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传统的统计能量分析法的基本公式是在相互独立的激励下获得的.本文从相关激励下的功率流分析入手,引入相关功率流的概念,得出相关激励下保守耦合系统功率流的表达式,给出了结构在相关激励下的统计能量关系式,数值计算表明,文中分析及结论是正确的. 相似文献
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耦合阻尼对非保守耦合振子能量分布与功率流的影响 总被引:2,自引:0,他引:2
作为非保守耦合系统统计能量分析的基础,本文研究了耦合阻尼对非保守耦合系统能量分布与功率流的影响.在给出各项有关的损耗因子和耦合损耗因子的定义后,本文从理论上推导了非保守耦合振子间各项功率流与振子平均振动能量之间关系的理论表达式,以及功率平衡方程式和振子能量比的表达式.理论分析和数值计算的结果表明,非保守耦合振子之间的原始功率流和附加功率流以及总功率流不仅取决于两振子的平均振动能量之差,而且取决于振子的平均振动能量之和,总功率流的方向即与两振子能量相对大小有关,也与耦合性质有关;小耦合阻尼是非保守耦合的特例,由此特例不足以得到非保守耦合情况的一般特点。 相似文献
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传统的统计能量分析(SEA)理论不能解决非保守耦合系统和保守或非保守耦合系统在相关输入时的能量分析问题。作为任意输入关系下非保守耦合系统统计能量分析的基础,本文研究了耦合振子在非保守耦合及任意输入条件下能量分布与功率流的一般特征,推导了功率平衡方程式及各有关功率项的计算式,讨论了振子间功率流的构成及各向功率流之间的关系。研究结果表明,耦合阻尼和输入形式对耦合振子能量平衡和功率总体特征有着显著的影响。 相似文献
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为了研究水下爆炸条件下船体冲击振动响应时频特征,针对某实船非接触水下爆炸实验冲击响应测试实验数据,基于小波分析及能量统计方法对响应信号进行时频特性分析,得到了实船非接触水下爆炸冲击振动响应的时频分布和能量分布。分析结果表明,采用基于小波变换的时频分析方法,可以成功获得船体冲击响应信号不同频率段下的强度、能量和作用时间等时频细节信息,包括响应信号各频段冲击峰值、衰减过程、振动能量及其在全频率段上所占的分数。通过对小波频段能量统计以及冲击强度分析发现,冲击响应能量频段分布较广,主甲板及以下甲板全频段振动能量的80%以上在312.5 Hz以上,上层建筑甲板平台各频段冲击振动能量分数向低频段转移。 相似文献
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Ⅰ.引言本世纪60年代初以来,工程界对数值方法,特别对有限元法感到极大的兴趣。这产生了两个重要的结果。首先,它促使完成大量有关计算技术和高效工程软件方面的工作。其次,它引起大量关于基本自然科学方法的研究,如变分法、混合法、加权残数近似法等。所有这些都有利于有限元法的发展,有利于使有限元法能解决范围更广的工程问题。工程师们很快 相似文献
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本文基于增量驻值势能原理,用罚函数的概念,建立适用于不可压缩的非线性橡胶类材料的增量形式的罚有限元位移法的计算列式.这种方法能克服混合法中存在的问题.实例计算表明,罚有限元位移法的计算结果与精确解符合得很好.文中还讨论了罚数的选择方法. ... 相似文献
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节点梯度光滑有限元配点法 总被引:2,自引:2,他引:0
配点法构造简单、计算高效, 但需要用到数值离散形函数的高阶梯度,而传统有限元形函数的梯度在单元边界处通常仅具有C$^{0}$连续性,因此无法直接用于配点法分析. 本文通过引入有限元形函数的光滑梯度,提出了节点梯度光滑有限元配点法. 首先基于广义梯度光滑方法,定义了有限元形函数在节点处的一阶光滑梯度值,然后以有限元形函数为核函数构造了有限元形函数的一阶光滑梯度,进而对一阶光滑梯度直接求导并用一阶光滑梯度替换有限元形函数的标准梯度,即完成了有限元形函数二阶光滑梯度的构造.文中以线性有限元形函数为基础的理论分析表明,其光滑梯度不仅满足传统线性有限元形函数梯度对应的一阶一致性条件,而且在均布网格假定下满足更高一阶的二阶一致性条件.因此与传统线性有限元法相比,基于线性形函数的节点梯度光滑有限元法的$L_{2}$和$H_{1}$误差均具有二次精度,即其$H_{1}$误差收敛阶次比传统有限元法高一阶, 呈现超收敛特性.文中通过典型算例验证了节点梯度光滑有限元配点法的精度和收敛性,特别是其$H_{1}$或能量误差的精度和收敛率都明显高于传统有限元法. 相似文献
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We present a new approach for modelling noise and vibration in complex mechanical structures in the mid-to-high frequency regime. It is based on a dynamical energy analysis (DEA) formulation which extends standard techniques such as statistical energy analysis (SEA) towards non-diffusive wave fields. DEA takes into account the full directionality of the wave field and makes sub-structuring obsolete. It can thus be implemented on mesh grids commonly used, for example, in the finite element method (FEM). The resulting mesh based formulation of DEA can be implemented very efficiently using discrete flow mapping (DFM) as detailed in Chappell et al. (2013) and described here for applications in vibro-acoustics. A mid-to-high frequency vibro-acoustic response can be obtained over the whole modelled structure. Abrupt changes of material parameter at interfaces are described in terms of reflection/transmission matrices obtained by solving the wave equation locally. Two benchmark model systems are considered: a double-hull structure used in the ship-building industry and a cast aluminium shock tower from a Range Rover. We demonstrate that DEA with DFM implementation can handle multi-mode wave propagation effectively, taking into account mode conversion between shear, pressure and bending waves at interfaces, and on curved surfaces. 相似文献
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Energy flow analysis (EFA) method is a vibration simulation tool developed for structures under single-frequency excitation.
