连云港淤泥流变特性研究

研究了体积容重为Ｃ＿ｖ＝０．０５７～０．４１连云港西墅地区淤泥的流变特性和弹性模量。在剪切率的变化范围２×１０￣（－２）ｓ￣（－１），淤泥具有三种不同的流变特性，在很低剪切率情况下，淤泥剪切力基本保持常值；在低剪切率范围，表现为宾汉流体性质，其屈服应力和宾汉动性系数以Ｃ＿ｖ指数增长；在高剪切率，淤泥流动体现出宾汉伪塑性特征，划分三个特征区的临界剪切率值是随淤泥含水量变化，最后指出，连云港淤泥弹性模量与高岭土结果很相近，对淤泥含水量的变化极其敏感。     

连云港淤泥流变特性研究

研究了体积容重为Ｃ＿ｖ＝０．０５７～０．４１连云港西墅地区淤泥的流变特性和弹性模量。在剪切率的变化范围２×１０￣（－２）ｓ￣（－１），淤泥具有三种不同的流变特性，在很低剪切率情况下，淤泥剪切力基本保持常值；在低剪切率范围，表现为宾汉流体性质，其屈服应力和宾汉动性系数以Ｃ＿ｖ指数增长；在高剪切率，淤泥流动体现出宾汉伪塑性特征，划分三个特征区的临界剪切率值是随淤泥含水量变化，最后指出，连云港淤泥弹性模量与高岭土结果很相近，对淤泥含水量的变化极其敏感。     

纤维复合材料的弹粘塑性行为体分比与应变率的影响

利用微观力学方法研究了纤维增复合材料的弹塑性行为，着重分析了纤维体分比和加载应变率对以金属基为主的复合材料应力－应变关系的影响。给出了不同体分比的Ｇｒａｐｈｉｔｅ／Ｔｉｔａｎｉｕｍ复合材料在不同常应变率下的应力－应变关系曲线，对这两种因素的影响进行了比较分析。     

可压缩均匀剪切湍流的二阶矩模拟

基于对可压缩湍流中脉动压力场和脉动速度场特征的理论分析以及ＤＮＳ结果,建立了可均匀剪切湍流中压力－变形率关联的压缩性修正模式,应用这个模式,加上Ｓａｒｋａｒ等建立的脉动体胀率项（ｄｉｌａｔａｔｉｏｎａｌ ｔｅｒｍｓ）的模式,预测可压缩均匀剪切湍流随时间的发展,所得雷诺应力各是性张量的平衡值与Ｂｌａｉｓｄｅｌｌ等的ＤＮＳ数据非常一致。这个模式准确地预测出均匀剪切湍流中压缩性导致的雷诺应力结构的“流向     

稀土金属材料填充方式对预混气体爆炸特性抑制研究

利用20 L球形爆炸装置，探究了在多孔稀土金属材料两种不同的填充方式（球状和片状）下甲烷-空气预混气体爆炸特性的变化规律，考虑了留空率和填充密度对预混气体爆炸特性的影响，并利用压力传感器记录球体内爆炸压力曲线。研究结果表明:甲烷爆炸压力、最大压力上升速率和爆炸指数均与留空率呈正比例关系，与填充密度呈反比例关系，片状材料下最大压力下降幅度大于球状材料下的；片状材料抑爆性能优于球状材料的，片状材料的双重抑爆作用对爆炸威力的影响更甚；2种不同填充方式下阻火抑爆的主要机理存在差异。     

随时间变化的食品的流动特性

本文试验了处于常剪切率下的一种新的粘度衰减模型,对一些有代表性的食品(酸牛奶,蛋黄酱,西红柿汁等)的触变行为作了实验分析。发现了在常剪切率下,经过足够长的剪切时间之后,某些食品的平衡粘度(或稳态粘度)可以用Herschel-Bulklcy模型很好地描述,也可以用指数模型很好地描述,而在指数模型中,最多只需取无穷级数的两项。粘度衰减模型就是常剪切率下粘度随时间而减小的模型,它假定是结构参数λ衰减的n次动力学方程。发现了对于λ的衰减,率常数k是剪切率的幂律函数。将结构衰减方程同关于剪应力的标量本构方程相结合,所得到的模型能够充分描述剪切率范围为50<γ<5420s~(-1)的食品的粘度衰减数锯。观察到象西红柿汁之类的悬浮体的数据并不遵从预期的结构破坏行为。实验的滞后曲线表明,根本找不到剪应力跟最大剪切率γ_0或达到γ_0的时间t_0之间相一致的图形,因而不可能使用根据粘度衰减实验的资料来预计滞后实验的结果。      

