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1.
The kinetics of crack growth in a viscoelastic orthotropic plate made of a composite material is analyzed. The external load is the superposition of a cyclic load and a constant tensile load. The level of the tensile load is assumed to exceed the amplitude of the cyclic load. The kinetic curves are compared with the constant tension curves. The effect of the cyclic component is studied.Translated from Prikladnaya Mekhanika, Vol. 40, No. 9, pp. 116–122, September 2004.  相似文献   

2.
The fracture problems near the similar orthotropic composite materials are interface crack tip for mode Ⅱ of double disstudied. The mechanical models of interface crack for mode Ⅱ are given. By translating the governing equations into the generalized hi-harmonic equations, the stress functions containing two stress singularity exponents are derived with the help of a complex function method. Based on the boundary conditions, a system of non-homogeneous linear equations is found. Two real stress singularity exponents are determined be solving this system under appropriate conditions about bimaterial engineering parameters. According to the uniqueness theorem of limit, both the formulae of stress intensity factors and theoretical solutions of stress field near the interface crack tip are derived. When the two orthotropic materials are the same, the stress singularity exponents, stress intensity factors and stresses for mode II crack of the orthotropic single material are obtained.  相似文献   

3.
1MechhacalModelThefractUreproblemwhichisthesameasthatinpaper[I]isfurtherdiscussedinthispaper.TheanalysisoffractUrebehavioursnearcracktipforinfinitelinearelasticorthotropiccompositeplatewithacentralthroughcrackoflengthZaiscarriedout.ThegeometryandloadingcondihonsareshowninFig.1.Tosolvesuchaproblem,weneedtosolvethepanaldifferentialequationwiththefollowingboundaryconditions:wherewisdeflectionofcoddleplane;M.andM,arebendingmoment,Ma.istwistingmoment,andstiffnessmatrixFromthetheoryofplateL'],w…  相似文献   

4.
Conclusions The results obtained here can also be used for a plate with a central through crack of the normal rupture type when it is subjected to tension by constant fillers and 1) the material of which the plate is composed, having orthotropic viscoelastic strain properties, can be modeled by a uniform orthotropic viscoelastic material; 2) the prefracture region at the edge of an advancing crack in the plate is small in the height direction; 3) the length of the prefracture region is constant during propagation of the crack.Institute of Mechanics, Academy of Sciences of the Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 27, No. 11, pp. 77–84, November, 1991.  相似文献   

5.
The subcritical growth of a mode I crack with nonsmall end zones in an aging viscoelastic plate under tensile loads applied at infinity is studied assuming that the fracture process zone is of constant length. The equations of incubation, transition, and major crack growth stages are obtained on the basis of the Volterra principle and critical crack opening criterion. The crack subcritical growth of a specific material is studied as an example __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 8, pp. 92–101, August 2007.  相似文献   

6.
The present study develops the fracture theory for a two-dimensional octagonal quasicrystals. The exact analytic solution of a Mode Ⅱ Griffith crack in the material was obtained by using the Fourier transform and dual integral equations theory, then the displacement and stress fields, stress intensity factor and strain energy release rate were determined, the physical sense of the results relative to phason and the difference between mechanical behaviors of the crack problem in crystal and quasicrystal were figured out. These provide important information for studying the deformation and fracture of the new solid phase.  相似文献   

7.
The paper studies the stress rupture behavior of a reinforced viscoelastic composite through which a penny-shaped mode I crack propagates under a constant load. The composite has hexagonal symmetry and consists of elastic isotropic fibers and viscoelastic isotropic matrix. The material is modeled as a transversely isotropic homogeneous viscoelastic medium with effective characteristics. The crack is in the isotropy plane. The ring-shaped fracture process zone at the crack front is modeled by a modified Dugdale zone with time-dependent stresses. The viscoelastic properties of the matrix are characterized using a resolvent integral operator. Use is made of Volterra's principle, the method of operator continued fractions, and the theory of precritical crack growth in viscoelastic bodies. The problem is reduced to nonlinear integral equations. Numerical results are obtained for certain components of the composite, constant volume fractions, and different fracture strengths Translated from Prikladnaya Mekhanika, Vol. 44, No. 8, pp. 45–51, August 2008.  相似文献   

8.
9.
THEEXACTSOLUTIONSOFELASTIC-PLASTICCRACKLINEFIELDFORMODEIIPLANESTRESSCRACKYiZhijian(易志坚)WangShijie(王士杰)WangXiangjian(王向坚)(Rece...  相似文献   

10.
11.
In this paper we consider the problem of rigid cylinder turning on a linear viscoelastic orthotropic half-space with Coulomb's friction acting along the contact area. Results for extents of contact area and pressure under the cylinder are obtained using Volterra's principle. The obtained functions of viscoelastic operators are interpreted by a method based on expansion of such functions in operator continued fractions. A solution is given for the general type of resolvent viscoelastic operators expressing rheological properties of half-space material. Algebra of resolvent Volterrian operators is used to facilitate the calculations. An example is given to illustrate the results for real viscoelastic material with the rheological properties expressed by the operators of Yu.N. Rabotnov.  相似文献   

