振动力场作用下的单螺杆挤出机固体输送理论

在单螺杆挤出机中,通过螺杆的轴向振动将振动力场引入聚合物固体输送过程,提出振动力场强化固体输送过程的新概念.以螺槽中运动的物料为对象建立了振动力场强化固体输送过程的数学模型,并获得了物料沿螺槽方向输送的压力（密度）、速度的近似解析解.传统固体输送过程就是当螺杆轴向振动的振幅为零时的特例,此时的压力降与Darnell and Mol 理论一致,但不同的是物料速度及密度沿螺槽方向是变化的,从而修正了Darnell and Mol 固体输送理论.螺杆的轴向振动提高了固体输送平均压力,缩短了固体输送的长度,增加了固体输送角.透明料筒全程可视化实验挤出机证明了螺杆轴向振动确实缩短了物料固体压实输送所需的螺槽长度.     

碳纳米管水泥基复合机敏材料的研究进展

具有机敏特性的功能性水泥材料能够用于监测水泥路面质量和通过车辆的载荷,有良好的应用前景。碳纳米管材料拥有优异的导电性能,作为水泥的添加剂提高其复合材料的机敏性能。对碳纳米管水泥基复合材料的机敏特性进行了系统考察,分析了CNT水泥复合材料机敏特性机理,对影响机敏性能的因素进行了分析。通过CNT水泥基复合材料在公路监测上的实际应用试验,展示了其作为一种新型智能道路监测技术所具有的良好应用前景。     

Nonisothermal analysis of a couple stress fluid in blade coating process

In this paper, a nonisothermal analysis for the process of blade coating of an incompressible couple stress fluid is presented using both plane and exponential coaters. The governing system is simplified using lubrication approximation theory (LAT). The interesting quantities from engineering point of view like normalized pressure, maximum pressure, pressure gradient, velocity, and effects of involved parameters on temperature distribution, which influence the coating process are evaluated. It is observed that pressure is at maximum near the edge of the blade whereas fluid velocity and temperature are at maximum near the substrate. An increasing couple stress parameter increases the load and decreases the coating thickness. It is worth mentioning that load and pressure are the most significant outcomes of the present exertion as these two physical quantities ensure thickness and the quality of coating.     

Size‐dependent vibration of double‐bonded carbon nanotube‐reinforced composite microtubes conveying fluid under longitudinal magnetic field

In the present research, vibration and instability of visco‐elastically coupled carbon nanotube reinforced composite (CNTRC) microtubes conveying fluid is investigated. Single‐walled carbon nanotubes are arranged in a longitudinal direction inside poly methyl methacrylate matrix. The longitudinal magnetic field is applied on coupled system. The surrounding medium is simulated by visco‐Pasternak model due to considerable damping and shearing effects. Based on Mori–Tanaka theory, the properties of composite microtubes are obtained. In order to achieve more accurate results, strain gradient theory is developed in Timoshenko beam model. The motion equations are derived utilizing Hamilton's principle and solved by means of differential quadrature method. Considering slip flow regime, the influences of various parameters such as magnetic intensity, elastic medium, Knudsen number, and volume fraction of CNTs on the vibration characteristics of coupled system are studied in details. Results demonstrated that the stability of coupled system can be significantly improved by applying magnetic field. The result of this study can be useful to control and improve the performance of micro‐mechanical systems conveying fluid. POLYM. COMPOS., 37:1375–1383, 2016. © 2014 Society of Plastics Engineers     

The two-dimensional adhesive contact problem in the theory of couple stress elasticity

Abstract

The adhesive contact problem of a half-space indented by a rigid cylindrical punch in the theory of couple-stress elasticity is investigated. Both the size effect and adhesion are considered to analyze the two-dimensional frictionless contact problem. The method of Mindlin’s stress function and the technology of Fourier transform are applied to reduce the mixed boundary value problem to the singular integral equations. Efficient computational techniques is used to obtain the influence of the size effect and adhesion parameter on the adhesive contact behavior. Results indicated that the size effect play an important role in contact with adhesion and can help understanding the mechanism of adhesion.     

Polymer composite materials based on modified synthetic fibres

The possibility of fabricating polymer composite materials (PCM) based on modified PCA and PP fibres was demonstrated. The kinetic features of curing of epoxy oligomer in the presence of profiled PCA and PP fibres were investigated. The optimum technological regime of spinning of PCM was selected using the method of the full factorial experiment. A series of samples of PCM based on profiled fibres was prepared and their properties were comparatively evaluated. Translated from Khimicheskie Volokna, No. 1, pp. 45–48, January–February, 1997.     

