台阶图像的特点,采用阈值法、多剖线平均法以及多项式曲线拟合法对图像中的白斑噪声,涨落噪声和其它噪声进行前期处理,去噪效果较好,使图像的有用信息损失小,提高了测量CCD成像系统调制传递函数的精度。实践表明,用这种数据处理方法测量CCD成像系统的MTF较为合适。 相似文献
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三维粒子成像测速(PIV)中粒子像斑定位的透视成像原理,方法及其可确定性 总被引:4,自引:1,他引:3
在三维粒子成像测速(PIV)方面,可运用体积光照明同时从不同光轴用多个照相机获得PIV图像,如何根据这些不同光轴获得的PIV图像确定出粒子物点的空间位置是实现三维粒子成像测速的前提。基于此,本文提出了根据多幅不同光轴的PIV图像的粒子像斑实现粒子物点三维定位的透视成像定位原理和方法,精确确定透视平面与透视中心在空间的位置是实现粒子物点三维定位的关键,直接测定透视中心(照相机的光学中心)和透视平面在 相似文献
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基于频率-波数域偏移的损伤被动成像识别研究 总被引:1,自引:0,他引:1
提出了一种应用Lamb波对板结构中多部位损伤源进行被动成像识别的方法.基于Mindlin板理论,推导了板结构中弥散性Lamb波频率-波数域的快速偏移方法,结合爆炸成像原理,对损伤源发出的Lamb波信号进行回传成像.由于损伤源的发生时刻未知,将使用不同假设发生时刻(即不同长度)的Lamb波信号生成一系列图像,通过最小熵原理从中确定最优图像,识别出损伤源的位置和发生时刻.进行了数值仿真研究来表明所提出方法的有效性. 相似文献
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A constitutive relation is developed to describe the nonlinear behavior of ferroelectric ceramics subjected to external stress and electric field. The theoretical development considers each domain as an inclusion. The Helmholtz and Gibbs free energy of the constituent element are derived by using a micromechanics approach. They are functionals of the orientation distribution function (ODF) that represents the domain distribution patterns. By applying the internal variable theory and expanding ODF in Fourier series, the yield condition, evolution of ODF, and constitutive relation are obtained. Theoretical results agree with experiments. 相似文献
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为实现对金属粉末压坯烧结过程的实时观测,从而验证现有的相关理论,本文利用同步辐射CT(SR-CT)技术,对铝压制陶瓷坯体的固相烧结过程进行实时投影成像;应用滤波反投影算法和数字图像处理技术,得到了陶瓷坯体在整个固相烧结过程中内部微结构演化的三维重建图像,实现了对铝压制陶瓷坯体整个固相烧结过程的无损原位观测,得到了样品由烧结中期进入烧结后期的完整的演化过程图像。通过重建图像,清晰观测了样品的固相烧结过程:在烧结前、中期(烧结时间t<180min、温度T<600℃),烧结颈形成并随烧结时间生长;由烧结中期开始进入后期时(烧结时间t≥180min、温度T≥600℃),样品内部结构演化加剧,气孔由相互连通演化为相互孤立并球化。进一步在实验图像的基础上分析了二面角等烧结特征的变化情况,得到烧结颈尺寸与时间对数有较好的线性关系,并可根据曲线分辨中期、后期。统计了样品在不同烧结时间的孔隙率,得到了孔隙率随烧结时间和烧结时间对数的变化曲线;分析了样品在不同烧结阶段的致密化特点,得到了烧结中期孔隙率和时间对数的线性关系。实验结果验证了现有的烧结理论,并为进一步完善烧结理论以及建立扩散和本构模型提供了高质量的实验数据。 相似文献
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Valérie Serin Pascal Lavieille Jacques Lluc Marc Miscevic 《Experiments in fluids》2011,50(5):1261-1271
An experimental setup was developed to study the vaporization of a liquid inducing capillary pumping. The study was performed
on a single square cross-section micro-channel of 500 μm internal edge, heated only on the upper and lower walls to allow
visualization through the 2 other faces. The images were obtained by a shadowgraph technique using a digital camera. A program
for processing the images was developed to allow the determination of several quantities characterizing the flow, supplemented
by information provided by the rest of the instrumentation equipping the experimental device. The results highlight the unstable
nature of the phase distribution. Despite these instabilities, films of liquid spread in an averaged manner over a length
substantially equal to the length of the zone where the heat flux was applied, independently of the intensity of the heat
flux. 相似文献
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IntroductionCeramic/metalfunctionalygradientmaterial(FGM)hasgradientingredientdistribution,soitspropertiesoftheheattransferan... 相似文献
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根据大量文献调查结果,从影响陶瓷材料摩擦磨损性能的内因(主要包括陶瓷材料的力学性能及微观结构)和外因(主要包括载荷、速度、温度、环境气氛及偶件的化学活性等)出发,讨论了陶瓷材料的摩擦磨损行为及机制,以促进正确选择、设计和使用陶瓷材料,在对陶瓷摩擦学研究现状分析评论的基础上,提出了陶瓷摩擦磨损今后研究工作中值得重视的发展方向. 相似文献
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基于数字图像的土、岩和混凝土内部结构定量分析和力学数值计算的研究进展 总被引:4,自引:0,他引:4
