一种简单高效的有限元网格优化算法及应用

针对三维有限元实体模型中网格形状优化的问题,提出了一种新的网格优化算法,并编制了基于这种算法的网格优化程序。该算法的优点是计算简单、节省机时,且网格优化效率较高,性能较为可靠。     

基于遗传算法的非线性控制系统参数优化方法

本文针对非线性控制系统参数优化问题,结合非线性控制系统理论、最优化理论及遗传算法,提出了一种新的仿真优化方法,该方法利用遗传算法来求解非线性控制系统参数优化问题,由于遗传算法是在解空间的多个区域内进行搜索,能以较大的概率跳出局部最优,因此可技巧以整体最优解。仿真结果表明,该方法是一种有效的非线性控制系统参数优化方法。     

Product configuration optimization using a multiobjective genetic algorithm

Product configuration is one of the key technologies in the environment of mass customization. Traditional product configuration technology focuses on constraints-based or knowledge-based application, which makes it very difficult to optimize design of product configuration. In this paper, an approach based on multiobjective genetic algorithm is proposed to solve the problem. Firstly, a configuration-oriented product model is discussed. A multiobjective optimization problem of product configuration according to the model is described and its mathematical formulation is designed. Secondly, a multiobjective genetic algorithm is designed for finding near Pareto or Pareto optimal set for the problem. A matrix method used to check constraint is proposed, and the coding and decoding representation of the solution are designed, then a new genetic evaluation and select mechanism is proposed. Finally, performance comparison of the proposed genetic algorithm with three other genetic algorithms is made. The result shows that the proposed genetic algorithm outperforms the other genetic algorithms in this problem.     

Tolerance design optimization of machine elements using genetic algorithm

An important problem that faces design engineers is how to assign tolerance limits. In practical applications, tolerances are most often assigned as an informal compromise between functionality, quality and manufacturing cost. Frequently, the compromise is obtained iteratively by trial and error. A more scientific approach is often desirable for better performance. In this paper, a genetic algorithm (GA) is used for the design of tolerances of machine elements to obtain the global optimal solution. The objective is to design the optimum tolerances of the individual components to achieve the required assembly tolerance, zero percentage rejection of the components and minimum cost of manufacturing. The proposed procedure using GA is described in this paper for two tolerance design optimization problems: gear train and overrunning clutch assemblies. Results are compared with conventional techniques and the performances are analyzed.     

基于进化元胞自动机的结构拓扑优化

实现元胞自动机算法自组织演化机制的关键是建立适合问题的局部规则。传统的方法是根据人们的经验或 其他算法得到的结果来建立局部规则,被称为局部间接规则。为了解决局部间接规则存在的局限性,计算量大等 缺点,提出用进化建立元胞自动机局部直接规则的方法。通过建立结构优化的多目标优化模型,用遗传算法寻求 最优的演化规则,得到适应相应问题的解。由仿真结果可见用遗传算法建立的元胞自动机局部直接规则对复杂系 统的自组织问题是很有效的。     

有限元结点编号的综合带宽优化算法

为提高有限元计算效率,减少计算数据所需存储量,提出一种新的有限元节点编号的综合带宽优化算法。即首先提出先用结点跨距或结点商,而不是结点的度,作为GPS算法层内结点的排序标准,获得更合理、更小的带宽;再通过合适的结点交换规则对带宽迭代优化,最终实现渐进式带宽优化的算法。通过对微机械陀螺的实际结点编号,验证了提出的综合带宽优化算法,对离散度大的复杂结构计算,具有后期节点编号方案再优化的优势,对提高计算效率是有效的。     

Combined finite volume and finite element method for convection-diffusion-reaction equation

