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《实验力学》2020,(3)
电子散斑干涉技术是一种非接触式,高精度的变形测量方法,适用于许多工业领域。由于其位移灵敏度与光学布置密切相关,因此难以在一次加载条件下实现三个方向的变形测量。针对这一问题,本文开发出一套能够同时测量面内和离面位移的测量装置。该装置采用波长为473nm、532nm和671nm的三种激光为光源,分别构建三组测量光路,使用一台3CCD彩色相机作为感光元件,一次记录三种光路获得的散斑干涉图像。通过对彩色相机的图像进行R、G、B通道分离,结合四步相移法可以同时获取物体的三维位移场。运用光纤技术优化光路设计,研制了集成化的电子散斑三维变形测量仪。通过相关的实验验证,评估了该装置测量物体三维变形的可行性和可靠性。 相似文献
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介绍了一种基于单个彩色相机的新型全靶面、单相机三维数字图像相关(3D-DIC)方法。借助于设计巧妙的颜色分光光路,被测物体表面图像可以通过两条不同的光路达到相机靶面,采集的标定靶和实验件表面的彩色图像可以分离得到蓝色和红色子图像。通过使用3D-DIC分析标定靶和实验件表面分离后的蓝色和红色子图像,可以获得物体表面的三维形貌和变形。形貌测量、面内和离面平移、以及静动态三维变形实验验证了该单彩色相机3D-DIC方法的有效性和测量精准度。由于可避免双相机同步,且能实现无分辨率损失的全靶面三维形貌和变形测量,本文方法在需要实现瞬态位移和变形测量的爆炸、冲击、振动等领域中具有广阔重要的应用前景。 相似文献
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本文用统计光学方法对双参考光全息——散斑干涉术进行了详尽的理论分析,给出了全息和散斑干涉场区域平均光强分布与光学系统主要参数及三维变形场各分量之间关系的解析表达式,进而讨论了离面位移和面内位移测量的上、下限,最后还给出了有关的实验结果。 相似文献
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本文重点讨论了应用电子散斑干涉法测量弹性元件的挠曲线的方法.将电子散斑测量离面位移的光路引入到高弹性连轴器挠性杆的横向弯曲变形测量中.新的离面位移测量光路并结合相移技术是其特点.首先采用类似于麦克尔逊式光路的方式将物光和参考光垂直分布,使得离面位移的结果是直接并且是纯粹的获得;其次,固体泵浦激光的相干长度很长,从而在设计光路时带来了便利,光路可以很紧凑而不考虑物光与参考光的光程差;最后,在参考光路中引入精密的PZT相移器,从而实现了位相技术,使得测量的结果能数字化输出.电子散斑干涉方法在光学非破坏性检测领域得到了广泛的应用,采用电子散斑干涉技术可以测量物体的变形、位移、振型等.该方法具有实时显示、全场非接触测量、精度和灵敏度高、采用位相技术可以方便的实现测量结果的数字化等优点.本文采用电子散斑干涉结合相移技术,得到了的数字化结果,再和有限元模拟计算进行了比较,证明了方法的正确性. 相似文献
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提出了用超声散斑干涉法来测量物体的位移,并且基于数字干涉和相移-频移技术对超
声散斑数字干涉测量法进行了初步的理论推导. 为了验证理论分析的结果,对一铝试件进行
了离面位移和面内位移的试验测量. 试验结果显示理论分析是正确的,在测量位移和变形时
此方法是有效可行的. 相似文献
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在传统的剪切电子散斑干涉中 ,直接观测到的是干涉条纹图样。因此 ,如何将位移导数场的定量信息从剪切电子散斑干涉条纹图案中提取出来 ,一直是人们关心的问题。本文运用传播光矢量对数字散斑剪切干涉的条纹形成作了理论解释 ,使其物理意义更加清晰。理论分析表明 ,物体的微小偏转可引入线性附加位相。因此 ,通过连续偏转物体可实现剪切电子散斑干涉的相移。本研究通过计算机控制载物平台的精细旋转实现相移 ,结合传统的数字散斑剪切干涉技术以及四步相移算法 ,实现了数字剪切散斑干涉相移系统。利用该系统进行了中心加载、周边固定的圆盘的典型实验 ,实验结果表明该系统可以方便有效地提取出位移导数场的定量信息。 相似文献
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动态液面波高场测量与面型三维重建是流体力学、晃荡动力学等研究领域中的重要问题,但目前仍缺乏一种简易且高效的高精度全场测量手段.基于光斑投影和三维数字图像相关(3D digital image correlation, 3D-DIC)原理,提出了一种动态液面波高场的测量方法.通过液体染色和光斑投影,在液体表面形成光斑纹理,设置双目相机拍摄动态液面的散斑图像.运用交比不变性标定板及张正友标定法获得双目相机内外参矩阵,并基于反向组合高斯牛顿(inverse-compositional Guass-Newton, IC-GN)的3D-DIC算法实现动态液面波高场的高精度三维重构.进一步建立光斑投影的几何光学模型,模拟规则波液面的双目图像,开展数值模拟测量以验证本方法的理论精度,同时开展真实液面波高场的测量验证.结果表明,本方法可实现动态液面波高场的高精度全场测量,模拟液面测量的均方差为0.004 mm,真实静态液面抬升测量的均方差为0.022 mm,真实动态液面测量的均方差小于0.037 mm.本文方法具有高精度、非接触和全场测量等优势,可在实验室流体测量和相关工程场景中推广应用. 相似文献
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随着电子技术、计算机技术的飞速发展,传统的全息干涉技术已经发展到了电子散斑和电子剪切散斑阶段。电子散斑和电子剪切散斑不仅可以完成表面变形量的测量,并且由于它们具有实时性、高灵敏度、非接触性和全场测量等优点,在工业和科研领域中得到了越来越广泛的应用。本文首先介绍了电子剪切散斑干涉的基本原理,然后着重介绍了自行编制的对离面位移的电子剪切散斑图像进行处理的系统。该图像处理系统的主要功能有平滑、区域标记、像素统计等。用该系统对图像进行处理后,可以直接得到缺陷的实际大小。通过对带有已知缺陷模型的实际测量,所得结果与实际吻合较好,说明该图像处理系统是可行的。 相似文献
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Digital Image Correlation (DIC) provides a full-field non-contact optical method for accurate deformation measurement of materials, devices and structures. The measurement of three-dimensional (3D) deformation using DIC in general requires imaging with two cameras and a 3D-DIC code. In the present work, a new experimental technique, namely, Diffraction Assisted Image Correlation (DAIC) for 3D displacement measurement using a single camera and 2D-DIC algorithm is presented. A transmission diffraction grating is placed between the specimen and the camera, resulting in multiple images which are then used to obtain apparent in-plane displacements using 2D-DIC. The true in-plane and out-of-plane displacements of the specimen are obtained from the apparent in-plane displacements and the diffraction angle of the grating. The validity and accuracy of the DAIC method are demonstrated through 3D displacement measurement of a small thin membrane. This technique provides new avenues for performing 3D deformation measurements at small length scales and/or dynamic loading conditions. 相似文献
