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针对离心压缩机在复杂运行工况下的失谐与裂纹问题,研究裂纹与失谐对叶轮结构振动响应和振动局部化的影响规律。首先,采用三维有限元模型建立具有复杂几何形状的叶轮结构的定量分析模型,并通过在裂纹界面上定义接触的形式模拟裂纹的呼吸效应。其次,通过采用混合界面模态综合法对系统自由度进行缩减,以解决了采用三维有限元模型分析非线性系统动态响应时所存在的计算量大和收敛困难的问题。最终,采用Monte Carlo方法对含裂纹的失谐叶轮结构进行统计分析,研究随机失谐和裂纹故障对叶轮结构振动局部化的影响规律。结果表明裂纹和失谐都会对结构的振动响应产生显著的影响,并会导致振动能量的集中和振动局部化现象。 相似文献
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模态局部化现象对弱耦镜像对称工程结构的动态分析与主动设计至关重要。基于小参数摄动理论,针对由左右两个完全相同但在几何上互为镜像的子结构所组成失调对称结构,用峰值振幅比定义模态局部化度,重点建立了预测模态局部化发生的定量判据。该判据确立了局部化度的具体数值与结构的几何、质量及弹性等参数之间的直接影响关系。以此为依据,可实现通过失调量的主动设计达到灵活控制模态局部化强弱程度的目的。对一个弱耦近频对称结构的单边刚度失调模型的局部化振动的数值分析结果表明:(1)联结刚度失调产生的模态局部化对失调对称结构的振型将产生显著的影响;(2)验证了所提出的模态局部化定量判据及局部化度的结构参数表征的可行性和有效性。 相似文献
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结构振动模态局部化评述 总被引:14,自引:0,他引:14
近年来,力学系统的振动模态局部化现象受到了人们极大的关注。研究表明,在一定条件下,小量失调对某些结构系统的振动特性有很大影响。为了促进模态局部化方面的研究工作,本文在总结国内外大量文献的基础上,根据我们自己的研究,较系统地介绍了结构振动模态局部化研究的历史、现状及前景等若干重要问题。详细讨论了结构失调的影响、与阻尼的类比特性;物理学局部化与结构动力学局部化的联系和区别;局部化现象的产生条件、产生机理、利与弊、与频率曲线转向的关系;针对不同结构系统的不同研究方法。同时,还列举了大量国内外参考文献,以备研究者参阅。 相似文献
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在理论推导梁轴向振动微分方程基础上,提出一种以轴向振动低阶模态振型二阶导数为损伤指标的结构损伤识别方法。在方钢管构件上布置加速度传感器进行轴向振动模态试验,测试时由信号发生器发出正弦波信号,经功率放大器放大后通过电磁激振器对结构进行激励,同时采集各测点的加速度反应信号。在确定结构共振点后,根据共振点处加速度值,编制轴向振动损伤指标的计算程序,分析结果表明该指标对结构损伤的位置和程度均很敏感,既能精确定位损伤,又能标定损伤程度,即在损伤位置将发生相反方向的突变,且突变幅度随损伤程度增大而增大。 相似文献
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Olivier Ezvan Xiaoshu Zeng Roger Ghanem Bora Gencturk 《International journal for numerical methods in engineering》2019,117(6):644-692
In this paper, an extension of modal analysis in linear computational structural dynamics is presented to deal with complex structures characterized by the presence of numerous local vibration modes and for which the high modal density leads to high-dimension reduced-order models. These local modes consist of isolated vibrations that are dissociated from the global vibrations of the structure skeleton and that turn out to often be of negligible contribution to the global dynamics. Therefore, an automatic mode sorting procedure is proposed to extract the dominant modes that represent the global dynamics of the skeleton. Next, an alternative filtering methodology based on a modified eigenvalue problem is presented, which allows to build, a priori, a small-dimension reduced-order basis of dominant global modes. The two methods are compared to classic modal analysis using three applications, namely, a heterogeneous plate, a simplified nuclear fuel assembly, and a detailed boiling water reactor fuel assembly. 相似文献
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Paul E. Castillo 《International journal for numerical methods in engineering》2010,81(12):1475-1491
The problem of reducing the stencil of the local discontinuous Galerkin method applied to second‐order differential operator is discussed. Heuristic algorithms to minimize the total number of non‐zero blocks of the reduced stiffness matrix are presented and tested on a wide variety of unstructured and structured grids in 2D and 3D. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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In this paper, a meshless local radial point collocation method based on multiquadric radial basis function is proposed to analyze the free vibration of laminated composite plates. This method approximates the governing equations based on first-order shear deformation theory using the nodes in the support domain of any data center. Natural frequencies of the laminated composite plates with various boundary conditions, side-to-thickness ratios, and material properties are computed by present method. The choice of shape parameter, effect of dimensionless sizes of the support domain on accuracy, convergence characteristics are studied by several numerical examples. The results are compared with available published results which demonstrate the accuracy and efficiency of present method. 相似文献
