共查询到20条相似文献,搜索用时 140 毫秒
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将键合图方法用于动态子结构研究,提出了一种求解多个子结构自由界面模态综合法的新方法。通过一系列物理和数学上的分析,详细推导出多个子结构自由界面模态综合法的计算过程。在本文给出的算例中,基于键合图方法的自由界面模态综合法,通过建立各个子结构的状态空间方程,计算子结构相应的特征值矩阵和振型矩阵;这些子结构在进行模态综合后,获得整体结构的特征值矩阵和振型矩阵,该结果和原来整体结构完全相同,这进一步说明了本文提出的新方法的正确性。运用本文提出的方法建立状态空间方程,在子结构的模态综合过程中,不会产生系统特征值的增失根问题,确保了子结构在综合后其整体结构模态信息的完整性。 相似文献
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基于局部模态的约束子结构模型修正法 总被引:2,自引:0,他引:2
针对局部子结构为修正对象的情况提出了约束子结构修正法,实现只利用整体结构模态中对应子结构部分的模态即可以修正子结构模型.由脉冲响应结合特征系统实现法识别出子结构的低阶模态;结合识别的模态和整体结构理论模型的高阶模态构造整体结构对应子结构位置的柔度矩阵;利用柔度矩阵的物理意义,在子结构的边界上施加数值支座,把子结构从整体结构中隔离出来成为约束子结构,同时构造出约束子结构的柔度矩阵;利用灵敏度的方法根据构造出的约束子结构柔度矩阵,优化修正约束子结构,即间接等效地修正子结构模型.通过一个平面桁架结构验证了约束子结构模型修正法的可行性与有效性,即使在5%或10%的噪声影响下,仍能得到满意的修正结果. 相似文献
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计算叶片力学特性的三维8节点非协调有限单元法 总被引:4,自引:0,他引:4
针对叶片结构几何形状复杂的特点,建立了能进行叶片力学特性分析的三维8节点非协调有限单元模型。该模型采用了几何非线性和线弹性模式,来考虑叶片径向刚度远大于弯曲刚度而引起的在不同转速下初应力对叶片的作用,能够正确反映叶片的弯曲和扭转耦合振动模态、叶片组的切向和轴向振动模态以及它的应力状态。根据质量等效和力等效的原理,导出了在非协调单元中计算单元变形能时,记入附加的内部自由度,而计算单元的动能、体积力、表面力、以及阻尼力所做的虚功时,不记入附加的内部自由度,这是不同于目前一些文献中的提法。最后,通过实例计算验证了该模型的正确性。 相似文献
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Jilin Hou Jinping Ou 《力学学报》2009,41(5):748
针对局部子结构为修正对象的情况提出了约束子结构修正法,实现只利用整体结构模态中对
应子结构部分的模态即可以修正子结构模型.
由脉冲响应结合特征系统实现法识别出子结构的低阶模态;
结合识别的模态和整体结构理论模型的高阶模态构造整体结构对应子结构位置的柔度矩
阵;利用柔度矩阵的物理意义,在子结构的边界上施加数值支座,把子结构从整体结构
中隔离出来成为约束子结构,同时构造出约束子结构的柔度矩阵;利用灵敏度的方法根
据构造出的约束子结构柔度矩阵,优化修正约束子结构,即间接等效地修正子结构模型.
通过一个平面桁架结构验证了约束子结构模型修正法的可行性与有效性,即使在5%或
10%的噪声影响下,仍能得到满意的修正结果.
