GENERALIZED CENTER METHOD FOR MULTIOBJECTIVE ENGINEERING OPTIMIZATION

This paper presents a new approach to multiobjective engineering optimization: the generalized center method (GCM). A multiobjective problem is solved by calculating the centers of a sequence of level sets. These sets comprise intersections of the original constraints and level constraints imposed on objective functions. In view of the different dimensions and conflicting nature of multiple objectives, some scaling and trade-off procedures are implemented. Several engineering optimization examples are given to demonstrate the effectiveness of the proposed method.     

STRUCTURAL OPTIMIZATION USING A NEW LOCAL APPROXIMATION METHOD

A new method for solving structural optimization problems using a local function approximation algorithm is proposed. This new algorithm, called the Generalized Convex Approximation (GCA), uses the design sensitivity information from the current and previous design points to generate a sequence of convex, separable subproblems. The paper contains the derivation of the parameters associated with the approximation and the formulation of the approximated problem. Numerical results from standard test problems solved using this method are presented. It is observed that this algorithm generates local approximations which lead to faster convergence for structural optimization problems.     

离散变量结构优化的拟满应力设计方法

本文以满应力设计思想为基础,提出了适用于离散变量结构优化设计计算的拟满应力设计方法。该方法能直接计算具有应力约束和截面尺寸约柬的离散变量结构优化设计问题,也能处理同时具有稳定性约束和位移约束的多工况、多约束、多变量的离散变量结构优化设计问题。算例结果表明,拟满应力设计方法对于离散变量结构优化计算是非常有效的。     

采用边界积分方程方法识别裂纹的一种优化算法

本文使用边界积分方程方法（ＢＥＭ）与迭代优化技术，建立了一种以静态边界位移测量为补充信息的裂纹识别方法，迭代中正问题的求解，采用了作者提出的高精度边界积分方程算法，结果表明在测量点充分、选位合理的前提下，该方法具有收敛快、识别精度好的特点     

AN OPTIMIZATION METHOD FOR THE DESIGN OF LARGE,HIGHLY CONSTRAINED COMPLEX SYSTEMS

A practical and efficient optimization method for the rational design of large, highly constrained complex systems is presented. The design of such systems is iterative and requires the repeated formulation and solution of an analysis model, followed by the formulation and solution of a redesign model. The latter constitutes an optimization problem. The versatility and efficiency of the method for solving the optimization problem is of fundamental importance for a successful implementation of any rational design procedure.

In this paper, a method is presented for solving optimization problems formulated in terms of continuous design variables. The objective function may be linear or non-linear, single or multiple. The constraints may be any mix of linear or non-linear functions, and these may be any mix of inequalities and equalities. These features permit the solution of a wide spectrum of optimization problems, ranging from the standard linear and non-linear problems to a non-linear problem with multiple objective functions (goal programming). The algorithm for implementing the method is presented in sufficient detail so that a computer program, in any computing language, can be written.     

直接确定Rayleigh阻尼系数的一种优化方法

为避免构造Rayleigh阻尼矩阵过程中选择两阶参考振动模态的任意性,提出了一种直接确定Rayleigh阻尼系数的优化求解方法。在该方法中,利用输入时程的位移反应谱和模态分析结果,以结构某一动力反应的峰值误差构造目标函数,使目标函数取最小值即可得到Rayleigh阻尼系数的优化解。随后,以一栋5层剪切型建筑的谐振反应为例,系统研究了结构动力特性、激励空间分布和频谱特性对Rayleigh阻尼系数的影响。同时,验证所提方法的精度与有效性。     

适用于支护拓扑优化的双向渐进优化方法

利用近年来发展的渐进结构优化方法(ESO)的概念,发展了适用于支护拓扑优化问题的双向渐进结构优化方法(BESO).本文方法能在优化过程中控制开孔数,有效地避免了棋盘格式的出现,提出了两个解决振荡问题的技巧.将加固后的岩体看成人工支护材料,可以把加固优化的问题转化为人工支护材料在原岩中的分布的拓扑优化问题.建立了防治底臌帮臌的准则及其敏感度,研究了均匀地基不同地应力条件给定加固量时使得底臌帮臌最小的洞室开挖支护的最优拓扑.最优设计的底臌量明显小于经验设计的底臌量,证明了方法的有效性.     

