Studies regarding simulation process to static loading of the structures obtained from polylactic acid, 3D printed

Being a relatively new process, additive manufacturing needs many studies to be able to produce parts with the required properties. The aim of the paper is to establish whether, based on the physical and mechanical properties determined by tensile testing and by applying finite element analysis (FEA), viable results can be obtained regarding the behavior of the 3D printed structures at the different, static loading. The application of FEA for the tensile testing of 3D specimens led to the results close to those obtained by the tests. The values of the results obtained by simulation are higher by up to 7.2% compared with those recorded by tests. The simulation was applied both for the printed specimens from a single material and from two materials (multi-material). Regardless of the materials used in printing and the simulation method, the results of applying FEA are close to those recorded by testing.     

Image-based extended finite element modeling of thermal barrier coatings

Further advances in Thermal Barrier Coating (TBC) design are linked with the evolution of numerical models for TBCs. The present paper, therefore, enhances the idea of a currently available FEM package (OOF) that has been designed for microstructural level simulations. The approach of Extended FEM (XFEM) is incorporated in an in-house developed program to account for the existence of cracks in TBCs; both for stress-strain analysis and for heat transfer analysis. The new XFEM program is then employed to carry out the analyses of a YSZ deposit and a multilayered TBC to predict the effective Young's moduli, the overall thermal conductivities, and to assess the fracture behavior of the coating.     

Sensitivity analysis based preform die shape design using the finite element method

This paper uses a finite element-based sensitivity analysis method to design the preform die shape for metal forming processes. The sensitivity analysis was developed using the rigid visco-plastic finite element method. The preform die shapes are represented by cubic B-spline curves. The control points or coefficients of the B-spline are used as the design variables. The optimization problem is to minimize the difference between the realized and the desired final forging shapes. The sensitivity analysis includes the sensitivities of the objective function, nodal coordinates, and nodal velocities with respect to the design variables. The remeshing procedure and the interpolation/transfer of the history/dependent parameters are considered. An adjustment of the volume loss resulting from the finite element analysis is used to make the workpiece volume consistent in each optimization iteration and improve the optimization convergence. In addition, a technique for dealing with fold-over defects during the forming simulation is employed in order to continue the optimization procedures of the preform die shape design. The method developed in this paper is used to design the preform die shape for both plane strain and axisymmetric deformations with shaped cavities. The analysis shows that satisfactory final forging shapes are obtained using the optimized preform die shapes.     

高炉铜冷却壁凝固过程数值模拟

在对铜冷却壁砂型 金属型复合铸造条件下的热态工况进行分析的基础上,利用有限元数值模拟的方法首次建立了铸型传热分析对称模型。在模型中对铸型传热系统中的对流、辐射、接触边界条件和凝固潜热进行了处理,利用有限元分析软件ANSYS,分析了紫铜冷却壁的温度场的变化。数值模拟的结果与实际生产相当吻合。     

对堆芯熔化条件下锆合金包壳腐蚀动力学有关问题的讨论

针对在堆芯熔化条件下建立铝合金包壳腐蚀动力学模型时所涉及的有关问题和已有的模型进行了讨论和评述。     

板料弯曲回弹的有限元模拟影响因素研究

阐述了板料成形数值模拟中回弹问题的研究历史和发展现状,分析了塑性弯曲加工中工件发生弯曲回弹的原因、特点及有限元模拟过程的影响因素,总结了回弹模拟的算法,从成形过程模拟和回弹计算两方面系统分析了影响回弹模拟准确性和收敛性的主要因素及改进方向,讨论了模具设计中回弹的补偿算法 ,并提出了当前控制回弹的基本方法     

Sampling average approximation method for a class of stochastic Nash equilibrium problems

We consider a class of stochastic Nash equilibrium problems (SNEP). Under some mild conditions, we reformulate the SNEP as a stochastic mixed complementarity problem (SMCP). We apply the well-known sample average approximation (SAA) method to solve the SMCP. We further introduce a semismooth Newton method to solve the SAA problems. The comprehensive convergence analysis is given as well. In addition, we demonstrate the proposed approach on a stochastic Nash equilibrium model in the wholesale gas–oil markets.     

图像处理建立混凝土有限元模型探讨

针对工程中常用的混凝土材料的不均匀特性,提出了一种基于图像处理技术建立二维混凝土有限元模型的方法.该方法综合图像处理过程中的图像增强、消除噪声和边缘检测技术建立人机对话平台,并结合网格自动划分技术建立非均匀有限元模型.通过一个实例,验证了该方法的有效性.     

Optimal blank design based on finite element method for blades of large Francis turbines

Metal pressing process that is widely used in industries has advantages over casting process for producing large Francis turbine blades from thick plates. Prior to the pressing process, blank design is firstly performed to determine flat blanks. The traditional trial and error approach is not applicable to blade design for Francis turbines that are not standard due to hydraulic characteristics of power plant sites. The rapid development of computing technology makes it possible to obtain optimal flat blanks by numerical modelling and simulation. In this paper, inverse finite element approach is investigated for blank design and an elasto-plastic model has been built using the well-known commercial software ANSYS. Numerical simulations for blade unfolding models with thick shell elements, solid elements and shell elements have given results with negligible differences. Unfolding tests with simple geometries have been carried out and the numerical results agree well with the analytical solutions. A large and thick shape of a Francis turbine blade for a hydropower plant has been successfully unfolded by inverse FE model. Sensibility analysis shows that the middle surface of the flat blank is independent of blade thickness. For ensuring the machining of the blade after the pressing process, a new contour is obtained by extending the boundary of the flat blank provided by the numerical model. This research may provide a useful tool for optimal blank design of Francis turbine blades.     

张家界机场气象预报指标诊断系统

张家界荷花机场气象预报室从业务需要出发,编制了一套指标诊断系统,应用于实际业务中,对提高预报的准确性、做好日常航空飞行的气象保障工作具有较好的指导意义。系统采用可视化编程,引进气象学诊断分析相关原理方法,使系统本身具有自动性、适用性和可再开发性等特点。