Contact search strategies for FEM simulation of the blow molding process

In this paper, the efficiency and accuracy of contact search algorithms for the blow molding simulation were discussed. In order to increase the efficiency of the contact search, we proposed and implemented three kinds of global search algorithms and compared them with two existing methods in terms of both formulation and CPU time. The proposed sorted moving box method was finally proved to be the most efficient one, without loss of stability. To increase the accuracy, a contact–tolerance–adjustable local search algorithm was also proposed. Successful simulation of the stretch blow molding process was given as an example. Copyright © 2000 John Wiley & Sons, Ltd.     

挤出中空成型机国内外的技术创新及发展趋势(三)

本文是在《塑料包装》杂志上连载的中空吹塑技术方面的文章,属连载文章的其中之一。紧接前文着重介绍了国内外知名的挤出中空成型设备生产厂家,在此基础上总结了当前适用于该行业的先进生产设计理念,阐述了行业内的技术创新。     

中空吹塑成型机三层型坯机头设计及其关键技术研究

目前,大型中空成型机的机头主要是单层机头,本文以国内外中空成型机的现状研究为基础,在中空吹塑机行业新颖性的提出了三层型坯机头的理念,在原材料的使用方面,三层型坯机头可以采用内层和外层为新料、中间层为再生料的方法,从而减低原材料的成本。此三层型坯机头中空成型机可对每层的原料百分比进行调整,以保证制品每层厚度的要求,从而达到制品的各项性能指标。     

一种地下车库空气环境数值模拟研究方法

利用某地地下车库模型，根据地下车库室内环境的特殊性建立数学模型，介绍采用计算流体力学软件FLUENT对地下车库通风时的气流组织作数值模拟仿真计算与分析，提出采用合理设置送、排风口的位置的方法来改进气流组织、加速污染物（主要是CO）排放的方案，并对其CO浓度场作进一步的模拟计算，从而为地下车库空气环境的数值模拟研究找到了一种新方法。     

Integrated FEM/BEM approach to the dynamic and acoustic analysis of plate structures

An integrated finite element/boundary element method approach to the prediction of the interior acoustic radiation of open ended box structures is presented. Dynamic response of the structure is predicted in terms of the nodal displacements under sinusoidal point force excitation using the finite element method. Theoretical results obtained in terms of frequency response functions are verified using the results from tests performed on a box structure. The interior acoustic field is then examined by the boundary element method using the boundary conditions obtained from the finite element analysis. Sound pressure levels produced inside the structure are calculated and the results are compared with the experimental measurements.     

A coupled FEM/DEM approach for hierarchical multiscale modelling of granular media

A hierarchical multiscale framework is proposed to model the mechanical behaviour of granular media. The framework employs a rigorous hierarchical coupling between the FEM and the discrete element method (DEM). To solve a BVP, the FEM is used to discretise the macroscopic geometric domain into an FEM mesh. A DEM assembly with memory of its loading history is embedded at each Gauss integration point of the mesh to serve as the representative volume element (RVE). The DEM assembly receives the global deformation at its Gauss point from the FEM as input boundary conditions and is solved to derive the required constitutive relation at the specific material point to advance the FEM computation. The DEM computation employs simple physically based contact laws in conjunction with Coulomb's friction for interparticle contacts to capture the loading‐history dependence and highly nonlinear dissipative response of a granular material. The hierarchical scheme helps to avoid the phenomenological assumptions on constitutive relation in conventional continuum modelling and retains the computational efficiency of FEM in solving large‐scale BVPs. The hierarchical structure also makes it ideal for distributed parallel computing to fully unleash its predictive power. Importantly, the framework offers rich information on the particle level with direct link to the macroscopic material response, which helps to shed lights on cross‐scale understanding of granular media. The developed framework is first benchmarked by a simulation of single‐element drained test and is then applied to the predictions of strain localisation for sand subject to monotonic biaxial compression, as well as the liquefaction and cyclic mobility of sand in cyclic simple shear tests. It is demonstrated that the proposed method may reproduce interesting experimental observations that are otherwise difficult to be captured by conventional FEM or pure DEM simulations, such as the inception of shear band under smooth symmetric boundary conditions, non‐coaxial granular response, large dilation and rotation at the edges of shear band and critical state reached within the shear band. Copyright © 2014 John Wiley & Sons, Ltd.     