土、岩及混凝土是一种内部结构极其复杂的材料,内部细观组成和结构决定了它们在外力作用下内部应力和应变等物理场的分布状态,在很大程度上控制了它们的宏观力学响应和破坏机理和过程。自1995年以来,数字图像处理技术作为一种材料细观空间结构及几何形态的精确量测和数字表述手段快速地被应用于沥青混凝土、水泥混凝土、土和岩体材料细观结构定量分析中来。本文在研究相关文献的基础上,分析和研究了数字图像技术在土、岩及混凝土内部结构定量分析和力学数值计算中的发展过程和研究成果,内容包括:单个骨料颗粒形态特征定量分析;土、岩和混凝土内部结构定量分析;岩体结构定量分析中的应用;基于数字图像处理的土、岩和混凝土细观结构力学计算。在此基础上,本文进一步对数字图像技术在岩土领域中的应用进展及未来的发展趋势进行了探讨,认为数字图像作为一种空间分布测量手段和数字表述方法使得它具有巨大的潜力,特别是在岩土领域的纵深发展过程中,它可能实现考虑细微观结构性的岩土力学和工程分析和预测的、新的方法和理论。 相似文献
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Mathematical simulation of a thermal shock method for reliability testing of functionally graded material (FGM) is performed
with the end to determine operating parameters of the testing device (power of a laser, laser beam radius, duration of heating)
and to investigate the effect of the composition of FGM on a magnitude of thermal stresses in a coating. An analytical method
for solution of the thermal elasticity problem is developed whereby the approach of a multilayer plate is used for determining
temperature and thermal stresses distributions in a coating. We considered the limiting case of the obtained solution when
the thickness of a layer is infinitesimally small and the number of layers tends to infinity. This procedure allowed us to
obtain the thermal stresses distribution in a FGM coating. The results for the FGM coating composed of WC (tungsten carbide)
ceramics and HS-steel are presented. It is showed that variation of the volume content of ceramics strongly affects thermal
stresses in a coating and they decrease significantly in the case of the uniform spatial distribution of ceramics.
Received on 21 November 2000 / Published online: 29 November 2001 相似文献
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Ultrasonic imaging techniques for portraying and evaluating cumulative internal microstructural damage in engineering materials
are described. A quantitative delineation of the damage is made in terms of acoustic attenuation obtained from computer analyses
of digitized ultrasonic images. Acoustic attenuation data are a basic ingredient in previously developed models of damage
processes in materials. The ultrasonic imaging methodology has been developed using filled polymer (inert solid rocket-propellant)
samples subjected to progressive uniaxial tensile strain. Successive ultrasonic images taken at various levels of applied
strain display dewetting and the evolving microvoid formation/growth which occurs. Both initially intact material and that
with pre-existing cracks are of interest. Changes in acoustic attenuation with strain, derived from the processing of digital
images, have provided results as to the degree of preferential damage accumulation at sites of filler particle agglomerations
appearing on the ultrasonic images. Also, the quantitative extent of an asymmetry in the damage-field distribution near the
tips of an extending crack was determined in precracked material. Iso-attenuation type contours generated by computer reveal
that kidney-shaped damage zones occur in the neighborhood of the propagating crack tips, reminiscent of the plastic-zone shapes
near crack tips in ductile metals under strain. Ultrasonic images of precracked samples show that before crack extension begins,
the material damage in the neighborhood of the crack already extends over a relatively large volume of the specimen.
G.C. Knollman is Senior Staff Scientist and Senior Member, Mechanics and Maternals Engineering Laboratory 相似文献