基于失效概率偏导数的局部与全局混合灵敏度分析

基于失效概率偏导数的局部灵敏度与矩独立的全局灵敏度定义了一种新的混合灵敏度指标,该灵敏度指标不仅继承了传统的矩独立灵敏度的优点,而且反映了矩独立灵敏度和基于方差的灵敏度之间的内在联系。针对该矩独立的混合灵敏度指标计算量大的问题,该文首先将其转化为基于方差的混合灵敏度指标,然后利用能够高效计算条件矩的态相关参数(SDP)法进行求解。为了进一步提高计算效率,该文建立了基于重要抽样和截断重要抽样的SDP方法。算例结果验证了该文所提指标的合理性及所提方法的准确性。方法方法     

基于分数阶Wigner分布的机械故障诊断方法研究

为采用分数阶Wigner分布的机械故障诊断新方法,讨论了分数阶Wigner分布中最优分数阶的选择。仿真研究表明,分数阶Wigner分布优于传统的Wigner分布,分数阶Wigner分布能有效地抑制交叉项干扰。将提出的方法应用到轴承故障诊断中,实验结果验证了提出的方法的有效性。     

基于MLS-SVM的结构整体可靠度与全局灵敏度分析

全局灵敏度分析,旨在考量结构系统中各输入随机变量对输出响应不确定性及风险水平影响的重要度。它能为后续的可靠度评估、故障诊断、系统设计、预测及优化等提供重要参考。尽管各类全局灵敏度分析方法不断涌现,但高维复杂结构(如风机叶片结构)灵敏度分析仍是目前的难题。该文针对空间分割全局灵敏度分析方法的三种可能计算形式及最优分割方案展开研究,通过标准算例分析和误差理论推导,提出能充分利用样本信息、有效减轻计算负担的求解形式及分割方案,并将其应用于风机叶片极限载荷工况下的全局灵敏度分析中,同时为未来设计更为高效、经济和可靠的风机结构提供参考。

     

基于全局灵敏度分析的某自动装填机构轻量化设计

针对某自动装填机构轻量化设计中出现参数多、模型计算量大等问题,提出将全局灵敏度分析与代理模型技术相结合的优化策略。通过基于Morris轨迹的全局灵敏度分析从32个系统参数中确定14个关键参数,基于拉丁超立方采样技术及径向基函数神经网络技术(Radial basis function neural networks, RBF NN)建立系统响应关于关键参数的代理模型,用多岛遗传算法对系统参数进行优化求解,致机构重量下降21.8%。数值检验结果表明仅含关键参数的代理模型预测精度较高,证明该方法在多参数复杂系统结构轻量化设计中的有效性。     

基于线性化Nataf变换的一次可靠度方法

首先引入等概率边缘变换的基本原理,证明了常用的Rackwitz-Fiessler变换是等概率边缘变换的一次近似形式,将当量正态化原理和线性变换相结合,提出了扩展的Rackwitz-Fiessler变换,并指出其存在的缺点。然后针对Nataf变换的非线性特征,提出了线性化Nataf变换,并将该变换与改进的HLRF算法相结合,给出了基于线性化Nataf变换和iHLRF算法的一次可靠度方法。将Nataf变换、线性化Nataf变换和扩展的Rackwitz-Fiessler变换通过算例进行了对比分析,结果表明:采用线性化Nataf变换的结构可靠度分析结果收敛于采用Nataf变换的计算结果,而采用扩展的Rackwitz-Fiessler变换的计算结果则有较大的误差。     

基于声辐射模态模型求解声功率灵敏度

声功率灵敏度分析揭示了结构振动引起的辐射声功率与结构设计变量之间的关系。通过利用声辐射模态模型来处理声辐射环节,利用有限元振动模型来处理结构振动环节,从而提出一种新的声功率灵敏度求解方法。在带障板的加筋板声辐射模型中,采用较常用的瑞利积分模型处理辐射环节的方法对其进行了验证。最终验证了这种方法的可行性。     

一种用子结构求解特征灵敏度的新方法

提出了一种利用子结构在p=p0处的固定界面主模态和约束模态作为Ritz基综合出非亏损对称系统的特征灵敏度的方法.与其它子结构灵敏度综合方法相比,该方法不需要对子结构的约束模态以及固定界面主模态作一阶或二阶灵敏度分析,只要有子结构的约束模态和固定界面主模态就可以得到整体结构的灵敏度.算例表明了该方法的有效性.     

