《实验力学》第3卷(1988)分类索引

综述实验力学发展前景1,1现代技术中的高级实验力学3,乳7恶劣环境中应变测量的国内外发展综述4,329电阻应变计测盘技术全息千涉术散斑计盆焦散线法声洲坦光弹塑性法有杆抽油泵井下抽油示功图计算机诊断系统2,97非稳态热应力测试及屈服后应力峰值的确定2,130动静态应变测量的采集系统2,173用双电流源的应变测量差值法原理及其联机2,177用数理统计方法评定电田应变计灵敏系数的精度等级4,349夹层全息千论法的残余应力测试1,24用夹层全息干涉法研究物体应变2,190微机计算机对全息位移与应变分析的冲击4,338激光散斑位移测量的可测范围研究1,68…     

激光超声无损检测

本文介绍自行研制的非接触式激光超声激励和检测系统，采用共焦式法布里—珀珞干涉仪实现对纳米量级微幅单次超声窄脉冲的检测，并应用该系统进行激光超声探伤及测定材料弹性常数的研究，实验结果表明激光超声技术是有效而且实用的     

高速旋转构件应力、应变的红外遥测

介绍了高速旋转构件应力，应变测量的新方法───红外遥测法，叙述了该法的基本工作原理、仪器结构方框图及其主要参数，并且提供了测试实例。     

用云纹干涉法测量和研究双层钴合金的挠度

运用云纹干涉原理对双层钴-合金材料进行三点弯曲试验,测试其常温与高温条件下的挠度值.通过大量试验,且与千分表测试的挠度值进行比较.结果表明,常温条件下的云纹测试挠度值与千分表法可以达到同样的精确度.同时,该实验方法体现了高温云纹干涉法在材料高温力学性能测试方面的优越性.高温云纹法是非接触式测量,在高温环境下有效地解决了量具高温变形的困难,且结合云纹图像可以对试件受力动态变形情况进行实时观测和分析,是一种较为精确测试常温及高温挠度的新方法.     

光声法测量材料热膨胀系数的实验研究

本文对光声技术测量材料热膨胀系数的原理和实验方法进行了研究,设计了传声腔结构和测试系统,该方法不仅能够测量材料横向、纵向的热膨胀系数,而且还能测量常规仪器所不能测量的一任一方向的热膨胀系数,并用该方法对复合材料Al2O3/Al的热膨胀系数进行了测量,通过已有的理论结果对该方法的测试结果的准确性进行了验证,证明了该检测方法的可靠性。     

分布式光纤传感测试系统(BOTDA)用于H型钢梁变形监测的实验研究

介绍了分布式光纤传感测试系统(BOTDA)的应变测量原理,并应用BOTDA技术对H型钢梁加载后的应变分布进行了测量。试验表明,BOTDA的应变测量结果与电阻应变片的测量结果及理论值具有良好的一致性。光纤测量的数据是连续的,因而更加适用于那些需要测试连续变形的结构。由BOTDA的实测应变分布推算出的H型钢梁的弯矩和挠度,与理论分析结果高度吻合。作为先进的监测技术手段,分布式光纤传感测试系统应用于SMW工法桩施工监测是完全可行的。     

基于光纤陀螺零偏稳定性的高精度寻北方案

为了进一步提高光纤陀螺寻北系统的测量精度,提出了一种基于光纤陀螺零偏稳定性分析的寻北算法设计方案.首先,分析了光纤陀螺寻北系统的原理和影响系统寻北精度的主要因素,指明在寻北时间一定的情况下,需要根据光纤陀螺零偏稳定性的测试结果来平衡单位置积分时间及位置数,来达到较高的寻北精度.实验数据表明,本系统利用精度为0.03 (°)/h的陀螺进行5 min寻北测试,采用56位置法可以实现3′的寻北精度.此方法突破了传统寻北算法的参数选择标准,能够最大程度抑制陀螺的测量噪声,大幅提高寻北系统性能,对其它陀螺寻北系统的参数选择具有借鉴意义.     

