基于UG的高精度棱体成形车刀CAD系统

根据成形车刀的设计理论,开发出了一种基于Windows XP和UG二次开发平台、以VC为编程工具的成形车刀CAD系统.该系统利用自动截形法获得成形车刀"零误差"刀刃廓形,利用最小半径控制点技术实现了棱体成形车刀基于特征的参数化设计,使用数据库技术实现成形车刀的切削角度、结构尺寸的参数化设计,解决了原来成形车刀设计的设计精度和效率较低等问题,彻底消除了双曲线误差.借助该系统可直接快速、准确地生成高精度棱体成形车刀工程图以及廓形的数控线切割加工程序.     

高精度圆体成形车刀的基于特征参数化CAD系统

根据成形车刀的设计理论,综合运用UG/OpenMenuScript、UG/Open UIStyler、UG/Open API和VisualC++6.0等UG二次开发工具,开发出了基于WindowsXP和UG二次开发平台、以VC为编程工具的成形车刀CAD系统。该系统利用自动截形法获得成形车刀"零误差"刀刃廓形;利用最小半径控制点技术实现了圆体成形车刀的基于特征参数化设计;使用数据库技术实现成形车刀的切削角度、结构尺寸的参数化设计;编程实现了工程图的尺寸标注功能及圆体成形车刀剖视图的建立;解决了原来成形车刀设计的设计精度和效率低等问题。借助该系统可直接快速、准确地生成高精度圆体成形车刀工程图以及廓形的数控车床加工程序。     

Pro／E在棱体成形车刀设计中的应用

成形车刀是一种加工回转体成形表面的专用工具,它以其加工精度稳定、生产率高、刀具使用寿命长和刃磨简便等特点广泛应用于卧式车床、转塔车床、自动及半自动车床以及生产自动线上。但由于成形车刀前角和后角的原因,刀具截形与工件廓形不同,这给成形车刀的设计和制造带来很大的困难,使得成形车刀的设计周期长,制造成本高。     

成形车刀在数控车床加工中的应用

在车削加工较大批量的中小尺寸复合成形表面时,采用成形车刀具有加工质量稳定、加工效率高等特点,因此成形车刀被广泛应用于各类车床及自动化生产线.以阀盖数控车床加工为例,介绍了成形车刀中刀头和刀柄的设计与制作,以及应用成形车刀后的工艺实现过程.     

基于AutoCAD的成形车刀截形作图设计方法

提出利用AutoCAD 2 0 0 0对成形车刀截形进行作图设计 ,讨论了棱体和圆体成形车刀截形的作图设计原理和方法 ,并举例说明了棱体成形车刀工作图的设计步骤     

成形车刀的反形法快速设计

反形法加工成形车刀是以同工件廓形一样的刀具去切削二类成形车刀的刀具坯。在SolidWorks三维设计环境中模拟工件和刀具在实际加工时相互位置关系 ,以此方法进行造型实现成形车刀的快速设计。     

成形车刀的一种简易精确设计法

针对成形车刀设计存在的问题提出了一种简单，易行的成形车刀精确设计法。     

棱体成形车刀的精确设计及圆锥形零件的成形加工

针对棱体成形车刀的某些不足，对侧置及径向棱体成形车刀的精确设计公式进行了推导，并提出一种简便的加工圆锥形零件成形车刀的精确设计方法。     

线切割机床加工成形车刀

一般的成形车刀,都是在刀具磨床上加工而成,不具备这种刀具磨床的单位,要自制成形车刀,只有靠手工在砂轮上磨出。但手工磨制的成形车刀。很难保证刀具的设计精度.从实践中,我们摸索到在线切割机床上加工成形车刀,其精度达到了设计要求。现介绍加工过程如下: 在线切割机床上加工成形车刀,需事先做一套割刀夹具(图1),使刀杆能在夹具中上、下、左、右自如地转动、倾斜及定位紧固。     

圆体成形车刀廓形的快速精确设计与制造

根据圆体成形车刀的设计理论，提出了一种利用三维造型技术并结合参数化设计技术实现成形车刀廓形上每一点的准确设计和参数化设计的方法，并采取PCBN刀具以车代磨在数控车床上加工成形刀具后刀面，实现了成形车刀廓形的CAD/CAM集成，可快速，精确地对成形刀具磨形进行设计与制造。     

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.