Additive-subtractive phase-modulated shearography with synchronized acoustic stressing

A robust electronic shearography technique is described that is immune to ambinet noise. In this technique, additive speckle-interference images containing information about the same two states of deformation of a test object undergoing acoustic stressing are acquired in each video frame. When a spatially nonuniform phase modulation is introduced in every other frame during the video sequence (using a tilting mirror) and the additive interference images are subtracted sequentially using a real-time image processor, the self-interference component of sheared-speckle interference pattern is removed. The susceptibility of this method to environmental noise caused by induced thermal noise and low frequency vibration is demonstrated to be lower than that of conventional substractive shearography methods; fringe visibility and contrast are significantly improved as well. The ability of this technique to work in a turbulent environment is demonstrated, and application to detection of structural defects in adhesively bonded structures, a problem of interest in nondestructive evaluation of structures, is shown.     

Diffraction grating interferometers for mechanical characterisations of advanced fabric laminates

It is demonstrated that two grating interferometers with high spatial resolutions can successfully be applied for the mechanical characterisation of the advanced fabric composite materials. Based on these two techniques, the mechanical properties of two kinds of fabric laminates are obtained without assumption of uniform strain fields to be used in the characterisation approaches using the local strain sensors. The degree of the yarn crimp effects of the two laminates is compared in terms of the out-of-plane displacement derivatives. Especially, it is shown that the grating shearing interferometer is appropriate for the crimped fabric structure requiring a three-dimensional analysis. The modification from moiré interferometer to grating shearing interferometer is performed by introducing a Michelson interferometer modified for image shearing.     

SU-8光刻胶应变分布光学全场检测方法

由于SU-8光刻胶的内应力将会影响高深宽比结构的全金属光栅的制作质量,本文针对近年来SU-8光刻胶应力测量困难的情况,提出了一种基于激光剪切散斑干涉技术的SU-8光刻胶应变分布测量的新方法。该方法通过对被测胶体加载前后两幅干涉图像的处理,直接得到被测胶体结构的全场应变分布情况,由胶体的应变变形数据即可反映出内应力的变化和分布趋势。同时使用ANSYS有限元分析软件对同一被测胶体进行应变仿真模拟研究,获得胶体结构的变形场仿真数据。组建了实验系统,进行了实验验证,结果表明:实际测量变形量约为1.189μm,仿真的最大变形量为1.088μm,测量误差在允许范围内,且测量的形变趋势与仿真模拟结果相一致,表明激光剪切散斑干涉技术可应用于SU-8光刻胶的应变分布全场无损检测。     

Speckle averaging by phase shift for digital shearography fringe

ＳｐｅｃｋｌｅａｖｅｒａｇｉｎｇｂｙｐｈａｓｅｓｈｉｆｔｆｏｒｄｉｇｉｔａｌｓｈｅａｒｏｇｒａｐｈｙｆｒｉｎｇｅＦ．Ｃｈｅｎ；Ｙ．Ｙ．Ｈｕｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆｍｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＯａｋｌａｎｄＵｎｉｖｅｒｓｉｔｙ，Ｒ...     

Several Phase Modulators for Digital Shearography

ＳｅｖｅｒａｌＰｈａｓｅＭｏｄｕｌａｔｏｒｓｆｏｒＤｉｇｉｔａｌＳｈｅａｒｏｇｒａｐｈｙ￥Ｆ．ＣＨＥＮ，Ｙ．Ｙ．ＨＵＮＧ（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＯａｋｌａｎｄＵｎｉｖｅｒｓｉｔｙ，ＲｏｃｈｅｓｔｅｒＨｉｌ...     

旋转锥镜散斑剪切术测量动态扭率和斜率

采用旋转锥镜技术，进行激光散斑剪切照相，测量变形物体的动态扭率和斜率，拍摄一幅散斑图可获得扭率和斜率动态变化的全过程。     

利用宽带音频扫描加载实现复合材料结构质量检测的数字散斑错位术研究

本文系统地分析了数字散斑错位术相关条纹的形成机理，并结合此项技术提出一种新的加载方式——宽带音频扫描加载，同时从理论上剖析了该加载方式的可行性，从而构造出一种新的无损测试系统．采用该检测系统对带有预制不同形状和尺寸缺陷的复合材料模型进行检测验证，发现该技术使用方便，检测时不受环境的影响，可以实现现场在线原位实时检测，并能够得到非常真实的检测结果，从而可以实现更为精确的定量计算．     

剪切散斑:一种光学测量技术及其应用

本文综述了剪切散斑测量技术及其成功的应用领域。剪切散斑技术是一种基于激光的全场、非接触表面变形(位移或应变)测量技术,它无需特殊的隔震装置,克服了因参考光束给全息干涉技术所带来的诸多限制。因此,它是用于现场测量的一个有效工具。剪切散斑测量技术已经得到了工业界的普遍认同,尤其是在工业无损检测方面更显示出了它的极大优势,它可以通过识别被诱发的异常变形来显示物体的内部缺陷。剪切散斑的应用还包括应变测量、材料特性表征、残余应力评估、泄漏探测、振动分析和三维形貌测量等。     

电子散斑方法的进展

本文叙述了电子散斑技术的国内外发展动态和应用现状。对该方法的部分最新技术—图像处理、自动分析、相位检测等做了基础性的分析     

数字剪切散斑干涉法研究铝合金中Portevin-Le Chatelier带的离面变形行为

作为Portevin-Le Chatelier(PLC)带的重要特征之一,其离面变形仍缺乏实验研究.本文提出使用数字剪切散斑干涉法研究GB6061铝合金中PLC带的离面变形.通过图像相减得到的条纹图,实时观察了PLC带的几何形貌和传播过程,并获得了PLC带离面位移分布.在1/15 s内,PLC带的最大离面位移为245 nm,位置偏向于PLC带传播的前沿.在条纹图中,PLC带传播前沿的亮条纹始终较窄.此外,实验还观察到PLC带位置变更和倾角转向的演化过程.实验表明,数字剪切散斑干涉法具有高灵敏度和防震性,是研究PLC带离面变形简便有效的方法.