Piezoelectric coupling factor calculations for plates of langatate driven in simple thickness modes by lateral-field-excitation

Piezoelectric coupling factors for langatate (La₃Ga_5.5Ta_0.5O₁₄) single-crystals driven by lateral-field-excitation have been calculated using the extended Christoffel-Bechmann method. Calculations were made using published materials constants. The results are presented in terms of the lateral piezoelectric coupling factor as functions of in-plane (azimuthal) rotation angle for the three simple thickness vibration modes of some nonrotated, singly-rotated, and doubly-rotated orientations. It is shown that lateral-field-excitation offers the potential to eliminate unwanted vibration modes and to achieve considerably greater piezoelectric coupling versus thickness-field-excitation for the rotated cuts considered and for a doubly-rotated cut that is of potential technological interest     

Detection and tracking of rotated and scaled targets by use of Hilbert-wavelet transform

In a recent work, we demonstrated the usefulness of the Hilbert transform in identifying the in-plane rotation angle between two objects. Here we use the Hilbert-wavelet bases instead of the Hilbert transform in the determination of the exact angle of rotation. We describe the design of the two-dimensional Hilbert-wavelet filter based on the spectral-factorization method to generate a Hilbert-transform pair of orthogonal wavelet bases. We compare the relative performance of the Hilbert transform and the Hilbert wavelet to identify both in-plane and out-of-plane rotation angles. We demonstrate that the Hilbert wavelet offers better rotation-angle determination than the Hilbert transform. We present correlation based rotated and scaled object identification and tracking using Hilbert or Hilbert-wavelet transformed infrared image sequences. We also demonstrate reduced data handling and improved tracking of distorted objects using the Hilbert-wavelet transform.     

Multiple circular-harmonic-function correlation filter providing specified response to in-plane rotation

The circular-harmonic-function correlation filter originally proposed by Hsu and Arsenault [Appl. Opt. 21, 4016 (1982)] for in-plane rotation invariance uses only one harmonic, which results in poor discrimination capability of the filter. Various methods to use multiple harmonics were explored previously by different researchers. We present a new method to combine multiple circular harmonics into a single filter that can provide the desired correlation response to in-plane rotation while minimizing the correlation-plane energy. Since multiple harmonics are included, the filter can discriminate well, and since correlation-plane energy is minimized, correlation peaks tend to be sharp. Since the designer can specify the desired in-plane rotation response, a variety of filter behaviors (including complete invariance to input rotations) can be obtained. Underlying theory is discussed, and simulation results are presented.     

Angle amplification for nanoradian measurements

A method to amplify the rotation angle of a mirror, based on multiple reflections between two quasi-parallel mirrors, is presented. The method allows rotations of fractions of nanoradians to be measured with a simple setup. The working principle, the experimental setup, and the results are presented.     

基于一阶剪切变形理论的新型复合材料层合板单元

基于一阶剪切变形理论(FSDT),本文构造一种新型的20自由度(每结点5个自由度),四边形复合材料层合板单元,适合于任意铺设情形的层合板的计算。它是按如下方式构造的:(1) 单元每边的转角和剪应变由Timoshenko层合厚梁理论来确定;(2) 对单元域内的转角场和剪应变场进行合理的插值;(3) 引入平面内双线性位移场来体现层合板面内与弯曲的耦合作用。本文单元,记为TMQ20,不存在剪切闭锁现象,在计算单层的各向同性板时可以退化为文[1]中优质的中厚板单元TMQ。在文[2]中将给出本文单元对于层合板问题的详细数值算例。     

Optical configuration for TV holography measurement of in-plane and out-of-plane deformations

A novel TV holography method is proposed for parallel evaluation of in-plane and out-of-plane deformation fields. The method permits a trade-off between in-plane and out-of-plane measuring sensitivity. A four-exposure, four-frame phase shifting technique is used in the experiments; the experimental results for an aluminum specimen subjected to both rotation in its own plane and a bending couple load at the center are presented.     

Speckle Photography Applied to the Measurement of in-plane Rotation

Speckle photography provides a simple, non-contact method of measuring in-plane displacements. By using the technique to measure the displacement at two points on an object which is being rotated about an axis parallel to the line of sight, the amount of rotation can be calculated without the need to identify the actual axis of rotation.     

