Wear on St. 5 steel due to jets of dilute aqueous solutions containing high polymers of various types

Wear cavities in St.5 steel samples created by jets of aqueous solutions containing polymers of various kinds are examined; the cavities are evidently formed by an impact mechanism arising as a result of the sudden deceleration of viscoelastic associates of the polymer solutions at the steel surface.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 25, No. 12, pp. 1059–1063, December, 1974.     

钢氧化磨损的轻微-严重磨损转变

研究了多种钢在400℃高温磨损行为,发现钢具有共同的磨损规律。在低载时钢的磨损率和磨损增长率均较低,随着载荷增加,在某一载荷磨损率快速提高。钢高温磨损的本质是一个包含磨面氧化、基体热软化和塑变的物理化学过程。对钢的高温磨损提出了氧化磨损中轻微-严重磨损转变模型及其特征。     

磨粒对齿轮箱磨损状态的影响

工程实践中迫切需要探究齿轮箱润滑油中磨屑的变化规律,从而实现对齿轮箱磨损状态的准确评价,进而系统性地揭示齿轮箱的失效机理。采用自主研制的齿轮箱磨损试验机进行摩擦试验探究,采用分散添加不同粒径铁磁性颗粒进入润滑油以及对纯净新油品中铁磁颗粒浓度规律进行跟踪监测的方法,结合对齿轮表面的形貌观测以及油样中的磨损颗粒的铁谱分析和磨损类型判断等技术方法,系统分析了齿轮箱的磨损失效机理。结果表明:磨粒的直径分布导致了不同的齿轮箱磨损失效机理,小尺寸颗粒易造成齿轮箱发生滑动磨损,而大尺寸磨粒主要引起齿轮箱发生疲劳磨损失效;工程应用中,润滑油铁磁颗粒浓度变化曲线的斜率达到tan50°时,齿轮表面发生轻微的点蚀磨损;浓度变化曲线斜率增至tan70°时,齿轮箱齿面已发生严重破坏,应做出预警处理。     

Erosive Wear and Wear Mechanism of in situ TiCp/Fe Composites

1.IntroductionMetal-based composite is a kind of environmental ma-terial that can be reused.It combines the beneficialproperties of the metal matrix,such as ductility,goodthermal and electrical conductivity and high toughness,with those of the reforcement phase[1~3].The latter isusually a ceramic,serving to increase the elastic modu-lus,shear strength and hot strength,fatigue and wearresistance.Its development has been widely studied[4~8].Wear of metal materials causes a tremendous loss of ec…     

滚动直线导轨副磨损特性和磨损机理试验研究

对国内外生产的45型滚动直线导轨副进行精度保持性对比试验,并对导轨副的精度保持性进行检测。基于Hertz接触理论和刚体动力学对滚珠和滚道的接触面进行了力学与变形分析,求出滚珠所受的最大接触应力,用Workbench进行仿真验证,为磨粒磨损机理和粘着磨损机理的研究提供参考。根据导轨副的运动工况和结构设计,使用场发射扫描电镜和白光干涉仪对上述试验后的导轨副的滚道和滚珠进行显微形貌观测,探究了导轨副的磨损特性和磨损机理。对比国内外滚动直线导轨副的滚道、滚珠的磨损程度,得出磨损是影响精度保持性的根本原因。     

Freeforming of polymers

Rapid prototyping and freeform fabrication methods are being increasingly used as a stage in the design cycle of polymers. They also represent new ways of processing materials and particularly provide much closer coupling between materials synthesis and materials processing. Freeforming techniques also allow new combinations of materials to be formed, such as functional gradients, oriented composites, porous structures and devices.     

Wear of metal by rubber

Rates of wear have been determined for steel and bronze scrapers sliding over rubber surfaces. The wear rates were found to depend strongly upon the particular elastomer used, varying by orders of magnitude even though the other ingredients in the compound and the physical properties of the rubber were largely unchanged. In the absence of oxygen the metal scrapers were found to wear away much faster in general; by a factor of 5 to 50 times, depending upon the elastomer. Butyl rubber was anomalous in this respect, however, causing three times greater wear in air than in nitrogen. These diverse observations are attributed to the direct attack upon metals of free radical species generated by mechanical rupture of elastomer molecules during abrasion. The rate of metal wear is closely correlated with the stability of polymeric radicals formed in this way. When the radical is highly reactive it is thought to take part primarily in internal reactions and thus cause little wear of the scraper. On the other hand, relatively stable polymer radicals appear to attack metals vigorously.     

