焊接缺陷力学影响场的研究

本文针对焊接缺陷存在的特点，提出利用缺陷影响场概念，采用实验方法研究压力容器常见焊接缺陷力学影响场与分布规律，通过对７组存在不同缺陷１６ＭｎＲ钢焊接试件和压力容器实际缺陷的监测实验结果分析认为，焊接缺陷在荷载作用下，在其线开至扩展过程中，在其表面所产生一个与工作应力和缺陷几何参数相关的力学影响场，通过地场内各点测量值的分析可预测缺陷损伤程度。     

激光扫描测厚的信号处理

简要介绍了激光扫描测厚的基本原理；分析了被测表面上光点线度和接收器光栏狭缝宽度对测量精度的影响；介绍了一种提高测量精度的双频脉冲计数信号处理方法。     

精确测量金属镀层工件表面缺陷的图像处理方法

设计了一套自动测量表面缺陷的系统．以面阵CCD采集图像,实现了对金属镀层工件表面图像的双面、高速、高分辨率测量．系统的图像处理采用模块化程序设计,方便实现工件表面精确测量的特定要求．通过两次分别选取闽值,采用经过改进的大津阈值分割法求取特征分割阈值时,能够十分理想地提取工件上的微小缺陷,实现了对金属工件表面的精确测量．该系统针对不同形状、不同镀层的工件表面可以调整LED照明光源的光强,在图像处理中可以调整去光圈和特征检测的灵敏度．通过方便调整系统的技术参数,满足工业现场的具体要求．以钕铁硼小型工件缺陷检测作为应用实例验证了该系统的可行性．     

钢铁制件热镀锌表面缺陷分析及控制

对钢铁制件热镀锌层表面的缺陷原因进行了分析，并根据生产实践提出一些控制表面缺陷的方法。     

使用GCP快速测量表面粗糙度

照射在样本表面的激光束随 表面粗糙度的不同，反射光的密度分布将不同，表面粗糙度增大时，反射光的密度将被扩展。本根据这一原理，提出一种使用激光束快速测量表面粗糙度的无触点光学方法。该方法利用高斯曲线的系数，通过测量反射光的密度分布曲线的宽度，由高斯曲线系数的标准差，利用ＧＣＰ测量表面粗糙度，给出了测量结果。     

行业/企业动态

国家煤矿安全计量器具产品质量监督检验中心落户山西，济钢 改进钢板表面缺陷在线检测，涟钢 通过测量管理体系年度监督审核，邢钢 认真贯彻落实GB17167-2006，大庆测试 多臂成像井径仪出口美国。[编者按]     

高精度平面度测量方法的研究

本以中等尺寸０００级平板为研究对象,采用双频激光测量系统的直线度测量部件进行平面度测量,分析计算了这一测量方法的测量不确定度,并进行了实际测试。     

用于生产过程控制的表面粗糙度在线测量

用于生产过程控制的表面粗糙度在线测量Ｈ．Ｂｏｄｓｃｈｗｉｎｎａ等１．前言现代工业的发展方向是不断提高产品质量并降低生产成本，为实现这一目标，迫切需要进行贴近生产过程的表面粗糙度的自动测量，这不仅是因为表面的微几何学特性是评价表面函数相关特性的最常用判...     

光探针式表面形貌测量技术的研究

本文针对机械探针是粗糙度测量仪的不足提出并采用基于差动像散法的光探针技术测量表面粗糙度，采用小波包分析法分离表面粗糙度信号。研究表明该系统不仅测量分辨率高，而且对工件表面无任何划伤，尤其适合对光盘等含有信息的表面及软、脆材料制作的高光洁表面进行形貌测量。对Ra为0．012μm的粗糙度样板进行测量，其测量重复性为2％。     

带钢表面缺陷视觉检测系统关键技术研究

为满足钢板表面缺陷在线检测系统宽幅面、高速、高分辨率的检测要求，讨论了基于线阵CCD的钢板表面缺陷视觉检测系统实现的关键技术；优化设计了视觉检测系统的光学照明部分，以检测不同类型的缺陷。通过软件系统的特殊设计，以保证实时在线检测。针对缺陷图像低对比度、高噪声的特点，提出了基于灰度统计特性的图像边缘检测方法，并实现了对缺陷图像的自适应阈值分割。依据图像的缺陷统计特性，定义了缺陷的灰度、几何等特征量，用于缺陷分类。本系统样机已在实验室环境下运行。     