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In-plane surface displacements, when measured with 2D Digital Image Correlation (2D-DIC), are very sensitive to out-of-plane displacement components. Any out-of-plane motion of the surface can pollute the measured field by introducing artificial displacements. These displacements are difficult to separate from the underlying response of the surface and thereby limit the application of 2D-DIC in inverse problems where the test specimen has significant motion in the out-of-plane direction. In the context of inverse problems, we propose to partially relax this condition of no out-of-plane motion in 2D-DIC. With this approach, only the out-of-plane rigid-body motion of the specimen surface, which is initially in-plane, needs to be avoided while the requirement of surface deformations to be primarily in-plane is essentially waived. Compensation, based on the pinhole camera model, for out-of-plane displacements of the surface in response to applied load is included within the error function of the minimization problem. The improvements in material parameter estimation, obtained by using the proposed compensation strategy, are demonstrated by an example. The proposed technique makes it possible to utilize 2D-DIC with a simple conventional lens for an increased number of inverse problems; and in the process avoiding the computational and experimental difficulties associated with 3D measurement methods as well as the high cost and magnification limitations of a telecentric lens. 相似文献
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By comparing two digital images of a test planar specimen surface recorded in different configurations, two-dimensional digital image correlation (2D-DIC) provides full-field displacements to sub-pixel accuracy and full-field strains in the recorded images. For the 2D-DIC systems using an optical lens, a simple pinhole imaging model is commonly used to describe the linear relationship between the measured sensor plane displacements and the actual displacements in the object surface. However, in a practical measurement, various unavoidable disadvantageous factors, such as small out-of-plane motion of the test object surface occurred after loading, small out-of-plane motion of the sensor target due to the self-heating or temperature variation of a camera, and geometric distortion of the imaging lens, may seriously impair or slightly change the originally assumed linear correspondence. In certain cases, these disadvantages may lead to significant errors in displacements and strains measured by 2D-DIC. In this work, the measurement errors of 2D-DIC due to the above three disadvantageous factors are first described in detail. Then, to minimize the errors associated with these disadvantages, a high-accuracy 2D-DIC system using a bilateral telecentric lens is established. The performance of the established 