注射成型中塑料熔体充填流动的粘度模型研究

对比研究了Cross_Exp 和Cross_WLF两种粘度模型 ,并分别利用这两种模型通过实例模拟研究了熔体粘度的压力依赖性对注射压力模拟的影响     

Application of BP neural network to semi-solid apparent viscosity simulation

1　INTRODUCTIONSincethethixotropic propertiesofvigorouslystirredtin leadslurrieswerediscoveredbySpenceretal[1] atMIT ,investigationandapplicationofthese mi solidtechnologyhavebeendevelopedquickly .Thestudyontheapparentviscosityisnotonlyoftheoreti calbutalsoofutilizationsignificance .Manyinvesti gatorshavecarriedoutagreatdealofexperimentalresearchandputforwardmanymathematicalmodelsofthesemi solidapparentviscosity .Someofthesemodels ,whicharerelatedto popularexponentialfunctionandaclassica…     

Correlation for estimating the effects of temperature on the viscosity of light hydrocarbon solvents

Viscosity-temperature correlation has been developed for light hydrocarbon solvents. The correlation is based on one-parameter viscosity model developed by Puttagunta et al. (Chem. Eng. Res. Des., Vol 70, 1992, p 627–631) for conventional crude oils, which has been modified by incorporating a solvent viscosity reduction factor, Ф. The correlation was compared with the model of Puttagunta et al. on 22 light hydrocarbon solvents for a total of 318 data points. The average absolute deviation improves to 1.9%, compared with 2.2% obtained with the model over a temperature range from −54.41 to 160 °C. The correlation can accurately predict the viscosity of any light hydrocarbon solvent without the need to determine multiple characteristic parameters. This eliminates the consumption of time, energy, and money by costly and cumbersome calculations.     

A New Hard Sphere Cubic Equation of State for Predicting Fluids’ Properties and Vapor-Liquid Phase Equilibrium Calculations

In this study, a new cubic hard sphere equation of state (EOS) was developed from standard classical thermodynamics. The new equation is applied to calculate properties of fluids and vapor-liquid phase equilibrium calculations. The derived equation is a simplified expression of the hard sphere equation which yields satisfactory agreement with the molecular simulation of hard molecule data. The EOS is written in a cubic form by combining the derived repulsive hard spheres with Redlich-Kwong (RK) empirical attractive term. Satisfactory calculated results for the saturated properties of pure fluids for temperature ranges from 303 to 523 K and pressure ranges from 50 to 5000 psi are obtained. Simplicity and generality of this equation combined with reasonable accuracy makes it a useable EOS for almost all areas of equipment design for separation processes and production operations including refinery and petroleum reservoir industries. The accuracy of the predicted properties from the developed EOS are greater than of other commonly used two parameter cubic equations of state, RK and Pang-Robinson (PR).     

一种新的多元金属熔体粘度预报模型

在热力学通用几何模型的基础上提出了一个预报多元金属熔体粘度的数学模型，推导了预报多元金属熔体粘度的公式用Cu-Ag-Au三元金属熔体进行了验证，预报的粘度数据与实验结果吻合较好，在此基础上预报了含Cu三元系Cu-Al-Au,Cu-Al-Sn,Cu-Au-Ni,Cu-Fe-Ni,Cu-Al-Mg及Cu-Ag-Sn金属熔体的粘度。     

Numerical simulation of welding-induced distortion in thin-walled structures

Abstract

A sequentially coupled thermal stress analysis approach is presented for modelling temperature and distortion profiles resulting from welding thin-walled structures. The material is modelled as thermo-elastic–plastic with isotropic strain hardening. The heat source is modelled as a three-dimensional (3-D) double ellipsoid, and 3-D finite element (FE) models are employed for predicting ensuing distortions. Comparisons between the simulation results and experiments performed for eight weld configurations are presented. The weld configurations include bead-on-plate, butt weld and tee joint welds with varying plate thicknesses. Temperature measurements using thermocouples and an infrared (IR) imaging radiometer are directly compared to the thermal simulations. Likewise, distortions measured directly on the experimental set-ups are compared to the FE distortion predictions. Very good correlation is obtained for temperature as well as distortion predictions between experimental and proposed numerical approaches. Lastly, details of a weld simulation for the rear section of a motorcycle frame are presented.     

