摩擦密封材料FKF复合矿物纤维(非石棉型)

我国非石棉型摩擦材料起步较晚 ,90年代中期后 ,非石棉型摩擦材料的应用在我国才越来越广泛。目前盘式刹车片方面 ,非石棉型产品已占配套市场和维修市场的 80 %以上 ,鼓式刹车片方面 ,为大型汽车厂的配套厂已普遍要求提供非石棉型刹车片。我国出口到国际市场的产品中 ,非石棉型摩擦材料占绝大部分。FKF复合矿物纤维是结合我国非金属矿物纤维和其他纤维的资源情况 ,充分考虑到摩擦密封材料对石棉代用纤维材料性能要求开发的。 FKF纤维是一种包括多种矿物纤维 ,主要化学组成有 Si O、Al O、Ca O、Mg O、Fe O和 C等。FKF纤维和其他纤维…     

汽车制动器摩擦材料的研究现状和发展

介绍汽车制动器摩擦材料的研究现状。探讨半金属基摩擦材料、非石棉有机摩擦材料和粉末冶金摩擦材料的优缺点。提出汽车制动摩擦材料研究的发展趋势。     

无石棉混杂纤维增强树脂基摩擦材料

研究了多种非石棉纤维经过混杂替代石棉制成的摩擦材料,并测定其摩擦磨损性能,确定了其中主要非石棉纤维的岩棉和钢纤维的最佳配合,并用蛭石增强摩擦材料的机械强度。从而不仅使摩擦材料的摩擦系数平稳、耐磨性增加、寿命延长,而且还可使对偶的磨损减少。经实际使用,该材料制成的制动片其综合性能优于石棉制动片。     

新型摩擦材料在沪通过鉴定

摩擦材料是各类机械设备制动器、离合器和传动装置中的重要配件,目前常用的摩擦材料是铜基粉末冶金摩擦片和石棉干式摩擦片。这次通过鉴定的湿式石棉摩擦材料不同于干式石棉摩擦     

石棉摩擦材料/钢摩擦副许用温度的试验研究

本文通过实验,分析了石棉摩擦材料／钢组成的制动摩擦副的摩擦系数温度特性和磨损温度特性,提出了石棉／钢摩擦制动副失效温度判据和摩擦材料许用温度的概念,建立了用温度表示的刹车装置摩擦副的许用条件,并测定出几种常用石棉刹车块的计用温度值。     

半金属摩擦材料在隧道掘进机中的应用

研制了半金属树脂基摩擦材料替代石棉摩擦材料，对其摩擦学等性能进行了研究，并在进口掘进机上进行了试用。结果表明：半金属摩擦片的摩擦因数在0．362～0．392之间，变化平稳，在250℃以上高温热衰退少；耐磨性在200℃以下时略低于石棉摩擦片材料，而在200℃以上时与石棉摩擦片材料相当；强度性能达到了原石棉摩擦片材料的技术性能指标。装机试验表明：所研制的摩擦片磨损总量最小，耐磨性能和使用寿命在正常使用或离合器打滑情况下优于石棉摩擦片。     

机械强度对石棉摩擦材料摩擦磨损的影响

本文通过对常温机械强度(冲击强度和布氏硬度)和高温机械强度(拉伸强度和布氏硬度)的近千个试验数据,进行编程电算分析,探讨了它们对石棉摩擦材料摩擦磨损的影响,从而为石棉摩擦材料的设计、加工和使用,提供了一定的参考依据。     

半金属离合器摩擦片性能研究

研制了半金属树脂基摩擦材料,对其摩擦学等性能进行了研究.结果表明：半金属摩擦片的摩擦因数在0.362～0.392之间,变化平稳,在250℃以上高温热衰退少;耐磨性在200℃以下时略低于石棉摩擦片材料,而在200℃以上时与石棉摩擦片材料相当;强度达到了原石棉摩擦片材料的技术性能指标.在进口掘进机上的使用表明：该摩擦片磨损总量较小,耐磨性能和使用寿命在正常使用或离合器打滑情况下优于石棉摩擦片.     

