带滚珠调节的面—面接触形式负荷传感器球头副

为降低传统负荷传感器球头的接触应力水平,提高传感器测量的准确度和长期可靠性,设计了一种带滚珠调节的面—面接触形式的负荷传感器球头副结构,同时通过对比实验进行了验证,实验结果显示采用该结构的球头副,一只20 MN柱式力传感器可在倾斜0.2°的状态下,测量得到重复性小于0.005%、方位误差小于0.04%。研究表明,该带滚珠调节的面—面接触形式负荷传感器球头副相对未带滚珠调节的面—面接触形式传感器球头副,球头相对球碗转动时摩擦阻力更小,不仅能实现水平自调节,而且还能灵活调整由负荷传感器上、下承压面不平行带来的角度偏差,使传感器在不同测量方位测得的载荷输出值更一致,方位误差更小。此外,由于采用了面—面接触形式,该结构球头副接触应力较小,具有较大的承载能力,保证在大载荷作用下具有足够的强度。

功果桥水电站导流洞进水塔与明拱段应力应变分析及止水变形控制

由于在导流洞进水塔与洞身段之间布置明拱段衔接,因而需在进水塔与明拱段间分缝并设置止水。为分析进水塔与明拱段间的相互作用机理和分缝位置止水的变形特征,结合功果桥水电站导流洞工程,以大型有限元分析软件ANSYS为平台,建立了包含导流洞进水塔、明拱段及基岩在内的三维有限元数值计算模型,采用面—面接触单元模拟进水塔与明拱段衬砌混凝土间的相互作用关系。计算结果表明,施工期与完建期间,进水塔与明拱段在底板位置接触;运行期间随水位的上升,进水塔与明拱段间的挤压力逐渐增大,接触范围由止水内侧逐渐扩大至整个接触面;封堵期间进水塔与明拱段完全接触,且止水最大变形量出现于顶部位置。

Anisotropic surface broken bond properties and wettability of calcite and fluorite crystals

Anisotropic surface broken bond densities of six different surfaces of calcite and three surfaces of fluorite were calculated. In terms of the calculated results, the commonly exposed surfaces of the two minerals were predicted and the relations between surface broken bonds densities and surface energies were analyzed. Then the anisotropic wettability of the commonly exposed surfaces was studied by means of contact angle measurement. The calculation results show that the （101^-4）, （213^-4）and （01 1^-8）surfaces for calcite and （111） for fluorite are the most commonly exposed surfaces and there is a good rectilinear relation between surface broken bond density and surface energy with correlation of determination （R^2） of 0.9613 and 0.9969, respectively. The anisotropic wettability of different surfaces after immersing in distilled water and sodium oleate solutions at different concentrations can be explained by anisotropic surface broken bond densities and active Ca sites densities, respectively.

Kinetics of reactive wetting of graphite by liquid Al and Cu-Si alloys

In order to reveal the physical essence of the spreading process of reactive wetting,a sort of model of energy to explain the driving force and wetting mechanism was presented.The reactive wetting of molten A1 and Cu Si on graphite was studied by a modified sessile drop method under a vacuum,in which the contact angles were measured by ADSA software.The thermodynamic and kinetic processes of the typical reactive wetting were focused on,the thermodynamic equations of energy relations were derived,the interfacial energy of graphite and solid-liquid interfacial energy versus time at the triple line were calculated,and the dynamics model of interface energy is established.The presented dynamics model is verified by means of experimental results,and it is shown that solid liquid interfacial energy decreases with time in exponential relationship.It provides a new method for reference to explain the process from the angle of energy.

Influence of microwave treatment under a hydrogen or methane atmosphere on the flotability of the macerals in Shenfu coals

The modification of Shenfu coals by a microwave treatment carried out under a hydrogen or a methane atmosphere, and the subsequent maceral separation by flotation, are described in this paper. The surface contact angle and the Zeta potential of the coal macerals were measured both with and without the treat- ment. The results show that the surface wettability of SFF (Shenfu Fusain) and SFV (Shenfu Vitrain) can be changed by the microwave treatment. An increase in the difference in surface wettability of SFF and SFV causes in a subsequent increase in the enrichment of inertinite and vitrinite. The results of the Zeta potential measurements show that the surface potentials of SFF and SFV are also changed by the treatment.

Tooth surface geometry optimization of spiral bevel and hypoid gears generated by duplex helical method with circular profile blade

In order to effectively improve meshing performance of spiral bevel and hypoid gears generated by the duplex helical method, the effects of straight lined and circular cutting edges profile on meshing and contact of spiral bevel and hypoid gears were investigated analytically. Firstly, a mathematical model of spiral bevel and hypoid gears with circular blade profile was established according to the cutting characteristics of the duplex helical method. Based on a hypoid gear drive, the tooth bearings and the functions of transmission errors of four design cases were analyzed respectively by the use of the tooth contact analysis(TCA), and the contact stresses of the four design cases were analyzed and compared using simulation software. Finally, the curvature radius of the circular profile blade was optimized. The results show that the contact stresses are availably reduced, and the areas of edge contact and severe contact stresses can be avoided by selecting appropriate circular blade profile. In addition, the convex and concave sides are separately modified by the use of different curvature radii of inside and outside blades, which can increase the flexibility of the duplex helical method.

