NYD型逆止器逆止过程的数值模拟

应用Pro／Engineer软件的虚拟样机技术,对NYD型逆止器进行三维实体建模,应用显式动力学弹塑性有限元软件ANSYS／LS-DYNA对逆止器逆止过程进行数值模拟分析,深化了对逆止过程的认识,对各部件受力情况进行了分析,对逆止器的设计和改进具有参考价值。     

NYD型逆止器异形块尺寸参数对逆止性能的影响

应用Pro／Engineer软件建立了NYD型逆止器的三维实体模型,并应用显式动力学弹塑性有限元ANSYS／LS—DYNA软件对具有不同偏心距和圆弧半径的异形块的逆止过程进行数值模拟分析,研究异形块工作面尺寸参数对逆止器逆止性能的影响。研究结果对逆止器异形块的设计和改进具有一定的参考价值。     

非接触偏心圆盘逆止器的设计

介绍作者研制的用于大倾角上运带式输送机的非接触偏心圆盘逆止器，并对这种新型逆止器的基本结构，工作原理，工作特性和强度进行了研究和探讨。     

带式输送机制动器和逆止器的浅析

介绍了带式输送机的工作原理、制动器与逆止器的种类、工作方式以及使用范围。重点指出了:①向上输送的皮带机在倾角小于5°时可不加制动器和逆止器;②向下输送的皮带机则必须加制动器;③对于特别重要的设备,为保证工作正常还必须加两套制动器(一台工作另一台备用)。     

对数螺旋线型面楔块逆止器的设计及动力学分析

对一种对数螺旋线型面的楔块逆止器进行了动力学分析,并对其核心零件--对数螺旋线型面楔块进行了设计。采用Pro/E建立了对数螺旋线型面楔块逆止装置的仿真模型,并将模型导入ANSYS/LS-DYNA软件对其逆止过程进行动力学分析,得到了新型逆止器的逆止接触力、楔合时间和逆止速度等参数的变化规律。该成果为新型对数螺旋线型面楔块逆止器的研制提供了理论依据。     

啮合式非接触逆止器及其受力分析

在分析原有逆止器结构的基础上,提出一种新型的由啮合元件传递力矩的啮合式非接触逆止器。论述了从停止到运转和从运转到停止的逆止工作原理,并对该逆止器在逆止状态下的受力情况进行了分析。     

带式输送机用异形块式逆止器的测试

低速轴用异形块式逆止器是国内最近开发的新产品，是为上运带式输送机设置的防逆转安全装置。本文根据多次的测试，分绍异形块式逆止器应检测的几个运行参数，测试方法及测试数据的处理，为今后生产逆止器进行可靠性评价提供一些依据。     

Third body formation on brake pads and rotors

The surfaces of a brake pad and rotor were investigated after a run-in period during which a stable coefficient of friction had developed. The Focused Ion Beam Technique (FIB) was used to reveal tribologically induced surface films and for cross-sectional preparation of superficial layers. Additional information was obtained by TEM/EDS of thin lamellae prepared with the FIB and by surface analytical methods (GDOS, XPS and RS). Microscopic contact areas of the pad showed bright contrast in Scanning Ion Microscopy (SIM). This was attributed to severe plastic deformation finally leading to a nanocrystalline microstructure. Metallic particles of the pad, the so-called primary contact areas, were mostly covered with a smooth oxide layer of less than 1 μm thickness. Above this layer a thin (100 nm) partly amorphous film was often observed. The film was not only restricted to the metal particles, but also spread over adjacent regions, suggesting that secondary plateaus had formed. Similar layers and films, although with slightly different composition and structure, were also observed at the surface of the rotor.     

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。     

滚子活齿行星传动的模糊可靠性优化设计

滚子活齿行星传动是一种新型的传动方式，它由K-H-V型少齿差行星传动演化而成。由于其传动过程中的特点，使用传统的常规设计方法往往不能够得到理想的设计效果，这里引入模糊可靠性优化设计方法，使得这一问题得到了较好的解决，并给出了应用实例。     

Friction and wear of sintered metallic brake linings on a C/C-SiC composite brake disc

The friction and wear of sintered metallic brake linings on a C/C-SiC composite brake disc were studied. This paper reports on the friction and wear properties of sintered metallic (MMC) brake linings, which appear to combine well with a C/C-SiC brake disc. The friction characteristics were examined with a dynamometer on two different commercial motorcycle brake systems, differing in terms of the brake caliper and the dimensions of the disc. The influence of the components, such as graphite, and the abrasives in the metallic matrix on the formation of the friction layer was investigated using a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The friction layer formed on the pad's sliding surface by oxidation wear, which consisted mostly of iron and copper oxides, was confirmed. The friction properties of the sintered metallic brake pads were determined and related to the composition and structure of the brake lining. This investigation of the friction characteristics of a brake couple comprising (MMC) brake linings and a C/C-SiC composite disc will increase our understanding of this material, which works in a completely different way to classical brakes based on metallic discs.     