关键词 模型修正,柔度矩阵,约束子结构,灵敏度,修正单元力 相似文献
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钢-混凝土组合箱梁梁段有限元法研究 总被引:1,自引:1,他引:0
组合梁界面滑移将减小组合梁刚度,增大变形,影响构件性能;剪应力沿截面横向分布不均匀,造成其弯曲正应力的横向分布呈曲线形状,即剪力滞效应;同时组合梁往往重载,具有较小的跨高比,剪切变形不可忽略.根据虚功原理,建立了同时考虑滑移效应、剪力滞及剪切变形效应的组合梁单元刚度矩阵及等效节点力向量,并在此基础上编制了组合梁梁段有限元程序.利用本文程序对现有组合梁试件的混凝土顶板应力、钢梁底板应力、跨中挠度和梁端滑移进行了计算,并将本文计算结果与解析法计算结果及试验结果进行了比较.结果表明,本文计算结果与解析法计算结果及试验结果吻合良好;同时,本文计算结果具有较好的稳定性,验证了本文计算方法的正确性.本文所建立的梁单元刚度矩阵同时考虑了剪切变形、剪力滞及滑移效应的影响,符合工程实际,为有限梁段法分析组合箱梁提供了理论基础. 相似文献
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界面连接刚度参数辨识的子结构分析法 总被引:2,自引:0,他引:2
以试验模态参数为基础,提出一种通过特征方程反问题辨识子结构界面连接刚度参数的子结构分析法。新方法以子结构动柔度矩阵特征方程为基础,建立求解界面结点内力和位移的方程,从而由子结构内部结点可测自由度上的位移用广义逆理论估计界面结点内力和位移。并通过迭代修正内部结点可测自由度上的试验值,以提高界面内力和位移的估计精度。最后通过连接子结构刚度矩阵建立的平衡方程求解相应的刚度参数。文中以太阳电池阵板间铰链副刚度参数辨识为例,将铰链副简化为两端结点各有6个自由度的弹簧连接元,考虑到自由度之间的耦合,推导了连接元的刚度矩阵。用上述方法辨识了铰链副6个自由度的刚度参数,得到满意的辨识结果。 相似文献
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The natural mode analysis of bladed disc system at an arbitrary constant rotational speed is investigated in this paper and the large deformation effect caused by the pretorsion of the blades is considered. The computational method of group theory is employed in substructure technique and equilibrium position and stress distribution of the bladed disc system in centrifugal field are obtained through simultaneous iteration, furthermore, the initial stress stiffness matrix, the large deformation stiffness matrix and the corresponding rotating natural frequencies and modal shapes are determined. Because the large deformation effect of the blades is considered and all the interface degrees of freedom between the substructures can be eliminated in the present method, the computation work can be cut down remarkably under the precondition that the computational accuracy is ensured. This shows that, in general, the substructure simultaneous iteration method presented in this paper has a good convergency, thus greatly reducing the computation work. 相似文献
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Localization in Nonlinear Mistuned Systems with Cyclic Symmetry 总被引:1,自引:0,他引:1
In forced systems with cyclic symmetry localization can occur due toparameter uncertainties. Often, Monte-Carlo simulations are used to findregions, where the system response is sensitive to parameteruncertainties. These simulations require a large computation time.Therefore, an approximate method to calculate the envelopes of thefrequency response functions is developed in this paper. An example of anonlinear system with cyclic symmetry is a bladed disk assembly withfriction dampers. Friction dampers can be installed underneath the bladeplatforms of turbine blades. Due to dry friction and the relative motionbetween blades and dampers, energy is dissipated, which results in areduction of blade vibration amplitudes. By optimizing the mass of thefriction dampers, the best damping effects are obtained, which lead toan increase in the reliability of the turbine. In this paper, thecalculated response of a mistuned bladed disk assembly with frictiondampers is discussed. An approximate method is developed to calculatethe envelopes of the corresponding frequency response function forstatistically varying eigenfrequencies of the blades. Regions wherelocalization can occur with a high probability, are calculated by thismethod. 相似文献
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The objective of this paper is to develop an integrated approach using artificial neural networks (ANN) and genetic algorithms (GA) for predicting the worst response of mistuned bladed disk. ANN is used to predict the responses of bladed disk system which are used further in evaluation of fitness and constraint violation in GA process. A multilayer back-propagation neural network is trained with the results obtained from finite element model for different bladed disk configurations. Subsequently, GA is employed for arriving at optimum configuration of the bladed disk system by maximizing the blade responses. By integrating ANN with GA, the computational time required for obtaining optimal solution could be reduced substantially. The efficacy of this approach is demonstrated by carrying out studies on mistuned bladed disk systems for different sets of mistuning parameters, namely mistuning in modulus of elasticity and length of blades. Finally, the effect of adding shroud at the tip of blades in reducing the maximum response of the bladed disk system was investigated. 相似文献
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Convergence predictions for aeroelastic calculations of tuned and mistuned bladed disks 总被引:1,自引:0,他引:1
Mistuning changes the dynamics of bladed disks significantly. Frequency domain methods for predicting the dynamics of mistuned bladed disks are typically based on iterative aeroelastic calculations. Converged aerodynamic stiffness matrices are required for accurate aeroelastic results of eigenvalue and forced response problems. The tremendous computation time needed for each aerodynamic iteration would greatly benefit from a fast method of predicting the number of iterations needed for converged results. A new hybrid technique is proposed to predict the convergence history based on several critical ratios and by approximating as linear the relation between the aerodynamic force and the complex frequencies (eigenvalues) of the system. The new technique is hybrid in that it uses a combined theoretical and stochastic/computational approach. The dynamics of an industrial bladed disk is investigated, and the predicted convergence histories are shown to match the actual results very well. Monte Carlo simulations using the new hybrid technique show that the aerodynamic ratio and the aerodynamic gradient ratio are the two most important factors affecting the convergence history. 相似文献
