脉动压力诱导注射成型充模过程熔体表观黏度的实时测量

以脉动压力诱导注射成型充模过程浇口流道中熔体壁面表观剪切黏度的数学模型为基础,通过实时测量记录螺杆位置变化以及浇口流道两端熔体压力变化,表征脉动压力诱导注射成型充模过程熔体实时表现剪切黏度的方法,通过实验研究发现,脉动压力的引入使充模过程、熔体的剪切应力和表观剪切黏度降低,同时加剧了熔体的剪切速率变化,在强烈的振动条件下会引起动态充模过程中某些时刻出现断流现象.     

Numerical analysis of the stress distribution in single-lap shear tests under elastic assumption—Application to the optimisation of the mechanical behaviour

The single lap joint is the most used test in order to analyse the behaviour of an adhesive in an assembly as on one hand, the manufacturing of such specimens is quite easy, and on the other hand they require only a classic tensile testing machine. However, such specimens are associated with complex loading of the adhesive, i.e. non-uniform shear stress along the overlap length, quite large peel stress at the two ends of the overlap and significant edge effects associated with geometrical and material parameters. In addition, the stress concentrations can contribute to fracture initiation in the adhesive joints and thus can lead to an incorrect analysis of the adhesive behaviour. Therefore, understanding the stress distribution in an adhesive joint can lead to improvements in adhesively bonded assemblies. The first part of this paper presents the influence of edge effects on the stress concentrations in single lap joints under elastic assumption of the material and using a pressure-dependent elastic limit of the adhesive. In the second part, some usual geometries, proposed in the literature about stress limitation, are compared with respect to the maximum load transmitted by single lap joint. The last part presents some geometries, which significantly limit the influence of edge effects and are more appropriate for analysing the behaviour of the adhesive.     

pH值对氧化铝高浓度悬浊液剪切流变性能的影响

1 INTRODUCTION The suspensions employed in ceramic processing are highly concentrated. These snspensions are normally known as slip or slurry in materials science and engi-neering. It is of great interest that concentrated sus-pension exhibit many of the phenomena of very dilute colloidal suspensions[i]. This is probablybecause both the snspension systems have charged particles, so that the principles of colloid chemistry can be applied for them.     

关于应力分类问题的一些认识

围绕杭州和上海两次研讨会的内容,就应力分析设计和塑性设计、峰值应力的自限性、有限元计算应力的等效线性化处理等问题谈谈看法。文中认为：从应力的性质和影响范围来看,峰值应力的基本特征是具有自限性和局部性,这和ASME规范从变形角度提出的“不引起任何显著的变形”的特性是一致的;等效线性化处理方法的重要性在于它是区分峰值应力的有效方法,对如何正确选择校核线的位置和方向提出了一种一般性的建议。     

Mixed-mode fracture behaviour of refractories with asymmetric wedge splitting test. Part II: Experimental case study

The asymmetric wedge splitting test for performing mixed-mode loading and its numerical evaluation has been presented in a companion paper (Part I). In this work (Part II), the influences of various levels of mode II loading on damage behaviour of refractories with different brittleness were experimentally investigated by comparing mode I and mixed-mode fractures under symmetric and asymmetric wedge splitting loading with seven different wedge angles. The digital image correlation technique was also used for strain maps visualization as well as the deformation parameters acquisition.With the increase of asymmetric wedge angle, the fracture behaviour becomes unstable what is associated with steeper load-displacement curves, more instantaneous energy release and restrained fracture process zone development. The in-plane shear loading contributes to the accelerated extension of the crack tip and its deviation from central plane. Meanwhile, the co-existing local shear stresses caused by the refractory's heterogeneity lead to crack path deflection as well.     

