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R K Pandey - One of the best experts on this subject based on the ideXlab platform.

  • modeling of Inlet Zone in hydrostatic extrusion process f or aluminum and aluminum alloys
    International Journal of Advancements in Technology, 2012
    Co-Authors: P Tomar, R K Pandey, Y Nath
    Abstract:

    The objective of this paper is to investigate the viscous shear heating effect on the formation of minimum film thickness in Inlet Zone of the hydrostatic extrusion process as function of various operating parameters. Minimum film thicknesses in the Inlet Zone has been evaluated at various extrusion speeds, material parameters, extrusion pressures, and die semi-angle for extrusion of low strength material. A strong numerical technique is used in the investigation of Inlet Zone of a hydrostatic extrusion process considering viscous shear heat generation and convection & conduction modes of heat removals for the study of the minimum film thickness.

  • film formation analysis with starvation in the Inlet Zone of cold rolling interface at high roll speeds
    Tribology Online, 2009
    Co-Authors: P K Singh, R K Pandey, Y Nath
    Abstract:

    For successful cold rolling operation at elevated operating conditions, the existence of desirable minimum film thickness at the roll-strip interface and awareness of its controlling by adjusting the process variables such as roll speed, reduction ratio, lubricant types, and roll cooling system etc. are essential. Moreover, the studies of the lubricant's starvation in the Inlet Zone and its influence on the film thickness at high roll speeds considering viscous shear heating effects are very important issues. Thus, the objectives of this paper are to analyze the Inlet Zone of cold rolling interface thermohydrodynamically and develop formulas for the prediction of minimum film thickness (for both isothermal and thermal cases) as functions of operating parameters including levels of starvation. Based on the investigations reported herein, it is observed that the existence of starvation up to certain level seems to be beneficial. It causes reduction in the temperature rise in the Inlet Zone and reduces the quantity of lubricating oil (leading to oil conservation) required during the cold rolling operation provided a thin continuous film exists at the strip-roll interface. Authors believe that the cold rolling industries may be benefited by the formulas reported in this paper.

  • an efficient thermal analysis for the prediction of minimum film thickness in Inlet Zone at high speed lubricated cold strip rolling
    Journal of Materials Processing Technology, 2008
    Co-Authors: P Singh, R K Pandey, Y Nath
    Abstract:

    Abstract The main objective of this work is to develop a formula for the prediction of thermal minimum film thickness at the roll/strip contact in terms of operating parameters particularly at the elevated roll speeds. The film thickness at the exit of Inlet Zone and at the entry of contact Zone is common. Therefore, in order to compute minimum film thickness accurately at the contact, an efficient thermohydrodynamic analysis of fully flooded Inlet Zone has been carried out. The effects of rolling speed, reduction ratio, material parameter and slip on minimum film thicknesses (isothermal and thermal) and maximum film temperature rise (in the Inlet Zone only) are rigorously investigated. The performance parameters in the lubricated domain have been evaluated for rolling speeds (up to 20.0 m/s), reduction ratios (0.05–0.20), and slip values varying up to 20%. Significant reduction in minimum film thickness (thermal) has been observed with the increase in the rolling speed and slip. Based on this study, empirical relations are developed for the prediction of minimum film thicknesses (isothermal and thermal) at the contact. A relation for evaluation of maximum film temperature rise in the Inlet Zone has been also developed. Authors believe that the empirical relations presented herein may be useful for designers and practicing engineers.

