叶切面最大厚度数值计算与应用

以叶切面最大厚度的数值计算方法为基础,探讨叶切面最大厚度计算的计算机实现,介绍叶切面厚度数值计算法的应用实例.     

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.     

膨胀套导向机构的设计

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。     

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。     

螺旋桨桨叶叶面加工过程中加工量的计算

根据螺旋桨桨叶曲面加工精度和公差的要求，编制了计算机辅助工艺生成程序，求取了桨叶加工过程的最小打磨量，从而既保证了质量又大大提高了加工过程的效率。     

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.     

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.     

Analysis of similarity of physical processes during simulation of cooling of machine crystallizers

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.     

Method of decomposition of the interval of the values of random variables based on results of optimization of the nonparametric estimate of the probability density

A new method of decomposition of the interval of the values of random variables based on results of optimization of the nonparametric estimate of the probability density of the Rosenblatt-Parzen type is proposed. Its application in the problem of testing the hypothesis of identity of the distribution laws of two sequences of one-dimensional random variables is considered.     

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.     

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。     

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.     

Determination of spectral densities of dynamic characteristics of a nonlinear model of structure

A stochastic problem of the dynamics of a nonlinear model of structure is considered. The problem is solved with the use of an expansion of the solution in the truncated orthogonal basis of eigenvectors of the linear model. It is assumed that nonlinearities of the system do not result in a fundamental change in its dynamical behavior, but contribute a significant quantitative correction relative to the linear model. The nonlinear characteristics are statistically linearized. The coefficients of statistical linearization are formally interpreted as some variations in the corresponding elements of the stiffness matrix of the linear model. Spectral densities, displacement variances of the linearized system, as well as its eigenvalues and eigenvectors, are represented as a power series expansion in the above variations considering linear or square approximations. To find the coefficients in the expansion, the sensitivity theory is used. This allows one to form a set of algebraic transcendental equations in displacement variances, which is solved by the method of successive approximations. Then all the target spectral densities are found. The results are illustrated by examples.     

Geometrical method of selection of features of diagnostic signals

The paper presents the method of selection of features of diagnostic signals relying on the geometry of observation space. The method presented here uses two criteria of ability to separate (isolate) classes of an object's state: the criterion of average scatters and the original criterion of number of prototypes of classes. The method can be successfully used for initial analysis of input data to a neural network dealing with recognition of patterns and classification of an object's state. It also possible to use the algorithm presented here for determining the prototypes of classes needed for creating the training set for the neural network.     

我校工业设计教育改革初探

针对目前市场对工业设计人才的需求,本文论述了我校在工业设计教育方面的改革措施,着重介绍了我校工业设计教育在软件和硬件方面所进行的一系列的改革。     

一起造船门式起重机减速器断轴事故分析

造船门式起重机起升机构减速器出现高速轴断轴的情况较为少见,分析事故原因有利于起重机的安全使用。文中以某造船厂一台造船门式起重机发生的减速器断轴事故为例,依据其设计图纸和实际受力情况,结合轴的力学、断口形貌和材质等方面进行分析,研究断轴发生的原因。该方法可以有效判断该类起重机事故原因,可为其它类型起重机事故分析提供借鉴。     

Euler-Savari determination of radii of curvature of cycloid profiles

The radius of curvature of a cycloid tooth profile is determined on the basis of the Euler-Savari theorem, without using profile equations. The formulas obtained may be used to determine radii of curvature of other cycloid couplings in which one of the contact profiles is a circle. A sample calculation is presented.     

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.     

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.     

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。