Rheologicai properties of tailing paste slurry

The initial shear stress (τ) and plastic cohesion (η) are the most important parameters reflecting the rheological properties of the paste slurry. The rheological parameters as well as the quantitative relationship among the consumption of different fill materials were obtained through the experiment and research on these parameters.They can be used to predict the scope of the values of τ and η in production for a given ratio, which can reduce the conveying resistance of fill slurry along the pipelines and avoid the blockage of the pipelines. It is found that the rheological model of the total tailing slurry belongs to the Bingham type, which has a feature of strong internal structure and large initial shear stress. The calculation formula for the resistance loss of pipelines conforms nicely to the field test and the actual production in Jinchuan Nickel Mine.     

Microstructure and mechanical properties of Al-Zn-Cu-Mg-Sc-Zr alloy after retrogression and re-aging treatments

The mechanical properties and stress corrosion cracking (SCC) resistance of an Al-Zn-Cu-Mg-Sc-Zr alloy under different aging conditions were investigated. The dependence of microstructure and mechanical properties on aging parameters was evaluated by tensile test, hardness test and conductivity measurement. The results show that for the alloys with retrogression and re-aging treatment (RRA), the conductivity increases with the retrogression time and temperature, while the tensile strength decreases. The transmission electron microscopy (TEM) results show that the precipitates η(MgZn₂) at grain boundary aggregate apparently with retrogression time and the precipitates inside the matrix exhibit the similar distribution to T6 temper, which comprises fine GP zones, large η′(MgZn₂) and η(MgZn₂) phases. According to the mechanical properties and microstructure observations, the optimal RRA regime is recommended to be 120 °C, 24 h + 180 °C, 30 min + 120 °C, 24 h. The strength level of the alloy after the optimum RRA treatment is similar to that in T6 condition and the SCC resistance is improved obviously in contrast to T6 condition.     

基于BP神经网络的充填料浆流变参数预测分析

为了合理分析充填料浆在长距离管道中的输送阻力,基于流变参数对输配管网设计的重要性,在全面评估不同因素对流变性能影响的程度后,采用BP神经网络原理,建立起干料中水泥含量X1、料浆浓度X2、料浆坍落度X3、料浆容重X4对流变参数(屈服应力Y1、粘性系数Y2)影响的函数模型.此BP网络为4-Hn-2结构,隐层和输出层分别用tansig、purelin函数传递,利用Levenberg-Marquardt优化算法trainlm训练网格.计算结果表明:该模型在预测充填料浆屈服应力Y1和粘性系数Y2中适应性较强,误差也在可控范围之内,可为充填管网布设及输配系统沿程阻力分析提供可靠依据.     

Rock fracture under anti-plane shear (Mode III) loading

Anti-plane punch-through shear test and anti-plane four-point bending test are used to study the crack initiation and propagation under anti-plane shear (Mode III) loading. The tensile and shear stresses at the crack tip are calcualted by finite element method. The results show that under Mode III loading the maximum principal stress σ₁ at crack tip is smaller or a little larger than the maximum shear stress τ_max. Since the tensile strength of brittle rock is much lower than its shear strength, σ₁ is easy to reach its critical value before τ_max reaches its critical value and thus results in Mode I fracture. The fracture trajectory is helicoid and the normal direction of tangential plane with the fractured helicoid is along the predicted direction of the maximum principal stress at the notch tip. It is further proved that Mode I instead of Mode III fracture occurs in brittle rock under Mode III loading. The fracture mode depending on the fracture mechanism must be distinguished from the loading form. Foundation item: Project (50374073) supported by the National Natural Science Foundation of China; project (2002032256) supported by the Postdoctor Science Foundation of China     

Dynamics of electrodeposition of tetraethylthioram disulphide (TETD) on pyrite surface

Ｄｉｅｔｈｙｌｄｉｔｈｉｏｃａｒｂａｍａｔｅ(ＤＤＴＣ)ｉｓｏｎｅｏｆｔｈｅｍｏｓｔｆｒｅｑｕｅｎｔｌｙｕｓｅｄｃｏｌｌｅｃｔｏｒｆｏｒｆｌｏｔａｔｉｏｎｏｆｈｅａｖｙ ｍｅｔａｌｓｕｌｆｉｄｅｍｉｎｅｒａｌｓ,ｓｕｃｈａｓｇａｌｅｎａ ,ｃｈａｌｃｏｐｙｒｉｔｅａｎｄｊａｍｅｓｏｎｉｔｅ ,ａｎｄｓｈｏｗｓｓｔｒｏｎｇｓｅ ｌｅｃｔｉｖｉｔｙ[1] .ＩｔｉｓｒｅｐｏｒｔｅｄｔｈａｔＤＤＴＣｉｓａｐｏｗｅｒｆｕｌｃｏｌｌｅｃｔｏｒｆｏｒｇａｌｅｎａａｎｄｖｅｒｙｓｅｌｅｃｔｉｖｅａｇａｉｎｓｔｐｙｒｉｔｅｉ…     

