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In a recent paper, the Ritz method with simple algebraic polynomials as trial functions was used to obtain an eigenvalue equation for the free vibration of a class of homogeneous solids with cavities. The method presented is here extended to the study of a class of non-homogeneous solids, in which each solid is composed of a number of isotropic layers with different material properties. The Cartesian coordinate system is used to describe the geometry of the solid which is modelled by means of a segment bounded by the yz, zx and xy orthogonal coordinate planes and by two curved surfaces which are defined by fairly general polynomial expressions in the coordinates x, y and z. The surface representing the interface between two material layers in the solid is also described by a polynomial expression in the coordinates x, y and z. In order to demonstrate the accuracy of the approach, natural frequencies are given for both a two- and three-layered spherical shell and for a homogeneous hollow cylinder, as computed using the present approach, and are compared with those obtained using an exact solution. Results are then given for a number of two- and three-layered cylinders and, to demonstrate the versatility of the approach, natural frequencies are given for a five-layered cantilevered beam with a central circular hole as well as for a number of composite solids of more general shape. 相似文献
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V. P. Dragunov E. G. Kostsov 《Optoelectronics, Instrumentation and Data Processing》2009,45(3):234-242
Specific features of operation of one- and two-capacitor microelectromechanical converters (MEMC) of energy of mechanical microscopic vibrations into electric energy with a modulated electrode-gap magnitude and with allowance for the mutual influence of electrical and elastic forces are analyzed, and the characteristics of these two devices are compared. The main factors restricting the increase in MEMC power are demonstrated to be the effects of “collapsing” and the condition of conservation of positive rigidity of the system. Expressions for estimating the limiting MEMC parameters are derived. The possibility of electrical energy generation in the presence of “real“ sources of wide-spectrum microscopic vibrations is considered. 相似文献
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V. G. Mikhailov 《Journal of Friction and Wear》2014,35(2):149-154
An analysis of the correctness of calculations during the modeling of oscillations of vehicles is carried out. A substantial difference between the calculation and experimental data in octave-frequency bands has been found and a low efficiency of suspensions of sprung seats has been emphasized. A comparative analysis of models of friction and dynamic characteristics used during the modeling of suspensions of vehicles is carried out. It has been shown that models of Coulomb and viscous friction do not ensure the required precision of the modeling process. A new model of friction in the form of totalities of models of elastic and viscous friction, as well as the implementation of this model using computer simulation, which ensures a calculation error of 5–15%, have been proposed. 相似文献
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大型港口机械钢结构细部结构处理问题研究,以卸船机为主要研究对象,基于板壳理论,采用有限元法,梁壳单元混合建模,对卸船机的细部钢结构进行分析,并得到细部结构处理问题的意见和建议。 相似文献
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Modern methods of implementation of the rule of positive gradient of mechanical properties are considered; this rule was formulated by I.V. Kragelskii and its application serves to minimize the friction and wear of solids. The given methods include the application of coatings with the method of finishing antifricton abrasion-free treatment; application of new metal-cladding lubricating materials; and creation of a nanostructural state of the surface iron nitride layer by nitriding steel with a positive gradient of hardness normal to the surface. 相似文献
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轮胎单个横沟泵吸噪声计算方法研究 总被引:2,自引:0,他引:2
以205/50R16子午线轮胎为对象,建立具有横向花纹沟槽的有限元法分析模型,利用Abaqus/Explicit进行瞬态滚动分析,得到滚动轮胎单个横沟的体积变化。将其导入Fluent中,利用计算流体力学方法对单个横沟泵吸效益流场进行分析,并结合Lighthill声学类比理论预测横向沟槽的噪声,同时基于涡声理论验证流场与噪声之间的关系。结果表明,单个横沟泵吸噪声第一峰值集中在0.8~2.0 kHz附近,仿真数据与试验结果在趋势上具有一致性;且噪声的声压峰值出现在泵吸状态发生转变的时间段;在时域中的3个噪声峰值出现涡量变化较大的时间段,已确定噪声的变化可由涡量来反映。 相似文献
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一种涡旋压缩机径向随变机构的设计 总被引:1,自引:0,他引:1
详细介绍了运用随变原理设计的一种新型径向密封机构的结构特点,工作原理及主要参数的确定方法,该机构可补偿由于涡旋体加工精度不高而造成的功率损失,适用于涡旋压缩机的批量生产。 相似文献
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Possibility of Nondestructive Testing of Operational Heating of Contact Surfaces of Rolling Bearings
Gorkunov E. S. Tabachnik V. P. Kogan L. Kh. Chernova G. S. Antenorova N. P. 《Russian Journal of Nondestructive Testing》2003,39(6):465-471
The coupling between variation of parameters of nondestructive testing and heating of rolling bearings associated with their operation regime in a helicopter reduction gear is demonstrated. The coercive force method and the eddy-current method of testing outer bearing rings made from ShKh15 steel are considered. 相似文献
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V. V. Stulov 《Journal of Machinery Manufacture and Reliability》2012,41(1):64-66
Similarity criteria describing physical the processes of boiling and condensation of a heat carrier were determined with a
model and natural experiments based on the analysis of dimensions of parameters in the heat exchange problem during cooling
of a crystallizer by heat pipes. Relationships of the geometrical sizes of heat pipes (diameter, length) were estimated. The
novelty of the results is confirmed by patents of invention of catalyst cooling by heat pipes. 相似文献
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通过分析膨胀套在实际使用产生滑移受阻现象、卡死现象原因的实质,并在分析产生问题原因的基础上提出了改进措施即:增加导向机构。 相似文献
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The article presents a brief review of the wear models based on the kinetic thermofluctuation approach. The materials were developed using SamGTU sclerometric programming software and a set of instruments developed at Samara Engineering University for assessing the parameters of kinetic thermoactivation for surface fracture deformed by friction. The first obtained results of assessments and the estimated prediction of wear resistance exemplified by tribocouple of the aircraft chassis are presented. 相似文献
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介绍了挖掘机液压系统的功率参数与流量控制机理,从液压系统的功率角度分析了液压挖掘机的功率控制方式,从挖掘机负流量液压系统与正流量液压系统的工作原理方面分析了其控制性能及优缺点,并总结了挖掘机负流量液压系统与正流量液压系统的技术价值、应用场合及改善方向。 相似文献
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本文以某些积算和双笔记录仪产品为例说明由于仪表功能设计的不合理或选型不当,影响了仪表的正常使用,制造厂和用户应关注这类问题。 相似文献
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微机械系统建模与仿真技术研究 总被引:5,自引:2,他引:5
简要分析了微电子机械系统建模仿真的原因,指出了微电子机械建模仿真需要克服的四个方面技术难题,即尺度效应、开发快速的表面力计算方法、多物理场耦合分析、宏模型的建立,为微电子机械系统的建模仿真指明了研究方向.详细分析了微电子机械系统建模仿真的技术关键,多物理场耦合计算的理论方法和器件及系统宏观模型的建立,介绍了用于MEMS系统级模拟仿真的宏模型建立的几种方法,最后结合硬件描述语言VHDL-AMS提出了建立微电子机械系统模型实现系统级模拟的方法. 相似文献
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