一种新型磁流体粘度测试系统的研制

阐述了磁场中磁流体粘度测试系统的工作原理，提出了其工作特性方程，进行了结构设计，用粘度已知的标准液体对其进行了标定，开发出一种新型的能对变磁场中磁流体粘度进行精确测量的测试系统，为磁流体动密封中外场下液体界面稳定性的深入研究奠定了基础。     

Development of viscosity model for aluminum alloys using BP neural network

Viscosity is one of the important thermophysical properties of liquid aluminum alloys, which influences the characteristics of mold filling and solidification and thus the quality of castings. In this study, 315 sets of experimental viscosity data collected from the literatures were used to develop the viscosity prediction model. Back-propagation (BP) neural network method was adopted, with the melt temperature and mass contents of Al, Si, Fe, Cu, Mn, Mg and Zn solutes as the model input, and the viscosity value as the model output. To improve the model accuracy, the influence of different training algorithms and the number of hidden neurons was studied. The initial weight and bias values were also optimized using genetic algorithm, which considerably improve the model accuracy. The average relative error between the predicted and experimental data is less than 5%, confirming that the optimal model has high prediction accuracy and reliability. The predictions by our model for temperature- and solute content-dependent viscosity of pure Al and binary Al alloys are in very good agreement with the experimental results in the literature, indicating that the developed model has a good prediction accuracy.     

Inhibitive properties of quaternary ammonium bromides of N-containing heterocycles on acid mild steel corrosion. Part II: EIS results

Four quaternary ammonium bromides of different heterocyclic compounds were investigated as corrosion inhibitors of mild steel in 1 N HCl using electrochemical impedance spectroscopy. The results were compared with data obtained by the polarisation resistance method. The influence of concentration and temperature (30-60 °C) was checked as well. Two structure models were found to describe the processes taking place at the interface mild steel/1 M HCl + inhibitor. The simpler one can be considered as a degeneration of the more complex one when the two time constants approach similar values. By fitting the structural models to the experimental results the parameter values were evaluated, as well as the time constants. A good correlation was established between the EIS and the polarisation resistance results.     

A statistical approach to estimate the experimental uncertainty of viscosity data obtained by the oscillating cup technique

The determination of the dynamic viscosity of metallic alloys at elevated temperatures is a key experiment for materials design and characterisation. To do so, the oscillating cup method is the most suited and commonly applied one. However, critical estimations of the experimental uncertainties are scarce, complicating the comparison of results obtained by different authors as well as with models set up in order to describe the changes of the dynamic viscosity with temperature and the alloy's composition. We present a statistical approach, first to estimate the uncertainties of the actual measured parameters of a torsional oscillation, and second to analyse the propagation of these errors when calculating the dynamic viscosity. Overall relative uncertainties in the range of 5–10% are obtained for selected experiments carried out on pure liquid Al, Sn and Cu. This figure is in good agreement with previous error estimations. However, method is ready to be involved in the usual numeric calculation procedure of the dynamic viscosity in the actual experiment and is thus able to take the individual conditions with a given sample into account.     

MODELING OF MICROSTRUCTURAL EVOLUTION IN MICROALLOYED STEEL DURING HOT FORGING PROCESS

~~MODELING OF MICROSTRUCTURAL EVOLUTION IN MICROALLOYED STEEL DURING HOT FORGING PROCESS~~1 C.A. Hernandez, S.F. Medina and J. Ruiz, Acta Materialia 44 (1996) 155. 2 P.D. Hodgson and R.K. Gibbs, ISIJ International 32 (1992) 1329. 3 S.I. Kim, Y. Lee and S.M. Byon, Journal of Materials Processing Technology 140 (2003) 84. 4 A. Laasraoui and J.J. Jonas, Metall. Trans. 22A(1991) 1545. 5 S.F. Medina and J.E. Mancilla, ISIJ International …     

Numerical simulation of die filling behavior of AZ91D in the semisolid process

In this work, numerical simulation of the die filling and solidification process of AZ91D semisolid alloy was investigated to produce a thin walled connecting rod demanding a high dimensional precision. The Carreau viscosity model was implemented to simulate the flow behavior of semisolid slurry during the filling. The fitted constants for the Carreau model were used to verify the simulation results. The predicted results from this model were in good agreement with the experimental results. Then the verified Carreau model was designed to predict die filling, casting defects and casting process. It was found that the predicted results had a good correlation with those in the experiment. The optimum parameters were obtained with a slurry temperature of 590 ℃, a die temperature of 250 ℃ and an injection velocity of 2 m/s.     

New corrosion inhibitors based on fatty materials—I. Epoxidized fatty materials modified with aliphatic amines

Six new inhibitors were prepared by modification of epoxidized linseed oil and oleic acid with methyl-, ethyl- and butylamines. The material used for testing was mild steel and the environments were 0.05N HCl at 70°C or vapours evolving from gasoline-2N HCl mixtures. Efficiency values as high as 92% were obtained for some compounds, the corresponding values for two commercial inhibitors being 91 and 64%. It has been shown that the efficiency in the gaseous environment increased with branching of the inhibitor molecule and with increase in the length of the chain attached to the functioning group. In the liquid environment branching lowered the efficiency of the inhibitor. The results conformed with predictions based on Taft's constants and Langmuir isotherms.     

