基于PVDF压电传感器测量振动结构体积位移

控制振动板结构的体积位移是降低结构总声功率的一种有效策略。本文以工程常见四端位移为零的振动板为例，提出一种新的压电式传感器的设计方法测量体积位移。利用正弦函数展开近似表示固定板振动位移，通过设计特殊形状的PVDF压电薄膜，使PVDF输出信号为所需要的振动结构体积位移。结果表明这种体积位移传感器不仅适用四边简支、四边固定以及介于两者之间的边界条件板结构，而且作为一种误差传感器测量振动结构体积位移是可行的。并对实验数据进行了分析比较。     

对体积位移传感器的讨论

以不同边界条件的振动梁为例,本文提出通过分部积分方法设计特定形状的PVDF薄膜测量体积位移。这种分部积分方法得到的PVDF传感器形状不但与外激励力的性质（如激励力类型、位置以及频率等）无关,而且不需要振动梁的模态信息。研究表明,可以把振动梁的边界条件分为两类,即一端固定一端任意和两端位移为零,对于每一类边界条件可以用一种特定形状PVDF传感器测量其体积位移。     

基于压电传感器获取任意边界板结构体积速度

介绍了一种设计体积速度传感器的新方法。设计策略为将PVDF压电薄膜黏结到结构表面上,两维振动结构的表面振速用Legendre多项式展开,利用两维分布式传感器压电方程,设计PVDF薄膜的形状,使传感器的输出电荷量正比于两维结构的体积速度。这样设计得到的传感器,其输出信号的实时性得到了保证,并且适用于任意边界条件,能测量振动结构的局部体积速度,拓宽了其应用范围。此外,还以简支板及其局部区域为例,通过数值计算,验证了设计方法的可行性。     

对体积位移传感器的研讨

以不同边界条件的振动梁为例,提出通过分部积分方法设计特定形状的PVDF薄膜测量体积位移。这种分部积分方法得到的PVDF传感器形状不但与外激励力的性质（如激励力类型、位置以及频率等）无关,而且不需要振动梁的模态信息。研究表明,可以把振动梁的边界条件分为两类,即一端固定一端任意和两端位移为零,对于每一类边界条件可以用一种特定形状PVDF传感器测量其体积位移。     

箱形正交异性矩形板结构的自由振动分析

箱形正交异性矩形板结构为由四块板组成的结构。可以用一般解析解来求解这种结构的自由振动问题。这种解能用于求解板具有任意边界。对于每块板,其上边和下边具有边界条件,而在相连的两块板边则具有连续性条件。由四块板的全部条件方程式即可求解自然频率及其振型。为求解所有频率,可利用变形的对称和反对称条件,以矩形的和正方形的板结构为例进行了计算和分析。     

转管机枪膛口振动位移的测试

转管武器发射时身管处于高速旋转状态,通过炮口安装加速度传感器测量炮口的振动很困难．本文利用非接触式的电涡流传感器,针对武器发射时的特殊环境,进行了传感器选择、传感器标定以及温漂的影响分析,设计了测量转管机枪膛口垂直振动位移和水平振动位移的测试系统,并在某车载转管武器上进行了静态和动态的现场测试,得到了膛口振动位移和身管组旋转中心的轨迹曲线．     

电涡流振动位移传感器动态校准技术研究

文章提供了利用已有的中频振动校准装置,对电涡流振动位移传感器的动态特性进行校准的方法。     

晶体结构对压电陶瓷微位移驱动器特性的影响

对钙钛矿结构的ＰＺＴ－５和钨青铜结构的ＰＢＮＮ二种压电陶瓷制成的压电微位移器进行了电压－位移特性的比较和分析，发现我们所研制的ＰＢＮＮ压电微位移器具有线性好、回零好、等优点。     

传感器测量位移

介绍单磁路电传感器,差动式电传感器,差动变压器式传感器测量位移的原理,并将讲解差动变压式传感器在锅炉自动连续给水控制装置的实例。     

Finite displacement plate flexure by the use of matrix incremental approach

A finite element incremental stiffness formulation for determining finite displacement flexure behaviour of thin elastic plates is presented. The solution of the finite displacement problems is based on a piecewise linear incremental approach. The procedural aspects of the incremental approach, the control of incremental sizes and the accuracy of the incremental approximation are investigated. The details concerning how to obtain in-plane stresses and how to treat edge conditions are discussed. Results include rectangular plates under lateral pressure with various edge conditions and aspect ratios. The laterally loaded plate with edges movable in the plane of the plate is also treated.     

A simple cubic displacement element for plate bending

Early attempts to construct a triangular finite element for plate bending problems from a compatible cubic displacement field are not entirely satisfactory. The present paper shows how an accurate plate element can be achieved using independent cubic polynomial assumptions for the internal and boundary displacements in conjunction with a modified potential energy principle. This approach yields a simple algebraic formulation with favourable connection quantities at the element vertices which will appeal to practical users of the conventional finite element displacement method. Moreover, in Appendix I it is shown that the cubic element is identical to a previous hybrid stress element with linear internal bending and twisting moments and cubic boundary displacements. The stresses obtained from the former hybrid finite element solution therefore satisfy the strain compatibility conditions exactly. This remarkable result has an important significance in the theory of hybrid finite elements.     

