CRIN介质用于面内位移的测量

本文把梯度折射率介质的面内位移与其折射率梯度联系起来,对面内位移导致的折射率变化进行研究,介绍了ＧＲＩＮ介质用于面内位移测量的基本原理,给出了双光束干涉法测量悬壁梁挠度的实验方法和实验结果。     

结合数码显微镜的数字散斑相关方法精度分析及应用

结合数字散斑相关方法和一种新型的显微镜数码显微镜,提出了一种测量多晶材料晶粒尺度面内变形的新方法,并通过零变形校准实验、重聚焦实验和平移实验等一系列验证实验分析了该方法的精度和实用性.作为应用实例,对一种镍基合金试件进行了单向拉伸和疲劳实验,得到了晶粒尺度下具有较大应变梯度的应变分布图像.结果表明,该方法能够得到精确的位移测量数据,是一种理想的测量晶粒尺度变形的光测方法.     

二维数字图像相关测量中离面位移引起的误差分析

二维数字图像相关方法作为一种非接触全场变形测量的光学方法,在工程上有着广泛的应用.由于其假设物体只发生面内位移,而实验中往往存在离面位移,从而引起测量误差.本文针对这一问题利用了针孔模型,从理论上分析了离面位移对普通镜头测量结果的影响,通过铝块平移实验验证了理论分析的正确性.利用提出的理论模型修正橡胶材料的变形测量结果,并与远心镜头测量结果进行对比,发现修正后的普通镜头测量的结果更接近远心镜头测量的结果.最后,本文根据理论分析和实验验证,给出了减小或消除离面位移造成误差的方法.     

超声散斑数字相关法应用于刚体面内转动测量的研究

在激光数字散斑相关法测量理论的基础上,阐述了超声散斑相关法测量的基本原理,并建立了相应的超声散斑数字相关实验分析系统。在实验分析时,首先应用模拟测量的方法对刚体面内转动对散斑场相关性的影响进行了分析;然后应用实验测量的方法再对此进行了分析;最后对刚体未知面内转角进行了实测。实验结果表明,刚体面内转动可测量的最大转角为9°,当转动角度为10°时,误差大于9%。实验中分别应用了爬山搜索法和相关系数拟合法来分别搜索整像素的位移和亚像素的位移。     

部分相干光云纹干涉法测三维位移场

本文提出了一种用部分相干光可同时获得面内位移和离面位移场的云纹干涉法。该法具有装置简单,无需防震,可用于观场测量等特点。文中论述了此法的基本原理,应用波前干涉理论和付里叶光学理论对变形前后波前的干涉、记录和再观进行了分析,导出了计算公式。实现了透射物体和反射物体表面的面内位移分量(U_0,V_(45),U_(90))和离面位移(w)的全场同时测量,典型实验证明,实验值与计算结果符合较好。     

超声散斑数字相关法应用于体面内转动测量的研究

在激光数字散斑相关法测量理论的基础上,阐述了超声散斑相关法测量的基本原理,并建立了相应的超声散斑数字相关实验分析系统。在实验分析时,首先应用模拟测量的方法对刚体面内转动对散斑场相关性的影响进行了分析;然后应用实验测量的方法再对此进行了分析;最后对刚体未知面内转角进行了实测。实验结果表明,刚体面内转动可测量的最大转角为9°,当转动角度为10°时,误差大于9%。实验中分别应用了爬山搜索法和相关系数拟合法来分别搜索整像素的位移和亚像素的位移。     

微尺度位移、形貌测量系统及应用

研制了一套可应用于MEMS器件的微尺度测量系统,可以在受载状态下实时检测MEMS器件的面内位移、离面位移和三维形貌.该系统中,面内位移测量是一个基于白光数字散斑相关方法的显微光学测量系统,与相应的力学加载系统结合,可以得到MEMS器件在受载状态下的实时面内位移;离面位移和三维形貌测量则是一个基于相移显微投影光栅方法的光学测量系统,与相应的力学加载系统结合,可以得到MEMS器件在受载状态下的实时三维形貌和离面位移.最后给出了几个典型的MEMS器件面内位移、离面位移和三维形貌的实测结果.     

