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.     

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.     

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.     

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.     

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。     

轮胎疲劳失效研究综述

轮胎寿命对车辆行驶安全性影响巨大,而轮胎失效方式主要是疲劳失效.针对轮胎的疲劳失效,综述国内外疲劳失效的几种研究方法的特点和应用状况,认为裂纹扩展方法为主要的研究方法;而在基于该方法的研究中,疲劳失效评价指标的合理确定,直接影响到轮胎疲劳寿命的评价;疲劳寿命预报的模型分析技术也是目前轮胎失效研究亟待解决的技术难题之一.通过对目前所使用的评价指标的相关文献和理论调查,指出采用断裂能指标对寿命的预测比其他指标更合理.在对比了目前用来建立疲劳寿命预报模型的分析技术后,指出基于裂纹扩展方法,结合考虑温度效应的断裂能评价指标,并采用EDT分析技术建立疲劳寿命预报模型,预测轮胎疲劳寿命,将是分析轮胎疲劳失效比较有效的途径.     

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。     

Diagnostics of the causes of the operational destruction of rotor blades of gas turbines

The results of technical diagnosis of the destruction of renewed rotor blades of a stationary gas turbine plant are described. Visual, fractographical, and metallographical inspection methods were used to determine the causes of the destruction. The causes of the operational destruction were determined. Practical recommendations for preventing similar destructions were formulated.     

一种谱片量化参数数值标准化方法的提取

本分析了已有的谱片量化参数数值标准化方法的不足，提取了一种简单准确的谱片量化参数值标准化新方法，并从理论上证明了该方法的正确和可行性。     

Statistical method of suppression of artifacts of tomographic reconstruction

A new method is proposed for suppressing artifacts of tomographic reconstruction. The method is based on selective estimation of the mathematical expectation of the residue between phantoms simulating a random distribution and their tomograms. The method is justified theoretically and is supported by a computational experiment.     

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。     

Limits of applicability of elastic contact models of rough surfaces

Recent stochastic models for analyzing the contact of rough surfaces assume that the asperities are microhertzian, i.e. that they can be approximated as second-order surfaces in the vicinity of contact points, and that the asperities deform elastically. Using a plane strain solution from the literature for a sinusoidally corrugated half-space, the range of validity of these assumptions is shown to be related to the mean square surface slope and the macrocontact pressure. By extension to random surfaces characterized by a one-dimensional spectral density function an interval on the surface spatial frequency is found over which the asperities deform elastically but without completely flattening. A numerical example is given.     

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.     

叶切面最大厚度的数值计算方法

叶切面最大厚度计算是螺旋曲面加工准备过程中必要的环节.探讨适合于叶切面最大厚度的数值计算方法.详细介绍叶切面厚度数值计算所包括的叶切面最大厚度区域搜索、叶切面最大厚度精确计算过程.     

Ranges of the validity of power scaling laws in the description of scale effects of the strength of extended elements of machines and structures

The ranges of the validity of power laws to describe the scale effect of the strength of machine parts and structural elements are evaluated based on the probabilistic-statistical approach to analyzing the scale effect. For small structures, it is necessary to refute the basic assumption of Weibull’s theory on the statistical independence of the values of local strength at various points of structures and transition to using the mathematical model of random field of local strength, which makes it possible to take into account the correlation of strength properties of material in closely spaced points of structure. The derived results underlay the creation of the combined probabilistic scaling law of strength.     

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.     

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.