Effects of shear flow on long-ranged correlations,spinodal demixing kinetics,and the location of the critical point and cloud point

A derivation of an expression for the shear rate-dependent Ornstein Zernike structure factor is discussed, together with the resulting anomalous behavior of the turbidity. The predicted scaling behavior of the turbidity, comprising the effect of both temperature and shear rate, is in good agreement with experiments on binary fluids. Then initial spinodal decomposition is discussed, and an explicit expression for the time- and shear rate-dependent effective diffusion coefficient is derived, which shows all the typical characteristics of anisotropic light scattering patterns that are observed experimentally for binary fluids. Next it is shown that the spinodal is shifted linearly with the (bare) Peclet number for not too large Peclet numbers, whereas the cloud point is singularly displaced into the unstable region due to a shear now. This is in agreement with an experiment on a two-polymer/solvent mixture and binary fluid mixtures. It is argued that light scattering is useless to determine the location of the spinodal of a sheared system.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

剪切停留对液固温区A356合金组织及瞬态流变化为的影响

采用自行研制的流变装置进行瞬态流变试验，研究了剪切停留对液固温区不同初生α相形态A356合金的组织变化及其瞬态液变化为的影响，结果表明，在相同的剪切条件下，随剪切停留时间的增加，瞬时峰值表观粘度增加，说明切停留期间半固态合金初生α相形态发生了变化；对半固态合金初生相形态观察发现，剪切停留促使初生相发生了“团聚”或“合并”，而且初生相形态变化的程度取决于剪切停留时间和初生相的退化程度，对试验结果进行曲线拟合，得到了描述半固态合金峰值表观粘度和剪切停留时间的瞬态流变方程。     

Viscosity of a phase-separating critical mixture

Onuki has predicted the existence of a significant enhancement of the viscosity of a liquid mixture in the course of spinodal decomposition. We discuss a method to measure this effect in a critical mixture of isobutyric acid and water in which spinodal decomposition is induced by a pressure-quench technique. In addition, by varying the static pressure in the homogeneous phase, experimental information about the dynamic critical exponent for the viscosity is obtained.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Critical dynamics of a sheared micellar solution

We have investigated the dynamic behavior of a nonionic micellar solution of tetra-ethylene glycoln-decylether (C₁₀ E₄) in water near its critical point in the presence of shear. The non-Newtonian behavior of the viscosity can be represented by * = [ 1 +a(S₄)=]², where* is the viscosity in the absence of shear,S is the shear rate. ₄ is the lifetime of the critical Iluctuations,a is a system-dependent constant, and = 0.02 In addition, we have found that, before attaining a steady state, the sheared mixture undergoing phase separation shows significant shear-dependent rheological effects due to the presence of concentration domains.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24. 1994, Boulder, Colorado, U.S.A.     

Viscosity and diffusivity of a binary liquid mixture of critical composition: Study of the system 2-butoxyethanol/water

Results of measurements of the temperature dependence of the shear viscosity and the mutual diffusion coefficient of a 2-butoxyethanol/water mixture of critical composition are reported. The shear viscosities are measured with a capillary viscometer, and the diffusion coefficients by dynamic light scattering. The viscosity data are used to determine the regular (background) and the singular (critical) part of the viscosity and to analyze the crossover regime.Q ₀ has a value ofQ _o = (1.54 ± 0.60) × 10⁶ cm^–1, which is small for a binary mixture of components of small molar mass. The viscosity is dominated by singular contributions in a narrow temperature range (T _c – T) 1.2 K. The singular contributions can be neglected for temperatures (T_c–T) 11 K. The function =_b expz H, given in the literature, represents the viscosity data in the temperature range 3 mK (T _c – T) 25 K using the asymptotic form of the functionH for (q _d/q _c) 0 (q _d,q _c, parameter of the theory). This limit corresponds to the case in which the background diffusion coefficient Lib can be neglected. The reduced diffusion coefficient D^* calculated from the light-scattering data as a function of the scaling variable x(=q) is represented by the approximation of the dynamic scaling function proposed in the literature.     

