Nondestructive evaluation of the characteristics of degraded materials using backward radiated ultrasound

The frequency dependency of Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in two kinds of degraded specimens by scuffing or corrosion. Then, the frequency dependency is compared with the residual stress distribution or the corrosion-fatigue characteristics for the scuffed or corroded specimens, respectively. The width of the backward radiation profile increases with the increase of the variation in residual stress distribution for the scuffed specimens. In the corroded specimens, the profile width decreases with the increase of the effective aging layer thickness and is inversely proportional to the exponent, m, in the Paris’ law that can predict the crack size increase due to fatigue. The result observed in this study demonstrates high potential of backward radiated ultrasound as a tool for nondestructive evaluation of subsurface gradient of material degradation generated by scuffing or corrosion.     

EXPERIMENTAL INVESTIGATION ON PARTICLE EFFECT IN PISTON RING-CYLINDER LUBRICATION

To study the tribological properties of the piston ring-cylinder liner in liquid-solid lubrication, the experiment is carried out on a modified piston ring-cylinder liner tester. Two kinds of liquid-solid lubricants are used, one with ultra-dispersed diamond (UDD) nano-particles suspending in pure lubricant, the other with micro-sized M0S2 particles. The particle concentrations are 0%, 0.02% and 0.1% by weight. The experimental temperature is 30℃ and 75℃ respectively. The results show that with the presence of ultra-dispersed diamond particles, the load when scuffing failure occurs is increased.For the lubricant contains MoS2 particles, the scuffing load is decreased. The liquid-solid lubricant also affects the thermal behavior of piston ring-cylinder liner. The surface bulk temperatures of cylinder liner specimen are measured. It has been seen that liquid-solid lubricant used in this research tends to improve the thermal properties generally and the measured friction forces also decreases with the presence of UDD nano-particles. The surface bulk temperature when scuffing occurs is also measured. The results show that the size effect and environment temperature have obvious influence on scuffing load and scuffing temperature. With some new findings, this work is an important complement to the existing research on particle effect on lubrication, because the existing results only show one aspect of this problem.     

SCUFFING MODEL CONSIDERING INFLUEN OF HYDRODYNAMIC LUBRICATION

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高重合度直齿渐开线圆柱齿轮传动承载能力与优化设计研究

本文系统地研究了高重合度齿轮齿副的变形与刚度、同时啮合齿对之间的载荷分配、胶合承载能力、弯曲强度、接触强度、参数优化设计.     

X-Rays as a Tool for Investigation of Scuffing and Boundary Lubrication

A suite of X-ray-based techniques has been adopted for the investigation of scuffing and other tribological failure modes. Depth-profiled X-ray diffraction, reflectivity, and fluorescence are being used to gather information on additive reaction film thickness, roughness, and electron density, presence and distribution of additive elements within those layers, identification of crystalline phases in the reaction film and subsurface material, and degree and depth of deformation. The differences between the samples and equipment used in development of this approach, and the production mechanical parts and laboratory X-ray systems, are discussed, with emphasis on application of the approach in industry.     

柴油机拉缸的机理、影响因素及解决的途径

阐述了柴油机拉缸的机理,分析了引起柴油机拉缸的设计、制造、装配和使用四方面的因素,并简要介绍了预防和解决拉缸的途径。     

Scuffing resistance of salt bath nitrocarburized medium carbon steel

The usefulness of the ferritic nitrocarburizing treatment for improving the tribological properties of ferrous components is well established. However, the thin compound layer of beneficial epsilon carbonitride that develops at the surface lacks the ability to bear high Hertzian stresses. Nitrocarburizing in the austenite phase field of the Fe---N---C system overcomes this disadvantage since the formation of a hard zone of martensite-bainite below the compound layer provides the back-up to withstand point loads. Results of the Falex scuffing test indicate that the failure load increases on account of the thicker compound layer at the surface. The results indicate further that the frictional heat generated during the test coupled with working by the jaws convert the retained austenite present in the sub-compound layer to harder microconstituents. The study suggests that the austenitic treatment could be useful for applications involving simultaneous heat and work such as hot working dies.     

齿轮胶合的计算和试验研究

根据基于系统和时变观点的齿轮胶合机理分析［１］，研究了齿轮传动的啮合特点，并以非稳态齿轮本体温度场的有限元分析，计算了齿轮本体温度场的分布，结合文献［２］的研究结果，建立了齿轮传动的胶合计算方法。还介绍了作者进行的齿轮胶合试验，试验结果表明：利用本研究的计算方法得到的胶合载荷与试验结果基本相符，试验结果还表明：在同一种“油－材料”组合下，由作者设计的齿轮温度测量装量测出的发生初期胶合时的齿面温度不是一个常数，它与转速、扭矩、运转方式及油量等都有很大关系；初期胶合发生后，齿轮传动还可继续工作。因此本研究认为，监测初期胶合，对于防止齿轮传动发生胶合、咬死等重大损坏有重要意义。     

Tribological behavior of boundary lubricated sliding surfaces using three different spacing of surface profiles

The ball-on-disk type sliding tests with boundary lubricated steels were carried out to verity the effect of initial spacing in surface profiles on wear and scuffing. Three kinds of surface spacing, which are closely related with initial surface micro-cracks on sliding surfaces, were produced onAISI 1045 steel surfaces using different grinding and polishing processes. Frictional forces and time to scuffing were measured, and the shape and amount of wear particles were analyzed to compare the with original surface profiles. From the tests, it was confirmed that the size of wear particles are related closely to the original spacing of the surface profile. The time to failure and amount of wear were sensitive to the surface spacing. The wider surface spacing shows much longer sliding life and smaller amount of wear than the others. Time to scuffing was increased with increasing surface profile spacing. The size of wear particles increased while the wear and wear rateK were decreased with an increase in surface spacing. After the sliding tests, surface cracks of inner parts of the wear track formed due to scuffing were observed and compared among the specimens having the different surface spacing.     

齿轮润滑中PV曲线新特性及计算模型

大量资料表明,预测齿轮胶合常用的PV曲线在较宽的速度范围内具有抛物线型特征,过去还没有一种理论能对此作出合理的解释,本文根据齿轮润滑中不同的节线速度范围提出了反应膜的机械磨损和化学分解两种失效机理,进而对这两种机理作出了定量描述。在此基础上建立了一个综合计算模型,即胶合载荷与节线速度间是近似的二次函数关系,该综合模型与有关文献的试验结果相一致。本文为PV典线的高—低—高变化规律提供了合理的解释。