Catalytic Liquefaction of Coal and Refining of Products

I have been asked to consider the present state of the art in the catalytic liquefaction of coal and refining of products by catalytic means and to suggest some directions for research and development in this very important area of our energy program. This is a large order, as any review of what has been done and what is known about coal liquefaction will quickly show. Coal liquefaction by catalytic means has a long history and has been prached on a commercial scale in various parts of the world. It has had a profound influence on the processing of petroleum. In developing this subject and trying to discern new directions it is very worthwile to review briefly the history of coal liquefaction by catalysis to determine how we have arrived at the present state. By doing this we can also gain knowledge of the constrains imposed on successful developments in this area. It should therefore be possible to determine dirctions for making the processes simpler amnd easier. If nothing else, it will make our attempts to see new things more efficient. Furthermore, the history of coal liquefaction is very interesting and is worth reviewing for itself.     

Water at the Interface

The subject of moisture-induced failure in glass-resin composite materials is reviewed. Emphasis is given to the fundamental surface chemistry and fracture mechanics involved. These disciplines offer substantial information about water adsorption on polar solids, including glass, and about the fracture of solids. However, this information is shown to be inadequate in describing the mechanisms involved in the failure of glass-resin materials. Some insight into these mechanisms is possible from various studies of the moisture-induced failure of bulk glass and adhesive/adherend systems. Also, some light is shed on moisture-induced failure by considering the empirical methods used to improve composite wet-strength, especially the use of silane adhesion promoters. Recent research on the silanes suggests that their action may involve a modification of the resin in the vicinity of the glass/resin interface.     

环境陶艺的公共性

随着后现代主义思潮在中国的普及,环境陶艺设计创作者们对当前中国艺术界的新形势进行了反思,他们理解艺术的精英时代在中国已经过去,取而代之的是艺术品走出工作室,与公众直接对话,公众参与、批评环境陶艺的设计创作,与环境陶艺设计制作者以及作品进行互动,即我要谈的环境陶艺的公共性.     

Catalytic Liquefaction of Coal and Refining of Products

Abstract

I have been asked to consider the present state of the art in the catalytic liquefaction of coal and refining of products by catalytic means and to suggest some directions for research and development in this very important area of our energy program. This is a large order, as any review of what has been done and what is known about coal liquefaction will quickly show. Coal liquefaction by catalytic means has a long history and has been prached on a commercial scale in various parts of the world. It has had a profound influence on the processing of petroleum. In developing this subject and trying to discern new directions it is very worthwile to review briefly the history of coal liquefaction by catalysis to determine how we have arrived at the present state. By doing this we can also gain knowledge of the constrains imposed on successful developments in this area. It should therefore be possible to determine dirctions for making the processes simpler amnd easier. If nothing else, it will make our attempts to see new things more efficient. Furthermore, the history of coal liquefaction is very interesting and is worth reviewing for itself.     

计入横向剪切时层合梁的弯曲弹性解

本文根据一阶横向剪切变形理论，导出了对称层合梁的挠曲线微分方程，求解了层合染在简单载荷作用下的挠度曲线和应力，横向剪切对挠度和应力的影响依赖于层合梁的材料常数，约束类型，载荷种类和跨高比，计算结果表明，横向剪切对层合梁挠度影响颇为显著，且当层合梁跨高比大于18时，可忽略横向剪切效应。     

Electrorheological properties of chemically modified chitosan suspension with various functional pendants

In this study, functional pendants of chitosan were focused on enhancing the shear stress of electrorheological (ER) fluids. Chitosan succinates and chitosan phthalate were synthesized for ER particles and ER fluids were prepared by dispersing the particles in silicone oil. After comparing the shear stress of all prepared ER fluids, obtained conclusions were that ER particle having two functional groups (one is +ve charge and another is ?ve charge) showed higher shear stress than that having only one functional group like the comparison between chitosan succinate(I) and chitosan succinate(II). However, though expect of the intermolecular overlapping between the π electrons clouds supporting the charge carrier generation and transport leading to a significant delocalization of electrons, chitosan phthalate shows lower shear stress than chitosan succinate(I) and chitosan succinate(II). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4937–4942, 2006     

搅拌混合中的循环与剪切

搅拌混合中的循环与剪切被定量化,搅拌功率分解为P=Q∑S_k,分解后的循环流量和总剪切强度,以及剪切强度在空间的分布应匹配．混合对偶合反应过程影响的实验结果表明,循环／剪切比适中的搅拌桨能较好地满足偶合反应工艺的需要,其分隔指数最小.用修正的拉格朗日法进行过程模拟,结果表明团块的循环经历影响其局部分隔指数,增大单位体积功耗、循环／剪切比以及循环区与桨叶区的能耗分配比能降低偶合反应的分隔指数．     

