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31.
The 3-D stress intensity factor for a half plane crack in a transversely isotropic solid due to the motion of loads on the crack faces 总被引:1,自引:0,他引:1
Three-dimensional analysis of a half plane crack in a transversely isotropic solid is performed. The crack is subjected to
a pair of normal point loads moving in a direction perpendicular to the crack edge on its faces. Transform methods are used
to reduce the boundary value problem to a single integral equation that can be solved by the Wiener-Hopf technique. The Cagniard-de
Hoop method is employed to invert the transforms. An exact expression is derived for the mode I stress intensity factor as
a function of time and position along the crack edge. Some features of the solution are discussed through numerical results.
The project supported by the Guangdong Provincial Natural Science Foundation and the Science Foundation of Shantou University 相似文献
32.
Penny-shaped and half-plane cracks in a transversely isotropic piezoelectric solid under arbitrary loading 总被引:5,自引:0,他引:5
E. Karapetian I. Sevostianov M. Kachanov 《Archive of Applied Mechanics (Ingenieur Archiv)》2000,70(1-3):201-229
Summary The problem of a penny-shaped crack in a transversely isotropic piezoelectric material loaded by both normal and tangential
tractions and by electric charges is analyzed. Closed-form solutions are obtained for the full electroelastic fields as well
as for the stress and electric displacement intensity factors. Solutions are also obtained for the (non-trivial) limiting
case of a half-plane crack. The results are illustrated on the example of piezoceramics PZT-6B.
Received 12 July 1999; accepted for publication 20 July 1999 相似文献
33.
提出一种针对层状结构模型的先进计算方法。研究的层状结构通常为水平层状板或者层状半空间,结构由横观各向同性(TI)材料组成,材料对称轴指向分层方向。本文方法可以考虑材料的多场耦合特性,即热弹性、多孔弹性和磁电弹性耦合。基于最近提出的傅立叶-贝塞尔级数(FBS)向量函数系和双变量/位置(DVP)方法,建立了本文的先进计算方法。DVP能够无条件稳定地将层矩阵从一层传播到下一层。FBS向量函数系具有以下特点,(1)反映了具有明确类型的广义变形/波,(2)将展开系数预先计算为Love数,然后将其用于涉及问题的模拟。层状地球中的断层(或位错)作用、土-结构相互作用以及近地表地球剖面中的瞬态波等三个典型算例,证明了提出方法的准确性和有效性。 相似文献
34.
The streamwise fluctuating velocity in the turbulent boundary layer is measured under approximately medium Reynolds Number
by hot wire in order to investigate the scaling properties of the overlapped turbulent spectrum among energy-containing area,
inertial subrange and dissipation range based on FFT analysis. The experiment indicates that the high Reynolds flow reported
before is not indispensable to produce −1 scaling. So far as the measured position is provided with much higher spatial resolution
and enough closing to the wall, −1 scaling is determinate to exist when approaching medium Reynolds. The scaling ranges are
supposed to begin at inner scale and end in outer scale, which reveals the local similarity of the energy spectrum over the
energy-containing eddies near the wall. In the logarithmic area (y
+ > 130), −5/3 scaling occurs in the energy spectrum, while moving away from the wall with Reynolds numbers increasing, the
inertial subrange extends to the lower wavenumbers. On the condition k
1
η ≫ 0.1, the curves of the turbulence spectrum in the logarithmic layer are superposed, which expresses the similarity of turbulence
energy distributed in Komogorov scaling area and exhibits local isotropy characteristics by virtue of the viscous dissipation.
Supported by the National Natural Science Foundation of China (Grant Nos. 10832001 and 10872145), the Program for New Century
Excellent Talents in Universities of Education Ministry of China, and the Plan of Tianjin Science and Technology Development
(Grant No. 06TXTJJC13800) 相似文献
35.
IntroductionInsoilmechanics,theproblemsdealingwithstressinfoundationsareusuallyreferredastheBoussinesqsolutionsandtheCerrutiones (Love[1 ] ;Lure[2 ] ) .Furtherinvestigation (Bardew[3 ] ;Gibson[4 ] )tookthefoundationasapproximationoftransverselyisotropichalf_space .M… 相似文献
36.
