光力学多波长法的研究

1.引言识别条纹级数的问题是全息光弹性、全息干涉位移测量和散斑干涉技术等光力学方法中一个共同的重要问题.在五十多年以前,Coker和Filon对光弹性的权威贡献中广泛地使用了白光.十几年以后Frocht曾描述过作为决定分数级条纹的“彩色匹配”的概念.在普通光弹性中白光用作识别等差线零级条纹和辨别最大及最小条纹级次,以及识别脊部以便确定条纹的增减.由于白光光源是连续光谱,条纹可以由任何的“补充色”定义.在偏振仪暗场情况下条纹的色序近似是浅黄、黄、红、兰、绿.一定数值的程差对应着一定的颜色,受力模型上程差为零的点对所有不同波长的光消光,零级条纹的颜色永为黑色.但当程差继续增加时,到一定数值将出现消光重叠现象,因此     

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 在条纹沟槽表面减阻的研究发展及其优点的基础上 对条纹沟槽表面减阻进行水洞实验,研究在航行器外表面加工条纹沟槽所具有的阻 力特性. 通过对光体、0.1mmV型条纹沟槽表面和0.2mmV型条纹沟槽表面3 种不同模型在零攻角、不同水流速度下进行阻力测量, 测得条纹沟槽表面减阻特 性曲线. 从特性曲线中可以看出减阻效果约为8.3%. 实验的结果表明, 条纹沟槽 表面能明显降低水下航行器的阻力.     

用二维FFT滤波消除ESPI条纹中的散斑颗粒噪声

在 ESPI 条纹中,由于存在散斑颗粒,使得条纹对比度极大地下降.并给进一步的分析造成较大的因难.本文用二维 FFT 方法,并配以多种低通滤波函数,有效地消除了条纹图中的散斑颗粒。该方法对原始条纹图质量无任何要求,适用于各种形状的条纹.     

高灵敏云纹干涉法测量应变场

云纹干涉法是一种新的实验力学方法,具有高灵敏度,测量范围广,条纹对比度好等优点.通过在光路中添加一楔块或晶体玻璃,可以实时的观察云纹条纹,一次曝光就可得到全场的应变.     

云纹干涉仪中偏振相移的实验方法研究

本文根据偏振相移原理,将其成功地应用于云纹干涉系统中,给出具体实施方案,利用该装置进行实验,得到一组相移条纹图,给出相移结果和条纹倍增结果.     

频率向导的单幅散斑条纹图位相提取方法

提出一种基于条纹频率向导的单幅散斑条纹图位相提取技术,可对一般的散斑条纹图进行自动化位相提取. 该方法利用加窗傅里叶运算求得散斑条纹图的条纹频率,并在条纹频率的向导下对散斑条纹图的位相进行提取. 数值模拟和实验结果证实了这一方法的有效性.      

对《用偏振全息术分离绝对程差条纹》一文的浅析

1.前言我们在1981年第三期《固体力学学报》上看到了山东工学院王季中和张文之俩同志发表的《用偏振全息术分离绝对程差条纹》的文章.从文中可以看出,他们做了大量的工作,在利用一张偏振全息图直接观察程差条纹图方面取得了一定的进展.我们觉得,这是一个有意义的研究课题.为使这方面的研究工作生动活泼地开展下去,并能在应用领域中尽快见到成效,我们经过对这篇文章的学习、分析及实验观察,提出几点     

基于激光干涉条纹的联合基座相对变形测量方法

在联合基座上安装CCD光电变形测量系统发射和接收单元,通过测量所得图像中条纹倾角的变化,来检测基座扭转角的变化,通过测得条纹中心位置在焦平面X和Y方向的变化来检测横向和纵向变形。针对条纹图像,通过对每个条纹放大以及条纹单行图像像素的灰度值细分,可以得出条纹每一行的中心点,所有行的中心点连线构成条纹的中轴骨架线,从而形成一种新的条纹细分检测方法;然后将细分后的条纹分组排列,根据所有条纹斜率相同,分组后组内和组间间距近似为常值的前提条件进行最小二乘拟合和运算便可求取倾角。误差分析计算和试验结果表明,系统对扭转角的检测精度可以达到25″,对横向和纵向变形的检测精度可达5″,成为试验船的实用方法。     

