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1.
雁形裂纹扩展的模型试验及断裂力学机制研究   总被引:22,自引:0,他引:22  
通过相似材料模拟试验的方法研究了双轴压缩载荷作用下闭合雁形裂纹的起裂、扩展和岩桥的贯穿机理,得到了双轴压缩载荷作用下,不同方位雁形裂纹的开裂角、起裂载荷、岩桥贯通载荷及临界失稳载荷等重要的断裂力学参数,提出岩桥的破坏模式有剪切破坏、拉剪复合破坏和翼裂纹扩展三种  相似文献
2.
It is of important significance to study the coalescence mechanism of splitting failure of crack-weakened rock masses under compressive loads. In this paper, a simplified mechanism of crack propagation, in which the crack grows along the direction of maximum principal compressive stress, is proposed. Thus, only mode I is taken into account in the formulation and solution. On the basis of the near crack line analysis method, the elastic–plastic stress field near the crack line is analyzed, and the law that the length of the plastic zone along the crack line is varied with an external loads have been established by the matching condition of the elastic- plastic fields on the boundary, the coalescence stress and the strength properties of rock masses have been determined. The solution is a function of the geometry of the crack array. The results show that the crack coalescence depends on the crack interface friction coefficient, the sliding crack spacing, orientation of the cracks, and the crack half-length. The conclusions are of important significance for rock mass engineering.  相似文献
3.
考虑三轴约束时孔洞的聚合机理及有效能量准则   总被引:9,自引:0,他引:9  
李振环  匡震邦 《力学学报》2000,32(4):428-438
通过体胞分析方法,对不同状孔洞在从光滑试样到裂纹试样的三轴应力场中的聚合机理进行了较精解的有限元分析,计算结果表明:(1)孔洞的相互靠近和横向扩展是导致相邻孔洞发生内颈缩聚合的两种基本机制,在应力三维度Rσ等于1.25附近,这两种机制发生较明显的变化。(2)单纯以孔洞体积分数fC概念为基础的材料破坏参数一般敏感于应力三维度,不能很好地预报不同三轴应力场中材料的破坏,在此基础上,提出了描述孔洞聚合的  相似文献
4.
5.
层裂的分形机理及分维和连接阈值的关系   总被引:2,自引:0,他引:2  
通过对微裂纹连接的动力学分析,提出了描述层裂损伤演化的统计分形模型,指出分形层裂面的形成机理与层裂中微裂纹级串连接的动力学过程密切相关,由此,得到了一种单峰的分维-连接阈值关系,定性解释了分维随专心韧性单峰变化的实验现象。  相似文献
6.
Bubble interaction in low-viscosity liquids   总被引:1,自引:0,他引:1  
An experimental study investigated how freely rising ellipsoidal bubbles approach each other, make contact and coalesce or breakup. Pulsed planar swarms of 10–20 bubbles with Eötvös numbers from 6.0 to 27.5 were released simultaneously in aqueous solutions of 0–48 wt% sugar with Morton numbers from 3.2 × 10−11 to 3.7 × 10−6. Bubble interaction was recorded by a video camera following the rising bubbles. Essentially, all coalescence and breakup events occurred after, not during, wake-induced collisions by a complex process related to the bubble vortex shedding cycle. This same process was also found in multi-bubble clusters and may account for excess turbulent kinetic energy generation in bubbly flow.  相似文献
7.
The combination of an electric field and a moderate turbulent flow is a promising technique for separating stable water–oil emulsions. Field-induced charges on the water droplets will cause adjacent droplets to align with the field and attract each other. The present work describes the forces that influence the kinematics of droplets falling in oil when exposed to an electric field. Mathematical models for these forces are presented and discussed with respect to a possible implementation in a multi-droplet Lagrangian framework. The droplet motion is mainly due to buoyancy, drag, film-drainage, and dipole–dipole forces. Attention is paid to internal circulations, non-ideal dipoles, and the effects of surface tension gradients.Experiments are performed to observe the behavior of a droplet falling onto a stationary one. The droplet is exposed to an electric field parallel to the direction of the droplet motion. The behavior of two falling water droplets exposed to an electric field perpendicular to the direction of their motion is also investigated until droplet coalescence. The droplet motion is recorded with a high-speed CMOS camera. The optical observations are compared with the results from numerical simulations where the governing equations for the droplet motion are solved by the RK45 (Runge Kutta) Fehlberg method with step-size control and low tolerances. Results, using different models, are compared and discussed in detail. A framework is otlined to describe the kinematics of both a falling rigid spherical particle and a fluid droplet under the influence of an electric field.  相似文献
8.
Coalescence of Pore Columns by Domain Switching   总被引:1,自引:0,他引:1  
The present paper studies the coalescence of pore columns in ferroelectric ceramics driven by back and forth domain switching under cyclic electric field. A finite element method that incorporates mass transfer capacity is formulated to simulate the evolution of point defects subjected to the kinetics of pore surface diffusion and domain wall migration. The merge of point defects provides a mechanism for the vacancy agglomeration that leads to the formation of large pores or microcracks.The project supported by the National Natural Science Foundation of China (10332020 and 10121202), and the National 973 Project (2004CB619304).  相似文献
9.
DROPLET COLLISION AND COALESCENCE MODEL   总被引:1,自引:0,他引:1       下载免费PDF全文
A new droplet collision and coalescence model was presented,a quick-sort method for locating collision partners was also devised and based on theoretical and experimental results,further advancement was made to the droplet collision outcome. The advantages of the two implementations of smoothed particle hydrodynamics (SPH) method were used to limit the collision of droplets to a given number of nearest droplets and define the probability of coalescence,numerical simulations were carried out for model validation.Results show that the model presented is mesh-independent and less time consuming,it can not only maintains the system momentum conservation perfectly,but not susceptible to initial droplet size distribution as well.  相似文献
10.
Computational approach for a pair of bubble coalescence process   总被引:1,自引:0,他引:1  
The coalescence of bubbles has great value in mineral recovery and oil industry. In this paper, two co-axial bubbles rising in a cylinder is modelled to study the coalescence of bubbles for four computational experimental test cases. The Reynolds’ (Re) number is chosen in between 8.50 and 10, Bond number, Bo ∼4.25-50, Morton number, M 0.0125-14.7. The viscosity ratio (μr) and density ratio (ρr) of liquid to bubble are kept constant (100 and 850 respectively). It was found that the Bo number has significant effect on the coalescence process for constant Re, μr and ρr. The bubble-bubble distance over time was validated against published experimental data. The results show that VOF approach can be used to model these phenomena accurately. The surface tension was changed to alter the Bo and density of the fluids to alter the Re and M, keeping the μr and ρr the same. It was found that for lower Bo, the bubble coalesce is slower and the pocket at the lower part of the leading bubble is less concave (towards downward) which is supported by the experimental data.  相似文献
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