Study of the generalized mixture rule for determining effective conductivity of two-phase stochastic models

The generalized mixture rule （GMR） is usually applied in determining mechanical properties such as the rheological property and Young’s modulus of multi-phase rocks. However, it is rarely used to determine electrical conductivity of multi-phase rocks presently. In this paper, we calculate the effective conductivity using the 3D finite element method for a large number of two-phase medium stochastic models. The GMR is then employed as an effective conductivity model to fit the data. It shows a very close relationship between the parameter J of GMR and the ratio of conductivities of the two phases. We obtain the equations of the parameter J with the ratio of conductivity of two phases for the first time. On this basis, we can quickly predict （or calculate） the effective conductivity of any twophase medium stochastic model. The result is much more accurate than two other available effective conductivity models for the stochastic medium, which are the random model and effective medium theory model, laying a solid base for detailed evaluation of oil reservoirs.

Densification Mechanism of Warm Compaction and Powder Mixture Designing Rules

By phenomenological analysis of warm compaction, it is found that, compared with the contribution of particle plastical deformation to densification of powder compact,the particle rearrangement is a dominant densification mechanism for powder warm compaction, and the plastical deformation of particles plays an important role in offering accommodating deformation for particle rearrangement and densifying powder compact at the final stage of pressing.In order to attain density gain as high as possible during warm compaction, six rules for designing warm compacting powder mixtures were proposed in detail.

PHASE EQUILIBRIUM OF COMPLEX MIXTURES WITH EQUATIONS OF STATE: AN UPDATE5

Here we review a new class of mixing rules (hat have extended range of mixtures and conditions that can now be described by equation of state models. One characteristic of these mixing rules is that they simultaneously satisfy the boundary conditions of producing a second virial coefficient that is quadratic in mole fraction, and a free energy of mixing like that of an activity coefficient model at high density, though the mixing rule is itself independent of density. We show that using this mixing rule, various asymmetric, highly nonideal mixtures can be accurately described. One serendipitous result is that the parameters in this mixing rule model are almost independent of temperature, which allows accurate extrapolations of phase behavior to be made over large ranges of temperature and pressure.

含R1234yf混合工质汽液相平衡的混合规则评估与预测研究

含R1234yf混合工质具有系统性能优良且对环境友好的特点,在当前制冷剂迭代中受到了广泛关注。汽液相平衡性质是混合工质的基础热物理性质,其理论计算至关重要。为提高含R1234yf混合工质汽液相平衡数据的计算精度,选取PR状态方程结合vdW、WS、MHV1三种混合规则和NRTL活度系数模型评估了16种含R1234yf二元混合工质的汽液相平衡性质。结果表明,WS混合规则和MHV1混合规则计算性能优于vdW混合规则;vdW混合规则对大多数混合工质计算性能较好。最后提出一种预测模型预测含R1234yf混合工质汽液相平衡性质,预测的相对压力偏差值为0.49%,气相摩尔分数绝对偏差值为0.0031,预测偏差满足工程应用。

熔压温度对光纤面板抗弯强度的影响

光纤面板在微光夜视、空间探测、核诊断、医学诊疗等领域有着广泛的应用,在使用过程中对强度有一定要求,目前缺少相关研究,本文研究了熔压温度对光纤面板x、y、z三个方向抗弯强度的影响,采用三点弯曲法测试光纤面板的抗弯强度。结果表明:熔压温度为660℃时,二次复丝之间熔合不充分,存在间隙,光纤面板抗弯强度较低,x、y、z方向抗弯强度分别为107、93、114 MPa;熔压温度为670℃时,二次复丝之间间隙消除,但依然存在界面,抗弯强度有所提升,x、y、z方向抗弯强度分别为110、109、125 MPa;熔压温度为680℃时,二次复丝充分熔合,此时光纤面板抗弯强度在x、z方向满足复合材料混合定律,分别为123、127 MPa,y方向芯玻璃作为增强相对皮玻璃起到增强作用,抗弯强度为113 MPa。本文研究对提高光纤面板强度以满足装管和使用需求具有重要意义。

