植物油的粘温性与润滑性

与矿物油相比,植物油具有良好的生物降解性,粘温性和润滑性。介绍了15种植物油的粘温性和润滑性。

氟氯碳的粘温性与分子结构的关系

在航空航天应用领域，用三氟氯乙烯齐聚物作为不可燃液压流体的候选物，现已证明具有很好的潜在优势。为了进一步研究不同分子组成（在商品ＣＴＦＥ流体中出现的）结构间的关系，现已设计出代表不同结构、特性优良的一系列化合物模型。通常描述液压流体在可用温度范围内的重要特性之一是粘度或粘度－温度特性。运用化学图解理论，导出氟氯碳分子的分子量、分子结构与粘度－温度特性关系的方程。

生物柴油低温凝固机理探讨

采用气相色谱法研究菜籽油生物柴油、大豆油生物柴油和花生油生物柴油中脂肪酸甲酯的分布和含量;采用多功能低温性能测定仪和旋转粘度计研究生物柴油的低温流动性及粘温性。结果表明,生物柴油低温流动性与其脂肪酸甲酯相对含量关系密切;温度高于生物柴油冷滤点时,其表观粘度与温度关系不大;温度低于生物柴油冷滤点时,其表观粘度随温度降低而增大;随着温度降低,生物柴油中析出针状蜡晶,并逐渐聚结形成三维网状结构,将液态的生物柴油吸附于其中,使生物柴油整体上失去流动性。

发动机润滑油品质对发动机磨损影响的分析

分析了发动机润滑油几个主要性能对发动机磨损的影响,为润滑油的生产、使用提供了一定的参考建议。

聚内烯烃的特性及使用性能

与矿物油相比,聚α-烯烃(PAO)以其粘温性好、倾点低、粘度指数高、高温抗氧化性优等特点广泛被 人们接受,但是由于其价格不菲而制约了推广。聚内烯烃(PIO)既保持了PAO的基本性能,又价格低廉,将作为 PAO的替代或补充而具有广泛的应用价值。

汽车发动机润滑油的分析及使用注意要点

文章对发动机润滑油的作用、性能、编号作了简明易懂的分析,提供了选择发动机润滑油的正确方法,介绍汽车润滑系统常见故障及排除方法。

高黏度苯甲基硅油的环体法制备及其性能研究

分别对甲基苯基混合环体体系、八苯基环体体系通过开环聚合所制备的高黏度苯甲基硅油性能进行了研究。结果表明,随着封端剂用量的增加,苯甲基硅油的黏度降低,封端剂的合理使用能有效控制苯甲基硅油的黏度;随着八甲基环四硅氧烷(D4)用量的增加,苯甲基硅油的折光率下降。由八苯基环体体系制备出的苯甲基硅油黏度受温度的影响小于混合环体体系,耐热性在质量损失率为10%时优于混合环体体系。

制动液、起动液、防冻液的使用

一、制动液及其使用制动液是机车液压制动装置中传递动力的介质。按其原料、工艺和使用要求的不同,可分为醇型制动液、矿油型制动液和复合型制动液三种。其中复合型制动液具有凝点低,低温流动性好,沸点高、不易生成气阻,粘温性好,抗氧化、腐蚀等优点,被广泛应用于高速。

Experimental investigation and development of new correlation for influences of temperature and concentration on dynamic viscosity of MWCNT-SiO2(20-80)/20W50 hybrid nano-lubricant

In current research, MWCNT-SiO2/oil hybrid nano-lubricant viscosity is experimentally examined. By dispersing 0.05%, 0.1%, 0.2%, 0.4%, 0.8% and 1% volume of MWCNTs and SiO2 nanopartide into the engine oil SAE 20W50, the temperature and solid volume fraction consequences were studied. At 40 to 100 ℃ temperature, the viscosities were assessed. The results indicated Newtonian behavior for the hybrid nano-lubricant. Moreover, solid volume fraction augmentation and temperature enhanced the viscosity enhancement of hybrid nano-lubricant. At highest solid volume fraction and temperature, nano-lubricant viscosity was 171% greater compared to pure 20W50. Existed models lack the ability to predict the hybrid nano-lubricant viscosity. Thus, a new correlation regarding solid volume fraction and temperature was suggested with R-squared of 0.9943.

