差动挂轮传动比较小的斜齿圆柱齿轮滚切方法

在普通滚齿机上滚切斜圆柱齿轮时，若出现差动挂轮的传动比小于滚齿机配换挂轮所能调整的最小传动比时，将会造成按正常加工方法无法选择差动挂轮。经过生产实践的研究，总结出了一种滚切这种情况下的斜齿圆柱齿轮的调整计算方法，今介绍如下，和有关人士商讨。     

滚切小螺旋角圆柱齿轮的新方法

滚切小螺旋角圆柱齿轮时,用滚切普通斜齿圆柱齿轮的差动计算式所得差动挂轮的比值很小,造成无法选择挂轮。本文介绍一种滚切小螺旋角圆柱齿轮的挂轮调整计算方法。     

滚切大质数直齿轮△Z的选择

1.问题的提出在Y3150E型滚齿机上滚切齿数大于100的质数直齿圆柱齿轮时,其分齿挂轮、进给挂轮和差动挂轮的传动比分别为:     

一种小螺旋角斜齿圆柱齿轮滚切挂轮选配方法

当斜齿圆柱齿轮螺旋角较小或其它情况时 ,用普通斜齿圆柱齿轮的滚切工艺会无法选配差动挂轮。针对这种情况 ,通过对滚切齿轮原理及调整公式的分析 ,得出了一种方便实用的调整方法和计算公式     

差动挂轮组的计算机优化选择

在滚齿机上加工斜齿圆柱齿轮、大质数圆柱齿轮(包括选不到所需要的分齿挂轮)和用切向进给加工蜗轮时,都需用差动挂轮。差动挂轮的速比直接影响被加工齿轮、蜗轮的精度。滚齿机上差动挂轮速比是一个复杂的数,特别是滚斜齿轮时,速比与螺旋角的正弦值成正比,因此几乎难以选到恰好速比的挂轮组。差动挂轮的速比误差将直接影响斜齿轮的螺旋角误差(即齿向误差),所以一般在加工8级精度的齿轮时,要求选用的差动挂轮速比精确到小     

小螺旋角斜齿圆柱齿轮的滚切加工

由于滚齿机的配换挂轮有限制，当斜齿圆柱齿轮的螺旋角较小或在其它情况下，用普通斜齿圆柱齿轮的滚切工艺就会造成无法选配差动挂轮，针对这种情况，通过对滚切各种齿轮原理及调整公式的分析，得出了一种方便实用的调整挂轮齿数计算公式。     

计算机辅助滚切圆柱齿轮调整计算

在机械设备中,圆柱齿轮是最重要的和最常见的传动元件之一。而最常用的圆柱齿轮加工方法是滚齿,即滚切加工。在滚切前,要进行一系列必要的调整计算,如计算滚刀的转速、进给量的大小、分齿挂轮、差动挂轮、滚刀安装角等等。不同参数     

滚切质数齿的挂轮选择

滚切质数齿的挂轮选择武汉工学院苏民当在具有差动机构的滚齿机上加工大于１００齿以上的质数圆柱齿轮时（如：１０１，１０３……等）．借助于差动挂轮来加工质数齿、是将不便于调整的质数齿Ｚ用可调整的数值Ｚ＇来代替．从而搭配分齿挂轮．使Ｚ＇＝Ｚ±△Ｚ，其中△Ｚ为...     

问题解答

[问]滚切圆柱斜齿轮时,怎样判定差动挂轮是否正确。(黑龙江吴憎)[答]用差动法在滚齿机上切削圆柱斜齿轮时,可按下述方法检查差动挂轮是否正确。为便于讨论问题,以Y38型滚齿机为例。1.调整好速度、进刀、分齿、差动挂轮以后、开空转试车,察看工作台转向。如果使用右旋滚刀加工,无论滚切右旋或左旋齿轮,工作台均应逆时针回转;如果使用左旋滚刀加工,也无论滚切右旋或左旋齿轮,工作台均应顺时针回转。否则,应增加或减去一个分齿挂轮的介轮。2.开快速试车(此时只有刀架的垂直进给运动和工作台     

提高滚铣100齿以上质数圆柱齿轮的齿向精度

一、问题提出有一次,在滚铣齿数z为26的直齿圆柱齿轮时,因z39和z65的交换齿轮丢失,只好采用滚铣100齿以上质数圆柱齿轮的方法来加工z26齿轮,首先选微齿数Δz为—1/6,差动挂轮的齿数查挂轮表,但是滚铣后的直齿圆柱齿轮经检查齿向误差超过齿向公差多倍,后又选微齿数Δz为—1/116,再查挂轮表,重选挂轮,滚铣后的直齿圆柱齿轮经检查齿向公差达到5级精度。为什么都是从挂轮表查得的挂轮比,而滚铣的齿轮有的能达到质量要求,有的却达不到质量要求呢?下面就讨论怎样提高滚铣100齿以上质数圆柱齿轮的齿向精度。     