沥青混合料疲劳损伤试验表征综述

针对沥青混合料疲劳损伤细观形态难以与宏观力学性能表征联系起来的现状,从损伤机理、表征模型及疲劳性能试验方法三方面综述了沥青混合料疲劳性能表征的发展现状、存在的问题,预测了其未来的发展方向。研究表明:由于沥青混合料是一种多相、多组分、多尺度的黏弹性材料,在评价其疲劳性能时,宏观的疲劳试验需要结合计算机断层扫描、数值模拟和数字图像相关技术等细观分析方法。沥青混合料疲劳性能试验方法目前应用最为广泛的是室内小型试件疲劳试验,由于不同试验方法中设置的试验条件各不相同,故其试验结果和性能参数呈现出显著的差异性。应重点研究沥青混合料抗疲劳开裂性能的细观结构损伤开裂形态与宏观性能表征的联系;改进现有疲劳试验方法的试验条件、开发先进的三维应力状态的加载设备,并增加试验的尺度以反映真实荷载环境下的疲劳性能;基于能量理论和黏弹性连续损伤揭示沥青混合料疲劳特性和历史荷载条件下的疲劳损伤规律。

First-principles calculations for the elastic properties of Ni-base model superalloys: Ni/Ni_3Al multilayers

A model system consisting of Ni[001]（100）/Ni3Al[001]（100） multi-layers are studied using the density functional theory in order to explore the elastic properties of single crystal Ni-based superalloys. Simulation results are consistent with the experimental observation that rafted Ni-base superalloys virtually possess a cubic symmetry. The convergence of the elastic properties with respect to the thickness of the multilayers are tested by a series of multilayers from 2γ′＋2γto 10γ′＋10γ atomic layers. The elastic properties are found to vary little with the increase of the multilayer＇s thickness. A Ni/Ni3Al multilayer with 10γ′＋10γ atomic layers （3.54 nm） can be used to simulate the mechanical properties of Ni-base model superalloys. Our calculated elastic constants, bulk modulus, orientation-dependent shear modulus and Young＇s modulus, as well as the Zener anisotropy factor are all compatible with the measured results of Ni-base model superalloys R1 and the advanced commercial superalloys TMS-26, CMSX-4 at a low temperature. The mechanical properties as a function of the γ′ phase volume fraction are calculated by varying the proportion of the γ and γ′ phase in the multilayers. Besides, the mechanical properties of two-phase Ni/Ni3Al multilayer can be well predicted by the Voigt-Reuss-Hill rule of mixtures.

Mechanical properties and failure mechanisms of Mg-Zn-Y alloys with different extrusion ratio and LPSO volume fraction

In long period stacking ordered(LPSO)phase containing Mg-Zn-Y alloys,high elastic modulus and deformation kinks of LPSO phase considerably enhance the tensile yield strength,with slight detriment of or benefit to the ductility depending on its volume fraction.In present work,uniaxial tensile tests and fracture toughness tests are carried out using Mg99.2Zn0.2Y0.6,Mg97Zn1Y2,Mg89Zn4Y7 and Mg85Zn6Y9(at%)materials with different extrusion ratios.Extrusion processing enhances both strength and ductility due to the recrystallization of Mg grains.Variable plastic deformation mechanisms are activated depending on volume fraction of Mg and LPSO phase as well as their relative size during bending.{1012¯}<101¯1¯>tensile twins in Mg grains and deformation kinks in LPSO phase are observed,which dissipate large amount of deformation energy favoring for toughness.However,inherently brittle LPSO phase is detrimental to toughness.Microstructure-motivated empirical models for yield strength and fracture toughness prediction based on rule of mixtures are calibrated by experimental data.Energy release rates of individual mechanisms are estimated,which quantitatively indicate strong Mg/LPSO interaction.

Microstructure, Dislocation Density and Thermal Expansion Behavior Using Thermo Elastic Models of Zircon Sand Reinforced as Cast ZA-27 Composites

In the present work stir casting route is used to fabricate the ZA27 Metal matrix composites containing 3 wt%, 6 wt%, 9 wt%, and 12 wt%. Zircon sand particulates of size 100 mesh. Microstructure studies using Optical Microscopy, SEM-EDAX are carried out to ascertain the distribution and morphology of particulates in the composites. Effect of zircon sand as reinforcement on bulk density, porosity, of the fabricated composites is studied. SEM studies are carried out to understand the behavior of as-cast ZA27 alloy reinforced with zircon sand. The dislocation density of the fabricated composite affects the strength of the composites and depends on the strain due to thermal mismatch and is found to increase with increase in weight% of zircon sand. However, it does not consider casting defects of voids/clustering observed in micrographs of the fabricated composite. Porosity in composites does not have influence on Coefficient of thermal expansion (CTE) of the ZA27 composites studied using thermoelastic models like Kerner and turner model and rule of mixtures of composite.