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J. S. Chen W. Hu H. Y. Hu 《International journal for numerical methods in engineering》2008,75(5):600-627
Standard radial basis functions (RBFs) offer exponential convergence, however, the method is suffered from the large condition numbers due to their ‘nonlocal’ approximation. The nonlocality of RBFs also limits their applications to small‐scale problems. The reproducing kernel functions, on the other hand, provide polynomial reproducibility in a ‘local’ approximation, and the corresponding discrete systems exhibit relatively small condition numbers. Nonetheless, reproducing kernel functions produce only algebraic convergence. This work intends to combine the advantages of RBFs and reproducing kernel functions to yield a local approximation that is better conditioned than that of the RBFs, while at the same time offers a higher rate of convergence than that of reproducing kernel functions. Further, the locality in the proposed approximation allows its application to large‐scale problems. Error analysis of the proposed method is also provided. Numerical examples are given to demonstrate the improved conditioning and accuracy of the proposed method. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Mohammad Hossein Abbasi Laura Iapichino Sajad Naderi Lordejani Wil Schilders Nathan van de Wouw 《International journal for numerical methods in engineering》2020,121(23):5178-5199
To circumvent restrictions of conventional drilling methods, such as slow control actions and inability to drill depleted reservoirs, a drilling method called managed pressure drilling (MPD) has been developed. In MPD, single-phase flow processes can be modeled as a feedback interconnection of a high-order linear system and a low-order nonlinear system. These nonlinearities appear locally both inside and at the boundaries of the computational domain. To obtain a fast simulation platform for real-time purposes (eg, online model-based controller implementation), model order reduction is required for MPD. However, the local nonlinearities render applying model order reduction techniques challenging. In this study, a new approach is proposed to deal with such nonlinearities within the reduced basis (RB) context and it is successfully tested on a model for MPD. Contrary to the classical RB technique, the proposed approach not only does not generate nonphysical spikes at the locations of these local nonlinearities but also yields high speedup factors. The obtained reduced-order model can be used for efficient online simulation and controller design for drilling systems with MPD. 相似文献
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《工程爆破》2022,(2)
以成渝客运专线新红岩隧道上方二层砌体结构为例,采用OMA(运行模态分析)方法研究了砌体结构在隧道爆破引起的地面振动作用下的安全性。结果表明:采用电子雷管爆破相比非电雷管能够有效降低地面振速,峰值振速最多降低约67%;二层砌体结构前4阶固有频率位于925Hz,有限元模型修正后其固有频率与实验值的误差明显减小,使其更加符合实际;非线性动力分析表明砌体结构门、窗的角部、砌体与混凝土材料的交界处及底层主应力集中程度高,但砌体的主压应力和主拉应力均小于规范值,表明砌体在爆破振动作用下是安全的,而且电子雷管更适用于结构安全性要求高的隧道爆破;现场调研发现砌体楼房在隧道爆破振动下没有发生损伤,表明基于OMA方法进行隧道爆破振动下砌体结构的安全评价是可行的。 相似文献
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以成渝客运专线新红岩隧道上方二层砌体结构为例,采用OMA(运行模态分析)方法研究了砌体结构在隧道爆破引起的地面振动作用下的安全性。结果表明:采用电子雷管爆破相比非电雷管能够有效降低地面振速,峰值振速最多降低约67%;二层砌体结构前4阶固有频率位于9~25Hz,有限元模型修正后其固有频率与实验值的误差明显减小,使其更加符合实际;非线性动力分析表明砌体结构门、窗的角部、砌体与混凝土材料的交界处及底层主应力集中程度高,但砌体的主压应力和主拉应力均小于规范值,表明砌体在爆破振动作用下是安全的,而且电子雷管更适用于结构安全性要求高的隧道爆破;现场调研发现砌体楼房在隧道爆破振动下没有发生损伤,表明基于OMA方法进行隧道爆破振动下砌体结构的安全评价是可行的。 相似文献
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