短纤维复合材料应力传递理论研究进展

对短纤维复合材料中应力传递理论领域近十几年来国内外的研究情况按照单／多纤维抽出剪滞模型分析、有限元分析以及新分析方法三部分进行了分类介绍。剪滞模型分析法因其简单而且参数物理意义明确而被广泛应用；有限元分析法是一种新近发展起来的更准确的分析方法，也逐渐被接受；最小补偿能原理和轴对称变化分析法等新研究方法也取得了显著的成效。近年来模型的建立和计算过程中更加接近于短纤维复合材料的真实情况。     

Dependence of solids conveying on screw axial vibration in single screw extruders

In the single‐screw extruder, the vibration force field is applied to the solids conveying process by the axial vibration of the screw and the novel concept on the solids conveying process being strengthened with the vibration force field has been brought forward in this study. We establish the mathematical model that describes the solids conveying process with the vibration force field and obtain the approximative analytical solutions of the pressure and velocity of the solids conveying in the down‐channel. In the new theory, if the screw has no axial vibration the solids conveying pressure is the same as that of the Darnell and Mol theory, but the density and velocity of solids conveying along the screw channel is variable, which has modified the Darnell and Mol theory in which the density and velocity of the solids conveying along the screw channel was considered invariable. The results reveal that the axial vibration of the screw can increase the average pressure of solids conveying, decrease the channel length of the solids conveying section and increase the solids conveying angle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2998–3007, 2006     

High-alumina composite concretes and coatings based on modified phosphate binder suspensions

Coatings and materials based on aluminum phosphate suspensions are studied that have high strength in a raw state and are suitable for carrying out combined firing of a refractory and coating. An aluminum phosphate binder provides preparation of high physicomechanical properties in the firing temperature range. Use of traditional mixes with a protective aluminum phosphate coatings, and also ceramic concrete based on this binder provide increased material corrosion resistance, and consequently an increase in object operating life and period between repairs for metallurgical and glass melting units.     

基于Eyring绝对速率理论的流体混合物黏度推算

为了建立起一个统一的、可同时应用于纯质与混合物高压黏度计算的绝对速率理论模型,基于此前已有的纯质黏度模型,提出了相应的混合法则,将其扩展至对混合流体的计算当中。为验证模型精度,首先选取了27种纯质流体,通过拟合其黏度数据得到模型参数。随后,对27种二元混合物以及3种三元混合物的黏度进行了计算。其中,对于二元混合物,仍需要引入额外的二元交互参数,可通过拟合混合体系黏度数据得到。结果表明,该黏度模型对所选纯质、二元混合物和三元混合物的黏度均有着较高的计算精度,其相对偏差的平均绝对值分别为1.54%、2.35%和3.86%,最大偏差为8.62%、12.9%和19.7%。最后,将本文模型与自由体积模型进行了比较,其对高黏度和互缔合流体的计算精度均高于后者。     

Development and study of composite refractory materials based on modified dispersed systems

Composite refractories and heat insulation materials of corundum, aluminosilicate and carbide ceramic compositions with improved operating properties have been prepared by modifying dispersed binder materials at different levels.     

Tensile fracture test of nanocomposite ceramics under ultrasonic vibration based on nonlocal theory

Based on non-local theory, the dispersion characteristics of ultrasonic vibration in Specimen tension are analyzed, and the effects of ultrasonic frequency and amplitude on the wave dispersion are obtained through theoretical analysis. Tensile tests were carried out using an ultrasonic vibration system and specimens, and the test process as well as test parts were observed and analyzed. The influence of the ultrasonic vibration on fracture properties and the change of grain micro-organization under different loading conditions were verified by experiments. The introduction of ultrasonic vibration changes the internal stress of the ceramic fracture, affects the hardness of the workpiece, and also leads to the scattering of particles, which leads to the aggravation of ultrasonic attenuation and phase velocity dispersion. SEM and XRD analyses showed that with the increase in ultrasonic frequency and amplitude,the trans-granular fracture was more obvious, the micro-cracks and dimples increased, and micro-pores increased in size and number. The tensile stress produced by ultrasonic vibration will induce the transformation from T-phase ZrO2 particles to M-phase ZrO2 particles and absorb strain, which greatly improves the plastic mechanical properties of nanocomposite ceramics. Due to the inherent phase transformation toughening mechanism, the material improves the plastic mechanical properties under the ultrasound excitation, and it is easier to achieve ductile domain processing.     

Polymer composite materials based on thermoset epoxy binders modified with diamond-containing nanofillers

Structural features and physicochemical properties of promising diamond-containing modifier fillers for industrial polymers, namely, detonation nanodiamonds and nanodiamond soot, are considered. Experimental results demonstrating the possibility to create prepregs with the use of the carbon fabric 1.5 К and a detonation-diamond soot-modified binder based on the epoxy-resin mixture Epikote828/Epikote154 with an anhydride-type curing agent are presented. The rheological characteristics of the diamond-sootmodified binder remain practically the same after storage for 2 or 3 days at room temperature. The dependence of the glass-transition temperatures of the binders on the content of diamond soot in the concentration range 0.025–0.1 wt % is studied, and the correlation between these results and the mechanical characteristics (breaking strength, flexural strength, and crack resistance) of the cured binders is ascertained. Within the entire range of diamond-soot concentrations, the parameters of gelation are determined and the activation energies of this process are calculated.     