聚合物悬浮体系的流变特性

应用搅拌法测定了聚合物粒子—水悬浮体系的流变特性,探讨了固相浓度、粒径、粒径分布、颗粒表面形态、pH值、剪切速率等因素的影响。对5个常用的相对粘度与固相体积分率的关联式作了验证,结果表明:Landel模型和Quemada模型有较好的关联精度。在较高浓度下的悬浮液为非牛顿流体,剪切应力和剪切速率的关系很好地符合Casson方程。     

Influence of interfacial strength on the fracture toughness of glass-ceramic matrix composites

Nine kinds of glass-ceramic matrix composites with different compositions and interfacial strength (τ _s) were prepared. The influence of τ _s on the fracture toughness(K _1c) of composites was studied. It was discoved that, for the system no chemical reaction taking place at the interface, K _1c increased proportionally with τ _s increasing at the first stage, then decreased when τ _s reached a certain value. According to this result, a model of relationship between τ _s, thermal mismatch (Δα _r) and K _1c was built up. If a chemical reaction took place and a new phase was formed in the interface, the K _1c of composite was effected by the combination of τ _s, chemical bonding, radial interfacial stress and other factors. Project supported by the National Natural Science Foundation of China Synopsis of the first author Wang Lingsen, professor, born in 1938, current research field: special ceramic and ceramic matrix composite, etc.     

浓煤浆管道输送压力损失计算及相似与模化研究

本文分析了可作为燃料直接燃烧的宾汉体浓煤浆的流变特性,及主要流动参数:点速分布、剪切应力、浆体平均流速和流量、压力损失梯度。浓煤浆在管道中以各种流态流动时都具有流动规律的相似性。运用相似理论获得表达其流动共性特征的准则关系式,及保证模型管流与原型管流现象相似所需的定性准则和相似模化条件。得出两者各主要流动参数间关系式。论证了可用模型管道浓煤浆流动模拟工业管道浓煤浆流动。为估算工业管道主要流动参数数据提供较经济方便手段。     

Viscoelastic properties of monodisperse spherical silica suspension

The viscoelastic properties of the suspension of monodisperse spherical silica produced by hydrolysis of tetraethoxysilane in alcohol solvent with ammonia as a catalyst in polyethylene glycol (PEG) were studied. The results show that the SiO2/PEG suspension possesses the reversible shear thinning and shear thickening behaviors. In the shear thinning region, the loss modulus (G″) almost remains unchanged, whereas the storage modulus (G′) decreases. In the shear thickening region, G″ and G′ increase for the formation of the "clusters". The larger G″ over G′ in all the stress studied shows that the system mainly possesses the viscous property, and that the energy dissipated(Ed) is larger than that stored. Ed of this suspension is proportional to the maximum strain (γmax) rising with the exponent of 1.92 under low shear stress; however, in the shear thickening region, Ed is proportional to γmax rising with the exponent of 5.00.     

浆体的管道输送阻力机理及减阻技术

浆体的流动阻力是浆体输送管道设计的重要参数,其大小直接影响到输送的费用.因此研究不同流态下浆体的流动阻力机理并采用适当的减阻技术具有非常重要的意义.在总结国内外对管道中浆体流动状态分析的基础上,对完全分层和完全混合两种流动状态下的阻力机理进行了探讨;针对影响浆体流动阻力的影响因素,对适当粒径级配减阻、减阻剂减阻、升温减阻等减阻技术做出了分析总结.     