微尺度位移、形貌测量系统及应用

研制了一套可应用于MEMS器件的微尺度测量系统，可以在受载状态下实时检测MEMS器件的面内位移、离面位移和三维形貌。该系统中，面内位移测量是一个基于白光数字散斑相关方法的显微光学测量系统，与相应的力学加载系统结合，可以得到MEMS器件在受载状态下的实时面内位移；离面位移和三维形貌测量则是一个基于相移显微投影光栅方法的光学测量系统，与相应的力学加载系统结合，可以得到MEMS器件在受载状态下的实时三维形貌和离面位移。最后给出了几个典型的MEMS器件面内位移、离面位移和三维形貌的实测结果。     

用散斑和全息干涉法测量汽车前桥的位移

本文分别用散斑和全息干涉法测量了汽车前桥模型的面内和离面位移.实验表明,所用方法简便可行、且精度较高.     

激光干涉测速中信号光纤色散测量

为对激光干涉测速系统(VISAR)中信号光纤的色散特性进行快速测量,搭建了一种基于时域法的 多模光纤色散测量装置。该装置由532nm 的皮秒激光器、快响应光电探测器以及宽带数字示波器组成,通 过对输入光纤前后的光脉冲时间宽度进行测量,来获得光纤的脉冲响应3dB脉宽(即色散时间)。利用该装 置分别对一根长度为123m 的国产梯度折射率光纤以及一根10m 长的阶跃折射率光纤在532nm 波长附近 的色散特性进行了测量。测得的梯度折射率光纤色散时间为(68316)ps,对应3dB频响带宽为646MHz; 阶跃折射率光纤色散时间为(163114)ps,对应频响带宽为271MHz。对实验结果进行了测量不确定度分 析,并与理论计算值进行了比较,获得了较好的一致性。研究表明,利用该实验装置,可对激光干涉测速应用 中信号光纤的色散特性进行迅速、准确的测量,从而为实验中信号光纤类型、长度等的合理选用提供参考。     

微悬臂梁生化传感系统的性能分析

在基于光杠杆原理检测微悬臂梁变形的生化传感实验系统中,液体折射率的变化会导致PSD上光斑的位移,从而影响系统的检测信号。本文从理论上分析了在不同检测光束的入射角度、微梁的放置角度等参数条件下,液体折射率的变化对系统检测信号的影响。结果表明：在传统的光路下,液体折射率改变10-3引起的光斑位移与一般的生化反应引起的位移相当,即液体折射率的改变严重影响系统的检测信号。通过理论分析还发现在适合的参数配置下,可以忽略折射率变化对系统检测信号的影响。同时,参数的改变不影响系统的检测灵敏度。理论分析的结果得到了实验验证。     

Error estimation of laser-Doppler anemometry measurements in fluids with spatial inhomogeneities of the refractive index

We report a combined experimental and theoretical investigation of the influence of spatial non-uniformities of the refractive index on the accuracy of laser Doppler anemometry (LDA) measurements in transparent fluids. One LDA beam is guided through heated air of a thermal boundary layer near a heated vertical flat plate. It is found that the hot air is deflecting the beam because of a modification of the refractive index n in the fluid. This deflection causes three effects: (1) spatial displacement of beam intersection, (2) waist mismatch in the measurement volume and (3) variation in interference fringe distance. With the help of a rotating disk calibration system the resulting displacement of the LDA measurement volume and the Doppler frequency variation is systematically studied at different temperatures. Using a simple model of beam propagation under the influence of well-defined temperature inhomogeneities, the displacement of measurement volume and change in Doppler frequency are calculated and are found to be in agreement with the experimental observations. The results provide a rational framework for an assessment of the accuracy of LDA data in arbitrary transparent fluids with non-uniform refractive index.     