简单熔体粘滞系数的普适性标度关系

运用分子动力学方法,对一系列简单熔体（包括Ag,Al,Au,Co,Cu,Mg,Ni,Pb,Pd,Pt,Rh和Si）的粘滞系数和过剩熵之间的标度关系进行了深入的研究．计算结果证实了Rosenfeld的粘滞系数标度关系,应用Dzugutov的方法定义了一个新的约化粘滞系数,并根据大量的模拟数据拟合出了一个新的粘滞系数标度关系．分析了在简单熔体中存在粘滞系数与过剩熵普适标度关系的物理本质,同时明确论证了标度关系与Arrhenius关系之间的密切联系,即过剩熵与温度的倒数存在正比关系．     

考虑压力对黏度影响的注塑填充过程数值模拟

为了研究熔体黏度模型对注塑成型数值模拟精度的影响,采用不考虑压力和考虑压力对黏度影响的WLF-Cross模型,利用Moldflow Plastics Insight软件对制品填充过程进行了数值模拟。结果表明,注射压力较高时,采用考虑压力影响的黏度模型计算得到的注射压力和熔体温度显著增加,型腔填充阻力越大,注射压力和熔体温度增加越大。     

半固态废弃铝硅合金的稳态流变性能的研究

利用同轴双筒流变仪研究了以废旧铝料为原料的半固态铝硅合金浆料的稳态流变性能.结果表明,半固态铝硅合金浆料的稳态表观黏度随固相分数的增加而增加,但随剪切速率的增大而减小,并得出稳态表观黏度的公式来描述固相率、剪切速率对稳态表观黏度的影响.     

进出口等流量四口液压变压器及其变压比特性研究

在不改变原液压系统的前提下,为避免液压系统节流损失,回收压差能、制动动能和重力势能,提出了一种进出口等流量四口液压变压器。阐述了四口液压变压器的基本结构和运行原理,其配流盘上均匀分布有四个形状大小相同的腰形槽,通过调节配流盘控制角可以改变其变压比,其中A和 B口等流量组合相当于液压马达,O和T口等流量组合相当于液压泵。建立了四口液压变压器的排量、转矩及变压比数学模型,通过偏导法得出负载回路流量、回收压差和油液粘度等因素与变压比的关系,通过Matlab仿真分析得到以上因素对变压比的影响规律。理论分析和仿真结果表明,在配流盘控制角不变时,随着负载回路流量和回收压差的增加变压比降低,而随着油液粘度的降低变压比增大。     

基于动态再结晶动力学方程的镍基高温合金热变形流变应力预测

采用等温热压缩实验,研究了一种典型镍基高温合金在1010-1160oC及0.001-1s-1条件下的高温流变行为。结果表明在合金的高温变形过程中发生了动态回复(DRV)以及动态再结晶(DRX)现象。通过深入分析不同变形条件下合金的高温流变行为,分别建立了合金在加工硬化-动态回复阶段以及动态再结晶阶段的流变应力本构方程。其中,在动态再结晶阶段,流变应力本构方程的建立是基于一种新型的动态再结晶动力学方程,该方程中引入了最大软化速率应变。此外,采用线性拟合的方法,建立了本构方程中材料常数与Zener-Hollomon参数间的函数关系。同时,通过对比分析流变应力的实测值和预测值,并计算两者之间的相关系数(R)和平均相对误差绝对值(AARE),验证了所建立本构方程的准确性,它可以精确预测所研究合金的高温流变应力。     

Modeling the viscosity versus temperature and pressure of light hydrocarbon solvents

Our viscosity-temperature correlation (Miadonye and D’Orsay,J. Mater Eng. Perform., 2006, 15(1), p 13–18; Ref 1) has been extended in this work to estimate the viscosity of light hydrocarbons between a temperature range of 223.15 and 433.15 K and a pressure range from 0.1 to 240 MPa. The correlation was modified to include a pressure term that contains the pressure parameters Ψ and Ω. The value for Ω was obtained as a constant, and the value of the parameter Ψ was derived from viscosity-temperature-pressure relationship and is unique for each hydrocarbon sample. With the pressure parameter, Ψ, and the shape factor constant, Φ, the model produces an average absolute deviation of 2.3% for a total number of 503 data points, an improvement of 46% on correlations with similar simple characteristics. The value of Ψ has been determined for several light hydrocarbon samples, including crude oil fractions.     

COMPUTERIZED PREDICTION SYSTEM FOR THERMOPHYSICAL PROPERTIES

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