Effects of Using Alternative Extreme Pressure (EP) and Anti-Wear (AW) Additives with Oxy-Nitrided Samples

Oxy-nitriding is a widely used industrial process aiming to improve the tribological properties and performance of components. Previous studies have shown the effectiveness of the treatment with friction and wear performance, but very few have focussed on optimising this behaviour. The lubrication properties of several EP and AW additives were examined to investigate their effectiveness in improving the tribological properties of the layers formed after treatment. Previous studies showed the presence of an oxide layer on the sample could improve the effectiveness of the sulphurised olefin (SO) and tricresyl phosphate (TCP) additives. The friction and wear behaviour of oxy-nitrided samples were analysed using a tribometer and surface profiler. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to identify the morphologies and chemical compositions of the treated surface before and after testing. No real effect on friction was observed when using the SO or TCP additives, mostly due to lack of interaction with the less reactive iron nitride layer and their roles as anti-wear additives. However, when the zinc dialkyldithiophosphate-containing lubricant was used, a higher friction coefficient was observed. Greater improvements in anti-wear properties with the presence of additives in comparison with only using base oil were reported, with the TCP additive producing the lowest wear rates. The study effectively demonstrated that the additive package type used could impact the tribological and tribochemical properties of oxy-nitrided surfaces.     

The role of personal dexterity and incentive gamification to enhance employee learning experience and performance

Cognition, Technology & Work - This paper aims to develop a concept of incentive gamification for organizations in the digital era. Incentive gamification is an incentive-based policy using the...     

Handover procedure and decision strategy in LTE-based femtocell network

Wireless systems have the capability to serve users over broad geographic area without using a costly network infrastructure. However, the main drawback of these systems represents the bandwidth restrictions and coverage. Deployment of femtocell as the emerging promising wireless access technology becomes one of possible solution how to overcome some of the drawbacks. In this paper, we investigate the handover procedure in femtocell network considering, both types of handovers, horizontal and vertical. The 3GPP LTE based handover procedure is analysed for three scenarios: hand-in, hand-out and inter-FAP. In addition, the reactive handover decision policy, based on the prediction of user movement and the prediction of target-FAP, is proposed as a way to eliminate frequent and unnecessary handovers.     

船用柴油机供油机构滚轮衬套混合热弹流润滑特性研究

以船用柴油机供油机构中滚轮–浮动衬套–滚轮销为研究对象,考虑其低速重载运行工况下衬套弹性变形,计入表面粗糙特征,构建了浮动衬套内外双层油膜混合热弹性流体动压润滑分析模型,并据此探究了内外层油膜间隙比、衬套宽径比、衬套厚度及其表面粗糙度对环速比、内外层最大油膜压力及承载能力等润滑特性的影响规律。结果表明：滚轮–浮动衬套–滚轮销结构运行过程中内层油膜厚度较小,润滑状态较为恶劣;低速重载工况下,衬套弹性变形与混合润滑效应不可忽略;宽径比越大、内外层间隙比越小,最大油膜压力越小,结构承载能力越强,但温升越高;混合润滑状态仅出现于衬套内层润滑油膜,且衬套表面粗糙度越大,润滑效果越差。     

Application of microwave radiation in the grafting of acidic sites on SBA-15 type material

Journal of Porous Materials - Mesoporous silica of SBA-15 type was modified for the first time with 3-(trihydroxysiyl)-1-propanesulfonic acid (TPS) by post-synthesis modification involving...     

Anti-Shudder Properties of ATFs—Investigation into Tribofilm Composition on Clutch Friction Material and Steel Surfaces and the Link to Frictional Performance

The friction response of an automatic transmission fluid (ATF) should ensure a smooth engagement process with no shudder in the process of power transmission. To study the effect of ATF chemistry on anti-shudder properties, the frictional characteristics of the baseline additive system used in ATFs with various friction modifiers and detergent combinations were assessed using a variable-speed friction test (VSFT) machine. Tests were performed on steel-versus-clutch friction material tribocouples, with the aim of studying the tribofilm formation on both friction couple (steel and friction material) surfaces and to establish the link between the lubricant-surface interactions and anti-shudder performance. An SAE No. 2 test machine was also used to investigate the friction performance of the same ATFs for comparison with the VSFT results. Similar performance rankings were obtained from those two tests. This article focuses on the posttest surface analysis and surface chemistry results of the test samples.

Energy dispersive X-ray spectroscopy (EDX) analysis, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) were used to assess the different surface conditions and chemical tribofilm compositions on the friction material and steel counterpart after the test. The mechanisms of the different friction performance provided by additive formulations and the correlation with the composition of tribofilms are discussed. Some adsorbed functional groups on the posttest sample surface, such as OH-, C-N, etc., were suggested to have positive effects on the anti-shudder performance of ATFs.     

Numerical Study of the Effect of Tribofilm Kinetics and Its Hardness on the Roughness Evolution of the Substrate in Boundary Lubrication Regime

Abstract

A tribochemical modeling framework that considers the growth of a tribofilm on the contacting surfaces has been used in this work. The model couples a fast contact mechanics model with the thermodynamics of interfaces and captures the growth of the tribofilm on the asperities. The model was shown to be able to capture the dynamics of a tribosystem and the evolution of surface topography. The model considers the effect of plastic deformation and wear in modifying the surface geometries. In a recent work by the authors (Ghanbarzadeh et al., Wear, 362–363, 2016), the same numerical model was validated against experiments in a micropitting rig (MPR) and the wear, topography, and tribofilm thickness results were compared. In this work, validation of the model is presented and the effect of tribofilm kinetics and its hardness have been numerically studied to assess the evolution of surface roughness in a rolling sliding contact. Results suggest that the kinetics of the tribofilm growth significantly influence the roughness evolution with higher kinetics resulting in a rougher interface. Similarly, the tribofilm hardness affects the roughness evolution and is more influential in the later stages of roughness evolution.