PHENOMENON OF CARVED DRIVING WHEELS

A newly found phenomenon of carved driving wheels of a rear-wheel-drive tractor used in an airport is discussed. The circum of every driving wheel is damaged at three regions,which distribute regularly and uniformly. Everyday,the tractor tows a trailer which are times heavier than the tractor,and moves on the same road in the airport. The phenomenon is explained by the torsional self-excited vibration system of the powertrain. The simplified torsional vibration system is discribed by a 2-order ordinary differential equation,which has a limit circle. Experiments and numerical simulations show the followings: Because of the heavy trailer,the slip ratio of the tractor’s driving wheels is very large. Therefore,there is severe torsional self-excited vibration in the tractor’s drivetrain,and the self-excited vibration results in severe and regular fluctuations of the rear wheel’s velocity. The severe fluctuations in velocity fastens the damage of the driving wheels. At the same time,the time interval in which an arbitrary point in the circum of the driving wheel contacts with the road twice is two times more than the period of the torsional self-excited vibration,and this times explained the existence of three damaged regions. At last,it points out that the phenomenon can be avoided when the torsional damping is large enough.     

Effects of prebuckling deformations on the elastic flexural-torsional buckling of laterally fixed arches

The effect of the prebuckling in-plane deformations on the elastic flexural-torsional buckling of laterally fixed circular arches is studied in this paper. The finite strains and the energy equation for the flexural-torsional buckling of arches have been derived based on an accurate orthogonal rotation matrix. A closed form solution for the elastic flexural-torsional buckling resistance of laterally fixed arches in uniform bending, including the effects of the prebuckling deformations, is obtained. It is found that the notion that the prebuckling deformations increase the flexural-torsional buckling moment of an arch or of a beam is not necessarily correct for a laterally fixed arch or beam in uniform bending, in deference to a laterally pinned arch. When a laterally fixed arch is subjected to positive uniform bending, the effects of the prebuckling deformations decrease the buckling moment, and the reduction of the buckling moment increases with an increase of the included angle and of the out-of-plane slenderness ratio of the arch. When a laterally fixed arch is subjected to negative uniform bending, the effects of the prebuckling deformations decrease the absolute value of its buckling moment when the included angle is very small, but increase the absolute value of the buckling moment when the included angle exceeds a certain value. The increase in the absolute value of the buckling moment increases with an increase of the included angle and of the out-of-plane slenderness ratio of the arch. When the ratio of the out-of-plane to the in-plane second moments of area of the cross-section is not small, both the reduction of the buckling moment of a laterally fixed arch in positive uniform bending and the increase of the buckling moment of a laterally fixed arch in negative uniform bending, are substantial.     

气化炉三维扫描测量与数据处理

以德士古气化炉耐火砖的内壁蚀损检测设备为基础,对采集到的点云数据做了进一步处理.通过对数据的筛选和剔除,实现了数据点的平滑降噪细化和精简.然后利用点云对整、网格划分和分色显示等方法,最终完成了内壁腐蚀情况的三维建模.重点讨论了点云数据的预处理及后处理的方法,并根据内壁耐火砖的腐蚀阈值,提出了一种气化炉内壁腐蚀区域的识别与分割方法.对耐火砖的腐蚀分析、气化炉的生产与维修提供了可靠依据,并在工程应用中获得了一致认可.     

VOLUME DEFECT FATIGUE FAILURE OF CERAMIC BALLS UNDER ROLLING CONDITION

A newly developed pure rolling fatigue test rig with three contact points is used to test the rolling contact fatigue properties of silicon nitride ceramic balls. Ball surfaces are examined after failure with optical microscopy and scanning electron microscopy. The failure cause,fatigue phenomenon and mechanics are analyzed. The research shows that subsurface cracks play a dominant role in the formation of spalling failure. These cracks originated from volume defects of the material and propagate,to form elliptical fatigue spalls under the action of principal tensile stresses. The principal tensile stress increases with increasing contact load,causing spall formation and reduction of rolling contact life. The greater the principal tensile stress is,the more severe the peeling of near surface is. Under the same condition,the closer volume defects are to the surface,the more likely failure occurs,the shorter the rolling contact life is.     

OUT-OF-PLANE COMPRESSIVE PROPERTIES OF HEXAGONAL PAPER HONEYCOMBS

The compressive behaviour of paper honeycombs is studied by means of an experimental analysis. Experiment results show how geometry aspects of hexagonal paper honeycombs,e.g. the height of paper honeycomb,the thickness and length of honeycomb cell-wall,the drawing ratio of hexagonal honeycomb,affect the compressive properties of the paper honeycombs. It is in good agreement with the theory model. The constraint factor K of the critical buckling stress is mainly determined by the length of honeycomb cell-wall. It can be described as K=1.54 for B type paper honeycombs and K=3.32 for D type paper honeycombs. The plateau stress is the power exponent function of the thickness to length ratio of honeycomb cell-wall,and the experiment results show that the constant is 13.2 and the power exponent is 1.77. The research results can be used to characterize and improve efficiently the compressive properties of paper honeycombs.     