Bending deformation of honeycomb consisting of regular hexagonal cells

In this study, the flexural rigidity of a honeycomb consisting of regular hexagonal cells is investigated. It is found that the bending deformation of the honeycomb cannot be evaluated by using the equivalent elastic moduli obtained from the in-plane deformation since the moments acting on inclined walls of honeycomb cell are different for the in-plane deformation and bending deformation. Based on the fact that the inclined wall of the honeycomb is twisted under the condition that the rotation angle in both connection edges is zero in bending deformation, a theoretical technique for calculating the honeycomb flexural rigidity is proposed. In the theoretical analysis, a torsion problem of a thin plate was solved by using the generalized variational principle. The validity of the present analysis is demonstrated by numerical results obtained by the finite element method.     

Spatiotemporal phase unwrapping for the measurement of discontinuous objects in dynamic fringe-projection phase-shifting profilometry

A spatiotemporal phase-unwrapping method is presented that combines the dynamic fringe-projection method and the phase-shifting technique and extends the phase-unwrapping method, which measures two phase maps at different sensitivities. The most important feature of the method is that it makes possible the automatic three-dimensional shape measurement of discontinuous objects with large dynamic range limits and high precision because the effective wavelength of the fringe-projection profilometry can be continuously varied over several orders of magnitude by rotation of the projection grating in its own plane. Only one grating and several steps of rotating the grating are required; therefore the method is inherently simple, fast, and robust. In the experiment, choosing the rotation angle was crucial for optimizing the measurement speed and the measurement accuracy. A criterion is presented for the choice of the minimum number of rotational steps for a given accuracy. The experimental results demonstrate the validity of the proposed method.     

Digital speckle-pattern interferometry: fringe retrieval for large in-plane deformations with digital speckle photography

The compensation of large in-plane motions in digital speckle-pattern interferometry (DSPI) with the use of digital speckle photography (DSP) is demonstrated. Ordinary recordings of DSPI are recombined and analyzed with DSP. The DSP result is used to compensate for the bulk speckle motion prior to calculation of the phase map. This results in a high fringe contrast even for deformations of several speckle diameters. In addition, for the case of an in-plane deformation, it is shown that the absolute phase change in each pixel may be unwrapped by use of the DSP result as an initial guess. The principles of this method and experiments showing the in-plane rotation of a plate and the encounter of two rounded plates are presented.     

Rotation angle measurement based on white-light interferometry with a standard optical flat

We propose a simple white-light interferometric method of measuring a one-dimensional rotation angle with use of an optical plane parallel plate of standard refractive index. The phase change of the interference pattern of the interferometer during the rotation of the flat plate of known refractive index and thickness placed in one of the interferometer's arms is used for determination of the rotation angle. This method has been demonstrated for an accurate angle measurement over the angle range from 0° to 40° within a maximum uncertainty of 0.057°.     

单向碳纤维/环氧树脂预浸料叠层的面内变形行为

为了充分了解热隔膜成型过程中预浸料的变形行为，通过偏轴拉伸测试探索了热固性单向碳纤维/环氧树脂预浸料在高温条件下的面内变形机制。研究参数包括试验温度、拉伸速率、预热时间和铺层顺序等。利用数字图像相关技术，在测试过程中监测单向碳纤维/环氧树脂预浸料的变形和纤维的旋转情况。结果表明，提高试验温度或降低拉伸速率均有利于促进单向碳纤维/环氧树脂预浸料的变形。铺层顺序对单向碳纤维/环氧树脂预浸料铺层的变形行为有很大影响，[45/–45/90]_S铺层方式比 [45/90/–45]_S铺层方式更有利于纤维旋转，且[45/–45/90]_S铺层方式变形阻力更小。采用铰链连接网(Pin-joined net, PJN) 理论对单向碳纤维/环氧树脂预浸料铺层变形过程中纤维角度变化进行预测并与实验结果进行对比，结果表明，用PJN理论预测的纤维旋转角度值与测试值存在较大偏差，说明其并不适用于预测热固性单向碳纤维/环氧树脂预浸料变形过程中纤维角的变化。同时，80℃预加热可以提高单向碳纤维/环氧树脂预浸料的变形阻力。      

Stokes polarimetry in multiply scattering chiral media: effects of experimental geometry

The spatial distribution of optical rotation alpha and surviving linear polarization fraction beta(L) of light scattered from cylindrical turbid chiral (glucose-containing) and achiral samples is studied using a linear Stokes polarimeter. alpha and beta(L) are measured in and off the incident plane as the detection angle changes from the forward to the backward direction. The experimental results exhibit a complex dependence on the detection geometry: alpha is more sensitive to glucose presence off the incident plane, whereas beta(L) exhibits larger effects in-plane, as validated by polarization sensitive Monte Carlo simulations. A rigorous methodology is presented for optimizing the experimental geometry in the polarimetric examinations of complex random systems.     

