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81.
The use of air as a lubricant in aerodynamic bearings is advantageous, particularly in the food industry. Aerodynamic bearings
with tilting pads have complicated stiffness and damping properties and need a very detailed theoretical and experimental
research. Response curves of rigid rotor supported on aerodynamic bearings are presented for a linear but evolutive mathematical
model. Due to non-monotone properties of stiffness and damping matrices at variable revolutions, a new resonance appears.
The mathematical model of rotor vibrations in the whole area of bearing clearance is also developed in the consideration of
strongly nonlinear properties of aerodynamic bearing. 相似文献
82.
J.M. Antunes J.V. Fernandes N.A. Sakharova M.C. Oliveira L.F. Menezes 《International Journal of Solids and Structures》2007,44(25-26):8313-8334
The main difficulty with the characterization of thin coatings using depth-sensing indentation tests is related to the determination of the contributions of the substrate and the film to the measured properties. In this study, three-dimensional numerical simulations of the Vickers hardness test are used in order to examine the influence of the elastic and plastic properties of the substrate and the film on the composite’s Young’s modulus results. The hardness of the film is equal to or higher than the substrate hardness. A study of the stress distributions and the indentation geometry of composites, film/substrate, was performed, taking into account the relative mechanical properties of the film and substrate. In addition, stress evolution during indentation was studied, in order to quantify the critical indentation depth under which the substrate is not elastically deformed. The accurate evaluation of the Young’s modulus of the films using weight functions is also examined: some of these have previously been proposed and one was introduced for this study. Two different fitting procedures were used to compare the results obtained from eight fictive film/substrate combinations using six weight functions. The first procedure, commonly used, considers the substrate’s modulus as a known parameter in the fitting process. In the second, the film and the substrate’s modulus are considered as unknown variables that are calculated simultaneously during the fitting process. The validity of the conclusions obtained using the fictive materials was checked by applying the weight functions to four real composites. 相似文献
83.
Eduardo Lutterbach Bandeira Marcelo Amorim Savi Paulo Cesar da Camara Monteiro Jr. Theodoro Antoun Netto 《Archive of Applied Mechanics (Ingenieur Archiv)》2006,76(3-4):133-144
This contribution deals with the nonlinear analysis of shape memory alloy (SMA) adaptive trusses employing the finite element method. Geometrical nonlinearities are incorporated into the formulation together with a constitutive model that describes different thermomechanical behaviors of SMA. It has four macroscopic phases (three variants of martensite and an austenitic phase), and considers different material properties for austenitic and martensitic phases together with thermal expansion. An iterative numerical procedure based on the operator split technique is proposed in order to deal with the nonlinearities in the constitutive formulation. This procedure is introduced into ABAQUS as a user material routine. Numerical simulations are carried out illustrating the ability of the developed model to capture the general behavior of shape memory bars. After that, it is analyzed the behavior of some adaptive trusses built with SMA actuators subjected to different thermomechanical loadings. 相似文献
84.
本文以分析变深度螺旋槽止推轴承为例介绍了边界元法在润滑力学研究领域中的应用,以及相应的边界条件的处理方法,同时还讨论了轴承的尺寸参数对其性能参数的影响。 相似文献
85.
86.
87.
研究了三阶非线性发展方程的初边值问题的解。采用基于Sinc函数的微分求积法发展了线性化有理逼近方法。通常的配点法不适用于上述三阶问题的求解。本文把提出的方法用于求解KdV方程,取得了良好的效果。 相似文献
88.
离散元方法是近年发展起来的一种新数值方法,但原则上只能用于动态问题。从静力平衡条件出发建立了离散元系统的准静态演化方程并证明了系数矩阵具有对称正定、稀疏、带状分布等特点,适用于“有效列”方法求解,该解法比高斯消去法节省更多的内存和机时。通过引入广义Maxwell体的元间作用模型建立起线性粘弹性材料准静态响应的离散元模拟方法。该方法独立于传统动态离散元方法,是传统动态离散元方法的拓展,可望在更多领域获得应用。 相似文献
89.
90.
Response of saturated porous media subjected to local thermal loading on the surface of semi-infinite space 总被引:2,自引:0,他引:2
Bing Bai 《Acta Mechanica Sinica》2006,22(1):54-61
Heat source function method is adopted in the present paper to derive elementary solutions of coupled thermo-hydro-mechanical
consolidation for saturated porous media under conjunct actions of instantaneous point heat source, instantaneous point fluid
source and constant volume force. By using the so-called fictitious heat source method and images method, the solutions of
a semi-infinite saturated porous medium subjected to a local heat source with time-varied intensity on its free surface are
developed from elementary solutions. The numerical integral methods for calculating the unsteady temperature, pore pressure
and displacement fields are given. The thermomechanical response are analyzed for the case of a circular planar heat source.
Besides, the thermal consolidation characteristics of a saturated porous medium subjected to a harmonic thermal loading are
also given, and the fluctuation processes of the field variables located below the center of heat source are analyzed.
The project supported by the National Natural Science Foundation of China (50578008) The English text was polished byYunming
Chen. 相似文献