用曲线大窗口平滑散斑条纹图的方法研究

提出一种计算条纹方向的简单算法,以及通过条纹方向图获得沿条纹方向的曲线窗口并对散斑条纹图进行曲线大窗口滤波的方法．实验表明此方法较好地消除了散斑条纹图的噪声,同时尽量减小了对条纹结构的损害．为从单幅散斑条纹图中应用条纹中心线法或全灰度法进一步提取相位场的后处理,奠定了良好的基础．     

条纹图的数字图象拼接处理

本文提出了一种光测数字干涉条纹图的拼接方案,解决了图象分块采集和条纹对接方法问题,大大地提高了采图精度,降低了对数字图象处理仪硬件系统及实验操作水平的要求,精度效果良好.     

西气东输管道工程中卫黄河穿越隧道场地工程地质条件评价

西气东输工程中卫黄河穿越隧道长1197.77m,高4.3m,宽5.6m。隧道入口高于黄河水位28m,出口高于黄河水位45m。隧道顶板高程为1130m。位于黄河水下100m。隧道场地围岩为寒武系磨盘井组灰绿色、银灰色浅变质中厚层细粒长石石英砂岩、千枚状板岩、绢云母化千枚岩。围岩为弱风化Ⅲ～Ⅳ类岩石。透水率为4～67Lu,纵波波速为500～3300m.s^-1。BQ为300～400。变形模量为6.11～9.22GPa。泊松比（μ）0.14～0.24。内摩擦角（ψ）为42.1°～44.7°。地下水为基岩裂隙水。含水层为寒武系浅变质岩,受大气降水渗入补给,单井涌水量为1.0～50m³.d^-1。隧道轴线穿越区岩体较完整—较破碎,未有全新活动断层。隧道位置选择和开挖深度设计是可行的。施工和长期运营是安全的。     

Acoustical scattering identification with local impedance through a spectral approach

Acoustical scattering in waveguides is studied in this paper. The Wave Finite Element (WFE) approach is mainly used, since it allows the reduction of problems dealing with periodic waveguides. The paper deals with guided acoustical propagation, that is, propagation in a main direction is privileged. The scattering by a locally reacting lining is first studied. The liner can be characterised by its local impedance in this case. The equivalent surface impedance is therefore calculated. Then, scattering by a porous layer is considered. A full three-dimensional modelling of the lining is preferred since porous materials are bulk reacting. The scattering matrix of the lined part is computed, and acoustical scattering of high-order modes and conversion between modes are highlighted. The acoustic power attenuation is further evaluated. The response of ducts subjected to constraining boundary conditions is also calculated. Numerical results are presented and compared to those obtained with conventional approaches.     

任意边界形状的二维刚塑性成形过程的无网格分析方法

将无网格伽辽金方法引入到塑性成形过程模拟,结合刚塑性材料假设,提出了基于刚塑性理论的无网格伽辽金方法,推导了其刚度矩阵方程和求解列式,给出了模具形状任意的二维塑性成形问题摩擦力边界条件的施加方法以及无网格方法应用于任意边界形状的塑性成形问题时的坐标转换关系,建立了无网格方法模拟任意边界形状的塑性成形问题的步骤,并编写了相应的计算程序。应用建立的方法对典型塑性成形过程进行了无网格方法分析,通过与刚塑性有限元方法分析结果的比较,验证了本文所建立方法的可行性。     

Chebyshev polynomial curve-fitting technique for strain-gage applications

A curve-fitting technique is presented which is especially suited to strain-gage measurements. The location of the strain gages is inherently specified by the method, and the number of gages to be used is also prescribed. The method of Chebyshev polynomial curve fitting assures a best fit in the least-squares sense. The procedure of using the method of strain-gage measurement and subsequent curve fitting is explained. The method is suitable for hand calculation but is more easily done on a digital computer. An example problem is given to illustrate the procedure, and a discussion of errors and error techniques is included.     

