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分析了SH波对一维六方准晶中直裂纹的散射问题。利用积分变换技术,结合Copson方法,通过求解对偶积分方程,得到声子场和相位子场应力、位移及裂纹尖端动应力强度因子的解析表达式。通过数值算例讨论了裂纹长度、入射角和入射波频率对标准动应力强度因子的影响,此研究在工程材料应用中有一定的参考价值。 相似文献
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Kuang-Chong Wu 《International Journal of Solids and Structures》2012,49(18):2681-2685
The response of an unbounded anisotropic elastic body containing a semi-infinite crack subjected to a concentrated impact force on one of the crack faces is studied. An exact solution of the dynamic stress intensity factors is obtained from a linear superposition of the solution of Lamb’s problem and a solution of a dislocation emitting from the crack tip. The stress intensity factors exhibit square-root singularity upon the arrival of the Rayleigh wave at the crack tip. As the Rayleigh wave passes through the crack tip, the stress intensity factors either instantaneously assume the static values or gradually approach to zero. Several numerical examples are given for isotropic, cubic and orthotropic materials. 相似文献
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SH波在正交各向异性功能梯度无限长条中心裂缝处的散射 总被引:3,自引:0,他引:3
研究了正交各向异性功能梯度材料无限长条中心裂缝对SH波的散射问题,为方便起见,材料两个方向的剪切模量和密度假定为指数模型.通过Fourier积分变换,将问题转化为对偶积分方程的求解.然后,用Cop-son方法求解对偶积分方程,定义了标准动应力强度因子,通过数值算例,讨论了在SH波作用下,裂缝尖端的标准动应力强度因子与入射波的频率、材料参数之间的关系. 相似文献
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Diffraction of an antiplane shear wave by two coplanar griffith cracks in an infinite elastic medium
The scattering of a time-harmonic antiplane shear wave by two parallel and coplanar Griffith cracks embedded in an infinite elastic medium is considered. The input wave normally impinges on the cracks. Fourier transformations are utilized to reduce the problem to two simultaneous integral equations which can be solved by the series expansion method. The dynamic stress intensity factors are numerically computed. 相似文献
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爆炸应力波作用下裂纹与孔洞的动态焦散线分析 总被引:4,自引:1,他引:4
将高速摄影技术与动态焦散线方法相结合,研究了爆炸应力波对裂纹、空孔的作用历史,记录了环绕它们的动态焦散斑图,给出了爆炸应力场中裂纹尖端复合应力强度因子的时间依赖关系以及空孔周围应力场分布的瞬态变化过程,为固体介质的爆破机理研究提供了新方法。 相似文献
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FengWenjie WangLiqun JiangZhiqing ZhaoYongmao 《Acta Mechanica Solida Sinica》2004,17(3):258-269
I. INTRODUCTION Owing to the intrinsic coupling characteristics between electric and elastic behaviors, piezoelectricmaterials have been used widely in technology such as transducers, actuators, sensors, etc. Studieson electroelastic problems of a piezo… 相似文献
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Ralf Müller Petia Dineva Tsviatko Rangelov Dietmar Gross 《Archive of Applied Mechanics (Ingenieur Archiv)》2012,82(1):97-110
The anti-plane dynamic problem of a functionally graded piezoelectric plane containing a hole–crack system is treated by a
non-hypersingular traction-based boundary integral equation method. The material parameters vary exponentially in the same
manner in an arbitrary direction. The system is loaded by an incident SH-type wave, and impermeable boundary conditions are
assumed. Using a frequency-dependent fundamental solution of the wave equation, the boundary value problem is transformed
into a system of integro-differential equations along the boundary of the hole and on the crack line. Its numerical solution
yields the dynamic stress intensity factors and stress concentration factors. A parametric study reveals their dependence
on the hole–crack scenario and its geometry, characteristics of the dynamic load and magnitude and direction of material inhomogeneity. 相似文献
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Dynamic behavior of two unequal parallel permeable interface cracks in a piezoelectric layer bonded to two half piezoelectric materials planes 总被引:1,自引:1,他引:0
IntroductionDuetotheintrinsicelectro_mechanicalcouplingbehavior,piezoelectricmaterialsareveryusefulinelectronicdevices.However,mostpiezoelectricmaterialsarebrittlesuchasceramicsandcrystals.Therefore ,piezoelectricmaterialshaveatendencytodevelopcriticalcracksduringthemanufacturingandthepolingprocesses.So ,itisimportanttostudytheelectro_elasticinteractionandfracturebehaviorsofpiezoelectricmaterials.Theincreasingattentiontothestudyofcrackproblemsinpiezoelectricmaterialshasledtoalotofsignificantw… 相似文献
