MPI-CUDA parallelization of a finite-strip program for geometric nonlinear analysis: A hybrid approach

A finite-strip geometric nonlinear analysis is presented for elastic problems involving folded-plate structures. Compared with the standard finite-element method, its main advantages are in data preparation, program complexity, and execution time. The finite-strip method, which satisfies the von Karman plate equations in the nonlinear elastic range, leads to the coupling of all harmonics. However, coupling of series terms dramatically increases computation time in existing finite-strip sequential programs when a large number of series terms is used. The research reported in this paper combines various parallelization techniques and architectures (computing clusters and graphic processing units) with suitable programming models (MPI and CUDA) to speed up lengthy computations. In addition, a metric expressing the computational weight of input sets is presented. This metric allows computational complexity comparison of different inputs.     

发动机缸体线性与非线性对比分析

采用线性分析发动机缸体时,在螺栓接触和绑定的位置会出现明显的应力集中点,且计算得到疲劳安全因数远远低于合理值.在考虑材料非线性的基础上对发动机缸体进行非线性分析,发现在螺栓接触和绑定位置处的应力明显降低,计算得到的疲劳安全因数也趋于合理.通过汽油机缸体线性与非线性对比分析可以发现,缸体非线性模型的计算结果更合理.若要改善螺栓孔周边的安全因数,一定要保证螺栓绑定和接触位置接近实际情况,特别在2个面过渡的位置不能绑定,这样可以避免造成应力集中.     

Fracture analysis of rock mass based on 3-D nonlinear Finite Element Method

Traditional fracture analysis is based on fracture mechanics and damage mechanics. They focus on the propagation of the fracture. However, their propagation criterions are not easily applied in practice and the current analysis is limited in planar problem. This paper presents a new theory that the occurrence of the unbalanced force (derived from the Deformation Reinforcement Theory) could be the criterion of the initiation of the fracture, and the distribution area and propagation of the unbalanced force c...     

Interactive modeling of complex geometric details based on empirical mode decomposition for multi-scale 3D shapes

In this paper we develop an interactive modeling system for complex geometric details transformation based on empirical mode decomposition (EMD) on multi-scale 3D shapes. Given two models, we aim to transfer geometric details from one model to another one in an interactive manner. Taking full advantages of the multi-scale representation computed via EMD, different-scale geometric details can be transferred individually or in a concerted way, which makes our algorithm much more flexible than cut-and-paste and cloning based methods in transferring geometry details. In this process, the target surface with new transferred details could be generated by a mesh reconstruction method widely used in Laplacian surface editing. With the original positions of target surface serving as the soft constraints, the overall shape of the target model will be fully preserved. Our method can also support real-time continuous details transfer. Compared with state-of-the-art algorithms, our method provides an easier-to-use modeling tool and produces varied modeling results. We demonstrate the effectiveness of our modeling tool with various applications, such as detail transfer and enrichment, model reuse and recreation, and detail recovery for shape completion.     

An efficient facet shell element for corotational nonlinear analysis of thin and moderately thick laminated composite structures

In the present work, an efficient facet shell element for the geometrically nonlinear analysis of laminated composite structures using the corotational approach is developed. The facet element is developed by combining the discrete Kirchhoff-Mindlin triangular bending element (DKMT), and the optimal membrane triangular element (OPT). The membrane-bending coupling effect of composite laminates is incorporated in the formulation, and inconsistent stress stiffness matrix is formulated. Using corotational formulation and the proposed facet element, some example laminated composite structures with geometric nonlinearity are analyzed, and the results are compared with those found using other facet elements.     

Integration of Hough Transform of lines and planes in the framework of conformal geometric algebra for 2D and 3D robot vision

This paper presents the application of 2D and 3D Hough Transforms together with conformal geometric algebra to build 3D geometric maps using the geometric entities of lines and planes. Among several existing techniques for robot self-localization, a new approach is proposed for map matching in the Hough domain. The geometric Hough representation is formulated in such a way that one can easily relate it to the conformal geometric algebra framework; thus, the detected lines and planes can be used for algebra-of-incidence computations to find geometric constraints, useful when perceiving special configurations in 3D visual space for exploration, navigation, relocation and obstacle avoidance. We believe that this work is very useful for 2D and 3D geometric pattern recognition in robot vision tasks.     