全息光学元件中编码与象质和衍射效率的关系

以平面波束变换为十字光束的全息光学元件为例，详细分析了ＨＯＥ的相位调制、编码与解主财过程，推导出ＨＯＥ的衍射效率近似解的表达式，计算出近似条件下最佳编码最大刻蚀深度值，并且对该编码方案对ＨＯＥ成象质量的影响进行了分析，得出了分析的结果和结论，同时对衍射效率近似解表达式的误差进行了研究，并给出了分析结果。     

Beam splitting of low-contrast binary gratings under second Bragg angle incidence

Beam splitting of low-contrast rectangular gratings under second Bragg angle incidence is studied. The grating period is between lambda and 2lambda. The diffraction behaviors of the three transmitted propagating orders are illustrated by analyzing the first three propagating grating modes. From a simplified modal approach, the design conditions of gratings as a high-efficiency element with most of its energy concentrated in the -2nd transmitted order (~90%) and of gratings as a 1 x 2 beam splitter with a total efficiency over 90% are derived. The grating parameters for achieving exactly the splitting pattern by use of rigorous coupled-wave analysis verified the design method. A 1 x 3 beam splitter is also demonstrated. Moreover, the polarization-dependent diffraction behaviors are investigated, which suggest the possibility of designing polarization-selective elements under such a configuration. The proposed concept of using the second Bragg angle should be helpful for developing new grating-based devices.     

Visual method of measuring reflection-type characteristics of holographic optical elements

A highly diverging laser beam is used to measure angular and spectral selectivities and grating vector direction for reflection-type holographic optical elements (HOE's). The intensity distribution of the beam transmitted from the HOE's reveals dark, ring-shaped patterns. Since these ring patterns are formed as a result of the beam diffracted by the HOE's, the thicknesses and the diameters of the ring patterns convey information on both the angular and the spectral selectivities of the HOE's. In addition the deviation of the ring centers relative to the center of the intensity distribution reveals the grating vector direction. Determination of values related to the ring patterns permits highly accurate measurement of HOE characteristics, such as the upper limit of the diffraction wavelength, the angular and the spectral selectivities, and the grating vector direction. This is proved experimentally.     

DPSM modeling for studying interaction between bounded ultrasonic beams and corrugated plates with experimental verification

Periodically corrugated structures play an important role in the field of vibration control and for designing structures with desired acoustic band gaps. Analytical solutions for corrugated plates are available for well-defined, smooth corrugations, such as sinusoidal corrugations that are not very common in the real world. Often corrugated plates are fabricated by cutting grooves at regular intervals in a flat plate. No analytical solution is available to predict the wave propagation behavior in such a periodically corrugated plate in which the equation of the plate surface changes periodically between a planar fiat surface and a nonplanar parabolic groove. This problem is solved here for steady-state case by a newly developed semianalytical technique called distributed point source method (DPSM), and the theoretical predictions are compared with the experimental results generated by reflecting a bounded 2.25 MHz ultrasonic beam by a fabricated corrugated plate. The main difference that is observed in the reflected beam profile from a flat plate and a corrugated plate is that the back-scattering effect is much stronger for the corrugated plate, and the forward reflection is stronger for the flat plate. The energy distribution inside the corrugated plate also shows backward propagation of the ultrasonic energy.     

Influences of twist phenomenon of partially coherent field with uniform-intensity diffractive axicons

The effects of twist phenomenon (beam rotation) of a partially coherent field are studied on the operation of two classes of uniform-intensity diffractive axicons. A general theory of axicon image formation is developed, discussed, and examined. We show that the intensity of the diffracted field is a multiple Bessel field, and only the energy of the zero-order Bessel field diffracts along the propagation axes. We also show that, at any twist strength in all correlation levels, the images can be evaluated by using the stationary-phase method. The three-dimensional stationary-phase formula of axicon images is derived. Such formula may be used in fast image evaluation, for designing diffractive axicons that perform a uniform axial intensity in a twisted partially coherent field.     

