Thickness and scratch resistance of adsorbed film formed by triblock symmetrical copolymer solutions

The thickness and scratch resistance of adsorbed films formed on mild steel samples (MS1020), which have been immersed in water copolymer solutions, are reported. The effects of bulk temperature and the copolymer structures, normal, poly(ethylene oxide)_m‐poly(propylene oxide)_n‐poly(ethylene oxide)_m, and reverse, poly(propylene oxide)_n‐poly(ethylene oxide)_m‐poly(propylene oxide)_n, are elucidated. The films' thicknesses are independent of structure but not of temperature. The adsorbed films of above cloud point solutions are thicker than below cloud point. However, nanoscratch experiments carried out to measure the scratch resistance of the films reveal that despite of thicker film formed by above cloud point solutions, it is relatively more prone to being detached than the thinner films of below cloud point solutions. The effect of extreme pressure additive, alkyl phosphate ester (APE), is also investigated suggesting the normal copolymer has comparable scratch resistance with APE when used at below the cloud point. Copyright © 2016 John Wiley & Sons, Ltd.     

Experimental and numerical study of O/W emulsion lubricated strip rolling in mixed film regime

An experimental and numerical study of cold rolling lubricated by O/W emulsion has been carried out. The strip rolling experiment was carried out on a Hille experimental rolling mill with a view to study the performance of emulsion lubrication in terms of practical rolling parameters. Accordingly, rolling parameters such as rolling force and torque were measured. The experimental measurements compare favourably with the computed results from a numerical scheme developed by the authors. The scheme, based on a two-phase lubricant model, is capable of calculating the oil concentration at any point within the inlet zone and work zone, rolling pressure, film thickness, and fractional contact area ratio associated with strip rolling under mixed film lubrication at different rolling speeds. Using this scheme, the intertwined effects of an emulsion’s parameters such as: oil concentration, mean oil droplet size, and rolling speed on strip rolling were investigated. The numerical study encompassed the mixed film regime for speed, S ranges from 10⁻⁴ to 10⁻², supply oil concentration level λ_ds from 1 to 10%, and oil droplet size D _S from 5 to 10. Experimentally, the differences between water, oil and emulsion-lubricated rolling are not discernible except for film thickness. At a low speed of 10 RPM, force and torque of water-lubricated rolling are marginally higher than oil- or emulsion-lubricated ones. However, the difference between emulsion and neat oil is not apparent. The numerical results show the occurrence of a moderate oil concentration increase in the inlet zone followed by a sharp one at the beginning of the work zone. The effect of the concentration process is predominantly seen in the film thickness and the lubricant pressure whilst its effect on the total pressure is less pronounced. The analysis of the results suggests that it is possible to lower the emulsion oil concentration without any adverse effect on the rolling process. This principle can be used to control the outlet lubricant film thickness and hence the surface quality of the rolled strip.     

Mixed film lubrication of strip rolling using O/W emulsions

A numerical study on the oil concentration effect of O/W emulsion in cold rolling operating in the mixed film lubrication regime has been carried out. The developed scheme is able to calculate oil concentration at any point within the inlet zone (IZ) and work zone (WZ), rolling pressure, film thickness, and contact ratio for various rolling speeds. Hence the intertwined effects of oil concentration of the supplied emulsion and rolling speed on strip rolling are discussed. The study encompasses mixed film regime with speeds S range from 10⁻⁵ to 10⁻³ and supplied emulsion's oil concentration levels λ_ds range from 5% to 90%. The result shows that a moderate rise in oil concentration occurs in the IZ followed by a rapid one at the beginning of the workzone. In most cases, the oil in the emulsion would have been transformed from disperse phase to continuous phase throughout the WZ. Notwithstanding further concentration, which depends on the oil concentration of the supplied emulsion, could still occur in the WZ. The effect of the concentration process is predominantly seen in the development of the lubricant pressure whilst its effect on the total pressure is less pronounced. The analysis of the results suggests that it is possible to lower the emulsion oil concentration without detrimental effects on the rolling process; and from the analysis of the outlet film thickness, it is shown that the variation of emulsions’ oil concentration could control the exit lubricant film thickness and consequently the strip surface quality.     

An analysis of sector-shaped thrust bearings operating in the transition regime

The purpose of this study was twofold: (i) to introduce a modified mixing length expression of Reynolds stress in transition and turbulent lubrication theory; (ii) to determine the performance characteristics of sector-shaped thrust bearings when operated in the transition regime taking into account the inertia effects.

A new model of Reynolds stresses for transition-turbulent theory is proposed. The approach relies on Prandtl's mixing length theory and a modified Van Driest mixing length formula which accounts for the effect of the shear stress gradient in thin film lubrication.

The mixing length model is used to analyse turbulent planar and non-planar flows. Turbulent coefficients obtained from the non-planar cases are used to analyse the sector-shaped thrust bearing in the transition region, taking into account the convective inertia forces and centrifugal forces. Bearing performance characteristics such as pressure distribution, load carrying capacity, pressure centre and inlet flow rate are calculated.     