A combined finite volume and finite element method is presented for solving the unsteady scalar convection-diffusion-reaction equation in two dimensions. The finite volume method is used to discretize the convection-diffusion-reaction equation. The higher-order reconstruction of unknown quantities at the cell faces is determined by Taylor’s series expansion. To arrive at an explicit scheme, the temporal derivative term is estimated by employing the idea of local expansion of unknown along the characteristics. The concept of the finite element technique is applied to determine the gradient quantities at the cell faces. Robustness and accuracy of the method are evaluated by using available analytical and numerical solutions of the two-dimensional pure-convection, convection-diffusion and convection-diffusion-reaction problems. Numerical test cases have shown that the method does not require any artificial diffusion to improve the solution stability. This paper was recommended for publication in revised form by Associate Editor Dongshin Shin Pramote Dechaumphai received his B.S. degree in Industrial Engineering from Khon-Kaen University, Thailand, in 1974, M.S. degree in Mechanical Engineering from Youngstown State University, USA in 1977, and Ph.D. in Mechanical Engineering from Old Dominion University, USA in 1982. He is currently a Professor of Mechanical Engineering at Chulalongkorn University, Bangkok, Thailand. His research interests are numerical methods, finite element method for thermal stress and computational fluid dynamics analysis. Sutthisak Phongthanapanich received his B.S. degree in Mechanical Engineering from Chiangmai University, Thailand in 1990. He then received his M.S., and Ph.D. degrees in Mechanical Engineering from Chulalongkorn University, Thailand in 2002, and 2006, respectively. He is a Lecturer of Mechanical Engineering Technology at King Mongkut’s University of Technology North Bangkok, Bangkok, Thailand. His research interests are finite element method, finite volume method, mesh generation and adaptation, and shock wave dynamics.     

基于遗传神经网络的压铸机座板结构优化设计

在对压铸机合模机构进行结构设计时,利用神经网络的非线性映射能力,通过少量样本的有限元分析结果,训练出表述结构参数间函数关系的神经网络模型,然后利用遗传算法的全局寻优性找到神经网络模型表述的目标函数的最优结构参数,从而解决结构优化设计的瓶颈和智能问题,利用这种优化设计策略,设计了压铸机合模机构座板,结果表明了该方法的高效性。     

基于有限元风机轮毂结构形状优化与模态分析

利用有限元分析方法,针对风机轮毂结构,建立形状优化分析计算的数学模型,在满足给定条件下,将使轮毂结构的质量降低到最小和结构应力分布得到改善。在此基础上,对轮毂优化前、后的结构进行了模态分析比较,得到的结果显示,结构形状优化设计不仅使轮毂的质量降低和应力分布更加合理,而且轮毂结构的抗振性也得到了改善,该优化结果现已被工程生产所采用。     

某型磁悬浮列车结构动力学有限元数值计算及优化分析

对某型磁悬浮列车的结构动力学特性进行了有限元数值计算,获得了列车结构体的动力学基本品质特性,即固有频率与振动模态.在此数值分析工作基础上,研究分析了车体结构的低频敏感部位与非敏感变量,由此建立了车体结构的优化数学模型,通过数值优化分析计算,在车体底盘梁式构件减重20%的条件下以及在车厢梁式构件减重10%的条件下,结构体固有频率特性没有明显改变,达到了保持结构基本动力学品质指标,而结构有一定幅度减重的工作目的.     

基于遗传算法的轿车轮毂轴承数值优化

为了提高设计效率和质量,优化系统性能指标,在给定的装配空间条件下满足几何和性能约束,以获得最大的疲劳寿命为目的,运用遗传算法对双列角接触球轴承结构的轿车轮毂轴承进行数值优化设计。并基于一个实际例子编制了优化程序,给出了运算结果。结果表明,遗传算法能够有效地解决离散变量全局寻优问题,全部约束得到满足并且优化设计方案在系统疲劳寿命方面显著优于当前设计方案。     

基于改进遗传算法的函数优化及其性能分析

工程应用中,常涉及到最优化问题.对很多问题进行数学建模后,都可以抽象为一个数值函数的优化问题.实践表明,遗传算法求解最优化问题的计算效率很高.提出了一种对简单遗传算法的编码方式、选择算子、交叉算子及变异算子都进行改进的算法,仿真试验表明,改进算法的函数优化计算在搜索效率和收敛速度方面都有很大提高.     