平片激振对分离剪切层的影响

实验研究了从前缘加入周期性扰动，对一个楔形体模型形成的含回流的分离剪切层影响问题，实验雷诺数Ｒｅ＿ｃ＝６．６７×１０￣５．揭示了含回流的分离剪切层在未激振与激振状态下峰值中心频率的演化特征；探讨了分离剪切层局部响应频率与激振基本频率的关系。研究表明：激振作用改变了分离剪切层峰值中心频率向下游的演化过程，增加了湍流脉动强度和湍流混合，加快了分离剪切层增长，致使剪切层中心线下弯，从而分离剪切层再附或分离泡缩短。     

铁基形状记忆合金耐磨性研究

对铁基Ｆｅ－３０Ｍｎ－６Ｓｉ形状记忆合金在滑动和滚动摩擦条件下的耐磨性进行研究，并与正火６５Ｍｎ钢进行对比分析。结果表明：铁基记忆合金在滑动摩擦条件下耐磨性较差，而在滚动摩擦条件下具有较好的耐磨性，为正火６５Ｍｎ钢的近３倍。这是由于在滚动摩擦条件下，作用在铁基形状记忆合金表面微突体的变形大部分为伪弹性变形，而在滑动摩擦条件下铁基记忆合金剪切强度低，更容易造成表面微突体的剥落从而产生严重磨损所致。研     

柱体形状对气液两相涡街的影响

本文试验研究了柱体形状对气液两相涡街的影响，得出了在气液两相流中的最佳涡街发生体和发生两相涡街时，两相斯托拉赫数，来流截面含气率，水流量三者之间的关系。试验工质为水和空气，混合物流动方向垂直向上。参数范围：相对压强０．０－０．２ＭＰａ；来流截面含气率０．０－０．３５；水流量０．０－２６ｍ３／ｈ。     

电子互连导电胶的率相关剪切力学行为表征

电子封装互连时芯片与封装基板力/热性能的不匹配及电子产品使役中所遭受的振动、跌落及冲击易使导电胶互连层发生不同程度的剪切变形乃至胶连失效，开展电子互连导电胶的率相关剪切力学行为表征是胶连封装结构可靠性研究的重要基础；针对率相关剪切力学行为有效获取有别于金属/合金类材料的胶连层，本文采用Instron万能材料试验机与分离式霍普金森压杆装置(SHPB)对50wt.%、60wt.%银含量导电胶搭接互连铜板双剪切试样开展了不同加载率下的剪切测试表征，通过对SHPB的入射波整形保证了胶连层开始发生剪切破坏前后较大时间范围内试样在恒应变率下的应力平衡及均匀变形状态；得到了不同工况下胶连件的剪切失效模式并给出了消除胶连件铜板弹性变形影响的胶连剪切应变与应变率获取方法，分析了加载率与导电颗粒对胶连剪切变形行为及剪切强度的影响；消除胶连件铜板弹性变形后的胶连剪切应变与剪切应变率值相对较小，不同工况下的导电胶互连剪切主要表现为胶粘接失效模式，准静态下较低银含量胶连件的剪切强度相对较高而动态下则相反；研究结果对导电胶在电子工业领域的高效应用及胶粘接结构剪切力学行为的有效表征具有重要意义.     

