某型号飞机起落架支柱减振筒内壁腐蚀原因分析

飞机起落架减振支柱在飞机起落和滑跑时,吸收撞击能量,对飞机安全起降的意义重大.减振筒是减振支柱中的重要部件,本文从工艺流程、理化分析、外场使用和腐蚀机理分析等方面,对减振支柱减振筒内壁的腐蚀原因及危害进行了综合分析,并提出了相应措施.     

Natural frequencies of vibration of a class of solids composed of layers of isotropic materials

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.     

油品含水率在线检测仪的研制

介绍油品含水率检测原理、电容／电压转换方法以及系统设计。实验结果表明，该仪器能够准确、快速地检测出油品的含水率．从而避免了润滑失效所带来的潜在危害。     

Modeling of coefficient of contraction of differential pressure flowmeters

The article provides a solution to the problem of contraction process modeling when measuring the flow of fluids and gases using differential pressure flowmeters. The article shows the feasibility of obtaining the coefficient of contraction from the mathematical model of the reduced/contracted flow of fluids or gases. An analytical expression is obtained for the coefficient of contraction, which agrees well with the results of the experiment. Analysis of this expression is performed and dependencies on the geometrical parameters of the pipeline and orifice plate are obtained.     

挖掘机液压系统控制性能分析

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。     

电主轴径向加载机构横轴结构参数优化

以轴段半径、轴段长度、轴肩过渡圆半径作为参考因素,以危险点的最大应力作为评价指标,对一种接触式径向加载机构横轴的结构参数进行优化。应用有限元分析参数灵敏度,考虑设计经济性,采用控制变量法对轴段半径r和轴肩过渡圆半径R d进行定量分析。在满足轴的体积尽可能小的情况下使得危险点的应力得到了显著降低,最后对横轴进行了安全系数和可靠性校核。     

Method of implementation of the positive gradient of mechanical properties of triboengineering materials

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.     

液压平衡回路的速度稳定性分析

分析了液压平衡回路稳定性与爬行原因及排除方法。这为排除此类故障以及正确使用和设计平衡回路提供了科学依据。     

轮胎单个横沟泵吸噪声计算方法研究

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。     

光的相干长度对两类光谱仪器分辨本领的影响

衍射光栅光谱仪和法布里-珀罗(F-P)干涉仪是两类非常典型和重要的光谱仪器。从波动光学的角度看,光栅衍射和F-P干涉都可看成是多波列的相干叠加。由于波列之间存在光程差,光的相干长度限制着同时参与相干叠加的最大波列数。针对现有理论将光栅衍射和F-P干涉同时参与相干叠加的最大波列数分别定为透光狭缝总数和无穷大的情况,分别引入有效透光狭缝数和有效透射光光束数来说明光的相干长度对衍射光栅光谱仪和F-P干涉仪这两类光谱仪器分辨本领的影响。     

Design evaluation of durability of extended constructions of mains

Basic concepts for evaluating durability of mains are formulated as problems of the strength and safety of extended constructions under the action of random operational loads and effects. A system of sequential operations resulting in determination of the critical time of exploitation of the pipeline section is constructed. Acceptable values of probability components of potential damage for pipeline sections belonging to three durability classes are given. The choice of the durability criterion of a construction element and conditions of safe operation of a pipeline section from the point of view of durability are considered as one of the fundamental blocks of the algorithm.     

Specific features of operation of electrostatic microgenerators of energy

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.     

密封齿对侧开槽对迷宫密封泄漏特性的影响

为了降低迷宫密封的泄漏量,提出一种在直通型迷宫密封的密封齿前端和后端设立凹槽的密封结构,基于CFD方法,建立迷宫密封数值仿真模型。通过与已有试验数据的对比,验证模型的正确性。探讨不同湍流模型的适用范围,并对比光滑表面、前置凹槽、后置凹槽3种结构在泄漏量、轴向压降及流场速度分布的差异性。结果表明:SST湍流模型更加适用于迷宫密封这种窄间隙的近壁面流动;前置凹槽结构降低泄漏量的效果较差,只有在高压力差下才能降低泄漏量;后置凹槽结构能改变迷宫密封腔内漩涡方向及状态,进而降低迷宫密封透气效应,加剧密封的能量耗散的同时降低泄漏量。因此,后置凹槽的迷宫密封结构具有较好的工程应用前景。     

Analysis of models of friction in suspensions of vehicles

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.     

摩托车发动机曲轴连杆总成动平衡测试系统

介绍了一种基于Labwindows／CVI虚拟仪器平台的摩托车发动机曲轴连杆总成动平衡测试系统的测量原理和计算方法,详细讨论了动平衡测量的硬件组成和软件设计。该系统能测量曲轴连杆总成的双面动不平衡量、主轴倾角、不平衡率等质量特性参数,具有功能完备、高精度、高效率、人机友好等优点。系统已在生产现场使用,可替代某些进口设备,降低企业费用。     

浊度计仪器示值误差测量结果不确定度评定

依据JJG880-2006浊度计检定规程,介绍了浊度计示值误差测量结果不确定度的评定方法,对配制标准溶液所使用的玻璃量器所引入的不确定度分量进行了分析和评定。     

Comparison of performances of the various shapes of asymmetric fins

A comparison between the heat loss of the asymmetric triangular fin and the asymmetric trapezoidal fins which have various slopes of the fin’s upper lateral side is performed. The relation between the slope factor of the fin and the non-dimensional fin length for equal amount of heat loss is shown. Further, the relation between the Biot number and the non-dimensional fin length for equal amount of heat loss is given. For these analyses, a forced analytic method is used. In particular, the same equation is used for both the asymmetric triangular fin and the asymmetric trapezoidal fins just by adjusting the value of the slope factor. It is shown that this equation can also be applied to a rectangular fin with very good accuracy. The base temperature, thermal conductivity of fin’s material and the heat transfer coefficient are assumed constant.     

Development of sclerometric method of studying activation of parameters of damage and fracture of friction deformable surfaces

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.     

双丝杠驱动机构同步分析

介绍了双丝杠驱动机构工作原理,论述了双丝杠运动产生不同步的原因以及如何判定与解决同步问题。     

The compression loading of solid spheres of plaster of Paris

Brittle solid spheres of plaster of Paris with and without bosses (i.e. cylindrical projections) and truncated spheres with two symmetrical circular flat ends were subjected to static loading and to explosive point loading from a detonator. The resulting terminal fracture patterns are shown and discussed. A characteristic feature of the fracturing modes is the formation of well defined cones at the loading region and the opposite end of the specimen.