管道内多巴胺超疏水涂层的制备

超疏水涂层在表面自清洁、流体减阻、防雾防冰冻和微流控等领域具有巨大的应用潜力,而工程应用中圆管内表面超疏水涂层微结构的调控具有一定的挑战性。利用电化学沉积法,在不同的剪切应力下将聚多巴胺 （PDA） 涂层制备到不锈钢圆筒内壁,并将正十二硫醇（NDM）修饰到PDA表面,进而制备出PDA/NDM超疏水涂层。采用场发射扫描电镜（SEM）、接触角测试仪（CA）、傅里叶变换红外光谱（FT-IR）、X射线衍射测试仪（XRD）进行分析和表征。结果表明PDA沉积过程可分为两个阶段,第一阶段为溶液中的PDA颗粒在不锈钢基底上面团聚;第二阶段以PDA颗粒团聚体为基础,PDA进行原位生长,并且生长过程受到剪切应力的控制。不同剪切应力最终生长的形貌有所不同,当剪切应力为1.85 mPa时,涂层表面呈“珊瑚状”小球,粒径大小约15~24 μm;而当剪切应力为7.41 mPa时,涂层表面呈“片状”结构,粒径大小约1~4 μm。所制备出PDA/NDM涂层润湿角均大于150°,属于超疏水,且涂层具有良好的化学稳定性、耐热性、耐磨性以及耐腐蚀性。本工作对圆管内表面涂层的制备和表面纳微结构的调控具有一定的指导意义。     

Super polyolefin blends achieved via dynamic packing injection molding: Tensile strength

The tensile strength of some polyolefin blends, HDPE/PP, HDPE/LDPE, HDPE/ LLDPE, and PP/LLDPE, achieved by dynamic packing injection molding have been investigated as a function of composition and melt temperature. Molecular architecture and phase behavior play an important role in chain orientation, hence the tensile strength. For HDPE, which has a linear structure, the highest enhancement of tensile strength is obtained. LDPE, which has a highly branched structure, the smallest enhancement is seen. PP and LLDPE lie in between. Super polyolefin blends with high tensile strength and high elongation have been obtained by this method. The shear‐induced morphologies with core in the center, oriented zone surrounding the core and skin layer were observed in the cross‐section areas of the samples. The tensile strength was found to be directly proportional to the area of the oriented zone. When the area of oriented zone is less than 35%, the tensile strength is not only the orientation dependency but the blending components dependency as well. When the area of oriented zone is more than 35%, however, our new finding is that the orientation will be the dominating parameter to determine the tensile strength of the blends, independent of the components, the composition, molecular architecture, phase behavior, and crystal morphology. The maximum tensile strength for all the polyolefin blends is extrapolated as to 230MPa, as the area of oriented zone reaches to 100%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 236–243, 2002     

Effect of high shear stress on microbial viability

Escherichia coli and Saccharomyces cerevisiae suspensions were submitted to controlled shear stress. Above a threshold value shear stress induced a decrease in micro‐organism viability. The threshold of shear stress efficiency depended on the micro‐organisms, being between 1292 Pa and 2770 Pa for S cerevisiae, and about 1250 Pa for E coli. Above 1810 Pa, E coli cells were disrupted whereas the S cerevisiae cells remained intact. The higher the cellular concentration, the greater the rate of decrease in viability. Viability loss was influenced by the number of passages through the experimental shear stress device and by exposure time. © 2001 Society of Chemical Industry     

