大跨拱支预应力网壳结构的模糊优化设计研究

针对武汉长江防洪模型展示大厅采用的大跨拱支预应力网壳结构,考虑优化目标函数与约束条件的模糊性,建立了该类结构体系的模糊优化设计数学模型;求解时首先通过约束水平截集法,将模糊优化模型转化为一系列确定性优化模型;然后基于拱支预应力网壳的结构特点,将预应力构件(拉索和吊杆)截面尺寸、预应力作用取值(构件初始应变)以及非预应力构件截面尺寸等优化设计变量分别归为不同的优化级别,采用分级优化思想对确定性优化模型进行求解;最后依据结构经济性与安全性平衡的目标求出结构的最优约束水平,从而得到最优的结构设计方案,并同时确定结构的合理预应力分布,由此形成了拱支预应力网壳结构的两阶段三级模糊优化设计方法。     

导管架海洋平台可靠性模糊优化设计

建立了基于可靠度的平台模糊优化设计模型。探讨了导管架平台结构主要失效模式和平台结构期望失效费用的确定方法,对平台构件及结构体系可靠性指标进行了灵敏度分析,给出了平台结构可靠性模糊优化设计流程。以胜利油川坦北采油平台为例进行可靠性模糊优化设计,并与确定性优化设计结果进行比较,算例结果显示进行可靠性模糊优化设计是非常必要的。     

基于可靠度的导管架海洋平台结构选型模糊优化

建立以重量为目标函数的导管架海洋平台优化模型,并对一油中心平台进行结构选型优化,对经优化平台的方案分析其强度可靠性与刚度指标,对供选的四种形式平台进行目标模糊优选,优化结果显示了四桩腿型式在中型平台设计中的优势。     

基于6σ的车身噪声传递函数稳健优化设计

为提高设计稳健性,将6σ稳健优化设计引入车身噪声传递函数优化过程。将6σ质量管理、可靠性设计稳健设计相结合,考虑设计变量、约束条件目标函数在内所有不确定性信息,不仅满足优化目标函数、提高系统可靠性要求,使系统响应均方差最小化,即提高稳健性。以某型汽车为例,在汽车声固耦合有限元模型基础上采用基于试验设计的二阶多项式响应面模型,以车身总质量一阶模态频率为约束条件驾驶员耳旁声压级响应均方根值为目标函数,在基本随机变量概率特性已知情况下对车身噪声传递函数进行6σ稳健优化设计,与传统确定性优化设计相比表明该方法的有效性。     

导管架海洋平台结构模糊可靠度优化分配

本文研究了体系的可靠性指标和各单元的可靠性最优分配,针对导管架平台的特点,在考虑影响因素模糊性前提下,将系统的可靠度合理地分配到系统的各个单元和各个功能层次,使导管架海洋平台在尺寸、重量、造价等限制条件下,利用最优模糊可靠性分配模型使体系达到模糊最优可靠性分配。并对体系可靠性的求解、主要失效模式的寻找、期望失效费用的加以确定。     

抗冰导管架平台疲劳可靠性优化

疲劳破坏是海洋工程结构的一种主要破坏形式。对于渤海有冰边际油田,需要在满足冰激疲劳要求的同时考虑平台成本。该文建立了抗冰导管架疲劳可靠性优化模型,利用虚拟激励法并结合兼顾整体和局部的混合有限元模型,实现了复杂管节点冰激疲劳的快速高效分析,并利用对数正态格式计算冰激节点疲劳可靠性。渤海JZ20-2NW平台算例分析表明,通过优化设计可以在满足节点疲劳可靠性要求的同时降低结构重量,可以为冰区海洋平台设计提供参考。     

汽车动力总成悬置系统鲁棒优化算法

应用鲁棒优化设计理论,考虑设计变量的不确定性对优化设计结果的影响,建立鲁棒优化模型。以动力总成悬置系统能量解耦为目标,悬置刚度参数为设计变量,考虑设计目标的均值和标准差,建立动力总成悬置系统的鲁棒优化模型。针对粒子群算法求解容易陷入局部最优解的问题,采用混合粒子群算法对动力总成悬置系统的悬置刚度参数进行鲁棒优化,并用Monte Carlo方法进行分析,以考察设计值的变化对目标函数的影响。结果表明,优化方法可以有效提高悬置系统的鲁棒性。     

探析地震作用下的导管架海洋平台结构动力优化设计

本文分析了在地震力的作用下,导管架海洋平台的结构优化方法,通过对比发现,设计人员采用动力优化的方式,可以有效的提高导管架海洋平台结构的稳定性,设计人员要提高该结构的抗震能力,还保证导管架的刚度、强度以及稳定性,这样才能降低地震力对海洋平台结构的影响。     

