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排序方式: 共有758条查询结果,搜索用时 15 毫秒
691.
采用大气等离子喷涂方法在316LN不锈钢剪切销表面喷涂了Al2O3+3%TiO2绝缘涂层,采用NiAl作为粘结层,得到了性能优良的绝缘保护涂层。按照ITER实际运行环境,采用ANSYS分析方法对剪切销进行应力分析,并在低温(液氮,77K)环境下对剪切销加载后进行循环往复摩擦磨损试验。循环5000、10000以及30000周后采用2点和3点法分别测定了涂层的表面电阻和体积电阻,剪切销表面电阻率均大于109Ω•m-2,体积电阻率均大于1010Ω•m,表明涂层具有较高的绝缘电阻,满足ITER所需工程条件。 相似文献
692.
This paper presents a systematic research for understanding mechanical shearing effects on the fluid flow and the solute transport behavior of rough fractures through a numerical simulation approach. The aperture fields were modeled based on a real rock fracture geometry and the normal displacement obtained from the shear-flow test. The fluid flow through the rough fracture under shear was simulated using a finite element code that solves the Reynolds equation, and the transport behavior through the rough fracture under shear was simulated calculating the advection–dispersion equation. The results show that the fracture apertures increase as the shear displacement increases, with a few major flow channels detected through the fracture. The shear-induced flow channels increase both flow connectivity and transport connectivity, which accelerate the movement of solutes in a particular direction and lead to early breakthrough of the contaminants. Adsorption, acting as a retardation term, has a decisive influence on the transport process. These results can give a basic knowledge of the hydromechanical and solute transport progress through fracture, and will be helpful to safety assessment for high-level radioactive waste disposal facilities. 相似文献
693.
Amjad Khabaz 《Composite Interfaces》2017,24(5):447-467
In fiber-reinforced concrete, it is important to choose an appropriate length in each fiber to develop its full yield strength without a failure in the bond strength between the fiber and the concrete. This length is called the fiber development length, Ldf. The bond capacity is evaluated between the fiber and the concrete using the pull-out tests. This test evaluates the bond capacity of various types of steel fiber surfaces relative to a specific embedded length. If the steel fiber is smooth and straight, the distribution of tensile stresses will be uniform around the fiber at a specific section and varies along the anchorage length of the fiber and at a radial distance from the surface of the fiber. Pull-out tests can be performed on an embedded straight steel fiber in concrete matrix, in this case, the tensile force, P, is increased gradually and the number of cracks and their spacings and widths is recorded. The bond stresses vary along the fiber length between the cracks. The strain in the steel fiber is maximum at the cracked section and decreases toward the middle section between cracks. If the embedded length of the straight steel fiber is greater than the development length, the steel fiber may yield, leaving some length of the fiber in the concrete. The linear elastic behavior of the fiber-matrix system is interrupted by interface debonding which occurs due to overall weak bonding between the concrete matrix and the surface of the steel fiber. This paper introduces new developed shear lag model and explains simplified method to find the development length of straight steel fiber in concrete matrix using finite element model and analysis of shear lag stresses, where the maximum tension force which is applied on the steel fiber is resisted by another internal force related with the ultimate average bond stress, steel fiber diameter and its yield strength. 相似文献
694.
Yongbin Zhang 《Theoretical and Computational Fluid Dynamics》2009,23(4):239-254
Boundary film shear elastic modulus effect is analyzed in a hydrodynamic contact. The contact is one-dimensional composed
of two parallel plane surfaces, which are, respectively, rough rigid with rectangular micro projections in profile periodically
distributed on the surface and ideally smooth rigid. The whole contact is consisted of cavitated area and hydrodynamic area.
The hydrodynamic area consists of many micro Raleigh bearings which are discontinuously and periodically distributed in the
contact. Analysis is thus carried out for a micro Raleigh bearing in this contact. The hydrodynamic contact in this micro
Raleigh bearing consists of boundary film area and fluid film area which, respectively, occur in the outlet and inlet zones.
In boundary film area, the film slips at the upper contact surface due to the limited shear stress capacity of the film–contact
interface, while the film does not slip at the lower contact surface due to the shear stress capacity large enough at the
film–contact interface. In boundary film area, the viscosity, density and shear elastic modulus of the film are varied across
the film thickness due to the film–contact interactions, and their effective values are used in modeling, which depend on
the film thickness. The analytical approach proposed by Zhang (J Mol Liq 128:60–64, 2006) and Zhang et al. (Int J Fluid Mech
Res 30:542–557, 2003) is used for boundary film area. In fluid film area, the film does not slip at either of the contact
surfaces, and the shear elastic modulus of the film is neglected. Conventional hydrodynamic analysis is used for fluid film
area. The present paper presents the theoretical analysis and a typical solution. It is found that for the simulated case
the boundary film shear elastic modulus effects on the mass flow through the contact, the overall film thickness of the contact
and the carried load of the contact are negligible but the boundary film shear elastic modulus effect on the local film thickness
of the contact may be significant when the boundary film thickness is on the 1 nm scale and the contact surfaces are elastic.
