Lubrication Studies with Alumina-on-Alumina, Steel-on-Steel, and Steel-on-Alumina Bearing Systems

In metal bearing systems, good lubricants for boundary lubrication generally show chemical interaction with the bearing surface under the conditions of temperature and pressure generated in the sliding contact. In this study, tests in a four-ball wear tester have been used to compare lubricants under similar loadings using steel-on-steel, steel-on-alumina, and alumina-on-alumina bearing systems. In general, the alumina appears to be far less reactive with lubricants than steel. Alumina-on-alumina bearing systems do show a sensitivity to lubricant chemical composition with generally higher wear values than the other two bearing systems. Steel-on-alumina bearing systems generally show better wear characteristics than the all-alumina systems which indicates the improved chemical interactions between the steel and the lubricant. This study shows that the chemical reactivity of the lubricant with the bearing surface is important in the wear process.     

Strategies for revealing deformation and wear mechanisms of polymer composites by combining scanning electron microscopy,energy dispersive x-ray spectroscopy and cross-section techniques—Exemplified by glass fiber reinforced poly-phenylene-sulphide

Polymers and polymer composites are frequently used in tribological applications. However, their use is often limited by excessive wear or plastic deformation, therefore research and development aiming to improve the materials is ongoing. Tribological evaluations of polymer composites often study the friction coefficient and wear rate for different types, sizes and amounts of fillers. But rarely are any mechanisms presented. Although polymer materials differ from metals, the techniques typically used for metal components, for example, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS), can be adapted to polymer materials, to achieve more informative SEM micrographs and EDS analyses. The aim of this article is to present useful analysis strategies, from sample preparation and selection of viewing angles, to selection of instrument settings and detector types. The strategies are exemplified by analysis of poly-phenylene-sulphide filled with glass fiber, evaluated against steel in a reciprocating ball-on-flat test set-up. This article takes its starting point with the worn surfaces, and subsequently analyze them using SEM and EDS. A selection of cross section preparation techniques, analysis parameters and microscopy settings are presented and discussed. By combining these techniques and settings, the observation of a strongly modified surface layer, as well as sub-surface plastic deformation and imbedded wear particles, is facilitated.     

难加工材料的高速铣削研究进展

目的 分析难加工材料在高速切削过程中的基本形式及其特点,归纳总结现有的高速切削理论及现象。方法 主要从难加工材料的实验现象和仿真出发,分析高速加工机理,将现有高速铣削方法及其进展进行解析。结果 高速切削在宏观领域的研究主要集中在切屑的形成与刀具磨损,而在微观加工领域,主要研究材料属性及微观结构对于加工的影响。结论 从研究趋势上看,对宏观加工模型和微观理论分析的研究均有进展,但对微观模型的研究逐渐成为了近年来的研究热点。     

冷喷涂Cu402F涂层激光重熔表面改性后摩擦学行为

目的研究激光重熔后冷喷涂Cu402F涂层在腐蚀介质中的摩擦学行为。方法采用冷喷涂技术在镍铝青铜9442合金上制备了厚度约为882.11μm的Cu402F涂层,并使用激光重熔技术对冷喷涂涂层进行表面改性。使用OM、SEM观察涂层截面与表面的微观形貌;使用XRD、X射线残余应力测试仪、多功能表面性能测试仪、多频直线往复磨蚀实验机,重点表征测试了涂层的组织、表面残余应力、摩擦学性能与磨蚀行为。结果激光重熔后的涂层分为表面重熔层、多孔的重熔过渡层以及冷喷涂遗传层。激光重熔前后,涂层的物相、残余应力均未发生较大变化。在20、50、100 N条件下,激光重熔态涂层的平均摩擦系数呈递增趋势,磨损率分别为1.01×10~(-2)、1.17×10~(-2)、1.34×10~(-2) mm~3/(N·m);由磨蚀实验可知,磨蚀是涂层表面产生钝化膜与钝化膜被破坏的此消彼长的过程,反映着摩擦与腐蚀的协同作用,涂层在磨蚀过程中,开路电位与摩擦系数呈正相关,说明激光重熔态涂层表面钝化膜产生的速度快于钝化膜被坏的速度。结论激光重熔保留了冷喷涂技术制备的Cu402F涂层的优点,同时激光重熔涂层上产生钝化膜的速度更快,有利于提高涂层的耐磨蚀性能。     

La2O3改性树脂基制动材料的摩擦学性能

通过定速摩擦试验、CHASE摩擦试验及磨损表面形貌观察等方法探讨La₂O₃含量对稀土La₂O₃改性树脂基制动材料的摩擦磨损性能、抗热衰退性能与恢复性能的影响。定速摩擦试验结果表明,制动材料中添加适量La₂O₃可有效提高其摩擦因数,降低其磨损率,同时还可增加其摩擦因数的稳定性;其中,添加20% La₂O₃试样的综合摩擦学性能为最优。CHASE摩擦试验结果表明,La₂O₃的加入可有效提高复合材料的抗热衰退性能与恢复性能。     

离子液体极压抗磨剂的研究进展

极压抗磨剂是一类重要的润滑油添加剂,是齿轮油不可缺少的主剂。相比传统极压抗磨剂,离子液体结构的可设计性、分子中含有的活性元素、优异的化学稳定性及较高的热分解温度,使其在摩擦学领域受到广泛关注。基础油的极性会对离子液体的溶解性能有所影响,基于此,本文归纳了离子液体分子构型对其在不同极性基础油中溶解度影响的研究进展,探讨了离子液体在不同极性基础油中的摩擦学性能及作用机理,总结了离子液体与其他添加剂复配的效果。文中指出,大多离子液体在极性油中有较好的溶解度,在非极性油中阳离子和阴离子结构对其溶解性都有影响;在极性油中与非极性油中,具有优异摩擦学性能的离子液体都含有活性元素;离子液体与其他添加剂的复配会对其性能有所影响。最后,结合目前工作中的不足之处,针对离子液体极压抗磨剂的未来发展方向提供了建议。     

一种基于口腔软摩擦学的奶茶顺滑特性评价模型

该文系统研究了奶茶主要原料植脂末（5.00~100.00 g）、冰块（5.00~200.00 g）和糖浆（0~12.00% m/m）添加量对奶茶顺滑特性,包括粒径分布、流变特性、感官评价及口腔软摩擦学的影响,通过补充和优化现有标准,成功建立了特异性针对奶茶口感顺滑度的感官评价新标准。结果表明奶植脂末添加量与奶茶的粒径呈负相关,与粘度呈正相关。当植脂末添加量为60.00 g时,奶茶的平均粒径为0.66 μm。通过对样品进行口腔软摩擦学分析,建立了奶茶口感顺滑度的预测模型和评判标准,即只有当口腔软摩擦学曲线同时满足K2∈(-0.23, -0.05)和vR2<40.00 mm/s时,奶茶表现出较好的顺滑特性,否则奶茶口感淡薄或厚重,口感顺滑度差。因此,该口腔软摩擦模型能够评价不同配方奶茶的顺滑特性,在快速评价流体食品的口感顺滑方面具有实际应用前景。