Free Vibration Analysis of FG-CNTRC Cylindrical Pressure Vessels Resting on Pasternak Foundation with Various Boundary Conditions

This study focuses on vibration analysis of cylindrical pressure vessels constructed by functionally graded carbon nanotube reinforced composites(FG-CNTRC).The vessel is under internal pressure and surrounded by a Pasternak foundation.This investigation was founded based on two-dimensional elastic analysis and used Hamilton’s principle to drive the governing equations.The deformations and effective-mechanical properties of the reinforced structure were elicited from the first-order shear theory(FSDT)and rule of mixture,respectively.The main goal of this study is to show the effects of various design parameters such as boundary conditions,reinforcement distribution,foundation parameters,and aspect ratio on the free vibration characteristics of the structure.

Material Selection of a Natural Fibre Reinforced Polymer Composites using an Analytical Approach

Material selection has become a critical part of design for engineers,due to availability of diverse choice of materials that have similar properties and meet the product design specification.Implementation of statistical analysis alone makes it difficult to identify the ideal composition of the final composite.An integrated approach between statistical model and micromechanical model is desired.In this paper,resultant natural fibre and polymer matrix from previous study is used to estimate the mechanical properties such as density,Young’s modulus and tensile strength.Four levels of fibre loading are used to compare the optimum natural fibre reinforced polymer composite(NFRPC).The result from this analytical approach revealed that kenaf/polystyrene(PS)with 40%fibre loading is the ideal composite in automotive component application.It was found that the ideal composite score is 1.156 g/cm^(3),24.2 GPa and 413.4 MPa for density,Young’s modulus and tensile strength,respectively.A suggestion to increase the properties on Young’s modulus are also presented.This work proves that the statistical model is well incorporated with the analytical approach to choose the correct composite to use in automotive application.

基于高斯分量标准化的K近邻故障检测策略

针对复杂多工况工业过程故障检测问题,提出一种基于高斯分量标准化的K近邻(Gaussian Component Standardization K-Nearest Neighbor,GCS-KNN)故障检测策略。样本数据应用高斯混合模型(Gaussian Mixture Model,GMM)进行训练,将数据分解为多个高斯分量;通过每个高斯分量的均值和协方差对该分量内的数据进行标准化处理;应用K近邻(K-Nearest Neighbor,KNN)算法对标准化后的样本进行检测。GCS-KNN通过高斯分量标准化消除数据的多模态特性,提高传统基于KNN检测方法的检测率。利用数值例子和半导体工业过程仿真实验验证了该方法的有效性,并与传统的主元分析(Principal Component Analysis,PCA)、KNN、动态主元分析(Dynamic PCA,DPCA)和加权KNN(Weighted KNN,WKNN)等方法进行对比,结果证实此方法具有显著的优势。

含HFO混合体系气液相平衡的理论模型评价

HFO类新型环保工质具有很低的全球变暖潜能,但受限于热工性能且具有可燃性。含HFO的混合工质可实现优势互补,具有良好的应用前景。气液相平衡是混合物最基本的热力性质,其理论模型极为重要。选取PR状态方程,vdW、HV、WS三种混合规则和NRTL、Wilson两种活度系数模型,构建了PR-vdW、PR-HV-NRTL、PR-WS-NRTL和PR-WS-Wilson共4套理论模型,对HFC+HFO、HC+HFO、CO_(2)+HFO类二元体系气液相平衡的计算性能进行了比较和评价,并进一步分析了模型对含超临界组元体系的计算效果和对三元体系相平衡预测能力。结果表明PR-vdW模型计算性能稳定,对大多数体系计算性能优良;PR-WS-NRTL模型和PR-WS-Wilson模型性能优秀,但预测混合体系临界轨迹线和三元相平衡时稳定性不够好,PR-HV-NRTL模型预测三元相平衡时性能良好。

钢结构重防腐涂层拉伸性能及本构研究

为研究钢结构重防腐涂层的拉伸性能和本构关系,以长效型底漆、中间漆、面漆及复合涂层为实验对象进行了单轴拉伸试验。通过对应力-应变曲线的阶段划分与实验数据拟合建立了涂层的本构表达式。基于实验结果确定了力学性能参数,结合混合物定律提出了用单一涂层预测复合涂层拉伸性能的表达式,并结合不确定度分析验证了理论预测的可靠性。研究表明:钢结构重防腐涂层为典型的塑性材料,涂层工作过程分为近似弹性、塑性强化、破坏3个阶段,本构关系可用线性函数与二次函数结合的分段函数表达。中间漆和底漆的弹性模量分别为面漆的54.11倍和7.22倍,为复合涂层的主要载荷承载部分,复合涂层的弹性模量和拉伸强度可由单一涂层加权预测且具有较高精度。

