真空低温环境下卫星天线变形摄影测量技术

介绍了一套在真空低温环境下使用的摄影测量系统。该系统主要用于真空低温环境下对卫星天线等由于热变形而导致的面形变形进行测量,其测量方法采用了摄影测量法的基本原理。该设备为国内首套自主研制的真空低温环境用非接触摄影测量系统,主要由CCD摄影组件、标尺、支撑机构、试件加热设备和专用图像处理软件组成。采用该测量系统在模拟空间环境下对Φ660mm口径反射面卫星天线进行了一次变形测量试验,通过试验完成了对被测天线的变形测量,获得了大量的数据,验证了采用该套测量系统在模拟空间环境下进行天线变形测量的可行性。通过分析,该套测量系统的相对测量精度达到了1/20000。     

基于双平面镜双相机组合测量全场变形的方法

针对单相机难以用于全场变形测量以及多相机在全场变形测量中复杂性等问题，提出一种利用双平面镜辅助的双相机系统来实现全场变形测量的新方法。该方法基于相机标定的坐标变换方法，即通过双平面镜实现从真实相机坐标系到虚拟相机坐标系之间的转换，进而实现从实物到虚像之间的转换。将该方法用于空心六角铝棒的热变形测量中，并与ANSYS软件的仿真结果进行比较，结果表明，该方法不但可以实现对被测件的三维重建，而且可以实现全场的变形测量，相对误差仅为0.51%，满足精度要求、效果良好。     

TEM纳米云纹法测量纳米碳管变形

提出了透射电子显微镜(TEM)纳米云纹法的新技术,首次将该方法用于单根单壁碳纳米管的残余变形测量。纳米云纹由计算机显示器扫描线与碳纳米管束TEM图像干涉而成。该方法具有纳米级空间分辨率,可直接测量碳纳米管的力学性能。对TEM纳米云纹法的原理进行了详细的阐述,并利用不同管径的单壁碳管束产生了云纹。对直径为7.5nm的弯曲碳管束的残余变形进行测量,直接得到了其中一根直径为1.0nm的单壁碳管的残余变形场。实验结果证明了该方法的可行性。该方法为纳米尺度的碳管力学性能测量提供了新途径。     

水转印栅线聚氨酯大变形及动态力学特性测量

将水转印工艺与数字图像处理方法结合,提出水转印栅线相移云纹法,该方法可用于聚氨酯类超弹性材料大变形测量。通过水转印制作试件栅与参考栅,并采用计算机对两者的数字图像进行算术相减,得到数字相移云纹条纹;运用Carré算法从相移云纹条纹图中提取出面内变形相关的相位。所提方法仅用一幅试件栅与参考栅图像实现试样变形信息的自动、准确提取,可为动态大变形的测量提供一种成本低、有效精确的测试手段。给出了所提方法用于聚氨酯圆环静载压缩变形定量测量,及圆棒的冲击压缩动态变形特性实验研究的结果。     

应力应变测量技术

<正> 美国国家标准技术研究院(NIST)的科学家们研究出了一种计算机控制的用于测量材料变形的光学技术,该系统利用激光器、电视摄像机和静片照像技术测量应变的三个分量以及刚体的转动。该系统能在63.5mm的方格内用约5h测量16000个位置的应变。目前正与福特汽车公司合作用于研究复合材料板材中裂纹的初始状态和扩展状态。     

基于带通滤波成像的高温数字图像相关方法

提出一种用于高温物体表面全场变形测量的高温数字图像相关方法.该方法采用带通光学滤波成像技术以有效减小高温物体表面热辐射对相机采集图像亮度增强的影响,在物体表面温度高达1000℃时仍可获得可被数字图像相关方法直接分析处理的高质量数字图像.用该方法测量了铬镍奥氏体不锈钢在1000℃高温时的全场热变形以及从室温到1000℃温...     