Free-vibration analysis of arches based on the hybrid-mixed formulation with consistent quadratic stress functions

The well-known two-node hybrid-mixed element with linear displacement interpolation functions and constant stress resultant functions proposed by Saleeb yields locking-free results in static analysis but shows unsatisfactory results in vibration analysis of arches. In this study, we investigate the role of higher-order interpolation functions and consistent stress resultant functions in developing an effective two-node hybrid-mixed finite element for free-vibration analysis of arches with a rectangular cross-section. The present thick element considering shear deformation is based on the Hellinger–Reissner variational principle and introduces additional nodeless degrees of freedom for displacement field interpolation in order to enhance substantially the numerical accuracy especially in predicting high vibration modes. In the performance evaluation of the present hybrid-mixed element, we examine the effect of the nodeless internal displacement functions, the field-consistent stress resultant parameters, the approximation of compliance matrix, and the shear correction factor in curved beam vibrations. Several numerical examples confirm the validity of the present element and also illustrate the dynamic characteristics of arches depending on the curvature, aspect ratio and boundary conditions, etc.     

基于有限元分析的ICF靶半自动装配系统的微夹钳设计

根据惯性约束聚变(ICF)靶零件的特点,确定用于ICF靶半自动装配系统微夹钳的技术指标,并完成其结构设计.该微夹钳采用柔性铰链机构和压电陶瓷驱动,可根据需要更换不同形状和开口距离的夹口,以适应夹持不同靶零件.以压电陶瓷的2种极限参数为载荷,分析了微夹钳的张合量、应力分布、应变量,并采用非线性接触分析对夹持力和夹持效果进...     

Predicting and evaluating the post-assembly shape of thin-walled components via 3D laser digitization and FEA simulation of the assembly process

Three-dimensional (3D) laser digitization has become a critical research field and a widely used technique for product quality inspection in the manufacturing and medical industries during the last decade. One common application of this technology is to analyze whether the final shape of an assembly component fulfills the designer’s geometric specifications. This task is currently performed by digitizing the component’s surface after mounting it into its final assembly or on a special testing frame. In order to speed up this process a new computational method is proposed for inspecting the final shape of an assembly component by virtually mounting it into the assembly, without the physical assembling process taking place. The developed computational method employs laser digitization to measure the initial shape of the assembly component and then finite element analysis (FEA) to predict its post-assembly shape. First, a laser-digitized dense mesh is smoothed and decimated to make it suitable for FEA. Material properties of the component, if not available, are then determined by a calibration process, and specific displacement boundary conditions are applied to reproduce the assembly process. After FEA is executed, the quality of the simulated post-assembly shape is checked using visualization tools such as light-reflection patterns and contour plots of the distance between the computed geometry and the target computer-aided design (CAD) geometry. Moreover, the accuracy of the proposed method is validated by comparing the simulated post-assembly shape with the actual post-assembly shape measured after physically assembling the component. Experiments show that the average distance between simulated shape and actual shape varies from 0.3 mm to 0.6 mm for objects with a characteristic size of a half meter, and that the isophotes and height fields of reflection (HFR) based indices are reduced up to 50%. The proposed method can thus predict the final shape of an assembled component well without assembling it, reducing the time and the cost of product quality inspection.     

基于刚体运动与弹性运动的机械系统动力学建模研究

讨论了具有刚体运动与柔性变形的机械系统的动力学建模,将刚体自由度与弹性变形自由度看作广义坐标,利用有限元法对具有刚性运动与弹性变形的机械系统的运动与变形进行了描述,得到了以刚体位移与弹性变形位移表示的单元的广义惯性力;从应力应变入手,得到了表示单元弹性变形与几何非线性变形的结构刚度矩阵与几何非线性刚度矩阵,使用Kane方程推导了弹性连杆机构的单元运动方程,这种建模方法,可以使用在任意结构的机械系统。     

A numerical algorithm for computation modelling of 3D nonlinear wave equations based on exponential modified cubic B-spline differential quadrature method

In this paper, the authors proposed a method based on exponential modified cubic B-spline differential quadrature method (Expo-MCB-DQM) for the numerical simulation of three dimensional (3D) nonlinear wave equations subject to appropriate initial and boundary conditions. This work extends the idea of Tamsir et al. [An algorithm based on exponential modified cubic B-spline differential quadrature method for nonlinear Burgers’ equation, Appl. Math. Comput. 290 (2016), pp. 111–124] for 3D nonlinear wave type problems. Expo-MCB-DQM transforms the 3D nonlinear wave equation into a system of ordinary differential equations (ODEs). To solve the resulting system of ODEs, an optimal five stage and fourth-order strong stability preserving Runge–Kutta (SSP-RK54) scheme is used. Stability analysis of the proposed method is also discussed and found that the method is conditionally stable. Four test problems are considered in order to demonstrate the accuracy and efficiency of the algorithm.     