Singular perturbation analysis of dynamic fields in a thermoelastic solid with a small surface-breaking crack

An asymptotic analysis is presented for a dynamic problem of a semi-infinite isotropic thermoelastic solid with a small surface breaking crack. The exterior surface of the solid is subjected to a series of short thermal pulses. The crack surface is traction free and an ideal thermal contact is assumed across the crack. The stress intensity factor is asymptotically evaluated as a function of the crack depth and time. The effect of a boundary layer associated with the diffusive term is identified. The theoretical model is supplied with numerical simulations.     

Mohr-Coulomb准则主应力回映算法及在地基问题的应用

针对Mohr-Coulomb准则在应力空间中存在奇异点的问题,提出了主应力空间应力回映算法。分析了多屈服面下塑性流动法则,给出了应力更新过程中应力回映区域的判定方法,推导了不同映射区域下塑性因子的Newton-Raphson迭代求解式和应力更新方程,建立了对应的一致切线模量表达式。利用C++语言,编制了弹塑性有限元求解程序,并对岩土地基问题进行求解,计算结果的比对证明了所编程序的可行性和精确性。     

Nonlinear deformation of elastomeric foams

The nonlinear deformation of a porous foam-type elastomeric material is studied, both theoretically and experimentally. The elastomer is modeled by the neo-Hookean material. The one-dimensional compressive behavior of the foam is analysed by using certain kinematic assumptions. The stress required to compress the foam is predicted by the model in terms of the porosity of the foam and the single constant in the neo-Hookean stress-strain form. A particular silicone foam is used as a test of the theory. The neo-Hookean constant is evaluated from a test of the homogeneous elastomer. Hence the behavior of the corresponding foam is predicted theoretically and compared with experimental results. The general results are applicable to closed-cells foams of intermediate density.     

数字全息计量技术及其在微小位移测量中的应用

数字全息是用数字的方式记录和处理全息图像，避免了传统全息照相的化学处理，既简化了处理过程，更便于用数字图像处理的方式来改进图像质量和提取信息。数字全息干涉计量技术是一种全场、非接触的光学测量方法，该方法测量精度高，光路简单，对防振要求低，实验条件容易满足，特别适合微小物体的微小位移或变形的精确测量。本文运用数字全息干涉计量法测定了两端固支梁的微小离面位移；经实验验证数字全息计量术能精确测量物体0．01微米量级位移或变形；而且该方法可靠性好、成本低；是非接触的无损测量。数字全息计量技术的这些特点使得该技术在小物体的微小变形测量上具有特别的优越性，因而在MEMS结构及MEMS材料参数(如弹性模量、泊松比、热变形系数等)的测定中有广阔的应用前景。     

Application and analysis of functionally graded piezoelectrical rotating cylinder as mechanical sensor subjected to pressure and thermal loads

The exact thermoelastic analysis of a functionally graded piezoelectrical (FGP) rotating cylinder is investigated analytically. The cylinder is subjected to a combination of electrical, thermal, and mechanical loads simultaneously. The structure is a simplified model of a rotational sensor or actuator. The basic governing differential equation of the system is obtained by using the energy method. A novel term, named as the additional energy, is introduced to exact the evaluation of the energy functional. The solution to the governing differential equation is presented for two types of boundary conditions including free rotating and rotating cylinders exposed to the inner pressure. The effect of the angular velocity is investigated on the radial distribution of various components. The mentioned structure can be considered as a sensor for measuring the angular velocity of the cylinder subjected to the pressure and temperature. The obtained results indicate that the electrical potential is proportional to the angular velocity.