The work described in this paper aims to extend the application of EFA to situations where structures are subject to random
broadband excitations. The proposed energy formulation for beam structures under random excitations, which is based on conventional
EFA, is referred to as random EFA. Due to the new capability of random EFA, a comprehensive relationship between random EFA
and the widely used statistical energy analysis (SEA) method in modeling energy response as well as power flow is established.
Both random EFA and SEA are utilized to model the vibration behavior of a complex planar frame structure on which random broadband
forces are applied. Good correlation between energy as well as power flow solutions is demonstrated between the two methods
for beam members in close proximity to the external excitations, which validates the random EFA development. 相似文献
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《力学快报》2020,10(1):16-22
In the area of naval architecture and ocean engineering, the research about the underwater explosion problem is of great significance. To achieve prolonged simulation of near-free surface underwater explosion, the underwater explosion transient numerical model is established in this paper based on compressible Eulerian finite element method(EFEM). Compared with Geers–Hunter formula, EFEM is availably validated by simulating the free-field underwater explosion case. Then, the bubble pulsation and flow field dynamic characteristics of the cases with different underwater explosive depth are compared in this work. Lastly, the height of the water hump and the pressure of flow flied are analyzed quantitatively through the simulation results. 相似文献
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研究了流体负载下的无穷大双周期加强板, 在周期谐振力作用下的振动响应和声辐射,并提出了一种基于有限元和空间波数法的半解析半数值方法. 首先利用有限元的方法对周期结构进行单元离散, 并将结构对薄板的作用力等效为节点力的作用. 然后通过周期结构的振动方程, 结合薄板与结构的位移边界条件, 建立了节点力与薄板节点位移的函数方程. 最后应用空间波数法和傅里叶变换, 并采用数值计算的方法求解出薄板的节点位移, 得到了周期加强板关于离散节点位移的振动和辐射声压方程. 在数值算例中, 对该方法的正确性进行了验证, 并且分析了周期结构对薄板的振动和声辐射的影响. 相似文献
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针对分级周期梁结构,进行了振动带隙特性优化研究,以期提高结构的减振性能。采用谱元法计算分级周期梁的频响曲线,并结合传递矩阵法计算结构的色散关系,将两种方法相结合来研究结构的振动带隙特性。构建带隙占比函数作为优化目标函数,将单胞结构的尺寸作为优化参数进行带隙特性优化。经过优化,使得在研究频段内带隙特性大大提高。通过与有限元法和振动实验相对比,验证了谱元法计算和优化结果的正确性。研究内容对于提高周期结构的振动带隙特性和减振应用提供有益参考。 相似文献
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Muhammad Treifi S. Olutunde Oyadiji 《International Journal of Solids and Structures》2013,50(14-15):2196-2212
A strain energy approach (SEA) is developed to compute the general stress intensity factors (SIFs) for isotropic homogeneous and bi-material plates containing cracks and notches subject to mode I, II and III loading conditions. The approach is based on the strain energy of a control volume around the notch tip, which may be computed by using commercial finite element packages. The formulae are simple and easy to implement. Various numerical examples are presented and compared to corresponding published results or results that are computed using different numerical methods to demonstrate the accuracy of the SEA. Many of those results are new, especially for the cases of bi-material notches where the problem is quite complicated. 相似文献
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A finite difference method is developed to study, on a two-dimensional model, the acoustic pressure radiated when a thin elastic
plate, clamped at its boundaries, is excited by a turbulent boundary layer.
Consider a homogeneous thin elastic plate clamped at its boundaries and extended to infinity by a plane, perfectly rigid,
baffle. This plate closes a rectangular cavity. Both the cavity and the outside domain contain a perfect fluid. The fluid
in the cavity is at rest. The fluid in the outside domain moves in the direction parallel to the system plate/baffle with
a constant speed. A turbulent boundary layer develops at the interface baffle/plate. The wall pressure fluctuations in this
boundary layer generates a vibration of the plate and an acoustic radiation in the two fluid domains.
Modeling the wall pressure fluctuations spectrum in a turbulent boundary layer developed over a vibrating surface is a very
complex and unresolved task. Ducan and Sirkis [1] proposed a model for the two-way interactions between a membrane and a turbulent
flow of fluid. The excitation of the membrane is modeled by a potential flow randomly perturbed. This potential flow is modified
by the displacement of the membrane. Howe [2] proposed a model for the turbulent wall pressure fluctuations power spectrum
over an elastomeric material. The model presented in this article is based on a hypothesis of one-way interaction between
the flow and the structure: the flow generates wall pressure fluctuations which are at the origin of the vibration of the
plate, but the vibration of the plate does not modify the characteristics of the flow.
A finite difference scheme that incorporates the vibration of the plate and the acoustic pressure inside the fluid cavity
has been developed and coupled with a boundary element method that ensures the outside domain coupling. In this paper, we
focus on the resolution of the coupled vibration/interior acoustic problem. We compare the results obtained with three numerical
methods: (a) a finite difference representation for both the plate displacement and the acoustic pressure inside the cavity;
(b) a coupled method involving a finite difference representation for the displacement of the plate and a boundary element
method for the interior acoustic pressure; (c) a boundary element method for both the vibration of the plate and the interior
acoustic pressure.
A comparison of the numerical results obtained with two models of turbulent wall pressure fluctuations spectrums - the Corcos
model [3] and the Chase model [4] - is proposed. A difference of 20 dB is found in the vibro-acoustic response of the structure.
In [3], this difference is explained by calculating a wavenumber transfer function of the plate. In [6], coupled beam-cavity
modes for similar geometry are calculated by the finite difference method.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献