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1.
The crack tip fields of stress, strain and damage for concrete under both antiplane shear and plane strain conditions are investigated based on the damage model proposed by Mazars and Lemaitre [2]. The structures of near tip fields obtained are similar to those for an elastic-perfectly-plastic material. It has been found that damage boundaries can not be determined by the near-tip analysis due to the discontinuities of stresses on the damage boundaries induced by the damage model used in the present paper.The Project is Supported by National Natural Science Fundation of China. 相似文献
2.
自适应分析在确定裂纹尖端塑性区中的应用 总被引:1,自引:0,他引:1
在分析裂纹扩展及材料强度时对塑性区的估算是很重要的,本文提出采用自适应有限元分析来确定裂纹尖端塑性区的方法,计算结果表明这种方法通过网格自动加密能够有效地跟踪出弹塑性的交界面。 相似文献
3.
A viscoplastic model accounting for developing damage in concrete is proposed by assuming the rate of damage to be dependent on viscous strain and stress rates. The damage is measured by a scalar parameter affecting both the yield stress and the material viscosity. For a post-critical range of deformation, the localized mode occurs for which additional constitutive equations are specified. The model is applied to simulate uniaxial strain rate controlled and creep response for the concrete. 相似文献
4.
An elastic-viscoplastic mechanics model is used to investigate asymptotically the mode Ⅲ dynamically propagating crack tip field in elastic-viscoplastic materials. The stress and strain fields at the crack tip possess the same power-law singularity under a linear-hardening condition. The singularity exponent is uniquely determined by the viscosity coefficient of the material. Numerical results indicate that the motion parameter of the crack propagating speed has little effect on the zone structure at the crack tip. The hardening coefficient dominates the structure of the crack-tip field. However, the secondary plastic zone has little influence on the field. The viscosity of the material dominates the strength of stress and strain fields at the crack tip while it does have certain influence on the crack-tip field structure. The dynamic crack-tip field degenerates into the relevant quasi-static solution when the crack moving speed is zero. The corresponding perfectly-plastic solution is recovered from the linear-hardening solution when the hardening coefficient becomes zero. 相似文献
5.
The paper is concerned with the fracture process zone at the tip of a crack at the nonsmooth interface between isotropic elastic
media. A plane symmetric problem is formulated. The zone is modeled by lines of discontinuity of the normal displacement at
the interface. The exact solution of the elastic problem is found by the Wiener-Hopf method
Translated from Prikladnaya Mekhanika, Vol. 44, No. 10, pp. 13–22, October 2008. 相似文献
6.
The crack tip zone shielding effect for the ductile particle reinforced brittle materials is analyzed by using a micromechanics
constitutive theory. The theory is developed here to determine the elastoplastic constitutive behavior of the composite. The
elastoplastic particles, with isotropic or kinematical hardening, are uniformly dispersed in the brittle elastic matrix. The
method proposed is based on the Mori-Tanaka's concept of average stress in the composite. The macroscopic yielding condition
and the incremental stress strain relation of the composite during plastic deformation are explicity given in terms of the
macroscopioc applied stress and the microstructural parameters of the composite such as the volume fraction and yield stress
of ductile particles, elastic constants of the two phases, etc. Finally, the contribution of the plastic deformation in the
particles near a crack tip to the toughening of the composite is evaluated.
The project supported by National Natural Science Foundation of China 相似文献
7.
On the direction of development of a thin fracture process zone at the tip of an interfacial crack between dissimilar media 总被引:1,自引:0,他引:1
The Wiener-Hopf method is used to study, under the conditions of plane strain, the direction of development of a thin fracture
process zone at the tip of an interfacial crack in a piecewise homogeneous isotropic elastoplastic body. The zone is modeled
by a straight line of tangential displacement discontinuity that emerges from the crack tip at an angle to the interface.
The dependences of the zone length and the angle on the load and other parameters of the problem are investigated
__________
Translated from Prikladnaya Mekhanika, Vol. 42, No. 2, pp. 14–23, February 2006. 相似文献
8.