Effects of Alginate Gel on Rheological Properties of Hair-tail (Trichiurus lepturus) Surimi

Effects of alginate gel at different concentrations on rheological properties of hair-tail (Trichiurus lepturus) surimi were investigated. Alginate gel (1% - 3%) exhibited enhanced effects, especially when alginate gel concentration increased. The rheological properties of mixture samples were studied by the time sweep, frequency sweep and temperature sweep. The critical strain values of the mixture samples for the onset of non-linear viscoelasticity were about 5%. The storage modulus G' of the mixture samples increased with time for 4 h. The frequency sweep showed that G' was greater than G" for all the mixture gels with different alginate gel concentrations, and values of both n' and n" for all samples were low (<0.2), these constants corresponding to G' and G", and indicating the elasticity of mixture gels. The values of storage modulus G' decreased during heating process and increased with decreasing temperature.

Fracture prediction in non-isothermal viscous pressure bulging of aluminum alloy sheet using ductile fracture criterion

The failure of AA3003 aluminum alloy sheet metal was predicted for non-isothermal viscous pressure bulging (VPB). Utilizing the coupled thermo-mechanical finite element method combined with ductile fracture criterion, the calculations were carried out for non-isotherm VPB at various temperatures and the influences of the initial temperature of viscous medium on failure mode of bulge specimens were investigated. The results show that the failure modes are different for the non-isothermal VPB with different initial temperatures of viscous medium. For the non-isothermal VPB of AA3003 aluminum alloy sheet with initial temperature of 250 ℃, when the initial temperature of viscous medium ranges from 150 to 180 ℃, the formability of sheet metal can be improved to a full extent. The validity of the predictions is examined by comparing with experimental results.

Viscoelastic Characteristics of Asphalt Binders at Softening Point Temperature

In this paper, in order to investigate the viscoelasticity of asphalt binder at the softening point temperature, more than 30 different asphalt binders were selected and tested by dynamic rheological scan method using a dynamic shear rheometer(DSR). The softening points and the rheological parameters of the asphalt samples were measured and analyzed. The results indicated that at the softening point temperature the neat asphalt and the SBS modified asphalt showed two different rheological states. The neat asphalt binders had a majority of viscous components in viscoelastic composition, with the phase angles being mostly higher than 80 o. The SBS modified binders had lower phase angles, with their elasticity still retained. Meanwhile, the Shapiro-Wilk normality test showed that at a confidence level of 0.05, at whatever aging state, the neat asphalt had a stable complex modulus corresponding to the softening point, which was 13.034 kPa at a standard deviation of 2.105 kPa under the same test condition. The softening point of neat asphalt binder can be calculated via the equivalent modulus rule. It is found out that there is a good relationship between the calculated and the measured softening points. And it is suggested that more data are needed to validate this finding.

Numerical Simulation of the Non-isothermal Viscoelastic Flow Past a Confined Cylinder

A collocated finite volume method on unstructured meshes is introduced to simulate the viscoelastic flow of the polymer melt with viscous dissipation past a confined cylinder.The constitutive equation for the simulations is non-isothermal FENE-P model,which is derived from the molecular theories.The temperature effect on the macroscopic fields(e.g.,velocity,stress) and microscopic fields(e.g.,molecular orientation,deformation,stretch) is investigated by comparison of isothermal and non-isothermal situations.This investigation indicates that temperature rise caused by viscous dissipation should not be neglected since it has significant effect on the macroscopic and microscopic properties of the polymer melt.

Magnesium (II) Adsorption from Aqueous Solutions on China Clay and the Stability Constants for Complex Formation

China clay was employed as an adsorbent for the removal of Mg 2+ from water at pH 7.0 within the temperature range of 303～328 K. The linearity of the plots indicated Langmuir type isotherms. The reaction was exothermic. A maximum removal of 35% was obtained at 0.50 mmol L -1 metal concentration and a pH of 7.0 at 303 K. The H + rel /Mg 2+ ads ratio changed from a fractional value to 2.5. Strong chemical bondings took place between oxygen atom of the surface and Mg 2+ , resulting in a surface complex species. Temperature had a significant effect on H + rel , and the stability constants also increased with increasing temperature.

Excess Molar Volumes and Viscosities of Binary Mixture of Diethyl Carbonate+Ethanol at Different Temperatures

The purpose of this work was to report excess molar volumes and dynamic viscosities of the binary mixture of diethyl carbonate （DEC）+ethanol. Densities and viscosities of the binary mixture of DEC+ethanol at temperatures 293.15 K—343.15 K and atmospheric pressure were determined over the entire composition range. Densities of the binary mixture of DEC+ethanol were measured by using a vibrating U-shaped sample tube densimeter. Viscosities were determined by using Ubbelohde suspended-level viscometer. Densities are accurate to 1.0×10-5 g·cm-3, and viscosities are reproducible within ±0.003 mPa·s. From these data, excess molar volumes and deviations in viscosity were calculated. Positive excess molar volumes and negative deviations in viscosity for DEC+ethanol system are due to the strong specific interactions.All excess molar vo-（lumes） and deviations in viscosity fit to the Redlich-Kister polynomial equation.The fitting parameters were presented,and the average deviations and standard deviations were also calculated.The errors of correlation are very small.It proves that it is valuable for estimating densities and viscosities of the binary mixture by the correlated equation.

