Reliability-based design optimization using a moment method and a kriging metamodel

Reliability-based design optimization (RBDO) has been used for optimizing engineering systems with uncertainties in design variables and system parameters. RBDO involves reliability analysis, which requires a large amount of computational effort, so it is important to select an efficient method for reliability analysis. Of the many methods for reliability analysis, a moment method, which is called the fourth moment method, is known to be less expensive for moderate size problems and requires neither iteration nor the computation of derivatives. Despite these advantages, previous research on RBDO has been mainly based on the first-order reliability method and relatively little attention has been paid to moment-based RBDO. This article considers difficulties in implementing the moment method into RBDO; they are solved using a kriging metamodel with an active constraint strategy. Three numerical examples are tested and the results show that the proposed method is efficient and accurate.     

利用产品模型与过程模型的集成进行产品开发

建立过程链和过程网络系统在工业界变得越来越重要。计算机的始终支持，尤其在产品形成的范围内，具有特别的意义。建立过程链需要按一定方法进行的计划，或者说是以产品模型和过程模型的集成为基础的方法。     

产品可装配性评价系统建模及装配优化的研究

面向装配的设计(DFA)的研究和实践，对实施并行工程具有重要的意义，目前得到了广泛的重视。笔者依据将可装配性评价系统做为一个模块集成到整个虚拟装配支持系统中去的思路。从系统工程的观点出发，以装配单元为研究对象，提出并构造了可装配性评价的指标体系，建立了可装配性评价系统模型，并探讨了最优装配方式的求解策略和方法。     

基于代理模型和改进遗传算法的注塑翘曲优化

提出一种最小化制品翘曲的注塑工艺参数优化集成方法.以空调柜机顶盖注塑制品开发为例,该方法使用Moldflow软件分析制品的翘曲变形,运用田口方法确定与制品翘曲量密切相关的工艺因素,然后采用响应曲面法(RSM)和改进的精英保留自适应遗传算法(EAGA)相结合的方法,建立主要影响工艺参数与制品翘曲量之间的关系模型,通过对模型寻优以实现对制品翘曲的优化.该方法的适用性在制品的实际生产中得到了验证.     

考虑众筹成功率的产品众筹定价策略研究

产品众筹作为企业创新产品的重要融资方式越来越受到关注。本文考虑众筹成功率时的产品众筹定价策略,构建了众筹阶段和正式销售阶段的两阶段定价决策模型,得到了产品众筹的最优定价策略。研究发现随着众筹成功率提高,越来越多消费者会选择在众筹阶段进行产品购买。通过数值算例分析可知产品众筹的最优定价随着众筹成功率和团体福利的增大而增大,随着市场利率的增大而减小。研究结论为企业产品众筹的顺利开展提供可行性建议。     

企业在社会偏好度下的产品线延伸策略

基于Hotelling模型,讨论企业在无社会偏好和具有社会偏好的情况下产品线延伸策略的选择问题。研究企业在无社会偏好和具有社会偏好时不同产品线延伸策略下的利润和定价策略,以及面临低质竞争者时企业的产品线延伸策略。结果表明,企业在无社会偏好度时,向下延伸产品线会产生挤出效应;而企业具有社会偏好后,企业生产母产品质量较高时,向下延伸产品线则会吸引竞争者进入市场。当企业具有社会偏好时,企业产品线的最优延伸策略与母产品的质量有关。     

军事冲突中战术欺骗的一个优化模型

军事冲突中实施战术欺骗已成为信息战的一个重要手段．基于军事冲突中战术欺骗所要达到的目标以及欺骗手段的资源约束和效果影响，建立了一个使军事欺骗总体效能达到最大的战术欺骗优化模型．给出的一个应用例子说明了该模型和方法的可行性．     

改进的质量功能配置在质量成本优化分析上的应用

在改进型的质量功能配置工具中,增加了质量保证成本和质量损失成本两个主要的评价指标,修正了市场竞争评价指数和技术竞争评价指数,并引入了层次分析法,对定性决策因素给以定量的测度权重.根据质量保证成本与技术重要度的关系,以及质量损失成本对质量需求的影响,提出了适合设计阶段的质量成本优化分析方法.最后的应用结果表明,利用改进型的质量功能配置工具进行质量成本分析是有效的.     

