微电子机械系统中转速测量的光学方法

利用显微测量技术和CCD图像传感器的线性积分成像特性,将数字图像处理技术与时间积分成像技术用于微电子机械系统(MEMS)中的转速测量。只需分别摄取被测物体上的标志点在静止状态下的时间积分图像和运动状态下的时间积分图像,即可测得物体在该段曝光时间内的转速。该方法对实验设备及实验条件要求较宽松。实验表明该方法对微系统中近似匀速转动时转速的测量是完全可行的,且具有较高的精度。     

Plastic surface strain mapping of bent sheets by image correlation

A technique using a single CCD camera, a precision rotation/translation stage, a telecentric zoom lens, and digital image correlation software is described for measuring surface profiles and surface plastic strain distributions of a bent thin sheet. The measurement principles, based on both parallel and pinhole perspective projections, are outlined and the relevant mathematical equations for computing the profiles and displacement fields on a curved surface are presented. The typical optical setup as well as the experimental measurement and digital image correlation analysis procedure are described. The maximum errors in the in-plane and out-of-plane coordinates or displacements are about ±5 and ±25 μm, respectively, and the maximum errors in surface strain mapping are about 0.1% or less based on a series of evaluation tests on flat and curved sample surfaces over a physical field of view of 15.2 × 11.4 mm². As an application example, the shape and surface plastic strain distribution example, the shape and surface plastic strain distributions around a bent apex of a flat 2 mm thick automotive aluminum AA5182-O sheet, which underwent a 90° bend with three bend ratios of 2t, 1t, and 0.6t, are determined using the proposed technique.     

Measurement of energy release rate and energy flux of rapidly bifurcating crack in Homalite 100 and Araldite B by high-speed holographic microscopy

High-speed holographic microscopy is applied to take three successive photographs of fast propagating cracks in Homalite 100 or in Araldite B at the moment of bifurcation. Crack speed at bifurcation is about 540 m/s on Homalite 100, and about 450 m/s on Araldite B. From the photographs, crack speeds immediately before and after bifurcation are obtained, and it is found that discontinuous change of crack speed does not exist at the moment of bifurcation in the case of Homalite 100, but exists in the case of Araldite B. From the photographs, crack opening displacement (COD) is also measured along the cracks as a function of distance r from the crack tips. The measurement results show that the CODs are proportional to √r before bifurcation. After bifurcation, the CODs of mother cracks are proportional to √r, though the CODs of branch cracks are not always proportional to √r. The energy release rate is obtained from the measured CODs, and it is found that energy release rate is continuous at bifurcation point in both cases of Homalite 100 and Araldite B. Energy flux that shows the energy flow toward a crack tip is also obtained.     

An optimisation method for separating and rebuilding one-dimensional dispersive waves from multi-point measurements. Application to elastic or viscoelastic bars

When using a classical SHPB (split Hopkinson pressure bar) set-up, the useful measuring time is limited by the length of the bars, so that the maximum strain which can be measured in material testing applications is also limited. In this paper, a new method with no time limits is presented for measuring the force and displacement at any station on a bar from strain or velocity measurements performed at various places on the bar. The method takes the wave dispersion into account, as must inevitably be done when making long time measurements. It can be applied to one-dimensional and single-mode waves of all kinds propagating through a medium (flexural waves in beams, acoustic waves in wave guides, etc.). With bars of usual sizes, the measuring time can be up to 50 times longer than the time available with classical methods. An analysis of the sensitivity of the results to the accuracy of the experimental data and to the quality of the wave propagation modelling was also carried out. Experimental results are given which show the efficiency of the method.     

球－盘微动摩擦件磨损体积的测量与计算

一般地说，由于微动磨损量很小，测定非常困难，所得结果的误差通常都相当大．尽管几十年来人们对微动磨损进行了好些研究，然而至今却还没有建立起统一而完善的微动磨损量的测量和计算方法，以至很难对试验结果进行定量比较．因此，根据ＳＲＶ微动磨损试验机的工作原理，利用几何和数学分析手段提出了一种能够比较精确地测量和计算球－盘接触型微动摩擦件磨损量的方法，并且利用不同的模型对计算方法进行简化，从而得出了球和盘的磨损体积计算公式。只要借助轮廓仪和读数显微镜测量出有关参数，就可以比较精确地计算出球和盘的微动磨损体积，为了验证这种计算方法的实用性和可靠性，还进行了５２１００钢对不同含钨量的Ｎｉ－Ｗ合金镀层的ＳＲＶ微动磨损试验，测量结果与计算结果具有较好的一致性，由此可见，根据所提计算方法得到的计算结果，不仅可以增强ＳＲＶ试验机测试结果的可比性，也为利用这种试验机深入开展微动磨损研究提供了参照依据。     

弱正交异性材料残余应力测量的声弹性方法

为了适应工程材料的残余应力无损测量的要求,本文将横波和纵波声弹性相结合,建立适用於弱正交异性材料的平面声弹性残余应力测量方法,并应用该方法及自行研制的横波换能器对焊接试件的二维残余应力进行了测试。     

反射焦散线实验中斜入射光对应力强度因子测试精度的影响

本文用空间解析几何方法,推导了在一般非平行斜入射光条件下,裂纹体表面所形成的反射焦散线和初始曲线的方程.分析了倾斜入射光造成的焦散线畸变,给出了这种畸变造成的裂端应力强度因子测量误差的解析表达式.     

Direct interferometric measurement of streaming birefringence

The two refractive indices in the flow of a colloidal birefringent liquid are measured separately by means of a Mach-Zehnder interferometer. For a quantitative evaluation of the resulting interferograms it is not necessary to linearize the respective equations relating the refractive index distribution to the deformation velocity in the flow. Therefore it becomes possible to perform velocity measurements in the non-Newtonian flow range. An additional measurement of the mean flow rate enables one to determine the velocity field without the need of a calibration of the observed interference fringes.     

无损残余应力测量及其新技术

简述及比较了主要的残余应力无损测量技术，重点为磁力法，并介绍一台新的磁力仪MAPS，且对MAPS及传统磁力仪作了比较，同时以X射线及中子衍射得到的结果验证了MAPS的可靠性，也介绍了文献上较少见的火车钢轨残余应力分布图。