AN OPTIMIZATION METHOD TO DESIGN HYDRAULIC NETWORKS

Nonlinear programming is applied to the solution of hydraulic network problems. The significant differences between the proposed optimization method and other conventional methods are that this method can solve problems with mixed unknowns (e.g. pipe sizes, discharges and pressures), it can optimize solutions involving unknowns defined by inequalities (e.g. specifled minimum discharge and pressure values), it can handle network control problems such as required valve adjustments or in-line booster pump needs, and it may solve problems of networks with continuous discharge distribution along the pipes.     

树脂传递成型加工注射口位置的快速优化法

树脂传递成型加工工艺是一种先进复合材料加工的方法。虽然计算机数值模拟的研究已经取得了很大进步,但计算机数值模拟非常耗时间。本文中提出了一种树脂传递成型工艺注射口位置的快速优化方法。该法假设树脂首先注满离注射口近的节点,再根据溢料口的位置安排要求避免干点的出现这一点来决定溢料口位置;如果设计的溢料口数量比计算出来的必须的溢料口数量少,则会出现干点区。把干点区的面积作为罚函数加入目标函数中,目标函数的主体是从注射口到溢料口的距离。因此,笔者是在固定溢料口和注射口数量的前提下优化注射口的位置,获得注射口位置后,经过计算将获得溢料口位置。由于注射口位置是在离散的节点位置上,优化的变量是节点编号,所以优化方法采用功能很强的遗传算法来进行。针对五种模型进行了优化,优化的结果说明了本方法的可行性。     

DISCRETE-TIME MINIMAX PRODUCTION PLANNING FOR MANUFACTURING SYSTEMS

This paper deals with the production planning problem for discrete-time manufacturing systems with deteriorating items. A minimax approach is presented throughout the paper for the case where the demand is unknown. Both the cases of finite horizon and infinite horizon are discussed. Moreover, the case of production planning for manufacturing systems with failure-prone machines is also considered. For this case, a stochastic approach is used in which the states of the machines are represented by a two-state Markov process with transition rates determined by the availability of the machines. Finally, a robust control policy to take care of plant uncertainties is developed. Simulation results are also presented to show the usefulness of the approaches.     

基于并行混沌和复合形法的桁架结构形状优化

针对多工况下受应力、位移和局部稳定性约束的桁架形状优化问题,提出了基于并行混沌优化算法和复合形法的混合优化算法。该算法综合利用了并行混沌的全局搜索能力,复合形法的快速局部搜索能力和混沌细搜索。首先,利用并行混沌优化算法快速搜索到全局最优解附近,然后应用改进复合形法以并行混沌的优化解为初始复形进行搜索,提高了最优解的搜索速度,最后应用混沌细搜索策略提高最优解的精度。两个典型数值算例验证了该混合优化方法对桁架形状优化问题的有效性和稳定性。     

A TWO-LEVEL DECOMPOSITION METHOD FOR SHAPE OPTIMIZATION OF STRUCTURES

The paper proposes a two-level decomposition method for shape optimization of structures. The optimization problem is divided into two subproblems on the basis of the different effects on structural behaviour of different kinds of design variables. A minimum mass subproblem is solved to determine the sizing variables and a constraint evaluation function based on norm optimization is minimized to determine the shape variables. An efficient coupling technique is used between the subproblems to ensure very rapid and steady convergence. Numerical results are presented to demonstrate the effectiveness of the method. © 1997 by John Wiley & Sons, Ltd.     