Superhydrophobic modification of ceramic membranes for vacuum membrane distillation

The hydrophobically modi fied ceramic membranes have great potential for energy-ef ficient membrane distillation.In this work,flat-sheet ceramic membranes with a superhydrophobic surface were fabricated by grafting 1H,1H,2H,2H-per fluorooctyltrichlorosilane or 1H,1H,2H,2H-per fluorodecyltriethoxysilane and followed by ultraviolet irradiation.The surface water contact angle was improved from 46° of original ceramic membrane to 159°,which exhibited a stable and excellent superhydrophobic effect.The modi fied membranes showed a high flux of 27.28 kg·m^(-2)·h^(-1) and simultaneously maintained an excellent retention rate of 99.99%,when used in vacuum membrane distillation process for treatment of a 1 wt% NaCl(75 °C) aqueous solution.These results suggested that superhydrophobic modi fication of ceramic surface is a facile and cost-effective way to achieve higher membrane distillation performance.The superhydrophobically-modi fied ceramic membrane with an excellent desalination capacity would show considerable potential in practical membrane distillation utilizations.

Effect of crack face contact on dynamic stress intensity factors for a hole-edge crack

In order to determine the dynamic stress intensity factors(DSIFs)for a single edge crack at the center hole of a finite plate under a compressive step loading parallel to the crack,the finite element method was employed to solve the cracked plate problem.The square-root stress singularity around the crack tip was simulated by quarter point singular elements collapsed by 8-node two-dimensional isoparametric elements.The DSIFs with and without considering crack face contact situations were evaluated by using the displacement correlation technique,and the influence of contact interaction between crack surfaces on DSIFs was investigated.The numerical results show that if the contact interaction between crack surfaces is ignored,the negative mode I DSIFs may be obtained and a physically impossible interpenetration or overlap of the crack surfaces will occur.Thus the crack face contact has a significant influence on the mode I DSIFs.

Surface Equation of State for Pure Phospholipid Monolayer at the Air/Water Interface

A surface equation of state, applicable to liquid-expanded (LE) monolayers, was derived by analyzing the Helmholtz free energy of the LE monolayers. Based on this equation, a general equation was obtained to describe all states of single-component phospholipid monolayers during comprassion. To verify the applicability of the equation, π-A isotherms of 1,2-dipalmitoylphosphatidylcholine (DPPC), 1,2-dipalmitoylphosphatidylglycerol (DPPG), and 1,2-dimyristoyphosphatildylcholine (DMPC) were measured. The comparison between model and experimental values indicates that the equation can describe the behavior of pure phospholipid monolayers.

Effect of surfactant type on interfacial area and liquid mass transfer for CO_2 absorption in a bubble column

The effect of different surfactants(n-octyltrimethylammonium bromide(OTABr),sodium dodecyl benzene sulfonate(SDBS) and Tween 80) with different critical micelle concentrations(CMC) on the CO_2 absorption into aqueous solutions in a bubble column is analyzed in the present work.The presence of these surfactants increased the gas-liquid interfacial area,and decreased the liquid phase mass transfer coefficient,but with significant different extent.The results indicated that the CMC can be a key parameter affecting the mass transfer of CO_2 absorption into a dilute aqueous solution of a surfactant.Sardeing's model was used to fit the experimental data successfully by re-correlating the parameters.

Wear and Contact Temperature on Steel Surface in Linear Dry Friction Contact with Polimers with SGF

In this paper, we tried to present a qualitative correlation, based on extensive experimental trials between the value and the evolution of the friction coefficient, wear and contact temperature in the case of linear dry contact, thermoplastic material reinforced with SGF （short glass fibres） and various steel surfaces. We tried, believing successfully, the graphic illustration of the evolution of the steel surface wear and of the contact temperature, depending on the friction coefficient. It was analyzed in detail the influence of the normal load and sliding speed, but also of the metallic surface roughness on the friction coefficient.

Interface energetics and engineering of organic heterostructures in organic photovoltaic cells

The reliable information about interface energetics of organic materials, especially the energy level alignment at organic heterostructures is of pronounced importance for unraveling the photon harvesting and charge separation process in organic photovoltaic(OPV) cells. This article provides an overview of interface energetics at typical planar and mixed donor-acceptor heterostructures, perovskite/organic hybrid interfaces, and their contact interfaces with charge collection layers. The substrate effect on energy level offsets at organic heterostructures and the processes that control and limit the OPV operation are presented. Recent efforts on interface engineering with electrical doping are also discussed.