  • thermal and starvation effects on the minimum film thickness in Inlet Zone in cold rolling
    Journal of Tribology-transactions of The Asme, 2008
    Co-Authors: P Singh, R K Pandey, Y Nath
    Abstract:

    In a recent paper (2004, "Elasto-Plastic Normal Contact of Three-Dimensional Fractal Surfaces Using Halfspace Theory," J. Tribol., 126, pp. 28-33) the author developed a halfspace model for the elasto-plastic normal contact of rough surfaces. This model is now used to study the influence of intrinsic surface parameters on constitutive contact laws, such as load-gap relation and load-area relation, for a specific type of surface topography known as fractal-regular surfaces. Numerical investigations show that the fractal dimension has only minor influence on the load-gap relationship, which is mostly determined by the dimensionless ratio between the transition length and the rms values of the height data. Due to the fractal nature of the surfaces at the small wavelength limit, initial deformation will always be in the plastic range. The load-area relation becomes then completely independent of the geometric surface parameters and is determined by material properties alone, at least if the predicted plastic deformation occurs at a length scale larger than the atomic scale.

  • effect of lubricant scarcity on the film formation in an Inlet Zone during high speed cold rolling process
    ASME STLE 2007 International Joint Tribology Conference Parts A and B, 2007
    Co-Authors: P K Singh, R K Pandey, Y Nath
    Abstract:

    Effective lubrication during the cold rolling is vital in achieving desirable tolerance and surface quality over the metallic sheets. However, in the process of cold rolling, it has been established that the lubricant’s viscosity drastically reduces (viscosity thinning) due to huge viscous heat dissipation in the lubricating film at the elevated rolling speeds. Thinning of lubricant viscosity increases the escaping tendency of the lubricant from the Inlet Zone. Thus, scarcity (starvation) of lubricant prevails in the Inlet Zone of roll and strip interface. Based on the present investigation, it is observed that the existence of starvation seems to be beneficial in terms of reduced temperature rise and less quantity of lubricating oil required provided there is a continuous film at the strip-roll interface.Copyright © 2007 by ASME

W M Elsarraf - One of the best experts on this subject based on the ideXlab platform.

R R Zahran - One of the best experts on this subject based on the ideXlab platform.

Scott Bair - One of the best experts on this subject based on the ideXlab platform.

  • The Effect of Shear-Thinning on Film Thickness for Space Lubricants
    Tribology Transactions, 2020
    Co-Authors: Scott Bair, Philippe Vergne, Mario Marchetti
    Abstract:

    The authors show that the difference between effective pressure-viscosity coefficients, obtained from film thickness, and coefficients obtained from viscometers for a PFPE space lubricant is substantially the result of shear thinning in the Inlet Zone of concentrated contact. Flow curves for the PFPE and a multialkylated cyclopentane are presented along with film calculations based on the Carreau model. Presented at the 57th Annual Meeting Houston, Texas May 19–23, 2002

  • The rheological assumptions of classical EHL: What went wrong?
    Tribology International, 2019
    Co-Authors: Scott Bair
    Abstract:

    Abstract The field of elastohydrodynamic lubrication (EHL) now has two very different approaches to the problem. For the first approach, two assumptions regarding the pressure, temperature and shear dependence of viscosity have been essential to the way that classical EHL developed over the last forty years. 1. The liquid in the Inlet Zone responds in Newtonian fashion. 2. The shear stress versus shear rate relationship of the liquid has the same form as the average shear stress versus average shear rate obtained from a traction curve. The new, quantitative, approach employs viscosities measured in instruments which do not rely upon these assumptions. There has been a rapid succession of advances in understanding of film forming and friction under the new approach.

  • pressure viscosity response in the Inlet Zone for quantitative elastohydrodynamics
    Tribology International, 2016
    Co-Authors: Scott Bair
    Abstract:

    Abstract The descriptions employed in classical elastohydrodynamic lubrication (EHL) of the piezoviscous effect at low pressures characteristic of the Inlet Zone are simply inaccurate for low viscosity liquids. This article offers the 1952 McEwen equation for accurately describing the pressure–viscosity effect at low Inlet pressures for those liquids with sufficiently high inflection pressure that the faster-than-exponential response does not significantly affect the viscosity in the Inlet. The parameters of this model have significance for the classical EHL film thickness formulas and these parameters are listed for several low viscosity liquids including a refrigerant.

