鼓膜法测定纳米多孔氧化铝薄膜的弹性模量

本文的多孔氧化铝薄膜含有直径均一、互相平行且与表面垂直的有序纳米孔阵列。它有广阔的应用前景。多孔氧化铝膜与氧化铝陶瓷材料的宏观力学性能有很大的区别。本文用鼓膜法结合实时电子散斑干涉(ESPI)技术，测量薄膜压力与离面位移的关系，再用周边固支平板小挠度模型计算出多孔氧化铝薄膜的宏观弹性模量。本实验中厚76微米的多孔氧化铝薄膜的宏观弹性模量为32.5GPa，比热压氧化铝陶瓷的弹性模量几乎小一个数量级，主要是由于晶相和细观结构不同造成的。这种方法较适合测量此类结构薄膜的力学性能。     

In-plane ESPI using an achromatic interferometer with low-coherence laser source

The use of an achromatic interferometer is explored as a means of doing in-plane ESPI measurements using a laser diode as the light source. This interferometer type, which uses a diffraction grating in place of the conventional beamsplitter, has two features that make it suitable for making ESPI measurements over extended areas, even when using a low-coherence laser diode source. First, the parallelogram optical geometry of the interferometer causes all rays passing through to have the same optical path lengths. Second, the interferometer is achromatic, whereby the piezo-actuated mirror that steps the illumination light does so by the same phase angle, independent of wavelength. This latter feature accommodates the spectral impurity of a laser diode source. A periodic variation of fringe visibility is observed in experiments, where narrow ranges of high visibility occur at regular spatial intervals. This behavior derives from the clustered discrete spectral character of laser diode light output. A method to “tune” the interferometer by slightly rotating the diffraction grating is described so as to achieve consistent high fringe visibility throughout the measured images.     

三维相移电子散斑干涉法在柴油机机身中的应用

本文通过一新的三维电子散斑干涉方法，结合四步相移技术和图象处理技术，从三幅全场散斑位相条纹图分离出独立的u、υ、w场位移。测量系统的特点是用三个激光器作为光源，一个PZT相移器推动三个反射镜产生参考光并实现相移以及CCD摄像机前放置大错位剪切镜。将该测量系统应用到柴油机机身部件测量上，得到了机身主轴承孔周的三维位移场，并将此结果作为有限元计算的边界条件，得到了精确的柴油机机身计算结果，证明这一新技术可为柴油机零部件的强度和刚度分析评价提供一种十分有效的方法。     

含有序孔洞的多孔氧化铝薄膜的力学性能测量和数值模拟

高纯铝箔在特定的溶液下经过电化学阳极氧化腐蚀,可在其表面生成一层多孔的非晶氧化铝层,其孔径分布非常均匀,孔大致呈六方密排布。由于此类薄膜具有规则的纳米级孔径,大的比表面积,良好的自组织排列性,所以其日益受到人们的关注。然而,到目前为止,对于此类薄膜力学性能的研究还很少,所以在一定程度上限制其功能的开发和应用。为了获得此类多孔膜的弹性常数,本文首先由实验出发,通过光力学检测(双光束散斑干涉)的方法得到薄膜拉伸时的整体表观弹性模量。然后对薄膜建立二维有限元模型,运用均匀化理论反推出其基体(无孔结构)的弹性模量,同时考察了不同的基体泊松比对模型整体表观模量的影响,并且用一般有限元方法验证了沿特定方向拉伸时均匀化模型计算的有效性。     

相移电子散斑干涉测量物面形状

本文提出了一种用于测量三维物体表面形状的新方案.利用电子散斑干涉仪,通过两次图像采集之间折射率变化,获得代表等高线的相关条纹图,应用相移技术,可以获得高精度的形状测量结果.文中还讨论了自制气体相移器原理及性能。     

Mural inspection by vibration measurements with TV-holography

A commonly encountered problem in the conservation of historical murals is the identification of sections in the plaster that have detached from the wall and thus threaten to fall off. Commonly, walls are inspected by the acoustic response to a gentle finger-tapping (percussion method). Since this is a costly and cumbersome technique, means for a more automatic inspection are searched for. A TV-holography system of increased sensitivity in combination with acoustic excitation of the object is shown to be a new and powerful tool for monitoring of loose areas. It has the advantage of non-contact and remote operation which, for example, is extremely useful in large buildings. Principles of the method, experimental results obtained at an artificial wall in the laboratory, and a thorough comparison of results from historical sites gained by the traditional percussion method and the new technique are presented. The latter shows very good agreement in the assessment of wall quality and thus is evidence of the suitability of the optical equipment for tasks in conservation.     

Displacement measurements in structural elements by optical techniques

Speckle metrology and holographic interferometry (HI) have been used in several civil engineering applications. We present the results obtained by applying speckle photography (SP) to the study of two quadratic shearwalls with different boundary conditions, and the potential of the technique in the study of this kind of structures is described. The analysis of Young's fringes obtained with this technique at certain points on each shearwall provides the whole field of displacement measurements. HI has been used to measure the three components of absolute displacement, verifying that the bulging phenomenon does not affect the in-plane components when the applied load remains on the same plane as the shearwall. A qualitative analysis is carried out following an electronic speckle pattern interferometry (ESPI) technique. The results obtained by optical techniques are compared to the numerical results obtained by the finite element method (FEM), finding good correlation between them in all the cases.     

Double shearography for engineering metrology: optical and digital approach

This paper presents a double shearographic configuration based on the optical method by using two Michelson interferometers in tandem. The problems associated with the extraction of second order derivatives by optical means and a comparison with the proposed novel approach by digital means are discussed in this paper.     

Electronic speckle pattern interferometry analysis of tensile tests of semihard copper sheets

Uniaxial tension tests of semihard copper sheets were studied by means of electronic spekle pattern interferometry (ESPI). The setup allowed the authors to analyze in detail the transitions from elastic to plastic behavior and from homogeneous to inhomogeneous plastic deformation. In agreement with the conventional definition of the yield point for copper fully plastic behavior starded at permanent strains close to 0.005. The strain-hardening coefficient was very low at the early stage of plastic flow (“easy glide”), increasing progressively until values on the order of 0.13 to 0.14 were reached at maximum load. A this point, the appearance of unequally spaced fringes signaled the beginning of inhomogeneous deformation. With ESPI, this occurrence may thus serve as a criterion to establish the forming limit of the material.