结构可靠性优化求解的解耦融合策略

在工程结构的可靠性优化过程中,求解的效率和精度是优化方法的关键。该文提出一种针对解耦优化的融合策略。所提方法在优化迭代解耦所用的失效概率函数为前几次迭代设计点构建的局部失效概率函数的加权融合形式。在对原可靠性优化问题进行解耦后,结合序列近似优化方法进行迭代求解。相比于常规的仅使用当次局部建立的失效概率函数而言,所提融合策略最大限度利用了各次迭代中产生的信息用于优化解耦求解,能够提高失效概率函数的近似精度,从而间接达到减少迭代次数和计算量的目的。最后给出了屋架和十杆结构的可靠性优化算例,验证该文方法的正确性和可行性。     

金属预成形优化设计及凝聚函数方法

研究了金属预成形设计中的形状优化设计问题及相应的求解算法,并讨论了凝聚函数在这类问题中的应用。金属预成形设计在本质上是一类反问题,给出采用形状优化设计方法求解这类问题的数学模型,讨论了目标函数构造方法对数值计算收敛性的影响。提出采用凝聚函数将∞-范数形式的形状误差函数转化为光滑可微的目标函数,显著提高了求解以金属预成形设计为背景的优化问题的收敛性。采用流动模型描述金属材料高温下的变形过程,利用基于梯度的数学规划方法求解了金属预成形优化设计问题。数值算例验证了所提出方法的有效性。     

一种基于非概率可靠性的结构水平集拓扑优化

该文在研究水平集拓扑优化方法的基础上,对具有区间参数的不确定性结构的非概率可靠性约束进行了分析,经对有限元公式的推导、变换,提出了包涵非概率可靠度信息的拟安全系数形式,从而将非概率可靠性约束问题显式化处理,使得优化过程形式简单、便于计算,避免了复杂的迭代运算。通过对算例中数据及拓扑图形的对比研究,表明该文中模型的合理性和方法的有效性。     

变温热源不可逆布雷顿制冷循环制冷率密度优化

用有限时间热力学分析方法,制冷率密度为热力学优化目标,分析了变温热源条件下不可逆布雷顿制冷循环的性能,得到了普适的解析关系式,并由数值计算分析了压比、热导率分配以及工质和热源间热容率匹配等参数对制冷率密率的影响特点.     

声场-结构耦合系统灵敏度分析及优化设计研究

给出了低频声－结构耦合系统的有限元方程，并在此基础上提出声一结构耦合系统的包含尺寸和形状设计变量的优化设计模型，建立基于灵敏度分析求解的优化设计方法，重点推导了耦合系统的特征频率和声压级响应关于设计变量的灵敏度方程。在JIFEX软件中实现上述理论和算法，并通过灵敏度比较和优化设计的数值算例，进一步说明该研究方法对声结构耦合系统的工程设计具有实用意义。     

PREFORM DIE SHAPE DESIGN IN METAL FORMING USING AN OPTIMIZATION METHOD

An optimization algorithm for preform die shape design in metal-forming processes is developed in this paper. The preform die shapes are represented by cubic B-spline curves. The control points of the B-spline are used as the design variables. The optimization objective is to reduce the difference between the realized and desired final forging shapes. The sensitivities of the objective function with respect to the design variables are developed in detail. The numerical examples show that the optimization method and the sensitivity analysis developed in this paper are very useful and the design results are satisfactory. Importantly, the preform die shapes designed by this method are easily manufacturable and can be implemented in practical metal-forming operations. This optimization method and the sensitivity analysis can also be applied in the preform design of complex industrial metal-forming problems. © 1997 by John Wiley & Sons, Ltd.     

16MnR钢疲劳可靠性分析单随机变量模型

本文提出了采用一个随机变量描述疲劳裂纹扩展统计不确定性方法,并且通过极大似然方法和二阶矩方法进行疲劳可靠性分析。通过21个紧凑拉伸试件的疲劳试验,表明本文提出的方法满足工程中疲劳可靠性评估精度的要求。