河道淤泥气泡混合轻质土剪切流变特性及模型

利用剪切流变试验对以水泥为固化剂的河道淤泥气泡混合轻质土的流变特性进行了试验研究。试验结果表明,经固化处理的河道淤泥气泡混合轻质土在荷载作用下具有类似于硬粘性土的流变特征。剪切流变可以分为3个阶段：在剪应力水平较低时,剪切流变曲线呈衰减稳定型;随着剪应力水平的提高,剪切流变曲线呈非稳定的等速型;当剪应力水平增大到一定程度时,剪切流变曲线呈加速型。河道淤泥气泡混合轻质土的流变性随着混合轻质土强度的提高而降低。根据试验所呈现的剪切流变规律,可以发现河道淤泥气泡混合轻质土的剪切流变符合七元件黏弹塑性剪切流变模型,模型能够比较好地描述河道淤泥混合轻质土在各种剪应力水平下的衰减、等速以及加速流变过程。     

靖三-靖二联管道原油停输后流变特性与再启动研究

长庆靖三-靖二联外输管线采用加热输送,所输送的是靖安油田典型的低胶质沥青质含量的高含蜡原油,这对安全、经济、高效的管输工艺提出了很高的要求。基于原油流变学、物理化学和凝胶化学理论,首先使用高精度控制应力流变仪对管道停输条件下,原油体系的黏-温、屈服、黏弹、触变等复杂流变行为进行了研究,然后拟合了适用于该原油的流变方程与触变模型,最后基于原油流变性、管流的流动与传热、热力与水力的耦合特性,对长庆靖三-靖二联管道的再启动特性进行了预测。结果表明,长庆原油在反常点温度以下剪切稀释性也随着温度的降低表现得更为明显。在凝点以及凝点温度以上,原油所形成的胶凝结构表现出一定的延性性质,而在凝点温度以下则表现出很强的脆性性质,并且随温度的降低,屈服值呈指数规律增大。在恒剪切速率的作用下,胶凝结构的破坏和重整发生在初期的10min内。所预测的长庆靖三-靖二联外输管线停输再启动特性,与现场数据相吻合。停输32h后,管道末端原油油温会降至其反常点附近,停输48h后,管道末端原油油温会降至其凝点附近。考虑管道运营的安全性,管道最大停输时间为32h,对应再启动压力为1.51MPa。     

基于扭剪试验的细砂区域长距离流滑机制分析

大量灾害现场发现,即使地面倾角极其平缓（1°~5°）,地表也可能因地震荷载而发生长距离的横向变形。为了解此类砂土变形特性,在改良的空心圆柱扭转剪切仪中采用涌水量概念进行试验,随后采用恒定剪应力静态液化试验,确定排水条件以及小初始静力剪切条件下试样流动的可能性。为突出对比,相同试样被用以进行不排水循环加载试验,观察其行为特征。研究发现：（1）在小初始静态剪应力下可以观察到丰浦砂连续流动的特性;（2）砂土的连续流动特性由初始密实度决定,初始密实度也影响砂土的体积膨胀特性;（3）静态液化试验显示流动砂土试样在涌水机制下可产生流动,而即使样本发生了液化,其在典型的不排水试验中却表现出非流动特性。     

Nucleation barrier of fcc(γ)→hcp(ε) martensitic transformation in Fe-based alloys

Based on the dislocation theory and Olson's stacking fault model, a model describing the nucleation of an hcp(ε) martensite embryo at low-angle grain boundary is proposed with the influence of external stress field taken into account. The dependences of temperature (T), shear stress (τ) and dislocation density at grain boundary on the martensite nucleation in FeMnSi based alloy, as an example, are numerically simulated. It has been shown that there exist the subcritical and critical embryos during the course of ε-phase nucleation. The free energy difference between them is just the energy barrier of embryo growth. Depending on T and τ. the characteristic embryo sizes may vary in wide ranges and decreases with increasing σ and decreasing T. The energy condition of martensitic transformation at M _s and critical shear stress (τ_c) is discussed from the viewpoint of kinetics and thus the TEM observed result that stacking fault energy is not zero at M _s temperature is reasonably explained. Besides, it is predicted that the high dislocation density at grain boundary can promote the nucleation of fcc→hcp transformation in Fe-based alloys.     

Measurements of in situ stress and mining-induced stress in Beiminghe Iron Mine of China

In order to obtain the distribution rules of in situ stress and mining-induced stress of Beiminghe Iron Mine, the stress relief method by overcoring was used to measure the in situ stress, and the MC type bore-hole stress gauge was adopted to measure the mining-induced stress. In the in situ stress measuring, the technique of improved hollow inclusion cells was adopted, which can realize complete temperature compensation. Based on the measuring results, the distribution model of in situ stress was established and analyzed. The in situ stress measuring result shows that the maximum horizontal stress is 1.75–2.45 times of vertical stress and almost 1.83 times of the minimum horizontal stress in this mineral field. And the mining-induced stress measuring result shows that, according to the magnitude of front abutment pressure the stress region can be separated into stress-relaxed area, stress-concentrated area and initial stress area. At the −50 m mining level of this mine, the range of stress-relaxed area is 0–3 m before mining face; the range of stress-concentrated area is 3–55 m before mining face, and the maximum mining-induced stress is 16.5–17.5 MPa, which is 15–20 m from the mining face. The coefficient of stress concentration is 1.85. Foundation item: Projects(10702072, 10632100) supported by the National Nature Science Foundation of China     