一种分析薄膜振动模式的结构光条纹时间平均法

提出了一种用于振动物体表面快速测量的光学测试系统和方法。该系统采用结构光三维传感技术,利用时间平均法来实现对振动表面的测量和振动模式分析。用低帧频商用CCD相机记录由光栅投影到振动物体表面上形成的一系列变形正弦条纹,对获取的一帧变形条纹经过二维傅里叶变换、频谱滤波、逆傅里叶变换等处理得到调制物体振幅的零级贝塞尔函数分布。给出了该方法的理论分析,推导了相应的计算公式。计算机模拟和实验验证了该方法的可行性。实验证明,该方法具有数据获取速度快,全场非接触测量以及实验装置简单等优点。     

傅立叶变换用于全息三维物体面形测量

介绍了将傅立叶变换用于全息三维面形测量的基本原理和实验装置。首先用全息干涉条纹替代投影条纹投影到待测物体上 ,在相位解调中 ,结合Gerchberg迭代算法对变形条纹进行处理 ,然后用汉宁窗口进行数字加权滤波。结果表明 ,该测量系统实验装置简单 ,测量精度高 ,速度快 ,适用于复杂大物体三维面形测量     

扫描离子束云纹法

提出了一种在微米尺度下测量物体面内位移的新型扫描离子束云纹法。对该方法的测量原理以及变形测量的精度进行了阐述。以平行云纹和转角云纹为典型实验对该方法的测量精度进行了检验。该方法成功地应用于微电子系统结构在去除SiO2牺牲层后的残余变形测量。实验结果证实了该方法的可行性。     

连续频率散斑光栅膜测量技术的研究

提出了一种新的连续频率散斑光栅膜测量技术，给出了该技术的理论和方法，它可用于研究很大范围内的变形，其灵敏度可从０￣６００１／ｍｍ范围内连续选取，或更高。     

表面热透镜技术测试光学薄膜特性研究

在薄膜特性的研究工作中，激光引起的表面形变是一种广泛应用的技术。在这种技术中，薄膜的形变(热包高度小于0．1nm)一般是采用光热偏转技术来探测的。介绍了一种通过光学衍射效应来研究薄膜表面形变的新技术即表面热透镜技术，它是研究薄膜特性的一种灵敏且易于控制的方法。探讨了其理论模型及在薄膜的吸收测量和缺陷特性测试方面，该方法相对于传统方法的优点和潜力。     

Deformation sensing with a multimode POF using speckle correlation processing method

A deformation sensing technique with a multimode plastic optical fibre based on intensity speckle patterns’ correlation coefficient measurement has been presented. Influence of the average speckle size on results of deformation measuring has been studied and discussed. The presented sensing technique provides a good linear response to the applied deformation in a relatively wide operation region. It is shown that the proposed technique is highly sensitive, low-cost and simple to implement in practice.     

偏振相位偏移电子散斑干涉术及其应用于变形测量

本文叙述了一种用于测量漫射表面变形的使用偏振相位偏移技术的电子散斑干涉术.由于采用共光路光学相位偏移技术,因而具有较高的稳定性;用计算机图像处理可精确地获得相位图;用去包裹技术(unwrapping)可直接得到表面变形的精确数据.     

A novel technique for measuring 3D deformation of adhesively bonded single lap joint

An easy-to-implement yet practical single-camera microscopic stereo-digital image correlation(stereo-DIC) technique is proposed for surface three-dimensional(3D) deformation measurement of singe lap joint(SLJ) samples subjected to mechanical loads. The basic principles, optical configurations and implementation procedures of the proposed technique are described in detail. Compared with existing single-camera 2D-DIC technique, which has been regularly used for in-plane deformation measurement of a SLJ specimen, the proposed technique offers the special merit of simultaneously determining all the three displacement components by simply adding two additional optical elements to existing single-camera 2D-DIC systems. The accuracy and effectiveness of the proposed technique is demonstrated by measuring the 3D deformation of a SLJ specimen subjected to quasi-static tensile loads.     

Incremental calculation for large deformation measurement using reliability-guided digital image correlation

Conventional digital image correlation (DIC) technique using a fixed reference image provides high-accuracy measurements but normally fails when serious decorrelation effect occurs in the deformed images due to large deformation, serious illumination fluctuations or other reasons. In this paper, an incremental reliability-guided digital image correlation (RG-DIC) technique, by combining the recently developed RG-DIC technique and an automatic reference image updating scheme, is proposed for large deformation measurement. In the incremental RG-DIC technique, a seed point is defined in the original reference image and searched in the deformed images, if the estimated correlation coefficient is larger than a preset threshold, which means no serious decorrelation effect exists in the deformed image, the RG-DIC technique is used to continue correlation analysis to obtain full-field displacements. Otherwise, the image recorded just before the current deformed image is chosen as an updated reference image to proceed with correlation analysis. Afterwards, the incremental displacements extracted by comparing the current deformed image and the updated reference image can be cumulated to determine the overall deformation. The effectiveness of the proposed technique is demonstrated by retrieving the full-field deformation of a foam sample subjected to large compressive deformation.     

