Finite element simulation of deep bed filtration

In this paper, the numerical model for separation efficiency and transport in periodic porous media is studied. Finite element method was used to simulate the development of a predictive model of behavior of porous media during injection of particles. This paper describes the effects of injected particle size, Reynolds number and particle drag coefficient. The numerical results show that the separation efficiency increased with injected particle size increase. The separation efficiency is found to increase with increasing Reynolds number. For the effect of drag force, C_D, in porous media, numerical results show that for C_D<10 and C_D>100, the separation efficiency is not affected by drag coefficient in the range of drag coefficient from 10 to 100, and the separation efficiency significantly depends on the Reynolds number.     

滚动状态下轮胎漏气过程的有限元模拟

在考虑轮胎与轮辋及地面接触的情况下,借助ABAQUS有限元分析软件,建立了轮胎的平面轴对称模型和三维有限元分析模型。首先,利用平面模型分析了轮胎与轮辋的装配过程和充气过程;然后,利用轴对称到三维的分析方法,分析了轮胎在垂直载荷作用下的接地问题和在低速滚动下轮胎的漏气过程。给出了轮胎与地面接触界面上的压力分布;分析了在不同时刻漏气后轮胎的变形情况,并预测了漏气过程中轮胎下沉量与时间的关系。     

Finite element simulation for coffee (Coffea arabica) drying

This paper describes moisture diffusivity, shrinkage, equilibrium moisture content and finite element simulated drying of coffee. The moisture diffusivities in different components of parchment coffee were determined by minimizing the sum of square of deviations between the predicted and the experimental values of moisture contents during thin layer drying under controlled conditions of drying air temperature and relative humidity. The drying of coffee bean and parchment was conducted in thin layers at a temperature of 40, 50 and 60 °C with relative humidity in the range of 14–25%. The mean diffusivity values of coffee bean and parchment are related to the temperatures and are expressed by Arrhenius-type equations. The moisture diffusivities of parchment are lower than those of the coffee bean. The shrinkage of coffee bean derived from experiments is expressed as a function of moisture reduction. GAB model is sufficient for the prediction for sorption isotherm of parchment coffee and the parameters of the GAB model are a function of temperature and it is expressed by Arrhenius-type equations. Sensory evaluation of the coffee dried at 40, 50 and 60 °C shows that the overall acceptance by coffee cupping test and the concentration of caffeine is within the acceptable limit. A two-dimensional finite element model was developed for simulate moisture diffusion during drying process of parchment coffee. The finite element model was programmed in Compaq Visual FORTRAN version 6.5. The model simulates the moisture contents in different components of parchment coffee well and it provides a better understanding of the transport processes in the different components of the parchment coffee.     

环形D模机头流道有限元数值模拟

通过有限元分析软件POLYFLOW建立了环形口模机头的三维等温流场模型.在改变机头流道结构参数以及工艺条件的情况下,对流道的压力场、黏度场及翦切场进行了研究.模拟的数字结果显示,随着口模间隙的增大,流道内的压力场减弱并随着间隙的增大而迅速降低,容易导致聚丙烯在机头内提前发泡.     

环形口模机头流道有限元数值模拟

通过有限元分析软件POLYFLOW建立了环形口模机头的三维等温流场模型。在改变机头流道结构参数以及工艺条件的情况下,对流道的压力场、黏度场及剪切场进行了研究。模拟的数字结果显示,随着口模间隙的增大,流道内的压力场减弱并随着间隙的增大而迅速降低,容易导致聚丙烯在机头内提前发泡。     

Material removal mechanism and grinding force modelling of ultrasonic vibration assisted grinding for SiC ceramics

In this paper, a varied-depth nano-scratch test of single grain is carried out on a nano indentation system. The critical depth of the elastic-plastic transition for SiC ceramics is 7.27 nm, as calculated by Hertz contact theory, and the critical depth of the brittle-to-ductile transition is 76.304 nm, as measured by AFM and SEM. Based on the varied-depth nano scratch test and the grain trajectory of ultrasonic vibration assisted grinding (UVAG), a theoretical model of the normal grinding force is acquired using the material removal in unit time as a bridge. The single factor experiment illustrates that the grinding force increases with the increase of the grinding depth, feed rate, and amplitude, while it decreases with the increase of the spindle speed. The contrast experiment results show that UVAG is beneficial for improving the surface quality and reducing the subsurface damage depth compared with common grinding (CG). A four-level and four-factor orthogonal experiment is designed, on the basis of which theoretical model of the normal grinding force for SiC ceramics is obtained using genetic algorithm. The tangential grinding force is obtained from the normal grinding force using the least square method. The experimental results show that the theoretical model is reliable.     