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The dynamic behavior of a limited-permeable rectangular crack in a transversely isotropic piezoelectric material is impinged by to a P-wave. The generalized Almansi theorem and the Schmidt method are used to determine the stress intensity factor and energy density factor as the primary fracture criterion of failure. The mixed boundary value problem entails the evaluation of the appropriate crack edge stress singularities that are characteristics of the fundamental functions. The stress and electric displacement intensity factors are also used to find the energy release rate that can be computed numerically and compared with the results corresponding to those of the stress intensity factor, and energy density factor. Graphical presentation shows that the energy release rate is always negative for the boundary conditions considered while the energy density factors always remain positive. Under certain conditions, the stress and electric displacement intensity factors can be negative and subject to physical limitations. Piezoelectric material boundary value problem solutions should therefore be qualified by the application of failure criteria by fracture of otherwise, particularly when the mechanical and electrical energy can release by creating free surface at the macroscopic and microscopic scales. Negative energy release rate found for the piezoelectric medium in this work can be a case in point.Positive definiteness of the energy density factor can be applied to mutliscale fracture. This is not true for the stress intensity factor nor the energy release rate. Hence, crack initiation behavior for the permittivity of a rectangular crack due to the wave propagation effects may be studied. In particular, the initiation of micro-cracks may be identified with certain critical stress wave frequency band. Negative stress intensity factor may not enhance macrocracking but it does not exclude microcrack initiation. 相似文献
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A mathematical formulation is presented for the dynamic stress intensity factor (mode I) of a finite permeable crack subjected to a time-harmonic propagating longitudi-nal wave in an infinite poroelastic solid. In particular, the effect of the wave-induced fluid flow due to the presence of a liquid-saturated crack on the dynamic stress intensity fac-tor is analyzed. Fourier sine and cosine integral transforms in conjunction with Helmholtz potential theory are used to formulate the mixed boundary-value problem as dual inte-gral equations in the frequency domain. The dual integral equations are reduced to a Fredholm integral equation of the second kind. It is found that the stress intensity factor mono-tonically decreases with increasing frequency, decreasing the fastest when the crack width and the slow wave wavelength are of the same order. The characteristic frequency at which the stress intensity factor decays the fastest shifts to higher frequency values when the crack width decreases. 相似文献
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References: 《Acta Mechanica Solida Sinica》2007,20(1):41-49
A dynamic weight function method is presented for dynamic stress intensity factors of circular disk with a radial edge crack under external impulsive pressure. The dynamic stresses in a circular disk are solved under abrupt step external pressure using the eigenfunction method. The solution consists of a quasi-static solution satisfying inhomogeneous boundary conditions and a dynamic solution satisfying homogeneous boundary conditions. By making use of Fourier-Bessel series expansion, the history and distribution of dynamic stresses in the circular disk are derived. Furthermore, the equation for stress intensity factors under uniform pressure is used as the reference case, the weight function equation for the circular disk containing an edge crack is worked out, and the dynamic stress intensity factor equation for the circular disk containing a radial edge crack can be given. The results indicate that the stress intensity factors under sudden step external pressure vary periodically with time, and the ratio of the maximum value of dynamic stress intensity factors to the corresponding static value is about 2.0. 相似文献
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A new formula is obtained to calculate dynamic stress intensity factors of the three-point bending specimen containing a single edge crack in this study. Firstly, the weight function for three-point bending specimen containing a single edge crack is derived from a general weight function form and two reference stress intensity factors, the coefficients of the weight function are given. Secondly, the history and distribution of dynamic stresses in uncracked three-point bending specimen are derived based on the vibration theory. Finally, the dynamic stress intensity factors equations for three-pointing specimen with a single edge crack subjected to impact loadings are obtained by the weight function method. The obtained formula is verified by the comparison with the numerical results of the finite element method (FEM). Good agreements have been achieved. The law of dynamic stress intensity factors of the three-point bending specimen under impact loadings varing with crack depths and loading rates is studied. 相似文献