Experimental and theoretical studies of the elastic behavior of knitted-fabric composites

This paper presents experimental and theoretical studies of the elastic behavior of knitted-fabric composites. In the experimental studies, two types of weft-knit preforms based upon plain-stitch and rib-stitch fabrics were first fabricated and fabric composites were consolidated by using a hand lay-up process. Tensile and rail shear tests were performed, and Young's moduli along the warp and weft directions and shear modulus determined. In order to correlate the preform microstructure with composite elastic properties, geometric models for plain-stitch and rib-stitch fabric composites were developed. Modeling of the elastic behavior was conducted by using an averaging method. The predicted elastic constants are in reasonably good agreement with experimental values. Finally, the limitation and potential of knitted-fabric composites are discussed.     

Spinodal decomposition and nucleation in the presence of flow

Spinodal decomposition and nucleation of critical fluids are discussed in the presence of laminar shear and turbulence on the basis of recent experiments. In such situations we can realize stationary emulsion-like domain structures due to dynamical balance between thermodynamic instability and shear-induced deformations. In the spinodal decomposition case, unique is the strong shear regime in which the shear exceeds the average relaxation rate of the order parameter. In the nucleation case shear can enhance aggregation of droplets, thus speeding up the growth. But if the shear exceeds a relatively small critical value, even critical droplets can be broken, then leading to complete suppression of the droplet formation. We also predict a considerable increase of the effective viscosity and a large non-Newtonian effect due to domains in the course of spinodal decomposition.Invited paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

RTM专用双马来酰亚胺树脂体系化学流变特性

进行了RTM 工艺专用双马来酰亚胺(BMI) 树脂体系的化学流变特性及工艺过程研究。采用DSC 热分析技术和粘度测量手段, 研究了该树脂体系固化特性以及固化过程中粘度与温度的关系, 根据对等温粘度曲线的分析, 建立了双阿累尼乌斯粘度模型和工程粘度模型。对比所建立的两种粘度模型, 结果显示两种模型都可以适用于RTM 工艺注射阶段, 工程模型在粘度转折点附近的预测精度要优于双阿累尼乌斯粘度方程。同时建立了恒温温度-凝胶时间之间的数学关系。验证了所建立的工程模型在工程中的实用性, 并指出了工程粘度模型的使用范围在固化体系交联结构形成之前, 所建立的工程粘度模型能够有效地预测体系RTM 工艺的粘度变化和工艺过程, 为复合材料成型工艺模拟分析以及工艺参数的准确制定奠定了基础。      

Experimental investigation of the dynamic behavior of frozen clay from the Beiluhe subgrade along the QTR

The dynamic behavior of frozen clay obtained from the Beiluhe permafrost subgrade along the Qinghai-Tibet Railway (QTR) was investigated through cryo-dynamic triaxial experiments. The effects of several key factors, including temperature, moisture content, frequency and confining pressure on the dynamic behavior, were analyzed. It was found that a hyperbolic model could describe the dynamic behavior of the frozen clay well. The maximum dynamic shear modulus of the frozen soil decreases as the temperature rises and as the confining pressure decreases; the reference shear strain magnitude decreases as the temperature and confining pressure increase and as the moisture content decreases; the maximum damping ratio increases as the temperature, frequency and confining pressure increase and as the moisture content decreases. There exists a critical moisture content (around 18%) that maximizes the dynamic shear modulus; at the critical frequency (about 6 Hz), the dynamic shear modulus is at its maximum, and the reference shear strain magnitude and the damping ratio attenuation exponent are at their respective minima. Moreover, functions were proposed to quantitatively describe the relationship between frozen clay dynamic parameters and various influencing factors.     