复合材料电缆支架结构强度的有限元仿真计算

介绍了复合材料电缆支架的应用背景,基于使用现场的实际受力工况,利用ABAQUS分析软件,对复合材料电缆支架的经典三托臂结构进行了静态有限元仿真计算,并进行了各种工况下的实验室测试。3种不同受力状态下的应力应变计算结果和实验室测试结果表明,该结构设计能够满足在静态力作用下的材料强度要求。     

Finite element simulation of geogrid manufacture using large deformation elastic formulation

Abstract

An elastic model of large solid polymer deformations has been used as a basis for numerical predictions of the shapes of polyethylene geogrids. These netlike products are made by solid phase deformation at elevated temperatures of extruded sheet containing arrays of suitably shaped holes. The elastic constitutive model is based on a theory of interacting polymer chains and is implemented within the finite element package ABAQUS in both two and three dimensions. Deformations correspond to extension ratios of up to 8. Good predictions of the final shapes of the geogrid products are obtained. It is concluded that the methods used are a valuable product development tool.     

收敛流道内聚合物熔体流动的有限元模拟

利用Polyflow软件包,对收敛流道内聚合物熔体的三维流动进行了模拟,得出了压力、速度、剪切速率和延伸应变速率的分布.在此基础上,对熔体在收敛流道内的流动规律及特点进行了分析.这为流场参数的控制和机头结构的优化设计和改进提供了理论依据.     

磨削加工对陶瓷制品强度的影响

通过阐明陶瓷的磨削机理,探讨在陶瓷磨削过程中产生的表面／亚表面损伤及表面／亚表面裂纹、残余应力对陶瓷材料强度的影响,提出了减小表面／亚表面损伤,提高陶瓷制品强度的措施。     

Preparation of ceramics with straight and uniform-sized channels

Firing of alumina powder-carbon fiber compacts in air at 1500–1600°C gave alumina ceramics with straight channels of uniform diameter. The diameter could be controlled by the size of carbon fiber.     

石英陶瓷比磨削能正交试验研究

磨削是陶瓷材料最常用的加工方法,选择合理的工艺参数,降低加工成本是陶瓷磨削加工研究的重要内容.通过大量的正交试验,研究陶瓷材料在低速下的磨削性能,优化陶瓷磨削参数,对于丰富陶瓷磨削理论,指导实际生产具有重要的现实意义.     

Finite element analysis of effect of grain orientation on the thermal conduction of h-BN ceramics

Study of thermal conduction process of ceramics by experimental and theoretical model analysis methods is complicated and non-intuitive. In this work, to analyze the influence mechanism of h-BN grain orientation on the thermal conduction of h-BN ceramics, new mesoscale finite element models considering the anisotropy in the thermal conductivity of h-BN grain were established based on random sequential adsorption method and periodic boundary condition. And the accuracy of the finite element models was verified by theoretical model and experimental results. The heat flux vector and temperature distributions intuitively show that the orientation of h-BN grains will significantly affect the thermal conduction process of the ceramics by affecting the heat flow path. The heat flow will propagate mainly along the “thermal conducting pathways” formed by the h-BN grains when the h-BN layer direction shows small angle with the external temperature difference direction, otherwise, h-BN grains will act as barriers to the heat conduction.     

Instrumented indentation test for advanced technical ceramics

The standard for advanced technical ceramics ENV 843-4 of 1995 (Vickers, Knoop and Rockwell superficial hardness tests) was validated within the framework of the CERANORM EC-project. The paper reports on depth sensing hardness measurements done for comparison with the other hardness tests. The instrumented indentation test is a modern technique (recent issue ISO/DIS 14577) that has the potential to take into account the specific response of materials in a much better way. An evaluation has been made to establish whether the instrumented hardness technique is a appropriate method for advanced technical ceramics and offers potential for additional applications.     

换热器管子-管板液压胀接的有限元模拟

采用ANSYS/CAE软件 ,对锅炉、换热器管子 管板的液压胀接过程进行了模拟。管子与管板孔之间采用面 面接触元以模拟相互之间的间隙及管子产生塑性变形并贴紧管板孔后对管板的作用。通过本文的模拟分析 ,可获得胀接时接头处的弹 塑性应力状态及卸除胀接压力后管子与管板之间的残余接触压力。值得注意的是此接触压力沿管板厚度方向分布是不均匀的 ;在管孔槽处会出现较高的数值 ;在管板内侧处 ,管子的过渡区会出现较大的残余拉应力     

Finite element analysis of fracture behavior in ceramics: Prediction of strength distribution using microstructural features

The estimation of the strength scatter caused by internal defects is necessary in analyzing a reliable design of advanced ceramic components. In this study, we proposed a finite element analysis methodology to predict the stochastic fracture behavior of ceramics based on the microstructural features obtained by the scanning electron microscopy and X-ray computed tomography. Here, the two- and three-dimensional distribution microstructural data are approximated by various probability density functions and are reflected in the dispersion of parameters of the damage model via a fracture mechanics model. We then applied the proposed method to alumina fine ceramics sintered at three different temperatures, and performed the three-point bending test. Furthermore, the numerically created Weibull distributions were compared with those obtained experimentally. Our analysis results confirm that the proposed method can reasonably predict the strength scatter in ceramics.