OPTIMIZING DESIGN OF MECHANICAL SELF-CENTERING DEVICE FOR SUSPENSION HEIGHT

Firstly, in view of the respective defects of existing self-centering devices for vehicle suspension height, the design scheme of the proposed mechanical self-centering device for suspension height is described. Taking the rear suspension of a certain light bus as a research example, the structures and parameters of the novel device are designed and ascertained. Then, the road excitation models, the performance evaluation indexes and the half-vehicle model are built, the simulation outputs of time and frequency domain are obtained with the road excitations of random and pulse by using MATLAB/Simulink software. So the main characteristics of the self-centering suspension are presented preliminarily. Finally, a multi-objective parameter design optimization model for the self-centering device is built by weighted sum approach, and optimal solution is obtained by adopting complex approach. The relevant choosing-type parameters for self-centering device components are deduced by using discrete variable optimal method, and the optimal results are verified and analyzed. So the performance potentials of the self-centering device are exerted fully in condition of ensuring overall suspension performances.     

CONCURRENT PRODUCT PORTFOLIO PLANNING AND MIXED PRODUCT ASSEMBLY LINE BALANCING

Reconfigurable products and manufacturing systems have enabled manufacturers to provide "cost effective" variety to the market. In spite of these new technologies, the expense of manufacturing makes it infeasible to supply all the possible variants to the market for some industries. Therefore, the determination of the right number of product variants to offer in the product portfolios becomes an important consideration. The product portfolio planning problem had been independently well studied from marketing and engineering perspectives. However, advantages can be gained from using a concurrent marketing and engineering approach. Concurrent product development strategies specifically for reconfigurable products and manufacturing systems can allow manufacturers to select best product portfolios from marketing, product design and manufacturing perspectives. A methodology for the concurrent design of a product portfolio and assembly system is presented. The objective of the concurrent product portfolio planning and assembly system design problem is to obtain the product variants that will make up the product portfolio such that oversupply of optional modules is minimized and the assembly line efficiency is maximized. Explicit design of the assembly system is obtained during the solution of the problem. It is assumed that the demand for optional modules and the assembly times for these modules are known a priori. A genetic algorithm is used in the solution of the problem. The basic premise of this methodology is that the selected product portfolio has a significant impact on the solution of the assembly line balancing problem. An example is used to validate this hypothesis. The example is then further developed to demonstrate how the methodology can be used to obtain the optimal product portfolio. This approach is intended for use by manufacturers during the early design stages of product family design.     

The effect of basic nitrogen compounds on the tribological performance of sulphurised olefin

The effect of the molecular structure of basic nitrogen compounds on the lubricating properties of sulphurised olefin has been investigated using a Timken tester. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Analysis (EDAX) were used to study the chemical states of sulphur and nitrogen on the rubbed surfaces and the reaction rates of sulphur and iron separately. It was found that the antiwear and friction reduction properties of sulphurised olefin are greatly influenced by the different molecular structures of the basic nitrogen compounds. A composite additive package containing basic nitrogen compounds with sulphurised olefin can produce either synergistic or antagonistic effects, due to the influence of the different molecular structures of the basic nitrogen compounds. XPS analysis revealed that a tribochemical protective film containing nitrogen and sulphur was formed on the rubbed surface. EDAX analysis indicated that the reaction rates between elemental sulphur and iron were influenced by the different molecular structures of the basic nitrogen compounds. It was found that the apparent reaction rates of elemental sulphur and iron are related to the tribological characteristics of the additive package.     

IMPROVED METHOD FOR HILBERT INSTANTANEOUS FREQUENCY ESTIMATION

In the mechanical fault detection and diagnosis field, it is more and more important to analyze the instantaneous frequency (IF) character of complex vibration signal. The improved IF estimation method is put forward aiming at the shortage of traditional Hilbert transform. It is based on Hilbert transform in wavelet domain. With the help of relationship between the real part and the imaginary part obtained from the complex coefficient of continuous wavelet transform or the analytical signal reconstructed in wavelet packet decomposition, the instantaneous phase function of the subcomponent is extracted. In order to improve the precise of IF estimated out, some means such as Linear regression, adaptive filtering, resampling are applied into the instantaneous phase obtained, then, the central differencing operator is used to get desired IF. Simulation results with synthetic and gearbox fault signals are included to illustrate the proposed method.     

集中管理式公用电话计费系统

简要介绍了集中管理式公用电话计费系统的组成及功能.系统由公用电话集中管理中心与集中管理式电话计费器组成.集中管理中心与集中管理式电话计费器之间可通过公众电话网以拨号方式建立双向通信链路,从而实现对集中管理式电话计费器的远程管理.文中对集中管理式公用电话计费器的硬件设计作了系统的描述.自己设计了电话计费器与电话线的独特接口电路.对计费器软件的重点,即摘、挂机及拨号脉冲识别程序的设计,提出了一套完整的理论依据.