A novel algorithm using an orthotropic material model for topology optimization

This article presents a novel algorithm for topology optimization using an orthotropic material model. Based on the virtual work principle, mathematical formulations for effective orthotropic material properties of an element containing two materials are derived. An algorithm is developed for structural topology optimization using four orthotropic material properties, instead of one density or area ratio, in each element as design variables. As an illustrative example, minimum compliance problems for linear and nonlinear structures are solved using the present algorithm in conjunction with the moving iso-surface threshold method. The present numerical results reveal that: (1) chequerboards and single-node connections are not present even without filtering; (2) final topologies do not contain large grey areas even using a unity penalty factor; and (3) the well-known numerical issues caused by low-density material when considering geometric nonlinearity are resolved by eliminating low-density elements in finite element analyses.     

企业和生产过程专用的产品模型──产品摸型是联网的产品开发过程的基础

根据面向生产过程的造型范例，提出了对产品模型的要求，发展了体系结构，讨论了具体实施的经验。     

旋转剪切式MR阻尼器的性能试验与改进滞回模型

基于Bingham力学模型,设计、制作小尺寸旋转剪切式MR阻尼器,通过数字式特斯拉计测量励磁线圈的磁感应强度.设计了阻尼器试验装置,并对此MR阻尼器进行2种激励位移、11种输入电流和4种激励频率共88种工况的力学性能试验,根据MR阻尼力—速度滞回曲线,克服Bingham模型在零速度附近不能说明阻尼力—速度的关系,引入惯性力项方法,提出了改进滞回曲线非线性力学模型.采用智能粒子群算法辨识修正的滞回力学模型参数,通过阻尼器试验数据与修正滞回力学参数值进行对比,证明此滞回模型能很好地描述MR阻尼器强非线性的动力特性.     

基于Kriging代理模型的改进EGO算法研究

 代理模型是复杂工程优化设计问题的关键技术之一．基于Kriging代理模型的EGO算法作为一种贝叶斯全局优化算法引入了EI函数来确定校正点,保证了算法的全局收敛性．首先针对原始EGO算法的不足之处,提出改进EGO算法．然后采用改进EGO算法对4个经典函数和1个工程算例进行测试,最后从算法的收敛速度和精度两方面将不同的算法进行比较．结果表明改进后的EGO算法达到原始EGO算法精度时所需迭代步数更少,与基于响应面的优化算法相比在收敛速度和精度方面更具有优势．说明该方法适应性强,具有很高的工程实用价值．     

Stress test optimization using an integrated production test and field reliability model

Numerous papers and texts have been written in the reliability literature regarding the determination of the optimum test duration for a production stress or a burn‐in test. The techniques presented have largely been based on the identification of the change point at which infant mortality has largely been removed from the units. The time‐on‐test is typically the only factor that influences this decision. Few of these models have attempted to integrate the field performance or the influence of warranty costs into this decision. This paper proposes and validates a methodology that integrates the influence of the production test failures and the field performance including their respective costs into a single unified model. The objective is to identify a production test duration that minimizes the overall cost. A Weibull model is initially developed for the production test that incorporates the failure observations in different time segments of the test based on the ability to detect latent defects in the product. A separate Weibull model is then developed for the product's performance in the field that includes the lifetime of the unit. This paper identifies how both these Weibull models can be combined into a single model including both test and field costs with the objective of minimizing the overall cost. The advantage of the proposed technique is that it does not require one to track individual units from production through to the field in order to develop an integrated test and field cost model. Copyright © 2009 John Wiley & Sons, Ltd.     

Continuum topology optimization considering uncertainties in load locations based on the cloud model

Few researchers have paid attention to designing structures in consideration of uncertainties in the loading locations, which may significantly influence the structural performance. In this work, cloud models are employed to depict the uncertainties in the loading locations. A robust algorithm is developed in the context of minimizing the expectation of the structural compliance, while conforming to a material volume constraint. To guarantee optimal solutions, sufficient cloud drops are used, which in turn leads to low efficiency. An innovative strategy is then implemented to enormously improve the computational efficiency. A modified soft-kill bi-directional evolutionary structural optimization method using derived sensitivity numbers is used to output the robust novel configurations. Several numerical examples are presented to demonstrate the effectiveness and efficiency of the proposed algorithm.     

A probabilistic solid-porous model to determine the shear strength of unsaturated soils

A probabilistic solid-porous model has been developed to determine the shear strength of unsaturated soils. The probabilistic model was built by analyzing the probability of a certain pore or group of pores of a network to fill or remain filled with water during a wetting or drying process, respectively. This model is used to determine the equivalent stress which represents the stress supported by the solid skeleton of an unsaturated soil and is related to the strength of the material. The probabilistic model is an alternative to the use of computational models and shows some important advantages. The theoretical results of the model are compared with a series of triaxial tests performed at constant suction and constant volume. These comparisons demonstrate that this model is adequate to establish the strength of unsaturated materials.     

