共查询到17条相似文献,搜索用时 203 毫秒
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将结构体系中不确定参数定义为区间变量,在随机疲劳谱分析方法的基础上,提出一种计算平稳高斯荷载作用下不确定结构疲劳损伤的新方法。该方法采用区间参数模型定义结构的不确定性,应用功率谱密度描述外荷载的随机性;利用有理级数和单位对称区间显式表达结构区间频响函数和不确定结构在平稳高斯荷载作用下的动力响应区间;根据Tovo-Benasciutti疲劳损伤预测模型,计算不确定结构在随机荷载作用下的疲劳损伤区间期望率;并可通过调整相应不确定参数的单位对称区间近似估计该不确定参数不同不确定半径的疲劳损伤区间期望率。通过数值算例,将该文提出的随机疲劳区间分析方法与顶点法进行比较,验证了该方法的准确性和适用性。 相似文献
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构建了对随机-区间混合型天线结构的有限元及可靠性分析模型,提出了一种新的处理不确定性因素的结构有限元分析方法,给出了结构保精度和保强度两工况的概率描述。同时考虑了结构的物理参数、几何参数的随机性和作用风载荷的区间性。首先将随机变量固定,利用区间因子法求得结构位移和应力响应的区间范围,然后在区间内任意点处利用随机因子法求结构响应的随机分布范围。构造了天线反射面位移响应和结构单元应力响应不确定变量的数字特征计算公式,进而得到结构各响应量的可靠性指标。对一8m口径天线结构进行了分析,分析结果表明文中所提方法具有合理性和可行性。 相似文献
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摘 要:针对区间随机桁架结构的动力特性分析,提出了一种区间随机有限元方法。当结构的物理参数和几何尺寸同时具有区间随机性时,利用区间因子法和随机因子法建立了结构的刚度矩阵和质量矩阵;从结构振动的瑞利商表达式出发,利用区间运算推导了结构动力特性区间随机变量的计算式;进而利用随机变量的矩法和代数综合法,推导出了结构特征值的数字特征的计算式。最后通过算例分析了区间随机桁架结构参数的区间随机性对其动力特性的影响,计算结果表明该方法是可行和有效的。
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基于函数的正交分解、次序正交分解与区间数学理论,推导出区间扩阶系统方程,并利用不确定性结构分析的扩阶系统方程对具有不确定性参数的结构系统进行静力分析。将不确定参数处理为有界区间数,基于有限元模型和区间结构力学矩阵的线性分解形式,通过区间扩阶系统方程和有约束的非线性优化方法,对具有区间参数的结构静力响应进行计算。通过数值算例,对区间扩阶系统方法的结果与解析结果进行对比,分析了区间扩阶系统的展开阶数和不确定度对计算结果的影响,数值结果表明了区间扩阶系统方法的可行性与有效性。 相似文献
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以工程中普遍存在的结构-声场耦合系统为研究对象,充分考虑系统本身及外载荷的不确定性,基于区间理论建立了含有非概率不确定参数的区间有限元分析方法及区间鲁棒优化模型。首先,利用区间对不确定性参数进行定量化描述,借助泰勒展式提出了求解耦合系统响应范围的区间有限元分析方法。然后,引入鲁棒优化设计的思想,基于区间序关系和区间可能度,分别建立了含区间参数目标函数和约束条件的转换模型,原区间不确定性优化问题就转化为确定性的多目标优化问题。最后通过数值算例,进一步说明了本文所建立鲁棒优化设计模型及算法的有效性。 相似文献
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针对随机智能梁结构参数的不确定性建立了其闭环控制动力响应随机模型.从结构动力响应的Duhamel积分出发,利用求解随机变量函数矩法导出了在三种情况下横向位移、转角位移和应力响应的数字特征表达式.并通过算例分析了在随机荷载作用下控制前后其物理参数、几何参数和控制力对闭环结构系统动力响应的影响.结果表明基于随机方法处理压电... 相似文献
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基于改进区间分析和频域疲劳计算方法,对参数不确定结构在平稳高斯荷载作用下的疲劳损伤进行研究,提出完全混合和简化计算两种方法。采用区间变量模型定义结构的不确定参数,功率谱密度描述外荷载的随机性;利用有理级数显式表示结构区间频响函数及在平稳高斯荷载作用下不确定结构的应力响应区间。通过数值方法验证疲劳损伤期望率关于不确定参数的单调性后,将应力响应中不确定参数的界限完全组合提出完全混合方法,准确估计参数不确定结构的疲劳损伤期望率区间;简化计算方法则将不确定参数的界限适当组合,由显式表达式近似计算结构的疲劳损伤期望率区间。算例表明,两种方法均具有较高计算精度,且大幅减少计算量。 相似文献
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Interval Finite Element Analysis using Interval Factor Method 总被引:1,自引:0,他引:1
Wei Gao 《Computational Mechanics》2007,39(6):709-717
A new method called the interval factor method for the finite element analysis of truss structures with interval parameters
is presented in this paper. The structural parameters and applied forces can be considered as interval variables by using
the interval factor method, the structural stiffness matrix can then be divided into the product of two parts corresponding
to the interval factors and the deterministic value. From the static governing equations of interval finite element method
of structures, the structural displacement and stress responses are expressed as the functions of the interval factors. The
computational expressions for lower and upper bounds, mean value and interval change ratio of structural static responses
are derived by means of the interval operations. The effect of the uncertainty of the structural parameters and applied forces
on the structural displacement and stress responses is demonstrated by truss structures. 相似文献