Prediction of refrigerant void fraction in horizontal tubes using probabilistic flow regime maps

A state of the art review of two-phase void fraction models in smooth horizontal tubes is provided and a probabilistic two-phase flow regime map void fraction model is developed for refrigerants under condensation, adiabatic, and evaporation conditions in smooth, horizontal tubes. Time fraction information from a generalized probabilistic two-phase flow map is used to provide a physically based weighting of void fraction models for different flow regimes. The present model and void fraction models in the literature are compared to data from multiple sources including R11, R12, R134a, R22, R410A refrigerants, 4.26–9.58 mm diameter tubes, mass fluxes from 70 to 900 kg/m² s, and a full quality range. The present model has a mean absolute deviation of 3.5% when compared to the collected database.     

2.5维自愈合C/SiC复合材料弹性性能预测

试验研究了2.5维自愈合C/SiC复合材料（2.5D-C/SiC）的面内弹性性能。根据复合材料的细观结构特点,建立了2.5D-C/SiC的弹性模量预测模型。计算结果与试验值吻合较好,证明了模型及计算方法的正确性。通过改变经纱编织角、纤维束中纤维数以及经纱穿过纬纱的层数,得到了经纱体积含量、纬纱体积含量、纤维总体积含量以及弹性模量随上述参数的变化规律。保持碳化硅与碳化硼总体积分数不变,改变碳化硼与碳化硅的体积比α,得到了弹性模量随α的变化关系。     

Gas–liquid flows in a microscale fractal-like branching flow network

Two-phase air–water flows in a microscale fractal-like flow network were experimentally studied and results were compared to predictions from existing macroscale void fraction correlations and flow regime maps. Void fraction was assessed using (1) two-dimensional analysis of high-speed images (direct method) and (2) experimentally determined using gas velocities (indirect method). Fixed downstream-to-upstream length and width ratios of 1.4 and 0.71, respectively, characterize the five-level flow network. Channels were fabricated in a 38 mm diameter silicon disk, 250 μm deep disk with a terminal channel width of 100 μm. A Pyrex top allowed for flow visualization. Superficial air and water velocities through the various branch levels were varied from 0.007 m/s to 1.8 m/s and from 0.05 m/s to 0.42 m/s, respectively. Two-phase flow regime maps were generated for each level of the flow network and are well predicted by the Taitel and Dukler model. Void fraction assessed using the indirect method shows very good agreement with the homogeneous void fraction model for all branch levels for the given range of flow conditions. Void fraction determined directly varies considerably from that assessed indirectly, showing better agreement with the void fraction correlation of Zivi.     

A 2D finite element based on a nonlocal constitutive model describing localization and propagation of phase transformation in shape memory alloy thin structures

Here, the effects of localization and propagation of martensitic phase transformation on the response of SMA thin structures subjected to thermo-mechanical loadings are investigated using nonlocal constitutive model in conjunction with finite element method. The governing equations are derived based on variational principle considering thermo-mechanical equilibrium and the spatial distribution of the nonlocal volume fraction of martensite during transformation. The nonlocal volume fraction of martensite is defined as a weighted average of the local volume fraction of martensite over a domain characterized by an internal length parameter. The local version of the thermo-mechanical behavior model derived from micromechanics considers the local volume fraction of martensite and the mean transformation strain. A 4-noded quadrilateral plane stress element with three degrees of freedom per node accounting for in-plane displacements and the nonlocal volume fraction of martensite is developed. Numerical simulations are conducted to bring out the influence of material and geometrical heterogeneities (perturbations/defects) on the localization and propagation of phase transformation in SMA thin structures. Also, a sensitivity analysis of the material response due to the localization and the other related model parameters is carried out. The detailed investigation done here clearly shows that the localization of phase transformation has significant effect on the response of shape memory alloys.     

Slip between the phases in two-phase water–oil flow in a horizontal pipe

This paper is devoted to slip phenomenon between the phases that occurs in unstable two-phase water–oil flow systems in a horizontal pipe. The emphasis is placed on the relation between the slip and the real (in situ) water fraction in a flowing mixture, as well as the substitute physical properties of the whole two-phase system. The experimental data collected throughout research served for the evaluation of the accuracy of the methods of real phase fraction in a water–oil flow system in horizontal pipes as they were referred to in the bibliography. Subsequently we have suggested the author indicate a method of determination of the fraction for two-phase liquid systems like O/W, W/O and W + O. In order to establish the specific equations, the drift-flux model has been used here.     