Coupling BEM/TBEM and MFS for the simulation of transient conduction heat transfer

The coupling between the boundary element method (BEM)/the traction boundary element method (TBEM) and the method of fundamental solutions (MFS) is proposed for the transient analysis of conduction heat transfer in the presence of inclusions, thereby overcoming the limitations posed by each method. The full domain is divided into sub‐domains, which are modeled using the BEM/TBEM and the MFS, and the coupling of the sub‐domains is achieved by imposing the required boundary conditions. The accuracy of the proposed algorithms, using different combinations of BEM/TBEM and MFS formulations, is checked by comparing the resulting solutions against referenced solutions. The applicability of the proposed methodology is shown by simulating the thermal behavior of a solid ring incorporating a crack or a thin inclusion in its wall. The crack is assumed to have null thickness and does not allow diffusion of energy; hence, the heat fluxes are null along its boundary. The thin inclusion is modeled as filled with thermal insulating material. Copyright © 2010 John Wiley & Sons, Ltd.     

Modeling and numerical simulation of the mechanical behavior of woven SiC/SiC regarding a three-dimensional unit cell

The mechanical behavior of a two-dimensional woven SiC/SiC ceramic matrix composite (CMC) under tensile loading is modeled by regarding a three-dimensional unit cell of the composite which takes the waveness of the fiber yarns in two directions into account. The numerical evaluation of the model is accomplished by means of the finite element method (FEM). Because of the small diameter (15 μm) of the fibers in the bundles, these fibers are not considered as single entities in the finite element mesh. Instead the mesh is constructed on the yarn scale considering the fiber bundles as homogeneous with ‘fiber bundle' properties. The brittle cracking of interyarn matrix as well as transverse cracking of the fiber bundles are considered by defining a fracture criterion for these components. The increasing degradation of the fiber bundles in fiber direction during progressive loading is described by three damage variables. Damage and cracks are modeled by reducing the elastic coefficients of the finite elements. The scattering of the strength values of the single components is regarded by using Weibull distribution. Before mechanical loading, the structure is subjected to thermal loading to consider the residual thermal stresses in the structure resulting from the cooling down process after fabrication of the composite. The effect of the scattering of the strength values on the behavior of the unit cell will be examined.     

A skewed kernel approach for the simulation of shocks using SPH

A wide variety of jump discontinuities, such as shock fronts, are abound in high‐speed flows. An accurate approximation of these fronts may require higher order techniques either under mesh‐based methods or mesh‐free methods. In the latter class, the smoothed particle hydrodynamics (SPH) is becoming popular as a promising method. However, the standard approach in SPH (like any other discrete methods) can result in highly diffusive solutions because of the inevitable use of artificial viscosity to suppress numerical oscillations. On the other hand, the SPH formulation allows innovative ways to model complicated phenomena. In this paper, we introduce the novel idea of a skewed Gaussian kernel, to improve the shock capturing capability in high speed flows. Here, the standard Gaussian kernel function is modified, and its ‘shape’ is altered with a predesigned tunable skewness parameter, while the basic unity property of the kernel function is still preserved. The SPH with the proposed skewed Gaussian kernel is then applied on a number of benchmark problems in computational fluid dynamics, featuring shocks. The simulations have shown significantly better shock capture through the skewed kernel approach as against the standard techniques, with almost no increase in computational time. Copyright © 2016 John Wiley & Sons, Ltd.     

A 3D finite element approach for the coupled numerical simulation of electrochemical systems and fluid flow

A comprehensive finite element method for three‐dimensional simulations of stationary and transient electrochemical systems including all multi‐ion transport mechanisms (convection, diffusion and migration) is presented. In addition, non‐linear phenomenological electrode kinetics boundary conditions are accounted for. The governing equations form a set of coupled non‐linear partial differential equations subject to an algebraic constraint due to the electroneutrality condition. The advantage of a convective formulation of the ion‐transport equations with respect to a natural application of homogeneous flux boundary conditions is emphasized. For one of the numerical examples, an analytical solution for the coupled problem is provided, and it is demonstrated that the proposed computational approach is robust and provides accurate results. Copyright © 2011 John Wiley & Sons, Ltd.     