绳系单体系统面内运动的定位控制

建立了绳系单体系统的非线性动力学模型,分析了弱非线性条件下受控系统的稳定性.设计了一实验系统并对绳系单体系统的面内运动进行了定位控制研究.实验结果表明,计人摩擦补偿的线性力反馈控制可以有效抑制原非线性系统的面内运动.     

地磁感应线圈法探测火箭弹的滚转运动

为了对火箭弹实施简易控制,需要实时探测火箭弹滚转角度。本文给出了完整的感应电动势与弹体运动关系,提出了基于记录感应电动势过零点来探测火箭弹滚转角的方法,讨论了探测盲区的形成条件。利用该方法组成的测试系统结构简单,容易实现低成本和高工作可靠性,适合实时测试的要求。     

Duality in Metal Cutting: Impact to the Surface Layer Residual Stress

This paper concerns the residual stress formation during the processes of rigid kinematics mechanical surface treatment. Taking conventional turning as example, we examine the features of the deformation zone, which cause the principal residual stress deviation from speed and feed directions and their in-depth rotation governing in-plane shear residual stress formation. Three stress components of the plane residual stress state are presented as functionally combined. The existence of materials providing residual stress distribution by principally different ways is theoretically predicted. The formation of the residual stress states of different types is confirmed by experimental results. A hypothesis based on the simple shear cutting deformation approach is advanced to explain the revealed relationships.     

Vibration analysis of rotating cantilever plates

A finite element technique is used to determine the natural frequencies and the mode shapes of a cantilever plate mounted on the periphery of a rotating disc. The plane of the plate is assumed to make any arbitrary angle with the plane of rotation of the disc. The distributed centrifugal force is resolved into two components—one acting in the plane of the plate and the other normal to the plate. The stresses produced in the middle surface of the plate due to the in-plane forces are first determined. The increase in the bending stiffness of the plate elements due to these in-plane stresses is obtained in a manner similar to that used in the stability analysis of plates. The component of the distributed centrifugal force normal to the plate surface is added to the inertia force. From the results of computations carried out for various values of the aspect ratio, the speed of rotation, the disc radius and the setting angle, empirical formulae are derived giving the effect of these parameters on the natural frequencies. These empirical formulae are observed to be in agreement with the corresponding known formulae for rotating cantilever beams, when the aspect ratio is high.     

Constrained optimization for interface cracks in composite materials subject to non-penetration conditions

A constrained problem for a composite material with an interface crack subject to non-penetration conditions is considered. The response of a composite consisting of two identical homogeneous orthotropic materials is described with respect to in-plane deformation. The coupling of the materials occurs at an interface with angle between their vertical planes of elastic symmetry. The model is not split into independent in-plane and anti-plane states. Well-posedness of the problem is proved by variational methods. For numerical computations, a semi-smooth Newton method is proposed and its convergence is studied. Using the proposed algorithms, numerical experiments for an interface crack under mode-3 loading are presented and analyzed with respect to the half-angle defining the coupling.     

Dynamic stability of stiffened laminated composite plates and shells subjected to in-plane pulsating forces

The dynamic stability of laminated composite stiffened or non-stiffened plates and shells due to periodic in-plane forces at boundaries is investigated in this paper. A three-dimensional (3-D) degenerated shell element and a 3-D degenerated curved beam element are used to model plates/shells and stiffeners, respectively. The characteristic equations to find the natural frequencies, buckling loads and their corresponding mode shapes are obtained from the finite element equation of motion. Then, the method of Hill's infinite determinants or the method of multiple scales is applied to analyse the dynamic instability regions. Numerical results are presented to demonstrate the effects of various parameters, such as skew angle, lamination scheme, stiffened scheme, in-plane force type and curvature of cylindrical shell, on the dynamic stability of stiffened and non-stiffened plates and shells subjected to in-plane pulsating forces at boundaries.     

Shape Measurement by use of Temporal Fourier transformation in Dual-Beam Illumination Speckle Interferometry

We outline a novel method for determining the shape of an object by use of temporal Fourier-transform analysis in dual-beam illumination speckle interferometry. The object whose shape is to be determined is rotated about an axis, and a number of frames of the image of the object motion are acquired. Temporal in-plane displacement that is due to the object rotation is related to the shape of the object and is retrieved from this large set of data by Fourier transformation. With this method one can determine the absolute height of the object with variable resolution, thereby allowing shapes of objects with large and small slopes to be determined. The theory of the method along with experimental results is presented.