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提高多体系统离散时间传递矩阵法计算精度的研究 总被引:5,自引:0,他引:5
深入探讨多体系统离散时间传递矩阵法对平面、空间刚体-光滑铰多体系统运动响应的研究。提出提高该方法计算精度和计算稳定性的方法,导出相应的多端刚体传递矩阵。设计了角坐标的迭代循环,该变量不必采用近似形式,因而提高了计算精度和计算稳定性。其它方法有:1)增加泰勒展开式的高阶项;2)合理选择将速度、加速度表示为位移的线性函数的方法(本文简称线性化方法);3)合理确定迭代循环的初值等。对4种多体系统进行了计算机仿真研究,表明本文提出的方法有效。 相似文献
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Aerospace structures with large aspect ratio, such as airplane wings, rotorcraft blades, wind turbine blades, and jet engine fan and compressor blades, are particularly susceptible to aeroelastic phenomena. Finite element analysis provides an effective and generalized method to model these structures; however, it is computationally expensive. Fortunately, the large aspect ratio of these structures is exploitable as these potential aeroelastically unstable structures can be modeled as cantilevered beams, drastically reducing computational time.In this paper, the non-linear equations of motion are derived for an inextensional, non-uniform cantilevered beam with a straight elastic axis. Along the elastic axis, the cross-sectional center of mass can be offset in both dimensions, and the principal bending and centroidal axes can each be rotated uniquely. The Galerkin method is used, permitting arbitrary and abrupt variations along the length that require no knowledge of the spatial derivatives of the beam properties. Additionally, these equations consistently retain all third-order non-linearities that account for flexural-flexural-torsional coupling and extend the validity of the equations for large deformations.Furthermore, linearly independent shape functions are substituted into these equations, providing an efficient method to determine the natural frequencies and mode shapes of the beam and to solve for time-varying deformation.This method is validated using finite element analysis and is extended to swept wings. Finally, the importance of retaining cubic terms, in addition to quadratic terms, for non-linear analysis is demonstrated for several examples. 相似文献
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Hamilton's variational principle is applied to derive a system of conditions which expresses the balance of momentum and energy of an ideal gas across the selvadges 1 The reviewer of this paper confesses to be unfamiliar with the term 'selvadge(s)' which appears frequently herein. Clearly, however, it (variously) means 'boundary', 'edge', 'projection of edge line' (meridional or axial), 'locus of leading edges', etc. of bladed zones within the flow tracts of turbines. This system provides the background for a correct formulation of optimal design problems for turbines and compressors. The exposition follows the model of a large number of blades when the basic equations can be averaged over the azimuthal co-ordinate. An analysis is given of the obtained conditions and a computational algorithm described. 相似文献
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液舱晃荡是一种在外部激励作用下部分装载的液舱内液体的波动现象,它会对液舱结构强度和运输船舶稳性产生危害.移动粒子半隐式法(moving particle semi-implicit,MPS)是一种典型的无网格粒子类方法,可以有效地模拟剧烈的液舱晃荡问题.但MPS方法存在计算效率低的缺点,难以模拟大规模三维问题,而GPU并行加速技术已广泛应用于科学计算领域.因此,本文将MPS方法与GPU并行加速技术相结合,采用CUDA程序语言编写,自主开发了MPSGPU-SJTU求解器,对三维液化天然气(liquefiednatural gas, LNG)型液舱晃荡进行了数值模拟.通过三种不同粒子间距的数值模拟,验证了求解器的收敛性,其中最大计算粒子数达到了200多万.与其他研究结果相比,MPSGPU-SJTU求解器能够准确地预测壁面砰击压力,并且捕捉晃荡过程中自由面的大幅度变形和强非线性破碎现象.相比CPU求解器的计算时间,GPU并行加速技术可以大幅度地减小计算时长,提高MPS方法的计算效率.本文将LNG型液舱与方型液舱的晃荡进行对比,结果表明在高充液率下LNG型液舱可以有效地减小晃荡幅值和壁面砰击压力.但在中低充液率下,LNG型液舱则会加剧晃荡,自由面呈现明显的三维特征.本文还进一步研究了水和LNG两种不同介质的液舱晃荡现象,数值模拟结果表明二者的流场基本相似,砰击压力则正比于液体密度. 相似文献
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A full-field, multi-axial computation technique is described for determining residual stresses using the hole-drilling method with DIC. The computational method takes advantage of the large quantity of data available from full-field images to ameliorate the effect of modest deformation sensitivity of DIC measurements. It also provides uniform residual stress sensitivity in all in-plane directions and accounts for artifacts that commonly occur within experimental measurements. These artifacts include image shift, stretch and shear. The calculation method uses a large fraction of the pixels available within the measured images and requires minimal human guidance in its operation. The method is demonstrated using measurements where residual stresses are made on a microscopic scale with hole drilling done using a Focused Ion Beam – Scanning Electron Microscope (FIB-SEM). This is a very challenging application because SEM images are subject to fluctuations that can introduce large artifacts when using DIC. Several series of measurements are described to illustrate the operation and effectiveness of the proposed residual stress computation technique. 相似文献