CFD simulation and optimization of the flow field in horizontal turbo air classifiers

This paper mainly presents a numerical study of the gas flow in horizontal turbo air classifiers. The effect of the air-inlet direction on the performance of classifier was also investigated through powder classification experiments. The simulated results show that the vertical vortex is the dominant flow in conical part of the classifier and there exists the horizontal vortex in the classifying chamber. The tangential velocity profile resembles a Rankine vortex inside the rotor cage. The vertical vortex intensity increases with increasing the inlet air velocity, while the rotor cage speed has limited effect on the control of gas pathlines in the classifying chamber. Horizontal turbo air classifiers are divided into four quadrants according to the air-inlet direction. For classifiers in quadrants I and III, a double-layer flow with opposite directions generates around the rotor cage which causes a secondary vortex. The secondary vortex is eliminated and the airflow becomes uniform in the classifier that belongs to quadrant Π or IV. The experimental results with fluidized catalytic cracking catalysts and fly ash demonstrate that cut sizes of this classifier decrease averagely by 5 μm and 2.2 μm respectively, and the classification accuracy increases by 7.5–10.3%.     

A coupled boundary/finite element method for the computation of magnetically and electrostatically levitated droplet shapes

A coupled finite element and boundary element method is developed to predict the magnetic vector and scalar potential distributions in the droplets levitated in an alternating magnetic or electrostatic field. The computational algorithm entails the application of boundary elements in the region of free space and finite elements in the droplet region, the two being coupled along the droplet–air interface. The coupled boundary and finite element scheme is further integrated with a WRM‐based algorithm to predict the free surface deformation of magnetically and electrostatically levitated droplets. Several corner treatments for the boundary and finite element coupling and their implications to free surface calculations are discussed. Detailed formulation and numerical implementation are given. Numerical results are compared with available analytical solutions whenever available. A selection of computed results is presented for mag‐ netically or electrostatically levitated droplets under both terrestrial and microgravity conditions. Copyright © 1999 John Wiley & Sons, Ltd.     

Integration of singular enrichment functions in the generalized/extended finite element method for three‐dimensional problems

A mapping method is developed to integrate weak singularities, which result from enrichment functions in the generalized/extended finite element method. The integration scheme is applicable to 2D and 3D problems including arbitrarily shaped triangles and tetrahedra. Implementation of the proposed scheme in existing codes is straightforward. Numerical examples for 2D and 3D problems demonstrate the accuracy and convergence properties of the technique. Copyright © 2008 John Wiley & Sons, Ltd.     

兖矿鲁化28000m~3/h空分设备流程和配置的选择

根据生产实际确定气体产品的技术参数,并结合国内外空分技术水平,选择新建设的28000m3/h空分设备的流程,详细介绍了精馏塔系统和换热器系统等静止设备和空压机、液体泵等运转设备的选型经验。     

天钢28000m~3/h内压缩流程空分设备配置及工艺特点

简介了天津钢铁有限公司两套28000m3/h内压缩流程空分设备的技术参数和流程,详细介绍了主要设备的配置,分析了两套空分设备具有的液体产量高、能耗低和运行安全、可靠等工艺特点。     

鲍德40000m~3/h空分设备调试及投产总结

简介了40000m3/h空分设备的工艺流程、技术参数和工艺特点,详细分析了在空分设备调试运行过程中遇到的问题及解决方法。     

福建省环境空气自动监测质量保证与质量控制现状及发展对策

分析了福建省环境空气自动监测QA／QC现状,并提出了存在问题及对策。     

A priori and a posteriori analysis of the meshless Galerkin boundary node method for three-dimensional elasticity

The meshless Galerkin boundary node method is presented in this paper for boundary-only analysis of three-dimensional elasticity problems. In this method, boundary conditions can be implemented directly and easily despite the employed moving least-squares shape functions lack the delta function property, and the resulting system matrices are symmetric and positive definite. A priori error estimates and the consequent rate of convergence are presented. A posteriori error estimates are also provided. Reliable and efficient error estimators and an efficient and convergent adaptive meshless algorithm are then derived. Numerical examples showing the efficiency of the method, confirming the theoretical properties of the error estimates, and illustrating the capability of the adaptive algorithm, are reported.     

60000m^3／h空分设备控制系统的开发应用

简介了武钢H台6000m^3／h空分设备控制系统的选型原则，详细分析了控制系统的硬件配置、软件组成、实现的基本控制功能和高级控制功能以及具体的控制方案，阐述了实际运行中存在的一些不足方面。     

60000m~3/h空分设备控制系统的开发应用

简介了武钢H台60000m3/h空分设备控制系统的选型原则,详细分析了控制系统的硬件配置、软件组成、实现的基本控制功能和高级控制功能以及具体的控制方案,阐述了实际运行中存在的一些不足方面。