改善塑料光学零件成型质量的几个问题

从改进注射成型技术和模具制造技术的角度介绍了提高塑料光学零件的质量所采取的措施。在抑制变形的成型技术中所采用的注射压缩成型方法中，用机械的方法对熔融塑料均匀加压以减小塑件的变形及残余应力。也可采用适当的补偿方法修正模具以补偿塑件的变形。在模具制造中可以在模芯表面镀一层非电镀镍，然后用金刚石车削机床加工，而获得很好的表面粗糙度和表面面形精度。     

Three-dimensional particle cluster tracking algorithm using affine transformation

In Particle Image Velocimetry (PIV), the cross correlation tracking technique is widely used to analyze the particle images. The technique assumes that the fluid motion, within small regions of the flow field, is given by parallel movements over short time intervals. However, actual flow fields may have some distorted motion, such as rotation and shear. Therefore, if the distortion of the flow field is not negligible, the fluid motion can not be tracked well using the cross correlation technique. The author proposed a new particle tracking technique, based on the particle cluster matching using linear Affine Transformation. The algorithm can be applied to flow fields which exhibit characteristics such as rotation and shear. The deformation of the cluster pattern is expressed by the linear Affine Transformation. The parameter of the transformation can be determined using the least square technique from the particle positions. The effectiveness of the tracking techniques, including 3D cross correlation, Spring Model and Affine Transformation, were evaluated with synthetic data of three-dimensional flow field. The cross correlation technique could be applicable to the small deformation cases. When the deformation of particle pattern between two images are very large, the pattern deformation could not be expressed by the Affine Transformation, i.e., linear transformation, resulting in mis-tracking. However, the Spring Model technique was found to be more effective even in the larger deformation condition, because the Spring Model does not assume the linear transformation.     

A modified digital phase-shift moiré technique for impact deformation measurements

Due to the short loading times and high deformation rates inherent to impact experiments, measurement of the occurring deformations is not straightforward. Presented in this paper is a technique to obtain the displacements and deformations of a specimen subjected to a uni-axial impact load. During the experiment the deformation of a line grating attached to the specimen is captured using a streak camera. From the recorded deforming grating the specimen displacements are automatically derived using an advanced numerical algorithm, based on the interference between the specimen grating and a virtual reference grating. Numerical interference is considered because it allows that the pitch of the reference grating is adapted to the changing amplitude of the deformation. Indeed, at each moment of the deformation process the pitch of the reference grating is chosen such that the highest possible accuracy and sensitivity is guaranteed. Because of this, large changes in deformation amplitude are allowed, and the technique is applicable to a wide range of materials. Eventual imperfections of the specimen grating and temperature effects are taken into account. Specimen displacements are extracted automatically by means of a phase-shifting technique.

The non-contact measurement technique yields high resolution, quantitative information on the specimen deformation, along the entire length of the specimen and during the full duration of the experiment. Interaction by the operator is excluded. Results are presented of a high strain rate tensile test on a steel sheet specimen showing local deformations up to about 170%.     

Experimental Investigation of Polycrystalline Material Deformation Based on a Grain Scale

We propose an experimental approach for investigation of the polycrystalline deformation behaviour at a grain scale. The technique is characterized by the joint application of micro material testing systems and the intragranular deformation analysis methods, It is attempting to map the deformation evolution at grain scale during the elastic and plastic deformations of polycrystalline specimens.     

Phase retrieval in DSSI for relatively large deformation

Methods for phase retrieval in digital speckle shearing interferometry (DSSI) with relatively large deformation are proposed using a single wavelength illumination with windowed Fourier filtering (WFF) and two-wavelength simultaneous illumination with iterative sine-cosine average filtering (ISCAF). For relatively large deformation measurement, WFF technique has a higher noise suppression capability than ISCAF technique but requires careful selection of the processing parameters, while ISCAF is a simple filtering with less parameter setting. Both methods for phase retrieval are discussed. Experimental results show that both methods are capable of noise suppression in the phase retrieval for relatively large deformation.