On the role of copper in brake friction materials

Copper is a major ingredient in friction materials used for automotive braking. The purpose of this study was to find out how copper contributes to good brake performance properties in addition to providing good thermal conductivity. Microstructural investigations of copper chips at the surfaces of brake pads revealed a zone of severe plastic deformation which provides high hardness, but there is also evidence of recrystallized copper nano-particles which are incorporated into friction layers as soft ingredient once detached from the pad surface. Thus copper seems to play a dual role, firstly as reinforcing element of the brake pad providing primary contact sites, and secondly as solid lubricant by contributing to the formation of a layer of granular material providing velocity accommodation between the rotating disc and fixed pad. Confirmation for this hypothesis was obtained by modelling contact sites on the nanometre scale with the method of movable cellular automata. Results show both, the similarity of steel fibres and copper macro-particles in respect to providing primary contact sites, as well as similar sliding behaviours of friction layers containing either copper or graphite as soft inclusions. Furthermore, it is shown that not only material properties, but also the concentration of solid lubricant particles in the friction layers, determine conditions for friction force stabilization and smooth sliding behaviour.     

圆筒式磁流变制动器的理论设计与分析

磁流变液是磁性颗粒分散于基液中形成的悬浮液,是一种新型智能材料,其屈服强度在外加磁场作用下可以在毫秒级内发生变化,利用磁流变液剪切应力可以进行动力的传递.本文应用Bingham模型描述强磁场作用下磁流变液的流变特性,并以此为基础分析了圆筒式磁流变液制动器的工作机理,建立了制动力矩的计算模型,根据磁流变制动器的特点,导出了制动器设计中主要几何参数的理论计算公式.     

Friction-induced vibration for an aircraft brake system—Part 1: Experimental approach and stability analysis

Friction-induced vibrations are a major concern in a wide variety of mechanical systems. This is especially the case in aircraft braking systems where the problem of unstable vibrations in disk brakes has been studied by a number of researchers. Solving potential vibration problems requires experimental and theoretical approaches. A non-linear model for the analysis of mode aircraft brake whirl is presented and developed based on experimental observations. The non-linear contact between the rotors and the stators, and mechanisms between components of the brake system are considered.Stability is analyzed by determining the eigenvalues of the Jacobian matrix of the linearized system at the equilibrium point. Linear stability theory is applied in order to determine the effect of system parameters on stability.     

盘式制动器结构优化及其制动噪声分析

为进一步研究盘式制动器在制动过程中制动噪声问题,运用序列二次规划理论对盘式制动器进行优化,以制动盘通风孔作为优化对象,将优化得到的几何数据代入几何模型,从而得到一种新型抑制制动噪声的盘式制动器结构,并针对新型结构制动噪声特性相关变化规律进行理论分析和试验验证。研究结果表明:序列二次规划优化算法对于计算盘式制动器制动盘通风孔几何参数问题具有稳定性和准确性,能够为后续产品优化提供计算依据;在制动盘几何模型上加入通风孔后有效地将制动器特征频率进行分离,明显抑制制动噪声问题;通过盘式制动器试验对优化前、后的模型进行验证,试验结果与仿真结果具有一致性,验证了通风孔盘式制动器对于抑制制动噪声尖叫具有重要作用。     

基于UG和3D-ICT扫描的机械零部件反求

主要讨论应用Unigraphics(以下简称UG)和 3D ICT(IndustryComputerizedTomography)扫描技术的方法 ,采用UG二次开发技术 ,开发UG与 3D ICT扫描数据的接口程序 ,并且结合实例 ,论述了从 3D ICT数据到UG可加工模型过程的具体实现方法。为相关机械零部件的逆向工程研究提供借鉴     

Performance and evaluation of eco-friendly brake friction materials

Eco-friendly brake friction materials were formulated without copper, lead, tin, antimony trisulfide, and whisker materials, to minimize their potential negative environmental impacts. A combination of scanning electron microscopy with energy dispersive microanalysis, profilometry, and thermogravimetry allows successful analysis of friction surface and thermal stability of friction materials. Extension evaluation method was applied to rank the friction materials using multi-parameter criteria, including friction, wear, thermal stability, cost of raw materials, and parameters from the brake effectiveness evaluation procedure (BEEP) assessment. The eco-pad (sample E) exhibited the best overall quality, expressed as the weighted average dependent degree in extension evaluation.