12.
In this paper, we prove the independence of the path of the J-integrals near models I, II crack tips in the plate of the orthotropic composite material. Then we derive the computing formulae of the J-integrals in the cases of <0and >0 by using a complex variable method and reducing J-integrals to complex form. The J-integral computational formulae derived in this paper have certain reference value for the theoretical researches and the experimental verifications in the plane fracture for composite material.Here the authors are particularly indebted to professor Li Hao of Huazhong university of science and technology who has gone over this paper.  相似文献   

13.
The problem of a Griffith crack in an unbounded orthotropic functionally graded material subjected to antipole shear impact was studied. The shear moduli in two directions of the functionally graded material were assumed to vary proportionately as definite gradient. By using integral transforms and dual integral equations, the local dynamic stress field was obtained. The results of dynamic stress intensity factor show that increasing shear moduli’s gradient of FGM or increasing the shear modulus in direction perpendicular to crack surface can restrain the magnitude of dynamic stress intensity factor.  相似文献   

14.
A newly developed Z fracture criterion for the composite materials was introduced, the new concepts of in-plane average strain, in-plane dilatational strain energy density factor and reciprocal characteristic function were presented. Many experimental results show that the Z fracture criterion can be well used to predict the crack propagating direction for mode f crack in carbon-fiber reinforced composite laminates.  相似文献   

15.
A suitable elastic stress field near the crack line which satisfied the far field boundary conditions and the boundary conditions of the crack surfaces has been obtained and successful analysis has been made of a near crack line field for an infinite elastic-perfectly plastic medium containing a quasi-statically propagating plane stress crack subjected to far field shear stress. It is shown that the solutions of the problem of mode II crack loaded by remote shear stress from the Westergaard method in some previous papers is used as the elastic stress field near the crack line, are inappropriate.  相似文献   

16.
S. P. Timoshenko Mechanics Institute, National Academy of Sciences of the Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 31, No. 9, pp. 66–72, September, 1995.  相似文献   

17.
The paper studies the subcritical stable growth of a penny-shaped mode I crack in an aging linear viscoelastic body with cylindrical anisotropy under tensile loads applied at infinity. The equations of quasistatic crack growth are derived using the Volterra principle for a modified Dugdale model and the critical crack opening displacement as a failure criterion. The kernel of the operator that describes the viscoelastic crack opening is found using operator-valued continued fractions. As an example, the subcritical stable growth of a crack in a specific material is studied numerically __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 1, pp. 82–92, January 2007.  相似文献   

18.
A mechanical model was established for mode Ⅱ interfacial crack static growingalong an elastic-elastic power law creeping bimaterial interface. For two kinds of boundaryconditions on crack faces, traction free and frictional contact, asymptotic solutions of thestress and strain near tip-crack were given. Results derived indicate that the stress andstrain have the same singularity, there is not the oscillatory singularity in the field; thecreep power-hardening index n and the ratio of Young‘s module notably influence the crack-tip field in region of elastic power law creeping material and n only influences distribution ofstresses and strains in region of elastic material. When n is bigger, the creepingdeformation is dominant and stress fields become steady, which does not change with n.Poisson‘s ratio does not affect the distributing of the crack-tip field.  相似文献   

19.
蠕变材料Ⅰ型动态扩展裂纹尖端场   总被引:5,自引:1,他引:4  
唐立强  蔡艳红 《力学学报》2005,37(5):573-578
为了研究黏性效应作用下的动态扩展裂纹尖端渐近场,建立了蠕变材料Ⅰ型动态扩展裂纹的 力学模型.首先,依据在稳态蠕变阶段,弹性变形和黏性变形同时在裂纹尖端场中占主导地 位,由量级协调可知,应力和应变具有相同的奇异量级,即(σ,ε)∝/ r- 1/(n-1). 其次,通过渐近分析推导出动态扩展裂纹尖端场的控制方程并求得了裂纹尖端应 力、应变和位移分离变量形式的渐近解.最后,采用双参数打靶法求得了裂纹尖端应力、应 变的数值结果.数值计算表明,裂尖场主要受材料的蠕变指数n和马赫数M的控制;在Ⅰ 型动态扩展裂纹前方,环向应变达到最大值,可据此建立断裂准则. 由于裂纹稳定扩展与非稳定扩展的主奇异项相同,因此对于稳定扩展裂纹的渐近分析方 法,同样适用于非稳定的裂纹扩展问题.  相似文献   

20.
通过复变函数论的方法,对非对称Ⅲ型界面裂纹扩展的动态问题进行了研究.采用自相似函数的方法可以轻易地将所论问题转化为Riemann-Hilbert问题,并求得了裂纹坐标原点分别受到变载荷$Pt/ x$, $Px^3 /t^2$作用下的解析解的一般表达式.通过Muskhelishvili方法可以相当简单地得到问题的闭合解. 利用这些解并采用叠加原理,可以求得任意复杂问题的解.   相似文献   

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