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71.
求解二维结构-声耦合问题的一种半数值半解析方法 总被引:2,自引:1,他引:2
基于传递矩阵法和虚拟源强模拟技术提出了一种求解在谐激励作用下二维结构-声相互作用问题的半数值半解析法.在足够小的积分步长内,文中对任意形状弹性环沿周向曲线坐标的非齐次状态微分方程组,建立了一种齐次扩容方法.对于外声场,采用多圆形虚拟源强配置方案。并在每一条圆形配置曲线上将源强密度函数用Fourier级数展开,同时结合快速Fourier变换法,提出了一种高精度、高效率求解任意形状二维孔穴Helmholtz外问题的快速算法.在耦合方程的求解方面,根据叠加原理,将外激励和虚拟源强的Fourier级数展开项作为广义力分别作用在弹性环上,借助齐次扩容方法和精细积分法求得弹性环的状态向量,再利用流固交接条件和最小二乘法直接建立了耦合系统的求解方程.文中给出了二个典型弹性环在集中谐激励力作用下声辐射算例,计算结果表明该文方法较通常采用的混合FE-BE法更为有效. 相似文献
72.
73.
An approach is developed to solve the two-dimensional boundary-value problems of the stress-strain state of conical shells
with circumferentially varying thickness. The approach employs discrete Fourier series to separate variables and make the
problem one-dimensional. The one-dimensional boundary-value problem is solved by the stable discrete-orthogonalization method.
The results obtained are presented as plots and tables
__________
Translated from Prikladnaya Mekhanika, Vol. 41, No. 9, pp. 26–37, September 2005. 相似文献
74.
The Fourier series method was extended for the exact analysis of wave propagation in an infinite rectangular beam. Initially, by solving the three-dimensional elastodynamic equations a general analytic solution was derived for wave motion within the beam. And then for the beam with stress-free boundaries, the propagation characteristics of elastic waves were presented. This accurate wave propagation model lays a solid foundation of simultaneous control of coupled waves in the beam. 相似文献
75.
Cecile Veerman Leonard M. C. Sagis Paul Venema Erik van der Linden 《Rheologica Acta》2005,44(3):244-249
To probe the behaviour of fibrillar assemblies of ovalbumin under oscillatory shear, close to the percolation concentration, cp (7.5%), rheo-optical measurements and Fourier transform rheology were performed. Different results were found close to cp (7.3%), compared to slightly further away from cp (6.9 and 7.1%). For 6.9 and 7.1%, a decrease in complex viscosity, and a linear increase in birefringence, n, with increasing strain was observed, indicating deformation and orientation of the fibril clusters. For 7.3%, a decrease in complex viscosity was followed by an increase in complex viscosity with increasing strain, which coincided with a strong increase in n, dichroism, n, and the intensity of the normalized third harmonic (I3/I1). This regime was followed by a second decrease in complex viscosity, where n,n and I3/I1 decreased. In the first regime where the viscosity was decreasing with increasing strain, deformation and orientation of existing clusters takes place. At higher oscillatory shear, a larger deformation occurs and larger structures are formed, which is most likely aggregation of the clusters. Finally, at even higher strains, the clusters break up again. An increase in complex viscosity, n, n and I3/I1 was observed when a second strain sweep was performed 30 min after the first. This indicates that the shear-induced cluster formation and break up are not completely reversible, and the initial cluster size distribution is not recovered after cessation of flow. 相似文献
76.
A numerical method to estimate spectral properties of nonlinear oscillators with random input is presented. The stationary system response is expanded into a trigonometric Fourier series. A set of nonlinear algebraic equations, solved by Newtons method, leads to the determination of the unknown Fourier series coefficients of single samples of the response process. For cubic polynomial nonlinearities, closed-form expressions are used to find the nonlinear terms at each step of the solution scheme. Further, a simple procedure yields an approximation of an arbitrary nonlinearity by a cubic polynomial. Power spectral density estimates for the response process are constructed by averaging the square modulus of the computed Fourier coefficients over various samples or by means of well-established smoothing techniques of spectral analysis. Two applications are presented illustrating the effectiveness of the method as compared to statistical linearization and digital Monte-Carlo simulation. 相似文献
77.
张慎学 《应用数学和力学(英文版)》1996,17(12):1137-1140
APPLICATION OF VECTOR TO SMALL DEFORMATIONZhangShenxue(张慎学)(ReceivedDec.16,1994,May28,1995,CommunicatedbyChienWeizang)Abstrac... 相似文献
78.
环形板与扇形板弯曲问题的级数解 总被引:1,自引:0,他引:1
由板的基本方程,将位移和荷载沿环向展开为傅里叶级数,可得用傅里叶级数及多项式表示的环形板和直边简支的扇形板的级数解.还用富里叶级数处理沿径向分段连续荷载的问题. 相似文献
79.
The kinetic theory of plasma has been employed to compute the test-charge potential distributions accounting for quantization effects in magnetized electron-positron-ion (EPI) plasmas. In this regard, the degenerate positrons and electrons are assumed to follow the Fermi-Dirac distribution, while inertial ions are modelled by Maxwellian velocity distribution. By solving the Fourier-transformed Vlasov–Poisson equations, a modified dielectric function and electrostatic potential is obtained. By imposing various constraints on the test-charge speed, the potential profile has been analysed in terms of Debye–Hückel (DH), far-field (FF), and wake-field (WF) potentials. It has been found that the amplitude of DH and FF potentials increases by the inclusion of quantization effects, and it becomes the opposite for the WF potential profile. Furthermore, the variation of positron concentration significantly affects the DH, FF, and WF potentials. The present findings are important to understand the shielding phenomenon in degenerate multi-species plasmas. 相似文献
80.
The inverse problem of determining 2D spatial part of integral member kernel in integro‐differential wave equation is considered. It is supposed that the unknown function is a trigonometric polynomial with respect to the spatial variable y with coefficients continuous with respect to the variable x. Herein, the direct problem is represented by the initial‐boundary value problem for the half‐space x>0 with the zero initial Cauchy data and Neumann boundary condition as Dirac delta function concentrated on the boundary of the domain . Local existence and uniqueness theorem for the solution to the inverse problem is obtained. 相似文献