结合非线性频谱与核主元分析的复杂系统故障诊断方法

传统非线性频谱分析方法对复杂系统进行故障诊断时,求解出的非线性频谱数据量庞大,不便于直接用于故障检测与分类识别.本文提出了一种非线性频谱特征与核主元分析(KPCA)结合的故障诊断方法,首先通过最小二乘算法估计出前3阶Volterra时域核,由多维傅立叶变换求取出广义频率响应函数,然后利用KPCA方法对谱数据进行压缩与提取谱特征,最后利用多分类最小二乘支持向量机进行多故障检测与识别.考虑到频谱数据具有非线性的特点,KPCA中的核函数选用由多项式函数与径向基函数构成的混合核函数,兼顾了局部特性与全局特性.论文基于非线性频谱数据,给出了核主元模型建立与在线故障诊断的具体算法.对非线性模拟电路和数控机床伺服传动系统进行了仿真实验,结果表明本文方法能够大幅度降低频谱数据维数,故障识别率高,是一种实用的故障诊断方法.     

An adaptive method for the determination of the order of element for acquiring the desired accuracy in 3D elastostatic FEM analysis

An adaptive method for the determination of the order of element (or element order) was developed for the finite element analysis of 3D elastostatic problems. Here the order of element means the order of polynomial function, which interpolates the displacement distribution in the element. This method was based on acquiring the desired accuracy for each finite element. From the numerical experiments, the relationship ξ=k(1/p)^β was deduced, where ξ is the error of the result of the finite element analysis relative to the exact value, p is the order of element, and k and β are constants. Applying this relationship to the two results of computations with different orders of element, the order of element for the third computation was deduced. A computer program using this adaptive determination method for the order of element was developed and applied to several 3D elastostatic problems of various shapes. The usefulness of the method was illustrated by these application results.     

Coupled model for the non-linear analysis of anisotropic sections subjected to general 3D loading. Part 1: Theoretical formulation

A numerical model for the coupled analysis of arbitrary shaped cross sections made of heterogeneous-anisotropic materials under 3D combined loading is formulated. The theory is derived entirely from equilibrium considerations and based on the superposition of the 3D section’s distortion and the traditional plane section hypothesis. 3D stresses and strains fields are obtained as well as a section stiffness matrix reflecting coupling effects between normal and tangential forces due to material anisotropy. Traditional generalized strains and stresses are maintained as input and output variables. The proposed model is suitable as a constitutive law for frame elements in the analysis of complete structures.     

Coupled model for the nonlinear analysis of sections made of anisotropic materials, subjected to general 3D loading. Part 2: Implementation and validation

A numerical model for the coupled analysis of cross-sections made of anisotropic materials under general combined loading was formulated in an accompanying paper (1). In this paper, additional aspects concerning its implementation and the scheme for nonlinear analysis are discussed. The model is validated by analyzing several isotropic and anisotropic elastic problems; excellent accuracy was obtained compared to closed-form solutions. Further, the case of a RC section presenting crack-induced anisotropy is investigated. The capability of the model to capture interactions between tangent and normal forces is proved. The conclusion drawn is that the developed model is a suitable sectional constitutive equation for 3D beam elements for realistic structural analysis.     

基于SQL Server和Abaqus的关节轴承数据查询与性能分析系统

该系统的研制是为方便轴承使用人员对关节轴承进行选型、数据查询和受力变形分析。简述了系统的功能特点、功能模块划分和包括关节轴承数据库的建立、多种查询方式界面的设计和通过脚本接口实现与Abaqus有限元软件集成的系统研制过程。该系统基于Visual Studio+SQL Server+Abaqus平台开发,可以实现关节轴承数据多方式查询,以及经简单的参数数据输入从而获取基于Abaqus有限元仿真分析后的关节轴承的应力分布和位移分布图。该系统具有极高的实用性,可推广运用到其他机械领域的研究开发。     

基于合成气的联供联产系统的3E分析

在Aspen Plus建模的基础上,计算了二甲醚单产系统、二甲醚与电力的联产系统、煤与天然气联供的二甲醚电力联产系统各自的热效率和(火用)变化情况,通过分析比较,二甲醚联产系统的热效率要比单产、单产系统的组合更好;(火用)用分析表明系统中化学朋转换为物理(火用)的过程是造成系统热效率差异的最重要因素。通过经济和环境的评价分析,指出投资和原料的价格是决定联供联产系统可行性的关键。在以泸州为背景的分析中,二甲醚与电力联产是符合当地实际情况的优选实施方案的结论。通过环境分析,证明了由于联产系统、联供联产系统内部的耦合作用,使得温室气体减排效果有显著提高。     

基于PANDA框架的并行有限元模态分析程序开发和应用

为提高大型结构振动分析的规模、精度和效率,基于面向对象有限元并行计算框架PANDA和高性能矩阵特征问题并行求解算法,开发出适用于大规模结构振动问题计算的并行有限元模态分析程序;在超级计算机银河YH和曙光5000A上,通过不同算例验证该程序的正确性和可靠性.以某靶室结构为研究对象演示该程序的应用,指出实际应用时需注意加速...