Natural frequencies of submerged piezoceramic hollow spheres 总被引:1,自引:0,他引:1
An exact 3D analysis of free vibration of a piezoceramic hollow sphere submerged in a compressible fluid is presented in this
paper. A separation method is adopted to simplify the basic equations for spherically isotropic piezoelasticity. It is shown
that there are two independent classes of vibration. The first one is independent of the fluid medium as well as the electric
field, while the second is associated with both the fluid parameter and the piezoelectric effect. Exact frequency equations
are derived and numerical results are obtained.
The project supported by the National Natural Science Foundation of China (No. 19872060) 相似文献
37.
38.
According to the classical hypoelasticity theory, the hypoelasticity tensor, i.e. the fourth order Eulerian constitutive tensor,
characterizing the linear relationship between the stretching and an objective stress rate, is dependent on the current stress
and must be isotropic. Although the classical hypoelasticity in this sense includes as a particular case the isotropic elasticity,
it fails to incorporate any given type of anisotropic elasticity. This implies that one can formulate the isotropic elasticity
as an integrable-exactly classical hypoelastic relation, whereas one can in no way do the same for any given type of anisotropic
elasticity. A generalization of classical theory is available, which assumes that the material time derivative of the rotated
stress is dependent on the rotated Cauchy stress, the rotated stretching and a Lagrangean spin, linear and of the first degree
in the latter two. As compared with the original idea of classical hypoelasticity, perhaps the just-mentioned generalization
might be somewhat drastic. In this article, we show that, merely replacing the isotropy property of the aforementioned stress-dependent
hypoelasticity tensor with the invariance property of the latter under an R-rotating material symmetry group R⋆
G
0, one may establish a natural generalization of classical theory, which includes all of elasticity. Here R is the rotation tensor in the polar decomposition of the deformation gradient and G
0 any given initial material symmetry group. In particular, the classical case is recovered whenever the material symmetry
is assumed to be isotropic. With the new generalization it is demonstrated that any two non-integrable hypoelastic relations
based on any two objective stress rates predict quite different path-dependent responses in nature and hence can in no sense
be equivalent. Thus, the non-integrable hypoelastic relations based on any given objective stress rate constitute an independent constitutive class in its own right which is disjoint with and hence distinguishes itself from any class based on another
objective stress rate. Only for elasticity, equivalent hypoelastic formulations based on different stress rates may be established.
Moreover, universal integrability conditions are derived for all kinds of objective corotational stress rates and for all
types of material symmetry. Explicit, simple, integrable-exactly hypoelastic relations based on the newly discovered logarithmic
stress rate are presented to characterize hyperelasticity with any given type of material symmetry. It is shown that, to achieve
the latter goal, the logarithmic stress rate is the only choice among all infinitely many objective corotational stress rates.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
39.
Jianguo Wang 《中国科学A辑(英文版)》1999,42(12):1323-1331
A state space formulation is established for the nonaxisymmetric space problem of transversely isotropic piezoelectric media
in a system of cylindrical coordinate by introducing the state vector. Using the Hankel transform and the Fourier series,
the state vector equations are transformed into ordinary differential equations. By the use of the matrix methods, the analytical
solutions of a single piezoelectric layer are presented in the form of the product of initial state variables and transfer
matrix. The applications of state vector solutions are discussed. An analytical solution for a semiinfinite piezoelectric
medium subjected to the vertical point forceP
z, horizontal point forceP
x along x-direction and point electric charge Q at the origin of the surface is presented. According to the continuity conditions
at the interfaces, the general solution formulation forN-layered transversely isotropic piezoelectric media is given.
Project supported by the National Natural Science Foundation of China (Grant No. 59648001). 相似文献
40.
采用传统的固相法合成了近零膨胀氧化物功能陶瓷材料Zr0.5Hf0.5V1.4P0.6O7,用X射线衍射(XRD)、Raman光谱和热膨胀法对Zr0.5Hf0.5V1.4P0.6O7的热膨胀系数、各向同性和相变进行了测试,通过Hf4+/P5+共掺杂使得材料具有较低的热膨胀系数,研究发现合成的Zr0.5Hf0.5V1.4P0.6O7具有Pa3立方相结构,从334 K附近到673 K较宽的温度范围内的线性热膨胀系数为-1.56×10-6 K-1,表现出稳定的近零热膨胀特性。由于固溶体内部微结构的影响造成膨胀仪实验结果与变温X射线衍射结果存在一定的差距。Zr0.5Hf0.5V1.4P0.6O7具有的近零膨胀特性为通过负热膨胀材料合成膨胀系数可控的材料提供了基础。 相似文献