基于遗传算法的孔群加工路径优化

为提高孔群加工的效率,采用遗传算法对孔群加工空行程路径进行了优化。对遗传算法的实施过程进行了细致的描述,通过实例演示了遗传算法的孔群路径优化性能,并对遗传算法的运行效率及影响因素进行了研究。实验表明,运用遗传算法对孔群路径进行优化能提高孔群加工的效率,减小孔群加工中空行程的消耗;遗传算法运行中可以根据最佳个体的保持时间在一个代中加入活性因子,防止早熟的出现;遗传算法的各个参数对遗传算法的运行有一定的影响。选用合适的运行参数,本程序可应用于工程中,提高少批量孔加工的生产效率。     

遗传算法在函数优化问题中的应用研究

系统地论述了遗传算法在函数优化问题中的应用，提出了基于遗传算法的函数优化问题的通用框架，通过实例的分析及计算，得出较为理想的结果。     

Minimizing makespan during environmental stress screening using a genetic algorithm and an ant colony optimization

The environmental stress screening (ESS) chamber employed in a typical electronics manufacturing service (EMS) provider’s facility is used for screening products, attempting to expose defects that cannot be detected by visual inspection or electrical testing. The ESS chambers are bottleneck work centers in most of the EMS facilities. This research uses a genetic algorithm (GA) and an ant colony optimization (ACO) to solve the job-scheduling problem at the ESS chamber where the makespan of the process is minimized. The performances of the two approaches were compared against some of the first-fit (FF) techniques from the literature. Both the GA and ACO techniques produced satisfactory results up to a job size of 40. Furthermore, ACO generally requires a longer computational time, while offering more consistent solution quality.     

基于遗传算法和BP神经网络的花盘结构优化设计

综合利用有限元法、正交试验法、BP神经网络以及遗传算法对大重型数控转台的花盘结构系统进行优化研究。首先对花盘结构系统进行谐响应动力学分析,找出对结构动态特性影响最大的模态频率,并确定BP神经网络的输入变量,然后利用正交试验法和有限元分析法确定出BP神经网络样本点数据,建立反映花盘结构特性的BP神经网络模型,最后利用遗传算法对建立的BP神经网络优化。仿真结果表明,花盘第一阶固有频率提高15.5%,其自重降低9.8%。     

基于遗传算法的桁架结构动力学形状优化

针对桁架结构动力学形状优化的复杂性及其设计变量的不统一性,本文采用实数编码技术进行统一处理,并提出了基于自适应遗传算法的结构动力学形状优化方法。算例结果表明本文方法的有效性和工程适应性。     

Predicting polygonal-shaped defects during hot ring rolling using a rigid-viscoplastic finite element method

We applied a rigid-viscoplastic finite element method to investigate polygonal-shaped defects that occur during ring rolling and developed an improved analysis model with relatively fine finite elements near the roll gap to reduce the computational time, along with a scheme to minimize the volume change. We also simulated the formation of a polygonal-shaped defect during hot ring rolling of a ball bearing outer race. The results were in good qualitative agreement with actual experimental phenomena.     

有限元分析涡流效应

以一片变压器的铁心叠片即薄平板导体为模型,用有限元方法直观地表现因涡流效应而引起的磁场与电流的变化,并分析影响涡流大小的因素和减小涡流损害的方法。     

Design of interference fits via finite element method

Studies of interference fits in ring gear-wheel connections show that the traditional design method based on thick-wall cylinder theory has some limitations. Application of the finite element method (FEM) for the three-dimensional stress analysis of interference fitted connections gives more complete and accurate results than the traditional method. An improved design method utilizes two safety factors, λ_s and λ_p, providing a new approach for evaluating the quality of interference fits. A tolerancing method utilizing the I_max and I_min curves provides a quantitative guideline for interference fit design. The selective assembly method combined with the FEM-based method for interference fit design provides an effective approach to achieve more reliable interference-fitted connections and more precise assembly with lower manufacturing cost.