Modeling transient churn-annular flows in a long vertical tube

This work investigates the transient behavior of high gas fraction gas-liquid flows in vertical pipes (annular and churn flows). Hyperbolic balance equations for mass, momentum and entropy are written for the gas and liquid, which is split between a continuous film and droplets entrained in the gas core. Closure relationships to calculate the wall and interfacial friction and the rates of droplet entrainment and deposition were obtained from the literature. A finite-difference solution algorithm based on a coefficient matrix splitting method was implemented to deal with sharp variations in the spatial and temporal domains, such as pressure and phase holdup waves. The model results were compared with steady-state experimental data from eight different sources, totaling more than 1500 data points for pressure gradient, liquid film flow rate and void/core fraction. The absolute average deviation between the model and the data was 17% for the pressure gradient and 5.8% for the void fraction. A comparison of the model results with fully transient air-water data generated in a 49-mm ID, 42-m long vertical pipe is also presented. The experimental results consist of two outlet pressure-induced and two inlet mass flow rate-induced transient tests. Two main transient parameters are compared, namely the local void fraction and the pressure difference between selected points along the test section and the outlet (taken as a reference). The comparisons between the experiments and the numerical model indicate that the model was capable of describing the transient annular to churn flow transition with absolute average deviations of 14.5% and 7.9% for the pressure difference and void fraction, respectively.     

A new constitutive model for fibre suspensions: flow past a sphere

A new phenomenological constitutive equation for homogeneous suspensions of macrosized fibres is proposed. In the model, the local averaged orientation of the fibres is represented by a director field, which evolves in time in a manner similar to the rotation of a prolate spheroid. The stress is linear in the strain rate, but the viscosity is a fourth-order tensor that is directly related to the director field. In the limit of low-volume fractions of fibres, the model reduces properly to the leading terms of the constitutive equation for dilute suspensions of spheroids. The model has three parameters: the aspect ratio R of the fibres, the volume fraction , and A, which plays the role of the maximum-volume fraction of the fibres. Experimental shear data are used to estimate the parameter A, and the resulting model is used in a boundary-element program to study the flow past a sphere placed at the centre line of a cylinder for the whole range of volume fractions from 0.01 to near maximum volume fraction. The agreement with experimental data from Milliken et al. [1] is good.     

A mass‐fraction‐based interface‐capturing method for multi‐component flow

An interface‐capturing method based on mass fraction is developed to solve the Riemann problem in multi‐component compressible flow. Equations of mass fraction with modified form, which is derived from conservative equations of mass, are employed here to capture the interface. By introducing mass fraction into Euler equations system, as well as other conservative coefficients, a quasi‐conservative numerical model is created. Numerical examples show that the mass fraction model performs well not only in multi‐component fluids modeled by simple stiffened gas equation of state (EOS) but also in that modeled by complex Mie–Grüneisen EOS. Moreover, the mass fraction model is applied to Riemann problem with piecewise EOS; the expression of which depends on density. It is found that the mass fraction model can well adapt to the analytic change in piecewise EOS and produce accuracy solutions with fewer unknown quantities, and the model can be easily extended to m‐component fluid mixture by using only m + 4 equations with no additional conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

Interfacial measurements in stratified types of flow. Part II: Measurements for R-22 and R-410A

A new optical void fraction measurement system has been coupled to a flow boiling test facility to obtain dynamic and time-averaged void fractions in a horizontal tube. A series of evaporation tests have been run for two refrigerants. R-22 was tested under mass velocity conditions of 70, 100, 150 and 200 kg/m² s and R-410A for 70, 150, 200 and 300 kg/m² s in a 13.6 mm diameter glass tube. Using our newly developed image processing system, about 227 000 images have been analyzed in this study to provide the same number of dynamic void fraction measurements. From these images, 238 time-averaged void fraction values have been obtained for vapor qualities from 0.01 to 0.95. These experimental points show very good agreement with the horizontal version of the Rouhani–Axelsson drift flux void fraction model.     

CONSIDER SAINT-VENANT''''S PRINCIPLE BY MEANS OF CHAIN MODEL

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