标准人工缺陷复型测量与直接测量的偏差分析

在检测无缝管材标准人工缺陷尺寸时,不同测量方法间存在偏差.本文通过一系列实验,对标准人工缺陷的复型测量与直接测量结果进行偏差分析.分析结果表明修正值为4％时,复型测量结果更接近于直接测量值.同时,对影响复型测量结果的因素进行了分析,认为采用激光共聚焦扫描显微镜比普通显微镜进行复型测量更加准确、直接.     

大圆周孔系角度测量

本文重点介绍了大尺寸圆周孔系孔间角度的测量方法，并进行了误差分析，指出了影响因素和减小误差采取的措施。测量方法切实可行，准确可靠。     

软测量方法及其工业应用

从软测量方法实施进程角度,探讨了软测量方法实施的内容、步骤以及应当注意的问题。最后,阐述了软测量方法在工业中的应用情况。     

立体显微图像的三维微尺度测量方法研究

针对微小复杂产品表面形貌、几何特征、关键点等综合测量的要求,提出了基于立体显微图像的三维微尺度测量方法.利用立体显微镜及两台数字相机获得被测对象两个不同观测角度的显微图像,通过图像处理技术和几何原理计算得到被测对象的空间三维信息,最终实现三维微尺度测量.为了验证所提出方法的有效性,以具有一定倾角的显微标定板为测量对象,在图像采集、滤波、二值化、边缘检测以及形心计算的基础上进行显微系统的标定,分别对左右各10个相同角度进行了实测.结果是相对误差均在3%以内,说明该测量方法可以获得较高的测量精度.     

差压式流量计孔板节流孔直径测量结果不确定度评定

一、测量方法万能工具显微镜是一种多用途的光学机械式两坐标测量仪器。通常用影像法及轴切法测量精密机械零件的长度和角度,以直角坐标或极坐标方法测量零件的形状。孔板节流孔内径的测量采用影像法。由物方远心照明系统发出的光,照射放置于仪器工作台上的被测孔板,而后通过中央显微镜物镜成像于目镜分划板上;分别移动仪器纵向或横向滑座     

一种用于微米／纳米硬度测试的具有纳米分辨率的压痕成像系统

与包括原子力显微镜在内的其他压痕形貌测量方法相比,光学显微镜以其非接触、大测量范围及较快的测量速度等优点在硬度测试中应用广泛,但包括共焦显微镜在内的常规显微镜其分辨率,特别是纵向分辨率,一直不能满足要求．为此开发了一种沿光轴方向的具有纳米分辨率的压痕成像系统．该系统基于层析全场显微术,即在常规光学显微镜的基础上引入结构光照明．应用移相方法得到样品的三维形貌．成像系统样机的测量结果表明,系统的纵向分辨率可达2nm,可以高精度地实现压痕的三维形貌测量,并量化揭示纳米压痕测试中常见的“坟起（pile-up）”及“沉入（sink-in）”现象．该系统有助于进一步研究显微及纳米硬度计量方法并降低计量的不确定度.     

精冲压件同轴度的测量

本文叙述用光学分度头，万能工具显微镜圆工作台，测量精冲压件的同轴度及测量方法的极限误差。     

特殊型燕尾槽参数的测量

介绍特殊型燕尾槽参数的测量方法,采用双圆球测量燕尾槽参数,尺寸参数计算不含角度参数,有效地避免了角度误差的影响;计算公式不含三角函数,简单、便于记忆.     

关于三槽丝锥测量方法的改进

三槽丝锥中径的测量,有些专业书籍中介绍了用三槽丝锥检查仪的测量方法和在万能工具显微镜上配用光学分度头的测量方法。然而,前者需要配备专用的三槽丝锥检查仪和成套的校准件,后者在测量中会出现三槽分度不均或不准带来的补偿麻烦。本人认为用三针法测量螺纹单一中径的原理可应用于此。其设想的测量方法为：将丝锥装夹在万能工具显微镜两顶针间,用丝锥手柄的光杆部分测得丝锥的转动中心坐标值,然后在校准部分的起点位置处找到牙凸等于１／２基本螺距的瞄准点,此瞄准点的横向坐标值与丝锥中心坐标值之差即为１／２单一中径尺寸。１．…     

一种样板的两种测量方法

图1示样板要求测量固定弦EF=42.000mm处的h值,在万能工具显微镜上有以下两种测量方法.     

