超声动态测距的一种直接数字解调处理方法

为了减少传统的相位差超声动态测距的复杂性,提出了一种基于直接数字解调的信号处理方法。运用STM32内部两路A/D同步采集超声测量信号与参考信号,对这两组信号数据通过最小二乘椭圆拟合方法,计算[-π,π]单周期范围内的实时相位差。在此基础上,对实时相位差进行解包裹运算,得到绝对相位差。最后,通过绝对相位差的变化量与距离变化量成正比的关系,计算出实时的动态变化距离值。实验结果表明:当目标速度不超过2.5 m/s时,该方法能够准确地将距离值直接解调出来,满足动态变化条件下跟踪测距要求。     

基于F28M35X的数字化电能表的设计

根据IEC61850标准,设计了一款基于F28M35X双核CPU为核心,结合光纤采样模块接口、PHY芯片等硬件组成的数字化电能表。并阐述了主要功能模块的硬件设计以及原理,给出了双核芯片两个软件设计以及计量算法的主要流程,并对电能表进行基本误差测试,结果表明本设计正确可靠,具有一定实用价值。     

基于pt100的温度测控实验装置的开发与应用

本文介绍了pt100作为温度传感器件的温度测控实验装置的开发与应用．该装置能够实现在恒温箱中进行的温度测控实验,可用于展示温度测量与控制的全过程．同时包含了信号检测、转换、处理和控制等电路．是一个开发综合性实验的范例．     

Large Deformation of Nitinol Under Shear Dominant Loading

Full-field quantitative strain maps of phase transformation and plasticity in Nitinol under large shear-dominated deformation are presented. To achieve a shear-dominated deformation mode with relatively uniform stresses and strains, a shear compression specimen (SCS) geometry was utilized. Shear deformation appears to impede the development of the strain localization during phase transformation that is seen in uniaxial testing. The shear-dominant deformation of Nitinol in the plastic regime exhibits low hardening and results in the development of significant strain inhomogeneity.     

Information reduction using lensless Fourier transform digital composite holography

An optical hologram contains substantially more information than necessary for some specific applications. Practical methodology of handling huge information contents in these holograms for such applications is cumbersome. In this paper, a method of information reduction, which aims at efficient storage and transmission of holograms, is investigated using digital composite holography in lensless Fourier transform configuration. The maximum information reduction factor obtained in our experiment is 105. The advantages/disadvantages of this method over an earlier method used in optical holography [Lin LH. A method of hologram information reduction by spatial frequency sampling. Appl Opt 1968;7:545] are also discussed.     

The influence of hologram aperture on speckle noise in the reconstructed image of digital holography and its reduction

Based on the whole process of the recording and reconstruction of digital holography, we study the formation cause of speckle noise in its reconstructed image and acquire the conclusion that the small size of hologram aperture diffraction aggravates the speckle noise of reconstructed image and the speckle noise has been one of primary noise sources in the reconstruction process. In order to reduce the speckle noise resulting from little hologram aperture diffraction, we set an appropriate aperture function matching the recording parameter and aperture size of hologram and deconvolve the reconstructed image with it. The validity has been proved in theory and experiment. Therefore, it offers a brand-new thought and practical way to reduce the speckle noise in the reconstructed image of digital holography.     

Feasibility study of a digital speckle pattern interferometry and bending test combined technique to investigate coating adhesion

This paper presents a feasibility study to assess whether digital speckle pattern interferometry could be used as a possible technique to investigate the adhesive performance of coatings. The approach is based on the measurement of the deflections produced by a pre-notched coated specimen subjected to a four-point bending test. When the bending load is increased, a delamination between the coating and the substrate is propagated with its length depending on the adhesion strength. Experiments carried out with specimens having simulated delaminations confirm that digital speckle pattern interferometry can be used to estimate the delamination length.     

数字全息变焦系统的研究及应用

从4f系统及照像机变焦镜头的设计思想出发,提出并设计了一个由三面透镜组成的数字全息变焦系统.该系统具有4f系统的性能,且可以方便地改变横向放大率,适应实际检测物体尺寸及形状的变化.用几何光学表述了变焦系统的工作原理,基于矩阵光学理论介绍了变焦系统的设计方法,利用衍射的角谱理论对像空间波面重构计算方法进行了介绍.并且,给出了实验证明及应用实例.     

Identification of Mechanical Material Behavior Through Inverse Modeling and DIC

Inverse methods offer a powerful tool for the identification of the elasto-plastic material parameters. One of the advantages with respect to classical material testing is the fact that those inverse methods are able to deal with heterogeneous deformation fields. The basic principle of the inverse method that is presented in this paper, is the comparison between experimentally measured strain fields and those computed by the finite element (FE) method. The unknown material parameters in the FE model are iteratively tuned so as to match the experimentally measured and the numerically computed strain fields as closely as possible. This paper describes the application of an inverse method for the identification of the hardening behavior and the yield locus of DC06 steel, based on a biaxial tensile test on a perforated cruciform specimen. The hardening behavior is described by a Swift type hardening law and the yield locus is modeled with a Hill 1948 yield surface.     

Overview of Identification Methods of Mechanical Parameters Based on Full-field Measurements

This article reviews recently developed methods for constitutive parameter identification based on kinematic full-field measurements, namely the finite element model updating method (FEMU), the constitutive equation gap method (CEGM), the virtual fields method (VFM), the equilibrium gap method (EGM) and the reciprocity gap method (RGM). Their formulation and underlying principles are presented and discussed. These identification techniques are then applied to full-field experimental data obtained on four different experiments, namely (i) a tensile test, (ii) the Brazilian test, (iii) a shear-flexural test, and (iv) a biaxial test. Test (iv) features a non-uniform damage field, and hence non-uniform equivalent elastic properties, while tests (i), (ii) and (iii) deal with the identification of uniform anisotropic elastic properties. Tests (ii), (iii) and (iv) involve non-uniform strain fields in the region of interest. Working group “Identification” of the French CNRS research network (GDR 2519) “Mesures de champs et identification en Mécanique des Solides / Full-field Measurements and Identification in Solid Mechanics”.