A thermal analysis of strip-rolling in mixed-film lubrication with O/W emulsions

Increase of both roll and strip surface temperatures can significantly affect a rolling process, roll conditions and strip mechanical properties. A comprehensive thermal analysis in cold rolling, especially in a mixed film regime, is needed to understand how thermal fields develop in roll and strip during rolling. It requires a simultaneous solution of the mixed film model for friction in the roll bite and the thermal model for roll and strip thermal fields. This paper presents a numerical procedure to analyse strip rolling process using lubrication with oil-in-water (O/W) emulsions. The thermal model includes the effect of heat generation due to the strip deformation and frictional shear stress at the asperity contacts. The numerical analysis employs a coupled thermal model and a mixed film lubrication model for calculating the friction and the asperity deformation in the bite. The thermal model considers the initial temperatures of the roll and strip, temperature rise due to the strip plastic deformation and friction. While the O/W mixed-film lubrication model takes into account the effect of surface roughness and oil concentration (%vol) of the emulsion. The thermal effect is analysed in terms of strip surface temperature and roll temperature, which are influenced by rolling parameters such as reduction, rolling speed, oil concentration in the emulsion. The results of the parametric study indicate that the effect of oil concentration on the thermal field is relatively small compared to that of reduction ratio and rolling speed. The reduction ratio increases the maximum interface temperature in the roll bite. In the mixed film regime, rolling speed also increases the maximum interface temperature and alters the temperature field of the strip. The numerical procedure was validated against known experimental data and can readily be extended to hot rolling or used to analyse roll strip temperature subjected to different cooling system.     

Particle Trajectories in Dilute Phase Pneumatic Conveying

A nonintrusive cross-correlation method to measure the particle velocities in dilute phase pneumatic conveying is described. The cross-correlation function generated gives information about the time it takes for a particle to travel between two optimally placed measurement planes. Experiments and CFD simulations are used to estimate an optimal inter-plane distance for various flow conditions.     

Variations in the microstructure and mechanical properties of the oxide layer on high speed steel hot rolling work rolls

This paper is part of a larger study to understand the wear of hot rolling rolls. A significant cost of the hot rolling process is associated with the consumption of rolls, which is why a comprehensive understanding of the wear of the roll material is important. Given that the surface of the rolls is covered by an oxide layer, it is important to know the tribological and mechanical properties of the oxides. Research in this area concentrates mainly on the morphologies and microstructures of the oxide layers. Previously published works give very little, if any, information of the mechanical properties of the layers on high speed steel. This paper presents a methodology to study the mechanical properties of the oxide layer formed on the surface of a high speed steel roll using combined nanoindentation tests and finite element simulations. Mechanical properties such as the elastic modulus (E), hardness (H), yield strength (σ_y), and Poisson's ratio (ν), have been determined, and the work has revealed a variation of microstructure, porosity (f), and mechanical properties of the oxide layer across its thickness. The outer sub-layer has a higher E and H than the inner sub-layer. This variation of mechanical properties in the oxide layer was consistent with variations in the porosity and grain sizes in the two sub-layers.     

Condition monitoring of naturally damaged slow speed slewing bearing based on ensemble empirical mode decomposition

There have been extensive studies on vibration based condition monitoring, prognosis of rotating element bearings; and reviews of the methods on how to identify bearing fault and predict the final failure reported widely in literature. The investigated bearings commonly discussed in the literatures were run in moderate and high rotating speed, and damages were artificially introduced e.g. with artificial crack or seeded defect. This paper deals with very low rotational-speed slewing bearing (1–4.5 rpm) without artificial fault. Two real vibration data were utilized, namely data collected from lab slewing bearing subject to accelerated life test and from a sheet metal company. Empirical mode decomposition (EMD) and ensemble empirical mode decomposition (EEMD) were applied in both lab slewing bearing data and real case data. Outer race fault (BPFO) and rolling element fault (BSF) frequencies of slewing bearing can be identified. However, these fault frequencies could not be identified using fast Fourier transform (FFT).     

Equilibrium and kinetic studies in adsorption of heavy metals using biosorbent: a summary of recent studies

Distinctive adsorption equilibria and kinetic models are of extensive use in explaining the biosorption of heavy metals, denoting the need to highlight and summarize their essential issues, which is the main purpose of this paper. As a general trend, up until now, most studies on the biosorption of heavy metal ions by miscellaneous biosorbent types have been directed toward the uptake of single metal in preference to multicomponent systems. In particular, Langmuir and Freundlich models are the most common isotherms for correlating biosorption experimental data though other isotherms, which were initially established for gas phase applications, can also be extended onto biosorption system. In kinetic modeling, the pseudo-first and -second order equations are considered as the most celebrated models.