3D打印碳纤维复合材料力学性能计算与实验

针对三维打印(3D打印)连续碳纤维热塑性复合材料力学性能计算需求,结合3D打印熔融沉积成型工艺特点,考虑填充率和沉积线角度等工艺参数影响,对传统复合材料混合定律进行改进,提出一种基于改进混合定律计算预测3D打印连续碳纤维增强热塑性复合材料结构件拉伸强度和模量的新方法。研究表明,在不同填充率下,所提出的基于改进混合定律计算得到的拉伸强度与实验结果更加接近,平均预测误差为1.8%;而根据传统复合材料混合定律计算拉伸强度与实际测试结果相比,平均预测误差为11.6%;相较传统复合材料混合定律,所提改进混合定律计算方法平均预测误差减小9.8%。研究结果为3D打印连续碳纤维增强热塑性复合材料结构件力学性能的可调可控打印提供了一种可行的理论计算方法。

不同成分铝/铜双金属复合材料的热变形行为及其本构模型

通过等温压缩实验,研究Al/Cu双金属复合材料在400~500℃、应变速率0.001~0.1 s^(-1)条件下的热变形行为,并考虑复合材料成分体积分数(Al含量为30%~51%)的影响。采用Arrhenius模型和混合定律(ROM)模型建立新的本构方程。流变应力(FS)实验表明,工艺参数和体积分数对复合材料的流变行为有影响,而Cu的体积分数对复合材料的高温流变行为影响更大。对于体积分数为51%、42%和30%Al的复合材料,建立的Arrhenius型本构方程和ROM模型的相关系数(R)分别为0.9826、0.9742和0.9718,其平均相对误差分别为0.18%、1.69%和-0.84%。结果表明,新建立的本构模型能较好地预测双金属复合材料的热加工行为。最后,研究不同工艺条件下复合材料的显微组织,确定三种不同成分Al/Cu复合材料在不同温度、应变和应变速率范围内的主要热变形机制。

Comparison on the mixture rules of sound velocities used in characterizing biomedium components

In this paper, several mixtrue rules of sound velocity and their usefulness in characterizing the components of biomedium are analysed. It is pointed out that for characterizing the components of biomedium, the rules are compatible with each other under certain conditions, and the errors between each rule and real sound velocity are difffcrcnt. It concludes that there is no general rule suitable for various media among above mentioned rules.

聚合物二元共混物拉伸强度混合规则的改进模型

改进了关于聚合物二元共混物拉伸强度混合规则的模型 ,保留了原模型中分别表征共混物界面和相结构对共混物拉伸强度产生影响的两个因子F和M .用此模型处理了三个共混体系的拉伸强度数据 ,反算出共混体系的界面强度因子F和相结构强度因子M ,结果表明 ,该改进模型的预测值与实验结果相符程度与原式几无差别 ,但使F和M的物理意义更为明确、合理 。

新型二元混合工质HFC32/HFO1234yf的热物性模型

在已有文献数据的基础上,优化了HFC32/HFO1234yf二元混合物相对应的交互系数和HFO1234yf适用于Peng-Robinson-Stryjek-Vera（PRSV）方程的纯物质特性参数,建立了用于该混合物的PRSV方程模型,并用该模型开发了二元混合物的热物性计算程序.比较实验数据发现,PRSV方程计算值的精度比PR方程有所提高.根据PRSV方程绘制了混合物饱和压力、温度随气液组成变化的关系图,并列出了定组成（0.3/0.7）时二元混合物饱和性质表,最后比较了不同混合比条件下混合物的潜热曲线.发现HFC32的添加有利于流体潜热的提高,考虑到GWP的因素,推荐了作为替代制冷剂时HFC32/HFO1234yf二元混合物所要满足的混合比范围为0.2/0.8~0.4/0.6.

TiNb/Ti-48Al-2Cr-2Nb复合材料的力学性能和断裂特征

采用粉末冶金、热压成型工艺制备了 Ti Nb/ Ti- 48Al- 2 Cr- 2 Nb(TACN)基复合材料。研究了复合材料的弯曲性能和断裂特征。实验结果表明 :复合材料的性能较基体有较大的提高 ,用混合法则来进行预测复合材料的力学性能和实验中所得结果十分接近 ;这种工艺制备的复合材料界面由全片层组织构成 ,纤维和基体的结合状态良好 。