Wear of Tailored Forming Steels

This study investigates the wear behavior of additively welded cladding layers on less wear-resistant base materials using plasma-transferred arc welding and laser hot-wire cladding. The cladding layers are made from atomized AISI 52100, AISI 5140, and a stainless steel with (0.52 wt% C, 0.9 wt% Si, 14 wt% Cr, 0.4 wt% Mo, 1.8 wt% Ni, 1.2 wt% V, bal. Fe) on unalloyed steel AISI 1022M as the base material. The specimens' microstructure and surface hardness are comparable with conventional specimens of monolithic AISI 52100 and AISI 4140, which is used as a reference. Tribometer tests are carried out in ball-on-disk configuration to investigate the wear resistance of the specimen. The multimaterial specimens show comparable wear behavior to their monolithic counterparts, and a good performance of the stainless specimen in pure sliding is proven. These findings suggest that additive manufacturing processes can be used to clad less wear-resistant base materials and achieve high wear resistance, making it possible to exploit the advantages of surface coatings under severe wear conditions.     

Fatigue of polymers

The general nature of fracture in polymers, when subject to alternating loads as distinct from static or steadily increasing loads, is reviewed; and the molecular mechanisms and micromechanics aspects of the fatigue fracture process are discussed. Some attention is given to thermal fatigue, where fracture results primarily from a large specimen temperature rise due to hysteresis heating. However, primary emphasis is devoted to mechanical fatigue, in which fracture is a result of initiation and propagation of a crack, as a result of the periodic nature of the applied load.Attention is given to the important internal, or material, variables such as polymer structure, molecular weight, crosslinking, and filler or diluent type and content; and to significant external variables such as stress or stress intensity factor amplitude, mean stress, temperature, frequency and environment. Various methods that can be utilized to provide significant degrees of enhancement in the fatigue resistance of polymers are outlined and discussed.

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Résumée On passe en revue la nature générale de la rupture dans les polymeres lorsqu'ils sont sujets à des contraintes alternées en contraste par rapport à des contraintes statiques on croissantes de manière régulière. On discute également les mécanismes moléculaires et les aspects micromécaniques qui prennent place dans le processus de rupture par fatigue. Une attention particuliere est accodée à la fatigue thermique où les résultens de fatigue résultent principalement d'une élévation sensible de la température de l'éprouvette en raison du chauffage par hystérèse. Cependant,l'accent est principalement consacré à la fatigue mécanique dans lequel la rupture est le résultat d'un amorçage et d'une propagation d'une fissure tels qu'ils resultent de la nature périodique des charges appliquées.On accorde une attention particulière à des variables importantes internes ou caractéristiques du matériau telles que la structure du polymère, le poids moléculaire, les liaisons et le type et contenu des agents de dilution. Des variables externes significatives telles que la contrainte ou 1'amplitude du facteur d'intensité de contrainte, la contrainte moyenne, la température, la fréquence et l'environnement sont également pris en considération. Des méthodes variées susceptibles d'être utilisées en vue d'accroitre de manière significative la résistance à la fatigue des polymères sont mis en avant et sont discutés.

     

Living polymers

A body of experimental evidence is now accumulating on the macroscopic and microscopic properties of living polymer solutions: solutions of active polymer molecules in dynamic chemical equilibrium with their constituent monomers. Computer simulations could provide a valuable complement to the experimental and theoretical work on these systems. We present the features of living polymer systems which are crucial to a relevant simulation. We give a set of questions which might be addressed by such simulations.     

Coordination polymers

The crystal engineering of coordination polymers has always held great potential for applications in many areas, such as molecular magnetism, heterogeneous catalysis, molecular sieving and non-linear optics. In recent times that potential has been realised, with many new materials with useful applications reported. In addition, many new interesting network topologies and unusual modes of interpenetration have been discovered.     

Wear resistant composite coatings

In the search for wear resistant coatings, nanolaminated composite films composed of alternating metallic and ceramic layers, namely, Al/Al₂O₃ and Ti/TiN were produced using radio frequency magnetron sputtering. The metal layer thickness in the as-sputtered films of Al/Al₂O₃ ranged from 70 to 500 nm, and 150 to 450 nm in Ti/TiN. The non-metals (Al₂O₃ and TiN) layer thicknesses ranged from 10 to 40 nm and total film thicknesses of 10–15 µm. All coatings were characterized and tested for their tribological properties. Friction and wear tests were performed under non-lubricated sliding conditions using a pin-on-disc type tribometer. The coefficient of friction of the composite coatings tested, against a stainless steel pin, varied with the sliding distance. At the early stages of sliding the coefficient of friction rose to a peak, followed by a decrease to a steady-state value. Wear rates and coefficients of friction were related to the hardness and to the structure refinement of the coatings.     

贝氏体和马氏体耐磨钢的高温磨损性能对比研究

目前,对贝氏体和马氏体耐磨钢在高温环境下的磨损性能研究较少。利用销盘磨损试验机,对400 HB级低合金贝氏体耐磨钢NR400和马氏体耐磨钢NM400的高温(400℃)耐磨性能进行了对比研究,利用扫描电镜及台阶仪等对其组织及磨损表面进行分析,并对磨损机理进行了探讨。结果表明:由于NR400钢具有高硬度、较好的回火稳定性和韧性,其磨损率小于NM400钢的,高温耐磨性较好;NM400钢的磨损机理主要为磨粒磨损、氧化磨损和疲劳磨损,NR400钢的磨损机理主要为磨粒磨损和氧化磨损。