Rheological behavior of a bismaleimide resin system for RTM process

The curing properties and rheological behavior of a bismaleimide resin system were studied with differential scanning calorimetry (DSC) analysis and viscometer measurements, respectively. A dual-Arrhenius viscosity model and an engineering viscosity model were established to predict the resin rheological behavior of this resin system. The two viscosity models were compared. The results show that the two models are both suitable for predicting the viscosity in the mold filling stage of resin transfer molding (RTM). However, the engineering model provides a more accurate prediction of the viscosity near the gel point. The effectiveness of the engineering viscosity model is verified both in isothermal and nonisothermal conditions. The limitation of the engineering model is that it cannot be used to predict the viscosity after cross-linking of the curing system. The engineering viscosity models can be used to predict the processing windows of different processing parameters of the RTM process, which is critical for the simulation and the optimization of composite manufacturing processes. Translated from Acta Materiae Compositae Sinica, 2006, 23(1): 56–62 [译自: 复合材料学报]     

方钢管混凝土框架-薄钢板剪力墙边框柱刚度研究

为研究大跨高比的对角槽钢加劲钢板墙结构,该文对3个1/3缩尺的钢板剪力墙试件进行了拟静力试验研究,包括一个拼接式钢板剪力墙和2个拼接式-对角槽钢加劲钢板剪力墙。试验结果表明钢板剪力墙有良好的耗能能力,对角加劲钢板墙滞回曲线饱满呈梭形。槽钢的两个翼缘与钢板连接,形成具有更大抗扭刚度闭口截面,在加载过程中避免了加劲肋的扭转而导致加劲效果降低。对角布置的槽钢加劲肋具有较大的抗弯刚度,在弹性阶段提高钢板的弹性屈曲荷载,限制钢板平面外变形;在弹塑性阶段能起到增大拉力带的作用,提高结构承载力。推导了框架柱的剪力、轴力和弯矩计算公式,结果表明对角槽钢加劲形式对边缘构件的附加轴力和剪力作用较大,因此在设计时应考虑加劲肋的支撑作用。     

塑料容器用新材料ETRPE的加工流变行为研究

为了优化设计高刚性和高韧性塑料容器用新材料ETRPE的成型加工工艺,用毛细管流变仪研究了ETRPE体系的流变行为.分析了ETRPE体系的流变特性,讨论了E-TMB,2种弹性体配比及温度对体系表观粘度的影响,发现ETRPE体系熔体的ηa与T关系符合直线方程:ηa=A CT,且属于低γ敏感性熔体.     

劲性装配式框架核心筒结构抗震性能试验研究

为研究劲性装配式框架核心筒体结构整体抗震性能,进行1:3的缩尺模型振动台试验,获得结构体系在地震作用下整体抗震性能与结构破坏模式,并考证叠合梁与钢管混凝土柱、叠合梁与抗震墙、楼板等连接节点在地震作用下的可靠性。结果表明,该结构体系具有较高的承载力及良好的整体抗震性能,节点连接形式总体能满足现行规范抗震设防要求。     

连续冷却搅拌A2017半固态合金流变行为研究

采用回转式熔体物性综合测试仪测定了A2017合金半固态浆料在连续冷却搅拌条件下的表观黏度变化,对其组织变化进行分析,研究了连续冷却搅拌条件下A2017合金半固态浆料的流变行为.实验结果表明,连续冷却搅拌条件下,A2017合金半固态浆料的表观黏度随固相率的增大而增大;在固相率一定的情况下,降低冷却速度或增大剪切速率,均导致表观黏度降低.显微组织观察表明,半固态浆料的流变行为与其微观组织结构有很强的关联,降低半固态浆料温度,浆料固相颗粒含量增加,表观黏度增大;降低冷却速度或增大剪切速率有利于半固态浆料固相颗粒形态向非枝晶形态的转变,因而半固态浆料表观黏度降低,流动性好.     

Experimental Procedure for Evaluating the Effective Power of a Solvent

An experimental procedure for determining the solvent efficiency index in cleaning and degreasing is proposed and substantiated.     

Experimental and numerical results of dynamics behavior of a nonlinear piezoelectric beam

This article presents a numerical formulation and experimental implementation for the dynamics behavior verification of the nonlinear piezoelectric beam through harmonic excitation. The nonlinear piezoelectric beam dynamic analysis program is developed with MATLAB software. To verify the nonlinear piezoelectric beam dynamic analysis results, the experimental results are used for the vibration analysis of a piezoelectric beam to the harmonic excitation of the base of the beam. Then, the piezoelectric effect on the output voltage, velocity, acceleration values, and the time response are obtained. Afterwards, the effects of the excitation velocity and the position of concentrated mass on the output voltage are verified.     