基于内向性的产品要素设计模型

目的从东方传统文化中提取内向性特征,构建一个符合内向性的产品要素设计模型,并验证模型可靠性。方法以焦点小组法对东西方文化现象进行差异对比,用Q-sort法对典型东方传统设计进行特征提取,提出产品要素设计假设模型。用设计实践及验证性因子分析法检验模型可靠性。结论提取并验证了东方传统文化中的内向性特征,基于此特征构建出一个可靠的产品要素设计模型,该模型从造型、色彩、材料、工艺和寓意5个方面诠释了体现传统文化内向性特征的方法。     

潜艇自航模试验系统可靠性冗余优化

可靠性设计水平直接影响潜艇自航模系统设计的成败.在某潜艇自航模任务与系统构成分析的基础上,开展了某潜艇自航模系统的可靠性分析,应用多阶段任务系统可靠性模型理论建立了该系统的任务可靠性分析和计算模型,综合潜艇自航模的设计约束条件,并结合满意度的概念,建立了系统可靠性冗余优化模型且利用微粒群算法求解.示例证明了模型的可用性及可信性.     

Reliability‐based topology optimization against geometric imperfections with random threshold model

This paper develops a new reliability‐based topology optimization framework considering spatially varying geometric uncertainties. Geometric imperfections arising from manufacturing errors are modeled with a random threshold model. The projection threshold is represented by a memoryless transformation of a Gaussian random field, which is then discretized by means of the expansion optimal linear estimation. The structural response and their sensitivities are evaluated with the polynomial chaos expansion, and the accuracy of the proposed method is verified by Monte Carlo simulations. The performance measure approach is adopted to tackle the reliability constraints in the reliability‐based topology optimization problem. The optimized designs obtained with the present method are compared with the deterministic solutions and the reliability‐based design considering random variables. Numerical examples demonstrate the efficiency of the proposed method.     

Topology optimization of fluid problems using genetic algorithm assisted by the Kriging model

A non‐gradient‐based approach for topology optimization using a genetic algorithm is proposed in this paper. The genetic algorithm used in this paper is assisted by the Kriging surrogate model to reduce computational cost required for function evaluation. To validate the non‐gradient‐based topology optimization method in flow problems, this research focuses on two single‐objective optimization problems, where the objective functions are to minimize pressure loss and to maximize heat transfer of flow channels, and one multi‐objective optimization problem, which combines earlier two single‐objective optimization problems. The shape of flow channels is represented by the level set function. The pressure loss and the heat transfer performance of the channels are evaluated by the Building‐Cube Method code, which is a Cartesian‐mesh CFD solver. The proposed method resulted in an agreement with previous study in the single‐objective problems in its topology and achieved global exploration of non‐dominated solutions in the multi‐objective problems. © 2016 The Authors International Journal for Numerical Methods in Engineering Published by John Wiley & Sons Ltd     

基于序贯层次Kriging模型的微型飞行器机身结构设计优化

在基于仿真模型的工程设计优化中,采用高精度、高成本的分析模型会导致计算量大,采用低精度、低成本的分析模型会导致设计优化结果的可信度低,难以满足实际工程的要求。为了有效平衡高精度与低成本之间的矛盾关系,通过建立序贯层次Kriging模型融合高/低精度数据,采用大量低成本、低精度的样本点反映高精度分析模型的变化趋势,并采用少量高成本、高精度的样本点对低精度分析模型进行校正,以实现对优化目标的高精度预测。为了避免层次Kriging模型误差对优化结果的影响,将层次Kriging模型与遗传算法相结合,根据6σ设计准则计算每一代最优解的预测区间,具有较大预测区间的当前最优解即为新的高精度样本点。同时,在优化过程中序贯更新层次Kriging模型,提高最优解附近的层次Kriging模型的预测精度,从而保证设计结果的可靠性。将所提出的方法应用于微型飞行器机身结构的设计优化中,以验证该方法的有效性和优越性。采用具有不同单元数的网格模型分别作为低精度分析模型和高精度分析模型,利用最优拉丁超立方设计分别选取60个低精度样本点和20个高精度样本点建立初始层次Kriging模型,采用本文方法求解并与直接采用高精度仿真模型求解的结果进行比较。结果表明,所提出的方法能够有效利用高/低精度样本点处的信息,建立高精度的层次Kriging模型;本文方法仅需要少量的计算成本就能求得近似最优解,有效提高了设计效率,为类似的结构设计优化问题提供了参考。