Summary A statistical theory of the fatigue crack growth at damage cumulation is proposed. The theory gives the average of fatigue
crack length at any time t, and deduces the evolution of failure probability with time varying. Furthermore, the variance and relative error of fatigue
crack length at any time t are acquired. The Paris equation for the average of the crack length at any time t is derived from the statistical theory. Therefore, the prediction of the probability distribution of the crack length can
be given for any time t. Actual applications of the theory are given, which conform to the experiments.
Accepted for publication 17 June 1996 相似文献
9.
1MechhacalModelThefractUreproblemwhichisthesameasthatinpaper[I]isfurtherdiscussedinthispaper.TheanalysisoffractUrebehavioursnearcracktipforinfinitelinearelasticorthotropiccompositeplatewithacentralthroughcrackoflengthZaiscarriedout.ThegeometryandloadingcondihonsareshowninFig.1.Tosolvesuchaproblem,weneedtosolvethepanaldifferentialequationwiththefollowingboundaryconditions:wherewisdeflectionofcoddleplane;M.andM,arebendingmoment,Ma.istwistingmoment,andstiffnessmatrixFromthetheoryofplateL'],w… 相似文献
10.
The near tip fields and temperature distribution around a crack in a body of hardening material containing small damage 总被引:1,自引:0,他引:1
Yu Shouwen 《Acta Mechanica Sinica》1989,5(4):343-352
In this paper, the following conclusions are reached: The influence of damage on the stress and strain feilds can be neglected
in an asymptotic sense for the solutions of damage field in a plastic solid containing small damage. The formulation of the
problem is simplified with an uncoupled approach. Based on experimental results of plastic damage, most of the damage in the
material are considered as small damage with the critacal damage variable ω
c
≪1. Using this approach, closed form expressions of the near tip damage fields for mode III, mode I and the temperature distribution
induced by plastic dissipation in a hardening material containing damage are deduced. We point out that the temperature distribution
in the process zone is strongly dependent on the damage of materials even for the small damage case. The results of the predicted
value of the temperature rise near the tip region ignoring the damage effect is appreciably higher than the observed data.
The main reason of this discrepancy is the presence of damage dissipation and the fact that its influence on the calculation
of plastic dissipation have not been appropriately taken account of. The calculation is improved by taking into account the
damage effect on the temperature rise, then theT
max value is in better accord with the experimental value.
The project supported by the National Natural Science Foundation of China. 相似文献
11.
混凝土率型内时损伤本构模型 总被引:1,自引:0,他引:1
混凝土是一种典型的率敏感材料,为了更好地描述混凝土结构在动力、冲击荷载作用下的强度和变形特征,本文结合内时理论和损伤理论建立了一种考虑混凝土率效应的内时损伤本构模型。该模型的特点:将混凝土材料的受力软化效应分解为密实状态的塑性效应和由微裂缝扩展引起的刚度退化效应。前者由内时理论来描述,这使该模型摆脱了一般弹塑性模型中屈服面的概念,从而更符合混凝土的变形特性,并且简化了非线性计算过程;后者由损伤理论来描述,根据混凝土的动力试验结果建立了增量型的损伤演变方程,从而使该模型能够较好地反映混凝土的动力特性。最后,应用本文建议的模型对一钢筋混凝土简支梁进行了非线性分析,结果表明:当结构承受快速荷载作用时,应变率对结构的受力性能影响较大,在进行结构分析时必须予以考虑。 相似文献
12.
In this paper, double dissimilar orthotropic composite materials interfacial crack is studied by constructing new stress functions and employing the method of composite material complex. When the characteristic equations' discriminants △1 〉 0 and △2 〉0, the theoretical formula of the stress field and the displacement field near the mode I interface crack tip are derived, indicating that there is no oscillation and interembedding between the interfaces of the crack. 相似文献
13.