Fabrication and Fatigue Testing of an Electrostatically Driven Microcantilever Beam

The reliability of a microelectromechanical system is an essential issue before the microdevice can be applied in practice. It is indispensable to investigate the mechanical properties of a microstructure to meet the requirements for longer lifetime and reliable performance. This paper studies the fabrication and the fatigue characteristics of a microcantilever beam, which is among the most widely employed microstructures in sensors and actuators. A pad is fabricated at the free end of the beam for larger effective external electrostatic load on the specimen. In fatigue tests, the specimen is actuated by the electrical voltage of 150 and 200 V at 100 Hz. The deflection of the beam is measured by the laser Doppler vibrometer. Based on the experimental results and ANSYS calculation, the displacement of the free end of the beam increases with the beam length and the applied load, and ranges from 61 to 600 nm. The fatigue life lies between 6.1 × 10⁶ and 1.4 × 10⁸ cycles. These results are consistent with the reference of a microcantilever beam subject to magnetic load.     

“Thermal Mirror” Method for Measuring Physical Properties of Multilayered Coatings

In this study theoretical principles underlying the photothermal displacement (“thermal mirror”) method for measuring physical properties of opaque multilayered and functionally graded coatings with low thermal conductivity are analyzed. In this method, the specimen is locally heated by a power laser beam, and a two-dimensional transient temperature field is formed in a specimen. The physical basis for the photothermal displacement method is the non-stationary buckling and displacement of an irradiated surface due to a non-uniform thermal expansion. The surface is monitored by a low-power probe beam of a second laser, which is reflected from the specimen, i.e., the system operates as a convex “thermal mirror.” The photoinduced displacement varies with time, and the probe beam is reflected at a different angle depending on the slope of the displacement. The deflection angle is measured as a function of time by a position sensor, and the results of these measurements are compared with the theoretical dependence of the deflection angle on time and physical properties of a coating. This dependence was determined analytically from the solution of the two-dimensional thermal elasticity problem. It is shown that for the specimen composed of a substrate and a coating it is feasible to determine the properties of the coating, e.g., the thermal diffusivity and coefficient of linear thermal expansion provided that the analogous properties of the substrate are previously measured or otherwise known.     

AFM轻敲模式中微悬臂振动的研究

针对原子力显微镜AFM（Atomic torce microscope）在轻敲工作模式下微悬臂在谐振频率附近振动的问题，依据振动学理论和仿真分析的方法，建立了微悬臂的振动模型，仿真出了微悬臂前几阶的振动模态。得到了在保证振幅不变的情况下微悬臂各参数与其自由端偏转角的关系，指出了轻敲模式下减小AFM测量误差的方法。     

Constant stress intensity factors through closed-loop control

A new way of obtaining a constant stress intensity factor is achieved for any test specimen geometry subjected to closed-loop control loading. In contrast to using only load or displacement control the method draws on combined feedback from both displacement and load sensing, reducing the variation in the stress intensity factor by two decades compared to that if tested under constant load or displacement. A change in the signal mix ratio for a rectangular compact tension specimen is equivalent to changing the angle of a tapered compact tension specimen. This method can eliminate the need for the use of ‘complex’ geometries or for geometries in which measured crack lengths are used in conjunction with a computer or some other means to adjust the loading continuously for achieving a constant stress intensity factor.     

Magneto-Nanomechanical Array Biosensor for Ultrasensitive Detection of Oncogenic Exosomes for Early Diagnosis of Cancers

Exosomes are a class of nanoscale vesicles secreted by cells, which contain abundant information closely related to parental cells. The ultrasensitive detection of cancer-derived exosomes is highly significant for early non-invasive diagnosis of cancer. Here, an ultrasensitive nanomechanical sensor is reported, which uses a magnetic-driven microcantilever array to selectively detect oncogenic exosomes. A magnetic force, which can produce a far greater deflection of microcantilever than that produced by the intermolecular interaction force even with very low concentrations of target substances, is introduced. This method reduced the detection limit to less than 10 exosomes mL⁻¹. Direct detection of exosomes in the serum of patients with breast cancer and in healthy people showed a significant difference. This work improved the sensitivity by five orders of magnitude as compared to that of traditional nanomechanical sensing based on surface stress mode. This method can be applied parallelly for highly sensitive detection of other microorganisms (such as bacteria and viruses) by using different probe molecules, which can provide a supersensitive detection approach for cancer diagnosis, food safety, and SARS-CoV-2 infection.     