基于6 的汽车发动机半主动悬置稳健性优化设计

针对一款汽车发动机控制节流孔式半主动悬置,建立其集总参数模型,通过灵敏度分析方法确定优化变量,以不同模式所处区间的力传递率最小为目标,采用遗传算法对其集总参数进行了确定性优化。考虑到加工制造误差导致的悬置性能变化,为提高产品的可靠性,采用蒙特卡洛法对确定性优化结果进行稳健性了分析,并运用6σ方法对半主动悬置进行了稳健性优化。研究结果表明:在允许的设计空间内,与确定性优化相比,基于6σ的稳健性优化设计能使半主动悬置的可靠性明显提高。     

基于模糊可靠度的SRC框架结构优化设计研究

基于"投资-效益"准则,建立SRC框架结构的优化数学模型,优化目标包括初始造价及结构失效损失期望最小化两部分。利用加权系数调整两者重要程度。为获得结构失效损失期望值计算结构失效概率;为获得接近实际的失效概率,对SRC框架结构进行模糊可靠度分析,主要内容包括:确定SRC框架结构抗震目标性能水平量化值,建立结构模糊功能函数,提出考虑模糊性Monte Carlo法。将SRC框架结构优化过程调整为含内外两层的迭代过程,外层对优化模型进行计算,内层对结构进行模糊可靠度分析。考虑优化模型中设计变量、约束条件过多、目标函数非线性程度较高等特点,提出适用于SRC框架结构的分阶段优化计算方法。通过对一榀单跨三层SRC框架结构优化设计,表明所提优化方法可获得理想、可靠的设计效果。     

随机波浪作用下海洋平台响应分析与结构优化设计

根据随机响应分析的确定性算法,提出了随机波浪作用下海洋平台结构响应灵敏度分析方法。采用虚拟激励算法,将随机响应灵敏度分析问题转化为稳态简谐响应分析,进一步求出结构随机响应的均值、方差、协方差等统计量的灵敏度。这一过程可直接利用响应分析的程序模块,避免计算振型导数的困难,具有较高的计算效率和精度。与差分法计算结果的比较验证了该方法的效率和精度。在此基础上,研究了随机波浪作用下海洋平台结构尺寸与形状优化方法。本文方法在有限元分析与优化设计软件系统JIFEX中实现,数值算例验证了算法的有效性。     

Topology optimization of thermoelastic structures using level set method

This paper describes the topology optimization of thermoelastic structures, using level set method. The objective is to minimize the mean compliance of a structure with a material volume constraint. In level set method, free boundary of a structure is considered as design variable, and it is implicitly represented via level set model. Objective function of the optimization problem is defined as a function of the shape of a structure. Sensitivity analysis based on continuum model is conducted with respect to the free boundary, which suggests the steepest descent direction. A geometric energy term is introduced to ensure smooth structural boundary. Augmented Lagrangian multiplier method is adopted to enforce volume constraint. Numerical examples are provided for 2D cases, considering design independent temperature distribution.     

An uncertain multidisciplinary design optimization method using interval convex models

This article proposes an uncertain multi-objective multidisciplinary design optimization methodology, which employs the interval model to represent the uncertainties of uncertain-but-bounded parameters. The interval number programming method is applied to transform each uncertain objective function into two deterministic objective functions, and a satisfaction degree of intervals is used to convert both the uncertain inequality and equality constraints to deterministic inequality constraints. In doing so, an unconstrained deterministic optimization problem will be constructed in association with the penalty function method. The design will be finally formulated as a nested three-loop optimization, a class of highly challenging problems in the area of engineering design optimization. An advanced hierarchical optimization scheme is developed to solve the proposed optimization problem based on the multidisciplinary feasible strategy, which is a well-studied method able to reduce the dimensions of multidisciplinary design optimization problems by using the design variables as independent optimization variables. In the hierarchical optimization system, the non-dominated sorting genetic algorithm II, sequential quadratic programming method and Gauss–Seidel iterative approach are applied to the outer, middle and inner loops of the optimization problem, respectively. Typical numerical examples are used to demonstrate the effectiveness of the proposed methodology.     