基于水泥净浆流变性的振动-剪切等效理论

为了分析振动条件下水泥净浆的流变特性,解释水泥净浆流变性模型的转化机制,提出适用于振动条件下水泥净浆流变性分析的振动-剪切等效理论. 根据修正HI理论和回转黏度仪径向分层算法,计算振动条件下回转黏度仪内水泥净浆流场的剪切速率,将振动台正弦振动过程转化为对水泥净浆的剪切过程. 采用自制回转黏度仪,开展20 Hz振动频率下的HI参数标定试验和30 Hz振动频率下的水泥净浆黏度试验. 结果表明,HI参数标定结果与数值计算结果之间的误差约为7%,水泥净浆的试验黏度与数值计算的黏度之间的误差为8%并趋于收敛状态. 增大振动频率,水泥净浆的黏度逐渐减小并达到峰值,流变性模型逐渐由Bingham模型转变为Hershel-Bulkley模型,最后转变为Power-Law模型.     

Existence of positive solutions in a delay logistic difference equation

The author studied the existence of positive solutions of the delay logistic difference equationΔyn=pnyn(1-yτ(n)), n=0,1,2,....where {pn} is a sequence of positive real numbers, {τ(n)} is a nondecreasing sequence of integers, τ(n)＜n and limn→∞τ(n)=∞. A sufficient condition for the existence of positive solutions of the equation was given.     

油基体系下天然气水合物浆液流动实验研究

在多相流管输体系下,水合物浆液在流动过程中会遇到崎岖不平的地形地貌,此时采用倾斜管道显得尤为重要。因此,研究了天然气水合物浆液在倾斜管内的流动特性对堵塞管路的影响。在低温高压可视水合物实验环路上,开展了油基体系下油＋天然气的水合物堵管实验,探究了初始压力、初始流量等因素对天然气水合物浆液流动和堵管时间的影响。同时,利用实时在线颗粒测试仪,对水合物生成、流动及堵管过程中水合物颗粒的微观变化进行了分析。结果表明,随着初始压力增大,天然气水合物的诱导时间、生成时间和浆液流动时间均缩短,天然气水合物堵管趋势增大;随着初始流量增大,天然气水合物的诱导时间、生成时间和浆液流动时间均延长,天然气水合物堵管趋势减小。对水合物生成至堵管的过程以及堵塞机理进行了分析。对油基体系下天然气水合物堵塞管路的研究结果表明,在油基体系下可以通过减小初始压力、增大初始流量来有效地减小天然气水合物堵塞管路的概率。研究结果可为维持和保证天然气水合物在管道中的安全流动提供理论参考及依据。     

Effect of particle inertia on temperature statistics in particle-laden homogeneous isotropic turbulence

One of the most fascinating aspects of turbulent fluid motion is that the diffusion of suspended scalar quantities will be greatly enhanced[1]. These scalars may be smoke or dye which are able to follow all of the velocity fluctuations. However, these scalars mayalso be heavy particles that cannot follow all of the turbulent motion, i.e. the motion of heavy particles in a turbulent flow field is somewhat more complicated because of the additional parameters, such as particle response time, flu…     

软土的等效时间线剪切流变模型

为反映软土剪切流变的非线性特性,建立剪切流变模型,修正了Singh-Mitchell提出的指数型剪切蠕变经验公式,使之适用于低修正应力水平工况.根据黏塑性剪应变-耗散剪应力-等效时间之间的关系方程推导出黏塑性剪应变速率与剪应力和黏塑性剪应变之间的函数表达式.把该表达式和剪切弹性模型相结合,建立了剪切弹黏塑性模型.以此模型为基础,不但获得了有效围压恒定时单级和多级荷载作用下的剪切流变解析解,而且还获得了有效围压和剪应力均随时间变化时的剪切流变积分解答.结果表明,流变模型能够较好地定量模拟三轴固结排水试验中多级加载作用下的剪切蠕变发展过程,合理地反映剪应变随修正应力水平(或剪应力)、有效围压和持续时间等影响因素变化的流变规律.