一种基于外腔式法布里-珀罗干涉仪的光纤加速度计

研制了一种基于外腔式法布里-珀罗(F-P)干涉仪的光纤加速度计,理论分析了影响标度因数的结构参数,并利用有限元分析软件ANSYS对该结构进行仿真分析。F-P干涉仪由光纤端面和固定在弹性膜片上的反射镜组成,膜片上加工两圈花瓣状分布的弧形阵列。这种F-P干涉仪结构标度因数高、横向串扰小。经实验测定,该光纤加速度计标度因数为155.48 rad/g,与仿真分析结果基本吻合,交叉灵敏度仅为4.87×10~(-2) rad/g,分辨率为100mg,零位稳定性为125mg,提出了进一步提高性能的方法。     

蒸散研究重点:一些发展中方法

蒸散方法随着对当前蒸散研究局限性的了解而发展和变化.发展中的方法包括:与冠层阻力项相结合的复合方法,与遥感数据相结合的地表能量平衡法,提供独立的潜热和感热通量测量值的涡关联法,以及与物理学原理相结合的土壤水平衡模型的改进.发展中的方法力求估算有效蒸散量而不是估算可能蒸散量或参照蒸散量.计算机技术和测试手段的发展,使我们能够得到地球表面能量通量的更详细的测量值和更准确的蒸散量测量值.     

钻孔法测量残余应力中几个问题的探讨

本文针对钻孔法测量残余应力中一些不能用“释放”理论解释的问题,通过对钻孔法基本测量原理的分析和与其它传统电测方法对比,认为常用于测量残余应力的电测方法中钻孔法应定义为“干扰法”,切条法和套孔法为“释放法”,Sach＇s镗削法则为“干扰-释放法”.根据实验结果推荐公式=(λ-1)~(1/2)为预测钻孔深度的经验公式.同时应用“干扰”理论分析了压痕法测量残余应力的基本特性,提出压痕法与电测法结合将发展成为一种近似无损的测量残余应力的新方法.     

Analysis of Two Collinear Cracks in a Piezoelectric Layer Bonded to Two Half Spaces Subjected to Anti-plane Shear

In this paper, the behavior of two collinear anti-plane shear cracks in a piezoelectric layer bonded to two half spaces is investigated by a new method for the impermeable crack face conditions. The cracks are parallel to the interfaces in the mid-plane of the piezoelectric layer. By using the Fourier transform, the problem can be solved with two pairs of triple integral equations. These equations are solved using the Schmidt method. This process is quite different from that adopted previously. Numerical examples are provided to show the effect of the geometry of the interacting cracks and the piezoelectric constants of the material upon the stress intensity factor of the cracks.     

采用压电机敏元件进行结构振动控制Ⅲ：控制系统设计与实验研究

采用作者在上篇导出的压电耦合体动力学模型，给出了压电主动阻尼控制系统的设计方法；导出了压电耦合梁系统的作动方程和检测方程的显式表达式。以此为基础，以简单梁为对象，对压电检测器和作动器的性能、粘结层的影响、压电主动阻尼控制及压电主、被动阻尼双控制进行了实验研究     

WAVE LOCALIZATION IN RANDOMLY DISORDERED PERIODIC PIEZOELECTRIC RODS

The wave propagation in periodic and disordered periodic piezoelectric rods is studied in this paper. The transfer matrix between two consecutive unit cells is obtained according to the continuity conditions. The electromechanical coupling of piezoelectric materials is considered. According to the theory of matrix eigenvalues, the frequency bands in periodic structures are studied. Moreover, by introducing disorder in both the dimensionless length and elastic constants of the piezoelectric ceramics, the wave localization in disordered periodic structures is also studied by using the matrix eigenvalue method and Lyapunov exponent method. It is found that tuned periodic structures have the frequency passbands and stopbands and localization phenomenon can occur in mistuned periodic structures. Furthermore, owing to the effect of piezoelectricity, the frequency regions for waves that cannot propagate through the structures are slightly increased with the increase of the piezoelectric constant.     

Electroacoustic waves in piezoelectric crystals: Certain limiting cases

The Christoffel equations for electroacoustic waves in unbounded piezoelectric crystals are solved in the limits of weak and strong electromechanical coupling and for the case where the unstiffened elastic constants satisfy the conditions of elastic isotropy. Lyubimov's proof that piezoelectric stiffening of the elastic constants increases acoustic velocities is extended to cover degenerate modes. It is shown that when the elastic contribution to the stiffened elastic constants is zero, only one acoustic branch survives with a finite velocity. When the unstiffened elastic constants satisfy the conditions of elastic isotropy one of the acoustic branches is unaffected by the piezoelectric stiffening and, moreover, Lyubimov's theorem holds nonperturbatively.     