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The random interval response and probabilistic interval reliability of structures with a mixture of random and interval properties are studied in this paper. Structural stiffness matrix is a random interval matrix if some structural parameters and loads are modeled as random variables and the others are considered as interval variables. The perturbation-based stochastic finite element method and random interval moment method are employed to develop the expressions for the mean value and standard deviation of random interval structural displacement and stress responses. The lower bound and upper bound of the mean value and standard deviation of random interval structural responses are then determined by the quasi-Monte Carlo method. The structural reliability is not a deterministic value but an interval as the structural stress responses are random interval variables. Using a combination of the first order reliability method and interval approach, the lower and upper bounds of reliability for structural elements, series, parallel, parallel-series and series-parallel systems are investigated. Three numerical examples are used to demonstrate the effectiveness and efficiency of the proposed method. 相似文献
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Uncertain static plane stress analysis of continuous structure involving interval fields is investigated in this study. Unlike traditional interval analysis of discrete structure, the interval field is adopted to model the uncertainty, as well as the dependency between the physical locations and degrees of variability, of all interval system parameters presented in the continuous structures. By implementing the flexibility properties of some common structural elements, a new computational scheme is proposed to reformulate the uncertain static plane stress analysis with interval fields into standard mathematical programming problems. Consequently, feasible upper and lower bounds of structural responses can be effectively yet efficiently determined. In addition, the proposed method is adequate to deal with situations involving one‐dimensional and two‐dimensional interval fields, which enhances the pertinence of the proposed approach by incorporating both discrete and continuous structures. In addition, the proposed computational scheme is able to establish the realizations of the uncertain parameters causing the extreme structural responses at zero computational cost. The applicability and credibility of the established computational framework are rigorously justified by various numerical investigations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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该文提出一种求解不确定性结构模态的二阶区间优化算法,首先应用拉格朗日乘子法将带有约束条件的模态优化问题转化为非约束优化,再用区间扩展的二阶泰勒展开式近似表述不确定性结构的模态区间函数。由于其二阶常数项(海森矩阵)的计算十分繁琐,这里采用DFP方法(Davidon and Fletcher-Powell method)近似迭代计算该常数项,同时计算满足约束条件和优化目标的结构参数和参数不确定性区间。在结构重分析中采用Epsilon算法,从而在保证计算精度的同时节省了计算时间。通过算例计算进一步证明该方法对于板壳加筋不确定结构的优化是有效的。 相似文献
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This paper proposes a non-stationary random response analysis method of structures with uncertain parameters. The structural physical parameters and the input parameters are considered as random variables or interval variables. By using the pseudo-excitation method and the direct differentiation method (DDM), the analytical expression of the time-varying power spectrum and the time-varying variance of the structure response can be obtained in the framework of first order perturbation approaches. In addition, the analytical expression of the first-order and second-order partial derivative (e.g., time-varying sensitivity coefficient) for the time-varying power spectrum and the time-varying variance of the structure response expressed via the uncertainty parameters can also be determined. Based on this and the perturbation technique, the probabilistic and non-probabilistic analysis methods to calculate the upper and lower bounds of the time-varying variance of the structure response are proposed. Finally the effectiveness of the proposed method is demonstrated by numerical examples compared with the Monte Carlo solutions and the vertex solutions. 相似文献