2D-DIC system and other two 2D-DIC systems using a conventional lens and an object-side telecentric lens are investigated experimentally using easy-to-implement stationary, out-of-plane and in-plane rigid body translation tests. A detailed examination reveals that a high-quality bilateral telecentric lens is not only insensitive to out-of-plane motion of the test object and the self-heating of a camera, but also demonstrates negligible lens distortion. Uniaxial tensile tests of an aluminum specimen were also performed to quantitatively compare the axial and transversal strains measured by the proposed 2D-DIC system and those measured by strain gage rosettes. The perfect agreement between the two measurements further verifies the accuracy of the established 2D-DIC system. 相似文献
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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。 相似文献
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超声散斑相关法能对物体的变形进行非接触式测量,但在相关运算时,由于相关系数是一个多峰函数,在搜索相关系数最大值时经常会将次峰误判为主峰,从而造成很大的测量误差。本文提出的超声散斑多谱值相关法,对位移前和位移后的散斑场中各散斑信号进行离散谱分析时,取多个振幅谱值分别组成数据矩阵并各自进行相关运算,比较运算得到的各个位移值来确定真实位移,它能避免因相关系数主峰误判所引起的误差。本文应用超声散斑多谱值相关法对水下物体的位移进行了实测,实验结果表明该方法不仅能有效地避免相关系数主峰的误判,而且提高了位移测量精度。 相似文献
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Full-field surface 3D shape and displacement measurements using a single commercial unfocused plenoptic camera (Lytro Illum) are reported in this work. Before measurements, the unfocused plenoptic camera is calibrated with two consecutive steps, including lateral calibration and depth calibration. Each raw image of a checkerboard pattern recorded by Lytro Illum is first extracted to an array of sub-aperture images (SAIs), and the center sub-aperture images (CSAIs) at diverse poses are used for lateral calibration to determine intrinsic and extrinsic parameters. The parallax maps between the CSAI and the remaining SAIs at each pose are then determined for depth parameters estimation using depth calibration. Furthermore, a newly developed physical-based depth distortion model is established to correct the serious distortion of the depth field. To realize shape and deformation measurements, the raw images of a test sample with speckle patterns premade on its surface are captured by Lytro Illum and extracted to arrays of SAIs. The parallax maps between the CSAI and the target SAIs are obtained using subset-based digital image correlation. Based on the pre-computed intrinsic and depth parameters and the disparity map, the full-field surface 3D shape and displacement of a test object are finally determined. The effectiveness and accuracy of the proposed approach are evaluated by a set of experiments involving the shape reconstruction of a cylinder, in-plane and out-of-plane displacement measurements of a flat plate and 3D full-field displacement measurements of a cantilever beam. The preliminary results indicate that the proposed method is expected to become a novel approach for full-field surface 3D shape and displacement measurements. 相似文献
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投影条纹法具有高精度、高分辨的特点,且实验设备简单,对实验环境要求低,适宜于不同尺度的三维形貌测量。双目投影条纹法通常采用有标准参照物的相机标定方法获取相机参数,以实现物体表面三维形貌重建。然而,在大型结构的三维形貌测量中参照物的相对尺度较小,传统的基于重投影的相机标定方法在特征检测中引入的误差会被放大,从而影响三维表面形貌测量的稳定性和准确性。本文结合双目投影条纹成像原理,提出了一种适用于大面积形貌测量的投影条纹系统标定方法。该方法利用投影条纹控制点以及对极几何约束对张氏标定法结果进行优化,从而可以在大视场标定中保持较高的精度。实验表明,在标定板与测量物大小相当时,本文提出的标定方法与传统标定方法的测量结果基本一致;当标定板远小于待测物时,本文方法的测量精度和稳定性明显优于传统方法。 相似文献