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A new formula is obtained to calculate dynamic stress intensity factors of the three-point bending specimen containing a single
edge crack in this study. Firstly, the weight function for three-point bending specimen containing a single edge crack is
derived from a general weight function form and two reference stress intensity factors, the coefficients of the weight function
are given. Secondly, the history and distribution of dynamic stresses in uncracked three-point bending specimen are derived
based on the vibration theory. Finally, the dynamic stress intensity factors equations for three-pointing specimen with a
single edge crack subjected to impact loadings are obtained by the weight function method. The obtained formula is verified
by the comparison with the numerical results of the finite element method (FEM). Good agreements have been achieved. The law
of dynamic stress intensity factors of the three-point bending specimen under impact loadings varing with crack depths and
loading rates is studied. 相似文献
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Dynamic fracture behaviour of crack curving in bent beams has been investigated. In order to understand the propagation mechanism
of such cracks under impact, an experimental method is used that combines dynamic photoelasticity with dynamic caustics to
study the interaction of the flexural waves and the crack. From the state change of the transient stresses in polymer specimen,
the curving fracture in the impulsively loaded beams is analyzed. The dynamic responses of crack tips are evaluated by the
stress intensity factors for the cracks running in varying curvature paths under bending stress wave.
The project supported by the National Natural Science Foundation of China and the Scientific Commission of Yunnan Province
of China 相似文献
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The dual boundary element method is used to obtain an efficient solution of the Helmholtz equation in the presence of geometric singularities. In particular, time-harmonic waves in a membrane which contains one or more fixed edge stringers (or cracks) are investigated. The hypersingular integral equation is used in the procedure to ensure a unique solution for the problem with a degenerate boundary. The method yields a solution for the entire membrane as well as the dynamic stress intensity factor. Numerical results are presented for a circular membrane containing a single edge stringer, two edge stringers and an internal stringer. Also, the first three critical wave numbers of the membrane with the homogeneous boundary condition are determined, and the dynamic stress intensity factors are found for problems with the nonhomogeneous boundary condition. Good agreement is found after comparing the results with exact solutions, and with results obtained using DtN-FEM and ABAQUS. 相似文献
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《International Journal of Solids and Structures》1999,36(2):285-309
In this study, the transient full field response of an interface crack between two different media subjected to dynamic body force at one material is investigated. For time t < 0, the bimaterial medium is stress free and at rest. At t = 0, a concentrated anti-plane dynamic point loading is applied at the medium as shown in Fig. 1. The total wave field is due to the effect of this point loading and the scattering of the incident waves by the interface crack. An alternative methodology that is different from the conventional superposition method is used to construct the reflected, refracted and diffracted wave fields. A useful fundamental solution is proposed in this study and the full field solution is determined by superposition of the fundamental solution in the Laplace transform domain. The proposed fundamental problem is the problem of applying an exponentially distributed traction (in the Laplace transform domain) on the interfacial crack faces. The Cagniard–de Hoop method of Laplace inversion is used to obtain the transient solution in time domain. Exact transient closed form solutions for stresses and stress intensity factors are obtained. Numerical results for the time history of stresses and stress intensity factors during the transient process are discussed in detail. 相似文献