Interface crack in sandwich specimen

Fracture of a sandwich specimen loaded with axial forces and bending moments is analyzed in the context of linear elastic fracture mechanics. A closed form expression for the energy release rate for interface cracking of a sandwich specimen with isotropic face sheets is found from analytical evaluation of the J-integral. An approach is applied, whereby the mode mixity for any combination of the loads can be calculated analytically when a load-independent phase angle has been determined. This load-independent phase angle is determined for a broad range of sandwich configurations of practical interest. The load-independent phase angle is determined using a novel finite element based method called the crack surface displacement extrapolation method. The expression for the energy release rate is based on the J-integral and certain stress distributions along the ends of the sandwich specimen. When the stresses from the crack tip interacts with the stresses at the ends, the present analytical calculation of the J-integral becomes inaccurate. The results show that for the analytically J-integral to be accurate the crack tip must be a certain distance away from the uncracked end of the specimen. For a sandwich specimen with face sheet/core stiffness ratio of 100, this distance is in the order 10 times the face sheet thickness. For sandwich structures with face sheet/core stiffness ratio of 1,000, the distance is 30 times the face sheet thickness.     

Evaluation of elastic fracture mechanics parameters for bend specimens

Existing solutions for stress intensity factor and mouth opening displacement of three-point bend specimens are shown to overestimate these quantities for shallow cracks by up to ±4.5 percent, because they do not account for the disturbance of the bending stress distribution by the concentrated force at the loading point. This error is far larger than the accuracy claimed by these solutions (0.2 to 0.5 percent).New expressions are therefore developed for stress intensity, crack mouth opening displacement and crack mouth open angle of single edge notched bend specimens loaded in three-point bending. As a reference, and to show the accuracy of the solutions, also the pure bending situation is treated. Rigorously derived asymptotic solutions are used for the shallow and deep crack limits, in order to prescribe both the proper limit values and gradients to the interpolation functions, of which the intermediate values are derived from refined finite element analyses.The crack mouth opening angle solutions are primarily intended to facilitate crack mouth opening measurement at other locations then the specimen surface, i.e. at an offset from the specimen surface as is the case when removable knife edges are applied. No solutions of the crack mouth opening angle of three-point bend specimens were available until now. For use with unloading compliance crack length measurement, also an inverse crack mouth opening relation is developed. This also includes crack mouth opening measurement at an offset from the specimen surface, which is lacking in presently available expressions of this kind.     

Nomarski imaging interferometry to measure the displacement field of micro-electro-mechanical systems

We propose to use a Nomarski imaging interferometer to measure the out- of-plane displacement field of micro-electro-mechanical systems. It is shown that the measured optical phase arises from both height and slope gradients. By using four integrating buckets, a more efficient approach to unwrap the measured phase is presented, thus making the method well suited for highly curved objects. Slope and height effects are then decoupled by expanding the displacement field on a functions basis, and the inverse transformation is applied to get a displacement field from a measured optical phase map change with a mechanical loading. A measurement reproducibility of approximately 10 pm is achieved, and typical results are shown on a microcantilever under thermal actuation, thereby proving the ability of such a setup to provide a reliable full-field kinematic measurement without surface modification.     

CTOA of a stable crack in a thin aluminum fracture specimen

A crack tip opening angle (CTOA) resistance curve was generated from the moiré interferometry data of thin single edge notched (SEN) and central notched (CN), 2024-T3 aluminum fracture specimens. This CTOA resistance curve, which has a steady state value of 6°, was then used to propagate the cracks in elastic–plastic finite element models of the CN specimen and a CN specimen with a simulated multiple site damage. The CTOA of curved crack growth in a biaxial fracture specimen scattered between 4° and 8° but the resultant crack tip opening displacement, which is the vector sum of the mode-I and the mode-II crack tip sliding displacement, remained a constant 0.18 mm. The CTOA of a rapidly propagating crack in 1.6 mm thick, 7075-T6 SEN specimens increased from 4.5° at a low-crack velocity to a constant 7° at the terminal crack velocity.     

Determination of critical CTOD using crack flank opening angle method in general yield regime

The crack tip opening displacement (CTOD) evaluation from CMOD values using compact tension (CT) specimen geometry and plastic hinge model (PHM) is well standardized in the literature. However, the model is found to be conservative for the general yielding situation. Moreover, the knowledge of the location of apparent axis of rotation which in turn depends on plastic rotational factor, r_pl, is essential for the conversion from CMOD to CTOD. In the present investigation, the ‘crack flank opening angle’ (CFOA) method has been suggested for the evaluation of plastic CTOD. This approach has facilitated the exact determination of apparent axis of rotation. The effect of the specimen thickness and notch root radius on CTOD has been investigated using the PHM and CFOA method. These results have been compared with finite element analysis results. Results achieved point out that the CTOD obtained from the traditional PHM are underestimated for the general yield situation.