Constructal optimization for an organic fluid shell-and-tube condenser based on entransy theory

A complex function composed of linear weighted sum of the entransy dissipation rate (EDR) caused by heat transfer and total pumping power is established in this paper. Under the conditions of fixed total condensation rate and heat transfer area, constructal optimization of a shell-and-tube condenser (STC) with organic fluid is carried out by taking minimum complex function as optimization objective. The minimum complex function and the optimal external diameter of the condensation tube are obtained. The results show that compared with the initial design construct, the optimal construct of the STC increases the total EDR caused by heat transfer by 10.70%, and reduces the total pumping power and complex function by 54.94% and 6.46%, respectively. This illustrates that the complex function sacrifices a certain heat transfer performance, and improves the fluid flow performance evidently, which leads to the overall performance improvement of the STC. The twice minimization of the complex function can be realized by choosing an appropriate number of the condensation tubes. New guidelines for the optimal structure designs of the STCs are provided by introducing entransy theory into constructal optimizations of the organic fluid STCs, and this method can be further extended to the optimal designs of the cycle systems with organic fluids.     

基于理论的有机工质管壳式冷凝器构形优化

建立考虑传热耗散率和总泵功率的线性加权复合函数,在总冷凝率和总传热面积一定的条件下以复合函数最小为目标,对有机工质的管壳式冷凝器进行构形优化,得到最小复合函数和冷凝管最佳外径。结果表明：冷凝器最优构形与初始设计结构相比,总耗散率提高了10.70%,而总泵功率和复合函数分别降低了54.94%和6.46%。这说明复合函数牺牲了一定的传热性能,使得冷凝器流动性能显著提高,最终使得其综合性能得到提高。选择合适的冷凝管数目可实现复合函数二次最小化。将理论应用到有机工质管壳式冷凝器的构形优化中,为其结构优化设计提供了新的指导,这一方法可进一步推广到有机工质循环系统的优化设计中。     

Study on a novel composite coating based on PDMS doped with modified graphene oxide

The low surface activity of graphene oxide (GO) stemming from its large conjugated electronic structure can easily affect the dispersion behavior of GO-based polymer matrices. This significantly undermines the properties of the resulting composite materials. Therefore, in order to increase the GO surface activity for use in polymer-based composites, GO was modified using silane coupling agent which was then doped into polydimethylsiloxane (PDMS) polymer to prepare novel paints by sol–gel reaction strategy. The subsequent novel composite coatings based on PDMS/modified GO (mGO) were finally cured with tetraethoxysilane as the hardening agent in the presence of dibutyltin dilaurate catalyst. The effect of doping mGO into PDMS polymer was systematically studied using infrared spectroscopy, micro-Raman spectroscopy, TEM, SEM, XRD, TGA, mechanical test, thermal conductivity test, and the erosion resistance test. It was concluded that the phase compatibility between GO and PDMS was enhanced due to the new interconnecting chemical bonds brought about by the mGO in the composite.     

Temperature distribution effects on buckling behavior of smart heterogeneous nanosize plates based on nonlocal four-variable refined plate theory

This work presents a theoretical study for thermo-mechanical buckling of size-dependent magneto-electro-thermo-elastic functionally graded (METE-FG) nanoplates in thermal environments based on a refined trigonometric plate theory. Temperature field has uniform, linear, and nonlinear distributions across the thickness. Nonlinear thermal loadings are considered as heat conduction (HC) and sinusoidal temperature rise (STR). A power law function is applied to govern the gradation of material properties through the nanoplate thickness. Considering coupling impacts between magneto, electro, thermo-mechanical loadings, the equations of motion, and distribution of magneto-electrical field across the thickness direction of the METE-FG nanoplate are derived. The exact solutions for critical buckling temperatures of METE-FG nanoplates are introduced implementing Navier’s method. Moreover, the accuracy of the present formulation is examined by comparing the obtained results with published ones. Furthermore, the effects played by the magneto-electrical field, various temperature rises, nonlocality, power law index, side-to-thickness ratio, and aspect ratio on the critical buckling temperature response are all investigated and reported.     

基于FLUENT的不定形耐火材料输送管内流动状态分析

利用流体力学理论分析了理想情况下不定形耐火物料在管内的流动特性,应用专业流体仿真软件FLUENT对不定形耐火物料在实际工况下流动状态进行数值模拟与流场分析,发现了缩短不连续泵送间断时间与设计合适的管道参数对于不定形耐火物料的连续输送都有较大影响,验证了不定形耐火物料柱塞状流动这一特性,为喷嘴以及风压的设计提供了依据。     

疏水改性淀粉/丁苯胶复合材料性能的研究

采用苄基氯对淀粉进行疏水改性,制备疏水淀粉/丁苯胶复合材料并对其性能进行研究。结果表明,随着疏水淀粉加入量的增加,硫化和焦烧时间总体呈缩短趋势,复合材料的邵尔A型硬度、拉伸强度、撕裂强度和拉断伸长率都呈现上升趋势,DIN磨耗量减小;耐热空气老化性能有所下降。