饱和地基上弹性圆板的固结位移

 采用Laplace变换及Hankel变换研究弹性圆板在饱和地基上的固结位移．在Laplace变换域上建立了求解弹性圆板固结位移的第二类Fredholm积分方程，由数值反变换获得时域解，给出了对工程实践有参考价值的计算结果．计算结果表明，弹性板的固结位移随饱和土的排水泊松比的减少而增加，而弹性板的初始位移随饱和土的不排水泊松比的减少而增加．     

Crack opening displacement in plate with bonded repair patch

Mathematical techniques are extended to compute crack opening displacements in a cracked plate with an adhesively bonded composite patch. The plate and the patch are considered as orthotropic materials. The problem is reduced to the solution of integral equations. A software program is written to compute shear stresses in adhesive, stress intensity factors in the plate and the crack openings at the centreline of the crack. The effects of adhesive thickness, adhesive modulus, patch thickness and plate thickness on crack openings are investigated. A test program is carried out to obtain crack opening displacements in plate with bonded patch. A good agreement with analytical predictions is obtained. The effects of patches bonded on one or both sides of a plate on stress intensity factors are evaluated.     

On the use of singular displacement finite elements for cracked plate in bending

The objective of this work is to assess the performance, convergence and accuracy of four different displacement crack-tip elements used in modelling a cracked plate subjected to out-of-plane bending. A methodology is developed for calculating the singular field from the computed results and optimizing the mesh used in the numerical solution. It was found that using the quarter-node triangular elements surrounded by quadrilateral transition elements yields very accurate estimates of the singular fields of displacements and stresses as well as the stress-intensity factor for various materials and thicknesses of plates. It was also found that when the transition elements are incorporated, the optimum length of the singular element ranges from 0.5 to 1 per cent of half of the crack length.

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Résumé Le but de ce travail est d'établir les possibilités, la convergence et la sécurité de quatre modèles différents d'éléments finis pour extrémités de fissure, utilisés pour représenter une plaque fissurée soumise à flexion hors de son plan. On a développé une méthodologie pour le calcul du champ singulier qui résulte des calculs, et pour l'optimisation du réseau utilisé dans la solution numérique.On trouve qu'en utilisant des éléments triangulaires quart-onde entourés d'éléments quadrilatères de transition, on est conduit à des estimations très précises des champs singuliers de déplacements et de contraintes ainsi que du facteur d'intensité de contrainte, dans le cas de divers matériaux et de diverses épaisseurs de plaque.On trouve également que lorsque sont incorporés les éléments de transition, la longueur optimale d'un élément singulier varie entre 0,5 et 1% de la demi-longueur de la fissure.

     

Control of thermally induced elastic displacement of an isotropic structural plate bonded to a piezoelectric ceramic plate

Summary The present paper deals with a thermoelastic problem in an isotropic structural plate to which a piezoelectric ceramic plate of crystal class 6mm is perfectly bonded. It is assumed that the combined plate is subjected to a thermal load and then is deformed. In this case, we try to control the deformation of the isotropic structural plate by applying an electric potential to the piezoelectric ceramic plate. By analyzing the piezothermoelastic problem in the combined plate, we obtain an appropriate applied electric potential which alters the isotropic structural plate to a prescribed deformation. Finally numerical calculations are carried out for an isotropic steel plate to which a cadmium selenide plate is perfectly bonded, and the results are illustrated graphically.     

Procedure for accurate calculation of the J-integral from digital volume correlation displacement data

The application of digital image and volume correlation techniques to obtain displacement fields from images has become ubiquitous in experimental fracture mechanics. In this paper, a procedure to extract the J-integral (J) from three-dimensional displacement fields obtained using digital volume correlation is presented. The procedure has been specially adapted to allow for experimental noise and errors, such as poorly defined crack front displacements, smearing of the displacement field across the crack faces, and knowledge of the imprecise crack front location. The implementation is verified using analytical crack-tip fields perturbed with synthetic image correlation errors to characterise the response of J. The method is then applied to experimental results using a Magnesium alloy WE43 loaded elastically in mixed mode. The steps outlined are intended as a guideline for the application of the volume integral from displacement fields to allow for accurate calculation of J along a crack front embedded within the volume.     

Nonlinear dynamics of FGM circular cylindrical shell with clamped-clamped edges

An analysis on the nonlinear dynamics of a clamped-clamped FGM circular cylindrical shell subjected to an external excitation and uniform temperature change is presented in this paper. Material properties of the constituents are assumed to be temperature-independent and the effective properties of FGM cylindrical shell are graded in thickness direction according to a simple power law function in terms of the volume fractions. Based on the first-order shear deformation shell theory and von Karman type nonlinear strain-displacement relationship, the nonlinear governing equations of motion are derived by using Hamilton’s principle. Galerkin’s method is then utilized to discretize the governing partial equations to a two-degree-of-freedom nonlinear system including the quadratic and cubic nonlinear terms under combined external excitations. Numerical results including the bifurcations, waveform, phase plots and Poincare maps are presented for clamped-clamped FGM cylindrical shells showing the influences of material gradient index, the thickness and the external loading on the nonlinear dynamics.