Semi-Infinite Anti-Plane Crack in a Piezoelectric Material

The problem of an impermeable semi-infinite crack in a piezoelectric material is considered. The electroelastic field due to a pair of concentrate forces and free charges applied at the crack surfaces is obtained by using the Mellin transform method, and the intensity factors of the quantities of concern and the mechanical strain energy release rate are given. The obtained results may be used as the fundamental solution, from which some general solutions can be calculated by superposition. The well-known solution for a purely elastic material will be recovered from the present solution if letting the coupling constant vanish.     

An Anti-plane Crack in a Piezoelectric Semiconductor

We investigate the dependence of stress intensity factors on elastic constants in two dimensional elastic isotropic bodies, using Bueckner’s weight function theory. This dependence is described in terms of Poisson’s ratio. The dependence on Poisson’s ratio shows up when the resultant tractions on each of the contours separately is non-zero in multiply connected bodies. As an example, we calculate mode I stress intensity factor KI for a crack under concentrated loading applied at one of crack faces.     

Analysis of Pre-Fracture Zones for an Electrically Permeable Crack in an Interlayer Between Piezoelectric Materials

The method of determination of the pre-fracture zone length and the crack opening displacement for a plain strain problem of electrically permeable crack located in a thin interlayer between two identical piezoelectric materials is suggested. This method takes into account certain stress distribution appearing at the crack continuation. This distribution is related to interlayer yielding or damage and it can be found experimentally or theoretically.     

A Numerical Solution For Half-Ellipse-Shaped Crack

A numerical solution for half-ellipse-shaped crack is presented. In the solution, the hypersingular integral equation in conjunction with the curve length technique is used. Particular attention is paid to the case when b/c (b and c the minor and major axis of an ellipse) is a small value, for example b/c=0.02. A reasonable accuracy requires a sufficient discretization.     

A Moving Mode-III Crack in a Functionally Graded Piezoelectric Strip

In this paper, the problem of a functionally graded piezoelectric strip with a constant-velocity Yoffe-type moving crack is considered. By using the Fourier transforms, the problem is first reduced to dual integral equations and then into Fredholm integral equations of the second kind. The electroelastic field near the crack tip is obtained for electrical impermeable boundary conditions and electrical permeable boundary conditions, respectively. The results obtained show that the gradient of the material properties can increase or decrease the magnitudes of the stress intensity factors, and the velocity can disturb the stress distribution near the crack tip.     

On The Use Of Vector J-Integral In Crack Growth Criteria For Brittle Solids

In this paper the criterion for crack-growth in solids is investigated on the basis of the concept of potential energy release rate. The expressions for path-independent vector integral J_i (i = 1,2) are derived for brittle crack growth. The relationship is then established between the value of the path-independent vector integral J_i and the potential energy release rate for crack growth in an arbitrary orientation. This allows the prediction of crack re-orientation angles on the basis of the maximum energy release rate (MERR) criterion. The crack growth angle is determined analytically as a function of (). This result is compared with other theoretical formulations of crack growth criteria, as well as with experimental results reported in the literature, and good agreement is found. The formulation provides a rigorous basis for numerical modelling of the processes of crack initiation and propagation.     

一种新型的压电材料参数的精确表征方法

针对压电材料精确表征问题,本文提出了一种包含材料损耗特性,基于模拟退火(Simulated Annealing,SA)优化算法的压电材料新型表征方法.并采用提出的新型表征方法对厚度振动模式下的高损耗偏铌酸铅压电陶瓷和l-3型压电复合材料样品的材料特性进行了研究,样品电子阻抗共振特性的理论优化结果与实际测量值准确拟合,表明该方法能够精确表征具有损耗特性压电材料参数.     

一种新型的多层复合软包装材料

综述了高阻隔性层合食品软包装的现状及发展趋势。介绍了以ＰＣ为结构层的新型多层复合材料ＰＣ／ＥＶＯＨ／ＰＰ，并评价了它在高阻隔性、高温、高湿、共挤加工等方面的综合性能及用于层含软包装的可行性。     

A Bilayer High-Temperature Dielectric Film with Superior Breakdown Strength and Energy Storage Density

The further electrification of various fields in production and daily life makes it a topic worthy of exploration to improve the performance of capacitors for a long time, including thin-film capacitors. The discharge energy density of thin-film capacitors that serves as one of the important types directly depends on electric field strength and the dielectric constant of the insulation material. However, it has long been a great challenge to improve the breakdown strength and dielectric constant...     

Rayleigh-Type Wave in A Rotated Piezoelectric Crystal Imperfectly Bonded on a Dielectric Substrate

Propagation characteristics of Rayleigh-type wave in a piezoelectric layered system are theoretically investigated. The piezoelectric layer is considered as a cubic crystal with finite thickness rotated about Y-axis and is imperfectly bonded onto a semi-infinite dielectric substrate. The imperfect interface between the two constituents is assumed to be mechanically compliant and dielectrically weakly conducting. The exact dispersion relations for electrically open or shorted boundary conditions are obtained. The numerical results show that the phase velocity of Rayleigh-type wave is symmetric with respect to the cut orientation of 45。 and can achieve the maximum propagation speed in this orientation. The mechanical imperfection plays an important role in the dispersion relations, further the normal imperfection can produce a significant reduction of phase velocity comparing with the tangential imperfection. Comparing with the mechanical imperfection the electrical imperfection makes a relatively small reduction of phase velocity of Rayleigh-type wave. The obtained results can provide some fundamentals for understanding of piezoelectric semiconductor and for design and application of piezoelectric surface acoustic wave devices.     