The influences of the microstructure morphology of A356 alloy on its rheological behavior in the semi-solid state

In this paper, the rheological behavior of semi-solid A356 alloy with different solid morphology was studied with an improved static shear test method. The results indicated that the rheological behavior of the alloy was significantly influenced by the structural morphology of the alloy. The alloy had quite different rheological properties even though the same fraction of solid existed in the semi-solid state. The rheological behavior of the alloy fitted a five-element model (H₁–[N₁|H₂]–[N₂|S]) for the as-cast microstructure with developed primary (α–Al dendrites, whereas it fitted a six-element model ([H₁|S₁]–[N₁|H₂]–[N₂|S]) for degenerated dendritic or spheroidal primary α–Al, which had been obtained by electromagnetic stirring and spray deposition, respectively. Computation results showed that the deforming capability and shear rate of the semi-solid alloy increased remarkably with the change of primary α–Al from developed dendrites to degenerated dendrites, and then to spheroidal structures. On the other hand, the temperature dependence of the rheological properties of the semi-solid alloy with spheroidal or degenerated dendritic primary α–Al was much less than that with developed primary α–Al dendrites.     

竹粉接枝改性及其对竹粉/PETG复合材料流变行为的影响

采用电子活化再生原子转移自由基聚合（AGET ATRP）法将甲基丙烯酸甲酯（MMA）接枝到竹粉（BF）表面,并采用哈克微量混合流变仪及旋转流变仪考察了竹粉接枝改性前后对竹粉/聚对苯二甲酸乙二醇酯-1,4-环己烷二甲醇酯（PETG）复合材料流变行为的影响。毛细管流变结果表明,竹粉/PETG复合材料属于假塑性流体,呈现剪切变稀的现象;应变扫描结果表明,与未改性竹粉/PETG复合材料体系相比,竹粉经接枝改性后其复合材料体系在更大的应变范围内属于线性弹性行为;频率扫描结果表明,竹粉的接枝改性处理有助于促进竹粉在PETG基体中的均匀分散。     

Experimental and numerical study of the impact behavior of SMC plates

Steel components absorb impact energy by plastic deformation whilst composite materials absorbing it by damage mechanisms such as fiber debonding, fiber fracture, and matrix cracking. Therefore, in order to properly substitute metal components with composite ones in industrial applications, the impact property of composite materials must be well known. In this study, the impact behavior of sheet molding compounds (SMC), which is widely used in automobile industry due to its relatively low cost and high productivity, was examined both experimentally and numerically. In order to investigate the impact behavior of SMC, an experimental study was carried out by setting up a drop weight impact test system. Using this system, the dissipated impact energies of SMC flat plates were measured to investigate the influence of the mass and shape of impactor, initial velocity, and specimen thickness on the impact behavior.

For numerical predictions, a modified damage model for SMC was developed and adopted in the user defined material subroutine of the commercial simulation program LS-DYNA3D. For the sake of improving efficiency of impact simulations, the SMC material property was determined in consideration of the local differences of the fiber volume fractions. The dissipated impact energies under various conditions and the reliability of the developed impact simulation process were examined through comparisons of the predicted data with the experimental results.

From this comparison, it was found that, in the scope of current study, the specimen thickness is the most important parameter that should be considered in the design of SMC components for the aspect of impact behavior.     

复合表面活性剂对油包水型高内相乳状液流变性和稳定性的影响

为了研究复合表面活性剂对油包水型高内相乳状液流变性和稳定性的影响,选用由PIBSA-TEA和油酸二乙醇酰胺、椰子油酸二乙醇酰胺、失水山梨醇单油酸酯等小分子表面活性剂组成的复合表面活性剂制备HCEs,并检测所制得HCEs的流变性和储存稳定性。结果表明:表面活性剂对HCEs的剪切应力和储能模量有较大的影响。采用复合表面活性剂制备的HCEs具有较高的剪切应力和储能模量。但是,复合表面活性剂制备的HCEs储存稳定性明显下降。在油相黏度比较高时,复合表面活性剂制备的HCEs储存稳定性有一定的提高。