Load transfer in adhesive double-sided patch joints

In this work, the application of adhesively bonded joints to connect two structural elements with a double-sided patch is studied. On the basis of the shear lag model, a simple closed-form solution was obtained. The analytical solutions can be used to predict the shear stress in the adhesive and the load transfer between the structural elements and the external patches. The load and shear stress distributions in the adhesively bonded region are presented. For verification of the analytical model, finite element analyses were employed to calculate the load transfer and shear stress for the double-sided patch joint under static tensile loadings. Good agreement was found between the theoretical predictions and numerical results. To obtain a better understanding of the joints, the effects of adhesive thickness, adhesive shear modulus and patch Young's modulus on the load transfer and shear stress distributions were investigated. The results show that the maximum shear stress occurs at the edge of the adhesive. The maximum value of the shear stress increases as the adhesive shear modulus and patch Young's modulus increase and as the adhesive thickness decreases. A more gradual load transfer can be achieved by increasing the adhesive thickness and decreasing the adhesive shear modulus. The simple analytical solution presented in this paper has the advantages of avoiding the numerical difficulties and giving explicit relationship between the stress state and joint parameters. Moreover, from the designer's point of view a closed-form and easy-to-use solution is preferred.     

剪切应力对红豆杉细胞悬浮培养的影响及CFD模拟研究

在同轴圆筒装置的均匀剪切场中研究了不同剪切应力(0.16, 0.46, 0.78Pa)对悬浮培养的南方红豆杉细胞生理的短期影响。结果表明剪切应力为0.16~0.46Pa时,有利于细胞的生长和初生代谢;剪切应力为0.46~0.78Pa时, 有利于细胞的次生代谢;另一方面利用计算流体力学(CFD)对20L生物搅拌釜(45-斜向上桨(45-PBT),桨距为(1/3)T的流场进行了三维模拟,获得搅拌釜内部的剪切场。结果表明搅拌釜内剪切应力分布极不均匀, 且主要集中在搅拌桨区和尾流区,约为主流区和挡板区值的3~5倍,有时甚至高达7倍。通过将实验结果和CFD模拟相结合,预测了20L生物搅拌釜剪切应力对南方红豆杉细胞生理的影响。表明当搅拌转速小于150 rmin-1时,搅拌釜内相应的剪切应力有利于细胞的生长和初生代谢;而当搅拌转速大于200 rmin-1时,则不宜于南方红豆杉细胞的培养。     

Effect of Oxidation on Single-Fiber Pullout Interfacial Shear Stresses in a Silicon Carbide–Borosilicate Glass System

The debonding, τ_d, and frictional, τ_f, interfacial shear strengths between 140-μm diameter SiC (with a 1-μm C-rich coating in which SiC particles are embedded) monofilaments and borosilicate glass were measured using the single-fiber pullout method as a function of postfabrication heat treatments [5 h at temperatures between 200° and 525°C] in 4% H₂–96% Ar and air. The debonding shear stress remained virtually unchanged after extended H₂ anneals. In air, however, τ_d, was found to initially increase and then subsequently decrease with increasing postfabrication heat treatment temperature. The initial increase in τ_d is due to enhanced bonding between the fiber and the borosilicate matrix as a result of the oxidation of the SiC particles embedded in the outermost carbon layer coating. At temperatures greater than about 450°C, oxidation of the C layer results in the severe degradation of the interfacial shear strengths.     

Bubble column fermenter modeling: A comparison,for pressure effects

Two models which describe the oxygen transfer, oxygen uptake, and axial mixing in a bubble column fermenter are described. Model I includes no pressure effects and can be solved analytically. Model II incorporates the influence of hydrostatic pressure on oxygen solubility and gas expansion and must be solved numerically. The liquid phase oxygen concentration profiles as obtained from both models are compared to ascertain for what parametric conditions and for what maximum column height Model I is valid. The results show that for many situations Model I can approximate the oxygen profiles in a 10 m column within 20%. As the transfer and uptake rates increase the deviation of Model I can reach 80% for a 10 m column.     

Flow behavior of enhanced oil recovery Alcoflood polymers

Flow behavior in terms of shear stress and viscosity versus shear rate is investigated for aqueous solutions of Alcoflood polymer materials. Rheostress RS100 is employed for operating, measuring, and analyzing this experimental investigation. Polymer concentration in the range of 100–10,000 ppm was covered. Fitting analysis is carried out for all the examined polymer solutions. Casson and Ostwald‐de‐Waele correlations can be employed for predicting flow behavior, depending upon polymer type. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2896–2904, 2002