一种新型改性PbTiO3压电陶瓷材料研究

研制了一种新型的添加Pb（Mn1／3Sb2／3）O3、碱土金属CaCO3、Bi2O3、NiO的改性钛酸铅压电陶瓷材料．该材料具有高压电活性、大压电各向异性、低介电常数及小的机械品质因素．实验确定其典型配方为Pb0．80Ca0．20［（Mn1／3Sb2／3）0．05Ti0．95］3＋0．5wt％NiO＋1wt％Bi2O3；在优化后的制备工艺条件下，其主要性能参数为：d33＝70×10-12C·N-1；Kt＝60．0；Hp≈0，Qm＝43，Nt＝2004Hz·m．     

压电驱动器的非对称迟滞模型

为了补偿压电驱动器的非对称迟滞,提出了改进型Maxwell迟滞模型.Goldfarb提出的经典Maxwell迟滞模型由多个基础单元并联叠加而成,其基础单元为单个弹簧-物块单元,迟滞特性为平行四边形,故只能描述对称迟滞.为了能描述压电驱动器非对称迟滞,提出了基础单元迟滞特性为梯形的模型.为了简化算法程序,将梯形单元优化为两个三角形单元组合而成.为了验证该模型,以压电工作台为实验对象,运用该迟滞模型的逆模型进行迟滞补偿控制.单独的迟滞逆模型前馈开环控制实验结果表明,位移跟踪相对误差从7.37％降到了1.56％,输入输出基本呈线性关系.逆模型结合PID复合反馈闭环控制实验结果表明,位移跟踪相对误差进一步降低到0.53％,输入输出呈很好的线性关系.这表明本文所建立的迟滞模型能很好地描述压电驱动器非对称迟滞特性.     

A State-Space Model of Fatigue Crack Growth

This paper proposes a nonlinear dynamic model of fatigue crack growth in the state-space setting based on the crack closure concept under cyclic stress excitation of variable amplitude and random loading. The model state variables are the crack length and the crack opening stress. The state-space model is capable of capturing the effects of stress overload and underload on crack retardation and acceleration, and the model predictions are in fair agreement with experimental data on the 7075-T6 aluminum alloy. Furthermore, the state-space model recursively computes the crack opening stress via a simple functional relationship and does not require a stacked array of peaks and valleys of stress history for its execution; therefore, savings in both computation time and memory requirement are significant. As such, the state space model is suitable for real-time damage monitoring and control in operating machinery. This revised version was published online in July 2006 with corrections to the Cover Date.     

An Overview Of Policy Priorities For Industrial Development In Taiwan

Taiwan's industrial development policies can be decomposed into three periods over the past four decades. The first is the period before 1980 when industrial policy gradually shifted from import substitution to export expansion; the next period is in the 1980s, when various government policies were introduced to encourage accumulation of capital and to enhance R&D efforts; and the most recent period is the 1990s, when special targeted industrial development programs have been introduced to strengthen Taiwan's overall industrial competitiveness in the world market. This paper examines and explains the evolution of these policy changes.     

带有垂直于极化方向穿透的直裂纹的压电狭长体平面问题的解析解?

通过构造新的广义保角映射,本文利用广义复变函数方法研究了裂纹面上受平面应力和面内电载荷共同作用的带有垂直于极化方向穿透的有限长直裂纹的压电狭长体的平面电弹性问题,给出了电不可渗透边界条件下裂纹尖端应力和电位移强度因子的解析解。结果表明,对于该问题应力场和电场是耦合的。若不考虑电场的作用,则可得到对应纯弹性材料的解析解。当压电狭长体的高度趋于无限大时,所得解析解可退化为已有结果。最后,通过数值算例说明了材料参数、裂纹长度和机电载荷对场强度因子的影响。     

On the Effect of Dielectric Breakdown in UD CFRPs Subjected to Lightning Strike Using an Experimentally Validated Model

Applied Composite Materials - To meet worldwide increases in energy demands Wind Turbine (WT) manufacturers are producing turbines with longer blades to generate more electrical energy. To...     

通信设备企业的项目管理模式探讨

面对通信设备市场高速成长和竞争的日益加剧,通信设备企业需要不断提升企业的核心竞争力。本文分析了现有通信项目管理模式的不足之处,提出适合通信产品设计、生产的中继式项目管理模式(RPMM),并探讨了其实施方式及需要控制的四个方面:质量控制、进度控制、成本控制和信息控制。     

一种精确的压电双晶片参数动态测试模型和方法

本根据悬臂染式压电双晶片的动态导纳矩阵，设计了一种器件参数动态测试模型，用于测量压电双晶片的几个主要参数：压电常数d31、机电耦合系数κ31、介电常数ε33^T、弹性顺度常数s11^E和等效电容等。中详细叙述了测试模型的建立和测试步骤，并提出了一种实际试样的测试结果。理论与实验表明，这种新的动态测试方法是精确、可行的。     

A Material Handling System Selection Model

A technique is presented which can be used to design, or assist in the design of, an integrated materials handling system for a manufacturing facility or a major department of the facility. The developed procedure selects the materials handling equipment to be used to perform a given set of moves in order to miriimize the system's costs associated with the handling, assuming the plant arrangement remains fixed. To demonstrate the selection procedure, an example problem is presented. Since the method is heuristic, no claim of optimality is made.