Application of particle image velocimetry to combusting flows: design considerations and uncertainty assessment

Methodological aspects concerning the application of the PIV technique to the study of turbulent flames are discussed in this paper. The physical features of the flow, which have implications for the experimental set-up, image processing and measurement accuracy are identified. Design considerations are developed focusing on several factors: spatial resolution, particle performance, seeding technique, image formation and recording, and image post-processing for the evaluation of the displacement. Relevant uncertainty concerns are related to the effect of the thermophoretic force, acting on a seeding particle while crossing the flame front, and to the non-homogeneity and time-dependence of the refractive index field. The uncertainty due to thermophoresis is assessed by numerically studying the motion of a particle crossing a reference temperature profile. The effect of the refractive index variation is evaluated by means of theoretical analysis of light propagation and image formation, supported by experimental tests designed for this special purpose. Received: 25 November 1999/Accepted: 31 March 2000     

应用梯度折射率透镜的光纤加速度计系统中的光功率耦合分析

研究了在光功率分布为高斯分布的情况下，光纤加速度计系统中光功率耦合的数学模型，并着重分析了几种情况下位移与光功率耦合之间的关系。通过对理论曲线的分析找出良好的线性区间，为该类加速度计的研制提供了科学依据。     

Measurement of 3D pore-scale flow in index-matched porous media

We present the experimental analysis of fluid flow at the pore-scale of a transparent porous medium with matched refractive indices of the solid and liquid phases. The planar laser-induced fluorescence (PLIF) technique described is the first to simultaneously visualize the 3D pore-scale flow of two immiscible liquid phases in porous media. Through the application of a highly precise index matching method and the employment of up-to-date CCD imaging hardware, the system features a high spatial resolution and sampling rate. The method was used to study the dispersion of a tracer dye in single-phase flow and the displacement of oil by water in an imbibition process.     

An iterative method for temperature gradient measurements in two-dimensional thermal boundary layer flows by speckle photography

An iterative method for measuring two-dimensional refractive index fields induced by convective heat transfer phenomena is presented. Starting from the so-called correction parabola, this reconstruction technique takes into account the local second derivative variation of the refractive index field. The efficiency of the method is analytically defined as a function of non-dimensional parameter and numerically investigated using a ray-tracing code for different classic index profiles and a thermal boundary layer case. Finally, as an implementation test, this algorithm is applied to an impinging jet heat transfer experiment using speckle photography measurement data set. The results show a relative dispersion of 20% compared to the parabola reconstruction when the refractive index gradient becomes more severe.     

含液多孔介质力学问题的边界元方法

提出了一种含液多孔介质力学问题的边界元求解方法.首先将问题分解为一系列含单孔流体夹杂的子问题,然后针对每个子问题建立了流体孔体积变化率与流体压力之问的函数关系,进一步采用边界元方法建立了以各流体孔压力为基本未知量的线性代数方程组,最后根据所求出的各流体孔的压力计算含液多孔介质内各点的位移、变形和应力.为了说明方法的有效...     

光纤模斑谱传感器复合材料固化监测研究

提出利用一种新型光纤传感器，通过测量光纤末端近场模斑谱反映光纤埋置周围树脂折射率的变化．计算了随着树脂固化过程中折射率变化的功率谱密度分布，给出截止频率与折射率的近似关系．给出了利用这种传感器进行复合材料树脂固化监测的实验结果．发现这种光纤传感器的信号可以用来反映固化凝胶点和固化结束点．由于固化后光纤仍保持光波导特性，该光纤还可以用来监测结构受环境的扰动如温度变化、振动等．     

Initial kinking of an interface crack between two elastic media under tension and shear

The initial kinking of a thin fracture process zone near the tip of an interface crack between two elastic media under plane strain is studied using the Wiener–Hopf method. The zone is modeled by the discontinuity plane of the normal displacement. This plane is assumed to emerge from the crack tip at an angle to the interface. The angle between the fracture process zone and the interface is determined from the condition that the potential energy is maximum in the zone. The dependence of the length of the zone and its angle on the external load and other parameters is analyzed in the cases of biaxial tension and pure shear. The results obtained are compared with theoretical and experimental data reported by other researchers     

离心力对干涉测量光路的影响及其修正

本文分析了旋转载体上离心力造成的干涉测量光路中空气介质压强的不均匀变化，给出了与光路介质折射率相应的分布规律，分析了由此引起的干涉测量系统动态测量的示值偏差，据此分析计算的结果可用于测量结果的精密修正。本文的讨论结果为精密离心机及类似的运动载体上的动态干涉测量系统的分析设计提供了依据。