组合圆筒管的优化设计

用外缠绕玻璃纤维增强复壁钢管来代替油气田内部承高压的高强度钢管,既可节省大量的优质钢材,又能对场内集输管道起到良好的外防腐效果。本文着重研究由玻璃钢/钢组合而成的厚壁圆筒管在管内高压作用下的优化设计问题。首先利用组合管的边界条件,由弹性理论导出了平面应变状态下组合管壁内三个主应力的计算公式;然后建立了以组合管总壁厚、玻璃钢外套管壁厚和玻璃纤维缠绕角为设计变量,单位长度组合管的材料成本为目标函数以及钢管的强度约束和玻璃钢的变形限制为约束条件的优化设计数学模型,采用复形法对本问题求得了最优解。作者还用所编的电算程序计算了各种管内径,各种内压及各种钢管强度等级所对应的设计变量最佳取值,从而讨论了管内径、内压及钢管强度等级变化对优化设计变量的影响,计算实例表明,在承受相同内压作用的情况下,组合管的材料成本较单纯钢管低,组合管的重量减轻尤为明显。主题词:组合圆筒管;内压;平面应变状态;优化设计;复形法。     

Hydro energy management optimization in a deregulated electricity market

When electricity prices were regulated, hydropower optimization often considered only the inflow uncertainty. In a deregulated electricity market, price uncertainty must be also considered in addition to inflow uncertainty. This makes the operation problem more challenging due to inclusion of the objective of minimizing risk. It also makes the objective function nonlinear while the estimation of risk is problematic. For dealing with uncertainty, a set of finite scenarios of inflow or price sequences may form the evolution of information over the stages that are used in optimization algorithms. Such implicit optimization methods can be seen as an extension of deterministic optimization. A disadvantage is the number of scenarios may grow exponentially in multi-stage optimization problems, even with only a few branches at each stage. An explicit method, denoted as the Fletcher-Ponnambalam model (FP), has been recently developed for the first and second moments of the storage state distributions in terms of moments of the inflow distributions. This method provides statistical information on the nature of random behaviour of the system state variables without any discretization and hence suitable for multireservoir problems. Also not considering scenarios makes it computationally inexpensive, as there is little growth to the size of the original problem. In this paper, we introduce the price uncertainty into the FP model; our results indicate that the method could achieve optimum policy considering also the reduction of risk, using the second moment information. Our study is for medium term operations of a single reservoir. The results are compared with corresponding results from simulation and where possible, with the well-known Benders' Decomposition method (BD).     

Multi-objective optimization of fuzzy structural systems

It is recognized that there exists a vast amount of fuzzy information in both the objective and constraint functions of the optimum design of structures. Since most practical structural design problems involve several, often conflicting, objectives to be considered, a multi-objective fuzzy programming method is outlined in this work. The fuzzy constraints define a fuzzy feasible domain in the design space and each of the fuzzy objective functions defines the optimum solution by a fuzzy set of points. A method of solving a fuzzy multi-objective structural optimization problem using ordinary single-objective programming techniques is presented. The computational approach is illustrated with two numerical examples.     

Structure optimization of connection frames based on frequency sensitivity in macro-micro motion platforms

High-performance connection frames are of great significance for ultra-high acceleration and ultra-precision positioning in macro-micro motion platforms. This paper first takes the connection frame as a research object,builds a finite element model(FEM) of the natural frequency of the frame, and then verifies the correctness of this model. The frequency sensitivity method is then used to perturb the structural parameters of the FEM of the connection frame, and the sensitivities of the first-order natural frequency and mass of the corresponding structural parameters are obtained by calculation and analysis. The design variables are also determined. The natural frequency is used as the optimization objective, and the design parameters and mass of the connection frame are constrained. The structural parameters of the connecting frame are obtained through optimization, and the model is built and verified by experiments. The results show that the first-order natural frequency of the connecting frame is effectively improved by the frequency sensitivity method, avoids resonance between the connecting frame and the voice coil motor, and realizes the lightweight design of the connection frame. This research provides a reliable basis for the stable operation and ultra-precision positioning of ultra-high acceleration macro-motion platforms.     

固定式导管架平台的H2振动控制技术研究

基于H2控制原理，研究了在无法获得海洋平台精确数学模型时仍能实施有效控制的振动控制技术。通过采用一滤波器来近似随机波浪力的设计方法，解决了将H2控制原理应用于海洋平台振动控制中非高斯白噪声的输入问题。此外，为了更清晰地描述海洋平台所具有的不确定性，在建立其数学模型时，将模拟随机波浪力的噪声与模型噪声分开表示。以一典型的固定式导管架平台为数值算例，研究了该控制方法对固定式导管架平台振动的控制效果，并对系统的不确定性进行了敏感性分析。仿真结果表明，该控制方法对固定式导管架平台在随机波浪荷载作用下出现超大振动的控制是有效的，并具有一定的鲁棒性能。