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1.
It has been suggested that microcracks do play a key role in the triggering of the bone remodeling process. In order to evaluate the influence of microcracks on the poroelastic behaviors of an osteon, a finite element model is established and investigated by using the Comsol Multiphysics software. The findings show that the presence of a microcrack in the osteon wall strongly modifies (enlarges) its local fluid pressure and velocity. Especially, the pressure and velocity amplitudes produced in the microcracked region are larger than those of the non-cracked region. Thus, this study can also be used for proposing a likely mechanism that bone can sense the changes of surrounding mechanical environments.  相似文献   
2.
左宏  陈宜亨 《力学学报》1999,31(4):493-497
通过对微裂纹屏蔽不同来源的分析及计算,发现在各向同性脆性材料中,残余应力释放引起的微裂纹对主裂尖产生最大屏蔽效应时该微裂纹的倾角与最大张应力的方向没有明显的对应关系.在Hutchinson[1]所指出的屏蔽效应的第二个来源中,还应计及微裂纹形成引起的远场应力在微裂纹处产生的应力场的释放从而导致应力场的再分布.  相似文献   
3.
Consider a steel-rust-concrete composite consisting of a circular cylindrical concrete cover and a coaxial uniformly corroding steel reinforcement. Prediction of the amount of rust penetrated into the microcracks of concrete cover from a set of data measured at the surface of the concrete is of particular interest. The steel is assumed to be linear isotropic and rust follows a power law stress–strain relation. For the concrete, anisotropic behavior and post-cracking softening model is employed. The formulations lead to a nonlinear boundary value problem which is solved analytically. A key parameter β, defined as the ratio of the volume of corrosion products inside the cracks to the volume of the cracks, is calculated. With some efforts, this parameter is also extracted from the available theoretical and experimental studies for the purpose of comparison. The effects of the mechanical properties of rust and concrete on β is addressed.  相似文献   
4.
The effective thermal conductivity of matrix-inclusion-microcrack three-phase heterogeneous materials is investigated with a self-consistent micromechanical method (SCM) and a random microstructure finite element method(RMFEM). In the SCM, microcracks are assumed to be randomly distributed and penny-shaped and inclusions to be spherical, the crack effect is accounted for by introducing a crack density parameter, the effective thermal conductivity is derived which relates the macroscopic behavior to the crack density parameter. In the RMFEM, the highly irregular microstructure of the heterogeneous media is accurately described, the interaction among the matrix-inclusion-microcracks is exactly treated, the inclusion shape effect and crack size effect are considered. A Ni/ZrO2 particulate composite material containing randomly distributed, penny-shaped cracks is examined as an example. The main results obtained are: (1) the effective thermal conductivity is sensitive to the crack density and exhibits essentially a linear relationship with the density parameter; (2) the inclusion shape has a significant effect on the effective thermal conductivity and a polygon-shaped inclusion is more effective in increasing or decreasing the effective thermal conductivity than a sphere-shaped one; and (3) the SCM and RMFEM are compared and the two methods give the same effective property in the case in which the matrix thermal conductivity λ1 is greater than the inclusion one λ2. In the inverse case of λ1 < λ2, the two methods agree as the inclusion volume fraction and crack density are low and differ as they are high. A reasonable explanation for the agreement and deviation between the two methods in the case of λ1 < λ2 is made. This work was supported by the National Natural Science Foundation of China and Chnese “863” High-Tech, Program.  相似文献   
5.
By using the concept of domain of microcrack growth(DMG),themicromechanisms of damage in quasi-brittle materials subjected to triaxial either tensileor compressive loading are investigated and the complete strew-strain relation includingfour stages is obtained from micromechanical analysis.The regime of pre-peaknonlinear hardening corresponds to the distributed damage,i.e.the stable propagationof microcracks.After the attainment of the ultimate strength of load-bearing capacity,some microcracks experience the second unstable growth and the distributed damage istransmitted to the localization of damage.These analyses improve our understanding ofthe hardening and softening behaviors of quasi-brittle materials.  相似文献   
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7.
通过解析和数值的方法研究了二维微裂纹体有效模量和有效导电系数之间的关联,针对二维含有任意取向和平行的微裂纹介质,通过基于象素的有限元方法分别计算了它们的有效杨氏模量和有效导电系数,并建立了两种不同物理量之间的关联.研究结果表明利用简单的解析Mori-Tanaka方法也可以建立上述关联,并且与数值结果吻合很好。  相似文献   
8.
含夹杂和微裂纹复合材料的损伤演化和分析   总被引:3,自引:0,他引:3  
利用细观力学的Eshelby和Mori-Tanaka理论,考虑纤维和微裂纹之间的相互作用,研究了定向分布微裂纹的演化规律及其对材料力学性能的影响,分析了纤维体积份数,弹性系数、微裂纹密度,纤维不同取向与基体开裂强度之间的变化关系,并给出了许多有意义的结论。  相似文献   
9.
Polymer-based materials are extensively used in various applications such as aircrafts, civilian structures, oil and gas platforms and electronics. They are, however, inherently damage prone and over time, the formation of cracks and microscopic damages influences the thermo-mechanical and electrical properties, which eventually results in the total failure of the materials. This paper provides an overview of the principal causes of cracking in polymer and composites and summarizes the recent progress in the development of non-destructive techniques in crack detection. Furthermore, recent progress in the development of bio-inspired self-healing methods in autonomic repair is discussed.  相似文献   
10.
Microcracks exert a large influence on the behavior of phase transformation ceramics. In this paper, the cause of microcracking is interpreted and the interaction between transformation particles and microcracks is described to estimate the stiffness and strength through the modified equivalent inclusion method by the authors. Three point bend experiments on Al2O3/ZrO2 ceramics are performed and a comparison between the theoretical and measured results confirms the rationality of the analytical model proposed in this paper and the important role of microcracks.  相似文献   
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