基于分数阶Fourier变换的经验模式分解方法研究

在分析了经验模式分解(EMD)及分数阶Fourier变换的基础上,提出了一种基于分数阶Fourier变换的经验模式分解方法,并且深入探讨了该方法的分解特性.对仿真和实际振动信号的分析结果表明,对直接采用经验模式分解分析结果不够明确的信号,基于分数阶Fourier变换的经验模式分解方法对信号进行分析是比较有效的方法.     

基于分数阶功率谱熵的未知水声脉冲信号检测方法

水声侦察的核心问题是在无先验知识条件下捕获其他平台发射的脉冲信号,单频(Continuous Wave,CW)信号和调频(Frequency Modulation,FM)信号是常用的水声探测脉冲.功率谱熵算法能有效检测低信噪比的CW信号,但对FM信号性能不佳,分数阶傅里叶变换(Fractional Fourier Tr...     

模糊分布参数的全局灵敏度分析新方法

为合理度量随机输入变量分布参数的模糊性对输出性能统计特征的影响,提出了模糊分布参数的全局灵敏度效应指标,并研究了指标的高效求解方法。首先,分析了不确定性从模糊分布参数至模型输出响应统计特征的传递机理,以输出性能期望响应为例,利用输出均值的无条件隶属函数与给定模糊分布参数取值条件下的隶属函数的平均差异来度量模糊分布参数的影响,建立了模糊分布参数的全局灵敏度效应指标。其次,为减少所提指标的计算成本、提高计算效率,采用了扩展蒙特卡罗模拟法(EMCS)来估算输入变量分布参数与模型输出响应统计特征的函数关系。最后通过对算例的计算,验证该文所提方法的准确性和高效性。     

An efficient method for estimating global sensitivity indices

An efficient method is proposed to estimate the first‐order global sensitivity indices based on failure probability and variance by using maximum entropy theory and Nataf transformation. The computational cost of this proposed method is quite small, and the proposed method can efficiently overcome the ‘dimensional curse’ due to dimensional reduction technique. Ideas for the estimation of higher‐order sensitivity indices are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Moment‐independent regional sensitivity analysis of complicated models with great efficiency

Moment‐independent regional sensitivity analysis (RSA) is a very useful guide tool for assessing the effect of a specific range of an individual input on the uncertainty of model output, while large computational burden is involved to perform RSA, which would certainty lead to the limitation of engineering application. Main tasks for performing RSA are to estimate the probability density function (PDF) of model output and the joint PDF of model output and the input variable by some certain smart techniques. Firstly, a method based on the concepts of maximum entropy, fractional moment and sparse grid integration is utilized to estimate the PDF of the model output. Secondly, Nataf transformation is applied to obtain the joint PDF of model output and the input variable. Finally, according to an integral transformation, those regional sensitivity indices can be easily computed by a Monte Carlo procedure without extra function evaluations. Because all the PDFs can be estimated with great efficiency, and only a small amount of function evaluations are involved in the whole process, the proposed method can greatly decrease the computational burden. Several examples with explicit or implicit input–output relations are introduced to demonstrate the accuracy and efficiency of the proposed method. Copyright © 2015 John Wiley & Sons, Ltd.     

Time-varying reliability method based on linearized Nataf transform

In actual engineering, material properties, load effects, and other factors of mechanical structures change due to long-term use. In order to understand the operation of a mechanical structure in real time, it is crucial to obtain the dynamic trajectory of its reliability. Considering the time variability of a mechanical structure over time, uncertain random variables are introduced to express the uncertainty of various parameters of structures, and the Wiener process is used to describe the strength degradation process of structures so as to solve the calculation problem of time-varying reliability of mechanical structures. Based on the advanced first-order and second moment method (AFOSM), the proposed linearized Nataf change is used to complete the transformation from related nonnormal variables to independent standard normal variables in order to simplify the calculation process of reliability solution and solve the reliability calculation problem of random parameters subjected to arbitrary distribution. The deduced random variable sensitivity factor indicates the degree of influence of different random variables on the reliability of the mechanical structure, providing a theoretical basis for the optimal design and maintenance of a mechanical structure. The proposed method is analyzed using the cantilever beam and compared with the nonlinear Nataf transform and verified by the Monte Carlo simulation results. The results show that the proposed method can effectively solve the reliability sensitivity problem of structural system strength degradation.     