MHD three dimensional flow of viscoelastic fluid with thermal radiation and variable thermal conductivity

The objective of the present work is to model the magnetohydrodynamic(MHD) three dimensional flow of viscoelastic fluid passing a stretching surface. Heat transfer analysis is carried out in the presence of variable thermal conductivity and thermal radiation. Arising nonlinear analysis for velocity and temperature is computed. Discussion to importantly involved parameters through plots is presented. Comparison between present and previous limiting solutions is shown. Numerical values of local Nusselt number are computed and analyzed. It can be observed that the effects of viscoelastic parameter and Hartman number on the temperature profile are similar in a qualitative way. The variations in temperature are more pronounced for viscoelastic parameter K in comparison to the Hartman number M. The parameters N and ε give rise to the temperature. It is interesting to note that values of local Nusselt number are smaller for the larger values of ε.

Experimental study on visco-elastic constitutive relationship and its parameters for geogrids

Geogrids are used as reinforcement materials widely in geotechnical and civil engineering fields. In this paper, a series of comparative tests on creep behavior of specific geoOgrids are conducted in the laboratory under different combinations of loading levels and environmental temperature. Based on the test results,comparative analyses are made to study long-term behaviors of isochronous load-strain curves, creep curves and relaxation curves for the specified geogrids. Furthermore, a constitutive model based on theory of visco-elasticity and tests results is proposed for geogrids and a rational procedure is presented in detail for determining the relevant parameters of the proposed model. Finally, the effect of tests temperature on model parameter values is investigated.

Densities, conductivities, and viscosities of aqueous solutions of N-hexyl,methylpyrrolidinium bromide and N-butyl, methylpyrrolidinium bromide at different temperatures

The densities, conductivities, and viscosities were measured for ternary solutions of N-hexyl,methylpyrrolidinium bromide([PP1,6]Br)- N-butyl,methylpyrrolidinium bromide([PP1,4]Br)-H2 O and its binary subsystems [PP1,6]Br-H2 O and [PP1,4]Br-H2 O at(298.15, 303.15, 308.15, and 313.15) K, respectively. The results were used to test the predictability of the simple equations established for the prediction of density, conductivity,and viscosity of the mixed electrolyte solutions. The results show that the examined simple equations can offer good predictions for density, conductivity, and viscosity of the mixed ionic liquid solutions in terms of the corresponding properties of its binary subsystems of equal ionic strength.

Key Variables Explaining Soil Organic Carbon Content Variations in Croplands and Non-Croplands in Chinese Provinces

Soil organic carbon (SOC) plays an important role in global carbon cycles.Large spatial variations in SOC contents result in uncertain estimates of the SOC pool and its changes.In the present study,the key variables explaining the SOC contents of croplands (CPs) and non-croplands (NCPs) in Chinese provinces were investigated.Data on SOC and other soil properties (obtained from the Second National Soil Survey conducted in the late 1970s to the early 1990s),climate parameters,as well as the proportion of the CP to the total land area (Pcp) were used.SOC content variations within a province were larger than those among provinces.Soil clay and total phosphorus content,ratio of annual precipitation to mean temperature,as well as Pcp were able to explain 75% of the SOC content variations in whole soil samples.Soil pH,mean temperature during the growing season from May to October,and mean annual wind velocity were able to explain 63% of the SOC content variations in NCP soils.Compared with NCP soils,CP soils had lower SOC contents,with smaller variations within and among provinces and lower C/N ratios.Stepwise regression showed that the soil clay content was a unique factor significantly correlated with the SOC content of CP soils.However,this factor only explained 24% of the variations.This result suggested that variables related to human activities had greater effects on SOC content variations in CP soils than soil properties and climate parameters.Based on SOC contents directly averaged from soil samples and estimated by regression equations,the total SOC pool in the topsoil (0-20 cm) of China was estimated at 60.02 Pg and 57.6 Pg.Thousands of years of intensive cultivation in China resulted in CP topsoil SOC loss of 4.34-4.98 Pg.