林拜松 《应用数学和力学(英文版)》1993,14(7):643-648
On condition that any perfectly plastic stress component at a crack tip is nothingbut the function ofθ.by making use of equilibrium equations,anisotropic plastic stress-strain-rate relations,compatibility equations and Hill anisotropic plastic yieldcondition,in the present paper,we derive the generally analytical expressions of theanisotropic plastic stress field at a mixed-mode crack tip under plane and anti-planestrain.Applying these generally analytical expressions to the mixed-mode cracks,wecan obtain the analytical expressions of anisotropic plastic stress fields at the tips ofmixed-modeⅠ-Ⅲ,Ⅱ-ⅢandⅠ-Ⅱ-Ⅲcracks. 相似文献
14.
Creep damage at crack tip in short fibre composites has been simulated by using the finite element method (FEM). The well-known
Schapery non-linear viscoelastic constitutive relationship was used to characterize time-dependent behaviour of the material.
A modified recurrence equation was adopted to accelerate the iteration. Kachanov-Rabotnov's damage evolution law was employed.
The growth of the damage zone with time around the crack tip was calculated and the results were shown with the so-called
“digit photo”, which was produced by the printer.
The project supported by the National Natural Science Foundation of China and the LNM of Institute of Mechanics, CAS 相似文献
15.
刘汉池 《应用数学和力学(英文版)》1995,16(8):779-789
This paper studies the stress-strain field near crack tip in a pure bending beam of rectangular section with one-sided mode
I crack by the analytic method of Ref. [1], then it gives the stress and strain components at the crack tip when the crack
propagates and further it obtains the formulas of calculating the elastic deformed area width, the deformed intensity area
width and the equation groups of calculating the critical stress of crack propagation, last the equation group of calculating
critical stress of crack propagation is verified by calculating instance. The maximum error is 0.18%.
First Received May 7, 1994. 相似文献
16.
In the 1920s, a closed-form solution of the moving Griffith crack was first obtained by Yoffe. Based on Yoffe's solution, the Dugdale model for the moving crack case gives a good result. However, the Dugdale model fails when the crack speed is closed to the Rayleigh wave speed because of the discontinuity occurred in the crack opening displacement (COD). The problem is solved in this paper by introducing a restraining stress zone ahead of the crack tip and two velocity functions. The restraining stresses are linearly distributed and related to the velocity of the moving crack. An analytical solution of the problem is obtained by use of the superposition principle and a complex function method. The final result of the COD is continuous while the crack moves at a Rayleigh wave speed. The characteristics of the strain energy density (SED) and numerical results are discussed, and conclusions are given. 相似文献
17.
18.
A plane strain mode I crack tip field with strain gradient effects is investigated. A new strain gradient theory is used.
An elastic-power law hardening strain gradient material is considered and two hardening laws, i. e. a separation law and an
integration law are used respectively. As for the material with the separation law hardening, the angular distributions of
stresses are consistent with the HRR field, which differs from the stress results[19]; the angular distributions of couple stresses are the same as the couple stress results[19]. For the material with the integration law hardening, the stress field and the couple stress field can not exist simultaneously,
which is the same as the conclusion[19], but for the stress dominated field, the angular distributions of stresses are consistent with the HRR field; for the couple
stress dominated field, the angular distributions of couple stresses are consistent with those in Ref. [19]. However, the
increase in stresses is not observed in strain gradient plasticity because the present theory is based on the rotation gradient
of the deformation only, while the crack tip field of mode I is dominated by the tension gradient, which will be shown in
another paper.
Supported by the National Science Foundation of China (No. 19704100), Science Foundation of Chinese Academy of Sciences (Project
KJ951-1-20), CAS K. C. Wong Post-doctoral Research Award Fund and the Post Doctoral Science Fund of China. 相似文献
19.
20.
混凝土损伤与试件尺寸效应 总被引:5,自引:0,他引:5
本文在运用概率方法确定了混凝土材料的初始损伤门槛值εD的前提下采用已有内时损伤本构模型,利用有限元方法对单边切口混凝土梁在三点弯曲荷载和四点剪切荷载作用下的力学行为进行了分析,计算了所有试件 的极限荷载Pmax,运用计算结果对混凝土断裂力学参数的尺寸效应规律进行了分析,并与已有试验结果进行了比较,其结果表明本文的数值分析怀华权及其它方法的分析结果吻合较好。 相似文献