A novel type of transverse surface wave propagating in a layered structure consisting of a piezoelectric layer attached to an elastic half-space

The existence and propagation of transverse surface waves in piezoelectric coupled solids is investigated, in which perfect bonding between a metal/dielectric substrate and a piezoelectric layer of finite-thickness is assumed. Dis- persion equations relating phase velocity to material con- stants for the existence of various modes are obtained in a simple mathematical form for a piezoelectric material of class 6mm. It is discovered and proved by numerical examples in this paper that a novel Bleustein-Gulyaev （B-G） type of transverse surface wave can exist in such piezoelectric cou- pled solid media when the bulk-shear-wave velocity in the substrate is less than that in the piezoelectric layer but greater than the corresponding B-G wave velocity in the same pie- zoelectric material with an electroded surface. Such a wave does not exist in such layered structures in the absence of pie- zoelectricity. The mode shapes for displacement and electric potential in the piezoelectric layer are obtained and discussed theoretically. The study extends the regime of transverse sur- face waves and may lead to potential applications to surface acoustic wave devices.     

Third-order elastic,piezoelectric, and dielectric constants

The definitions of the third-order elastic, piezoelectric, and dielectric constants and the properties of the associated tensors are discussed. Based on the energy conservation and coordinate transformation, the relations among the third-order constants are obtained. Furthermore, the relations among the third-order elastic, piezoelectric, and dielectric constants of the seven crystal systems and isotropic materials are listed in detail.These third-order constants relations play an important role in solving nonlinear problems of elastic and piezoelectric materials. It is further found that all third-order piezoelectric constants are 0 for 15 kinds of point groups, while all third-order dielectric constants are0 for 16 kinds of point groups as well as isotropic material. The reason is that some of the point groups are centrally symmetric, and the other point groups are high symmetry.These results provide the foundation to measure these constants, to choose material, and to research nonlinear problems. Moreover, these results are helpful not only for the study of nonlinear elastic and piezoelectric problems, but also for the research on flexoelectric effects and size effects.     

AN INVESTIGATION ON TWO CRACKS PERPEN DICULAR TO THE INTERFACES IN A PIEZOE LECTRIC LAYER BONDED TO TWO HALF SPACES BY THE SCHMIDT METHOD

The behavior of two collinear anti-plane shear cracks in a piezoelectric layer bonded to two half spaces is investigated by the Schmidt method. The cracks are vertically to the imerfaces of the piezoelectric layer. By using the Fourier transform, the problem can be solved with two pairs of triple integral equations. These equations are solved using the Schmidt method. This process is quite different from that adopted previously. Numerical examples are provided to show the effect of the geometry of the interacting cracks and the piezoelectric constants of the material upon the stress intensity factor of the cracks.     

Generalized Bleustein-Gulyaev type waves in layered porous piezoceramic structure

The propagation of a Bleustein-Gulyaev (B-G) type wave in a structure consisting of multiple layers and a half-space of porous piezoelectric materials is theoretically studied. The solutions of the problem in terms of the mechanical displacements and electric potential functions are obtained for each layer and the half-space. The dispersion equation is obtained for electrically open and shorted boundary conditions by use of the transfer matrix method. A peculiar kind of B-G waves is investigated, which can propagate only in the layer over the half-space. The relationship between the piezoelectric constants and the dielectric constants is found for the existence of a peculiar kind of propagation modes. The numerical results in terms of the phase velocity and the electromechanical coupling factor with different thicknesses of the layer stack are presented.     

Study on the 3D Green's functions of the fluid and piezoelectric bimaterials

Because most piezoelectric devices have interfaces with fluid in engineering,it is valuable to study the coupled field between fluid and piezoelectric media.As the fundamental problem,the 3 D Green's functions for point forces and point charge loaded in the fluid and piezoelectric bimaterials are studied in this paper.Based on the 3 D general solutions expressed by harmonic functions,we constructed the suitable harmonic functions with undetermined constants at first.Then,the couple field in the fluid and piezoelectric bimaterials can be derived by substitution of harmonic functions into general solutions.These constants can be obtained by virtue of the compatibility,boundary,and equilibrium conditions.At last,the characteristics of the electromechanical coupled fields are shown by numerical results.     

PZT-4紧凑拉伸试样的断裂分析

基于线性压电材料的复势理论,通过解析分析,导出了一种分析有限压电板裂纹问题的解析数值方法. 首先,计算了含中心裂纹有限板的断裂参数,与Woo和Wang的解析数值法(Int J Fract, 1993, 62: 203$\sim$218)相比较,表明该方法具有很高的精度和很好的计算效率. 随后,采用该方法和有限元法计算了PZT-4紧凑拉伸试样在绝缘裂纹面边界条件下断裂时的断裂参数,发现各断裂参数的临界值分散性很大,不能作为压电材料的单参数断裂准则. 进而,针对试样真实的裂隙形状,采用有限元法计算了裂隙尖端的应力、电位移场,比较了裂隙内介质的介电性能对裂隙尖端场的影响,计算了带微裂纹的真实裂隙模型的断裂参数并进行了理论分析.