Freeform lens arrays for off-axis illumination in an optical lithography system

We propose a method of designing a freeform lens array for off-axis illumination (OAI) in optical lithography to produce desired OAI patterns and improve efficiency. Based on the Snell law and the conservation law of energy, a set of first-order partial differential equations are derived and the coordinate relations for each OAI pattern are established. The contours of the freeform lens unit are calculated numerically by solving the partial differential equations, and the freeform lens array is obtained by arraying the lens units. Moreover, the optical performance for each OAI pattern is simulated and analyzed by software. Simulation results show that the irradiance distribution of each OAI pattern can be well controlled with a maximum uniformity of 92.45% and a maximum efficiency of 99.35%. Also, analysis indicates that this method has the advantages of reducing the complexity of the exposure system and having good tolerance to the input intensity variations of the laser beam.     

Optimal annular computer-generated holograms for the generation of optical vortices

We analyze a method for efficiently generating optical vortices by use of annular computer-generated holograms and a spatial light modulator. We found that there exists an optimal annular width by which the reconstructed vortex ring in the focal plane has the steepest gradient and the worthless subbright rings can be largely suppressed. We fitted a general formula for determining the value of this optimal annular width and propose a method for designing a multiring structure of optical vortices and specialized interferometric vortex patterns. Finally, we discuss the situation of a Gaussian beam as illuminated light and find that there exists an optimal beam waist that results in the best energy efficiency.     

基于剪切耗能假设的黏弹性夹芯梁的振动和阻尼特性

基于一阶剪切变形理论和哈密顿原理建立了三层粘弹性夹芯梁结构的有限元模型并对其振动和阻尼特性进行了研究。建模时认为粘弹材料层不可压缩,振动能量是依靠粘弹性层的剪切变形来耗散的。为验证本模型的正确性,将其与解析解作了对比。同时,为了证明本方法的优越性,将其与常用的“实特征模态”、“近似复特征模态”、“钻石法”和“近似法”四种数值方法做了比较。结果表明本方法的精度在这几种数值方法中是最好的。最后,讨论了粘弹性夹芯梁结构参数变化对系统固有频率和损耗因子的影响,得到了一些有工程实际意义的结论。     

基于能量有限元法的功能梯度梁振动分析

功能梯度材料(Functionally Graded Material,FGM)由于其优良的结构性能和重要的应用价值,近些年来得到了广泛的研究和关注。采用能量有限元法对功能梯度梁和耦合梁的弯曲振动特性进行研究,推导了功能梯度材料梁的能量密度控制方程、能量有限元矩阵方程以及耦合梁的能量有限元方程,从而得到梁中的能量密度和能量流。以一简支功能梯度梁为例,分别采用该方法和传统有限元法计算了梁弯曲振动时的能量密度,通过对比验证了能量有限元法求解的准确性。在此基础上进一步对耦合功能梯度梁结构的能量密度和能量流进行了求解,得到其能量分布特征。该研究为基于能量有限元法分析复杂功能梯度材料结构的振动特性提供了理论基础。     

Postbuckling analysis of a nonlinear beam with axial functionally graded material

The postbuckling analysis of a modified nonlinear beam composed of axial functionally graded material (FGM) is investigated by a canonical dual finite element method (CD-FEM). The governing equation of the axial FGM nonlinear beam is derived through a variational method. The CD-FEM is adopted to find the nonconvex postbuckling configurations of the beam according to Gao’s triality theory. Using duality transition, the original potential energy functional becomes a functional of deformation and dual stress fields. By variation of the mixed complementary energy, the coupling equations are derived to find deformation and dual stress fields. In FEM, matrices of a beam element depend on the gradient of material property (elastic modulus). To obtain general forms of matrices of a beam element, the graded elastic modulus is approximated by piecewise linear functions with respect to axial position. Numerical examples are presented to show the effects of graded elasticity on the postbuckling configurations of the beam.