  • Pressure–viscosity response in the Inlet Zone for quantitative elastohydrodynamics
    Tribology International, 2016
    Co-Authors: Scott Bair
    Abstract:

    Abstract The descriptions employed in classical elastohydrodynamic lubrication (EHL) of the piezoviscous effect at low pressures characteristic of the Inlet Zone are simply inaccurate for low viscosity liquids. This article offers the 1952 McEwen equation for accurately describing the pressure–viscosity effect at low Inlet pressures for those liquids with sufficiently high inflection pressure that the faster-than-exponential response does not significantly affect the viscosity in the Inlet. The parameters of this model have significance for the classical EHL film thickness formulas and these parameters are listed for several low viscosity liquids including a refrigerant.

  • The Generalized Newtonian Fluid Model and Elastohydrodynamic Film Thickness
    Journal of Tribology-transactions of The Asme, 2002
    Co-Authors: Scott Bair, Farrukh Qureshi
    Abstract:

    The nature of real shear-thinning in elastohydrodynamic contacts is well-known from both experimental measurement and nonequilibrium molecular dynamics to follow a power-law. Shear-thinning will affect the film thickness when the Newtonian limit is low enough to occur in the Inlet Zone (less than about I MPa shear stress). Then kinetic theory tells us that film thinning should occur for molecular weight greater than 2000 kg/kmol. We present a review of generalized Newtonian models, flow curves for real lubricants and comparison of calculated and measured film thickness. The calculations utilize measurable liquid behavior, in contrast to most previous work.

G.h. Sedahmed - One of the best experts on this subject based on the ideXlab platform.

  • Mass-transfer-controlled impingement corrosion at the jet Inlet Zone of an annulus under turbulent flow
    Industrial & Engineering Chemistry Research, 2006
    Co-Authors: R R Zahran, G.h. Sedahmed, O E Abdelwahab, W. M. El-sarraf
    Abstract:

    Diffusion-controlled impingement corrosion of the lower part of the inner cylinder of an annulus caused by a perpendicular Inlet jet was studied using the diffusion-controlled dissolution of copper in acidified dichromate technique. Variables studied were solution velocity, physical properties of the solution, diameter of the perpendicular feed nozzle, and the effect of drag-reducing polymers. For blank solution, the rate of mass-transfer-controlled impingement corrosion was correlated by the equation Sh = 2.74Sc 0.33 Re 0.46 (d n /d) -0.4 . Drag-reducing polymers were found to decrease the rate of mass-transfer-controlled impingement corrosion by an amount ranging from 29.9 to 68.9% depending on electrolyte concentration, polymer concentration, and feed nozzle diameter. The importance of the present results to the design of annular equipment was noted.

  • mass transfer controlled impingement corrosion at the jet Inlet Zone of an annulus under turbulent flow
    Industrial & Engineering Chemistry Research, 2006
    Co-Authors: R R Zahran, G.h. Sedahmed, O E Abdelwahab, W M Elsarraf
    Abstract:

    Diffusion-controlled impingement corrosion of the lower part of the inner cylinder of an annulus caused by a perpendicular Inlet jet was studied using the diffusion-controlled dissolution of copper...

  • Mass transfer at a pipe Inlet Zone in relation to impingement corrosion
    International Communications in Heat and Mass Transfer, 1998
    Co-Authors: G.h. Sedahmed, M.s.e. Abdo, M.a. Amer, G Abd El-latif
    Abstract:

    Abstract Rates of mass transfer required to predict the rate of diffusion controlled corrosion of the Inlet Zone of a tube fitted with a perpendicular Inlet nozzle were studied using the diffusion controlled dissolution of copper in acidified FECl3. Variables studied were Inlet nozzle diameter, solution velocty and physical properties of the solution. The rate of corrosion of the tube Inlet Zone was found to increase with decreasing Inlet nozzle diameter and increasing solution velocity. The mass transfer coefficient of the diffusion controlled corrosion of the tube Inlet Zone was related to different variables by dimensionless equations. Implications of the present results to the design and protection of pipelines against corrosion in industry is highlighted.