工程结构整体可靠性分析研究进展

结构整体可靠度评估一直以来是结构可靠度领域研究的热点与难点。该文将结构整体可靠度分类,并给出其对应功能函数的统一描述;结合提出的有效维度两步分析法和共轭无迹变换法,发展了改进统计矩点估计法;结合最大熵原理和改进统计矩点估计法,提出了适用于两类结构整体可靠度的统一分析方法;通过2个数值算例对该文方法进行了验证。算例分析结果表明：同一精度水平下,该文方法的计算效率较传统的三变量降维近似统计矩点估计法高2.3倍~2.6倍;该文方法具有高的精度水平,其最大相对误差低于2%,适用于结构整体可靠度评估。     

Global sensitivity analysis for fuzzy inputs based on the decomposition of fuzzy output entropy

To analyse the component of fuzzy output entropy, a decomposition method of fuzzy output entropy is first presented. After the decomposition of fuzzy output entropy, the total fuzzy output entropy can be expressed as the sum of the component fuzzy entropy contributed by fuzzy inputs. Based on the decomposition of fuzzy output entropy, a new global sensitivity analysis model is established for measuring the effects of uncertainties of fuzzy inputs on the output. The global sensitivity analysis model can not only tell the importance of fuzzy inputs but also simultaneously reflect the structural composition of the response function to a certain degree. Several examples illustrate the validity of the proposed global sensitivity analysis, which is a significant reference in engineering design and optimization of structural systems.     

The identification of model effective dimensions using global sensitivity analysis

It is shown that the effective dimensions can be estimated at reasonable computational costs using variance based global sensitivity analysis. Namely, the effective dimension in the truncation sense can be found by using the Sobol' sensitivity indices for subsets of variables. The effective dimension in the superposition sense can be estimated by using the first order effects and the total Sobol' sensitivity indices. The classification of some important classes of integrable functions based on their effective dimension is proposed. It is shown that it can be used for the prediction of the QMC efficiency. Results of numerical tests verify the prediction of the developed techniques.     

Performance‐based design sensitivity analysis of steel moment frames under earthquake loading

A performance‐based design sensitivity analysis procedure for inelastic steel moment frameworks under equivalent static earthquake loading is presented in this paper. Analytical formulations defining the sensitivity of displacements to modifications in member sizes are derived based on a load‐control pushover analysis procedure. Material non‐linearity under bending moment is alone accounted. Although the formulations were derived based on continuous design variables, they are readily extended to the case of discrete design variables. A 3‐storey moment frame example illustrates the applicability and accuracy of the developed methodology. Copyright © 2005 John Wiley & Sons, Ltd.     

Comparison of global sensitivity analysis techniques and importance measures in PSA

This paper discusses application and results of global sensitivity analysis techniques to probabilistic safety assessment (PSA) models, and their comparison to importance measures. This comparison allows one to understand whether PSA elements that are important to the risk, as revealed by importance measures, are also important contributors to the model uncertainty, as revealed by global sensitivity analysis. We show that, due to epistemic dependence, uncertainty and global sensitivity analysis of PSA models must be performed at the parameter level. A difficulty arises, since standard codes produce the calculations at the basic event level. We discuss both the indirect comparison through importance measures computed for basic events, and the direct comparison performed using the differential importance measure and the Fussell–Vesely importance at the parameter level. Results are discussed for the large LLOCA sequence of the advanced test reactor PSA.     

基于灵敏度分析的结构动态载荷识别研究

对结构动态载荷反演问题进行深入研究,提出了一种基于灵敏度分析法的结构动态载荷识别时域分析技术。将结构输入动态载荷表示为一系列参数的形式,通过灵敏度迭代分析来确定相应的载荷参数,从而确定结构的动态输入载荷。在灵敏度迭代求解过程中,为减少响应测量噪声引起的影响,引入正则化求解技术来寻求满足工程要求的稳定近似解。最后提出的方法成功应用于正弦级数迭加形式的输入载荷识别,仿真结果表明灵敏度分析法在载荷识别中是有效的。