提升机盘形制动器闸瓦材料摩擦性能实验研究

用XDZ-A型摩擦材料制样机将石棉闸瓦材料制备成试验所需的标准试样,用X-DM型调压变速摩擦试验机模拟实际工况,对标准试样开展不同正压力、不同滑动速度和多种温度下的组合实验,全面研究了石棉闸瓦材料与16Mn钢摩擦盘对磨的摩擦学特性。实验结果表明:随着正压力、滑动速度和温度的变化,闸瓦材料摩擦因数均发生变化;摩擦因数随正压力的升高而增大,随滑动速度的增加而减小,但滑动速度对摩擦因数的影响大于正压力的影响;摩擦因数随温度的升高而减小,在200℃左右,摩擦因数下降比较明显。     

摩托车盘形制动器摩擦片材料磨损形貌分析

采用XDZ-A型摩擦材料制样机将有机石棉摩擦片材料制备成试验所需的标准试样,用X-DM型调压变速摩擦试验机模拟摩托车制动实际工况,对标准试样开展不同压力、滑动速度和温度下的组合试验.对扫描电子显微镜(SEM)观测到的有机石棉摩擦片材料与灰铸铁HT250摩擦盘对磨后的磨损形貌进行了分析.分析结果表明:无论是正压力、速度的增大还是温度的升高,都使得摩擦片磨损越来越严重,形貌越来越复杂.     

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.     

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.     

DESIGN AND CAD SYSTEM OF THE FOOL FOR DRILL FLUTE

Based on the principles of differential geometry and kinematics, a mathematical model is developed to describe the grinding wheel axial cross-section with the radial cross-section of the flute in a given drill under the basic engagement condition between the generating flute and the generated grinding wheel (or disk milling tool). The mathematical model is good for the flute in the radial cross-section consisting of three arcs. Furthermore, a CAD system is also developed to represent the axial cross-section of the grinding wheel (or disk milling tool). With the system, the grinding wheel (or disk milling tool) axial cross-section that corresponds to the three-arc flute cross section can be conveniently simulated. Through the grinding experiment of drill flutes, the method and the CAD system are proved to be feasible and reasonable.     

孔隙阀式磁流变阻尼器准静力分析

建立了孔隙阀式磁流变阻尼器的轴对称模型.推导了孔隙阀内磁流变液压力梯度方程.对Herschel-Bulkley模型的磁流变阻尼器压力梯度进行了数值求解.应用代数方程理论,得到了Bingham模型的磁流变阻尼器压力梯度的解析解.最后,结合算例计算了孔隙阀内磁流变液的流速分布及阻尼器的阻尼力.     

车门静态强度的有限元分析模拟

轿车门系统结构设计与优化是整车开发过程中的重要环节。车门的强度直接关系到整车在冲击、碰撞等载荷下的安全问题,车门结构静态强度的计算分析,在车门结构设计进程中非常重要。文中首先简要介绍了静态强度所涉及到的非线性有限元的基本理论,然后以某中高级轿车前车门为例,利用计算机辅助分析车门的静态强度,考虑变形的非线性因素,通过对车门的非线性有限元求解来分析车门强度,由计算所得到的车门强度性能指标来指导车门的结构设计。     

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.     

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.     

平面应变颈缩扩展与剪切断裂的数值模拟

采用虚功率增率有限元法及Ｊ２形变理论，模拟韧性金属平面应变颈缩扩展，剪切断裂演化过程。运用载荷控制的自动识别方法以及各增量步间Ｅｕｌｅｒ控制方法，实现了均匀变形与非均匀变形临界状态的稳定过渡，采用本构方程的Ｅｕｌｅｒ显式积分，对Ｊ２形变理论塑性加载与弹性卸载的不连续性进行了改进，保证了变形局部化模拟过程的可靠性，最后，讨论了不同硬化指数及初始几何不均匀性对局部化力学行为的影响。     

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.     

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.