In Part II will be presented detailed results showing boundary film shear elastic modulus effects in different operating conditions.
相似文献
相似文献
695.
Experimental study on the effects of shear induced structure in a drag-reducing surfactant solution flow 总被引:1,自引:0,他引:1
Hongxia Zhang Dezhong Wang Hanping Chen 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(8):773-778
In this paper, The drag reduction characteristics of surfactant solutions have been experimentally studied, as well as, the
shear viscosities of turbulent drag-reducing surfactant solution have been measured as a function of concentration, shear
rate and temperature by using AG-G2 (TA Instruments, New Castle, USA) rheometer. In comparison the rheological property with
the macroscopic behavior of the solutions in turbulent channel flow, a deeper insight into the mechanisms of drag-reducing
surfactant solution has been obtained. For no shear induced structure of surfactant solutions they just show features shear
thinning, but the drag reduction is very significant phenomenon. Surfactant solution of the shear induced structure is not
a surfactant fluid drag reduction of the necessary elements. 相似文献
696.
In this paper a general solution for the analysis of shear deformable stiffened plates subjected to arbitrary loading is presented.
According to the proposed model, the arbitrarily placed parallel stiffening beams of arbitrary doubly symmetric cross section
are isolated from the plate by sections in the lower outer surface of the plate, taking into account the arising tractions
in all directions at the fictitious interfaces. These tractions are integrated with respect to each half of the interface
width resulting two interface lines, along which the loading of the beams as well as the additional loading of the plate is
defined. Their unknown distribution is established by applying continuity conditions in all directions at the interfaces.
The utilization of two interface lines for each beam enables the nonuniform distribution of the interface transverse shear
forces and the nonuniform torsional response of the beams to be taken into account. The analysis of both the plate and the
beams is accomplished on their deformed shape taking into account second-order effects. The analysis of the plate is based
on Reissner’s theory, which may be considered as the standard thick plate theory with which all others are compared, while
the analysis of the beams is performed employing the linearized second order theory taking into account shear deformation
effect. Six boundary value problems are formulated and solved using the analog equation method (AEM), a BEM based method.
The solution of the aforementioned plate and beam problems, which are nonlinearly coupled, is achieved using iterative numerical
methods. The adopted model permits the evaluation of the shear forces at the interfaces in both directions, the knowledge
of which is very important in the design of prefabricated ribbed plates. The effectiveness, the range of applications of the
proposed method and the influence of shear deformation effect are illustrated by working out numerical examples with great
practical interest. 相似文献
697.
A new design of the shear compression specimen (SCS) for investigating the viscoelastic shear response of polymers is presented.
The specimen consists of a polymer gage section with two metal ends that remain essentially rigid during deformation. Two
closed-form analytic models are developed to predict the average stress and strain in the gage section from the deformation-load
histories. This new SCS design and its analytic models are thoroughly evaluated via laboratory measurements and numerical
simulations. These simulations show that the deformations in the gage section are more uniform than in the original design,
and the distribution of the average shear stress and strain are highly homogenous. The simulation results yield good agreement
with those of closed-form analytic results and the experiments demonstrate that the new SCS geometry and its analytic models
are as reliable as other commonly employed specimens. It can also generate higher strain rates under usual loading conditions
because of its smaller specimen gage length. The need for care in specimen preparation is also discussed in detail as illuminated
by the experimental and simulation results.
相似文献
W.G. Knauss (SEM Fellow)Email: |
698.
Francisco J. Galindo-Rosales Francisco J. Rubio-Hernández José F. Velázquez-Navarro 《Rheologica Acta》2009,48(6):699-708
We have found in this study, by means of steady and dynamic rheometry, that Aerosil® R816 particles, in which hydroxyl groups have been mostly substituted by alkyls groups, form nonflocculated suspensions in polypropylene glycol, in comparison to what was expected from previous studies. Steady flow curve shows shear-thickening behavior between two shear-thinning regions. The transient rheological response has been analyzed using a protocol proposed a long time ago by Cheng (Rheol Acta 25:542–554, 1986). It has been found that, within the reversible shear-thickening region, all the constant structure curves overlap, which suggests that the response at a certain shear rate does not depend significantly on the previous state. As a consequence, this protocol is proposed as an alternative technique for distinction between flocculated and nonflocculated suspensions. 相似文献
699.
This paper exposes an extension of an activation model previously published by the authors. When particles arranged along
the compression axis of a sheared suspension, they may overcome the electrostatic repulsion and form force chains associated
with shear thickening. A percolation-based consideration allows an estimation of the impact of the force chains on a flowing
suspension. It suggests that similar to mode coupling models, the suspension becomes unstable before the critical stress evaluated
from the activation model is reached. The percolated force chains lead to discontinuous shear thickening. The model predictions
are compared with results from two experimental studies on aqueous suspensions of inorganic oxides; in one of them, hydration
repulsion and in the other hydrophobic attraction can be expected. It is shown that the incorporation of non-Derjaguin–Landau–Verwey–Overbeek
forces greatly improve predictions of the shear thickening instability. 相似文献
700.