Mixed Lubrication Model for Cold Rolling Considering the Inlet and Deformation Zones

2012 ◽  
Author(s):  
Martin Bergmann ◽  
Klaus Zeman ◽  
Alexander Kainz ◽  
Konrad Krimpelstätter ◽  
Dieter Paesold ◽  
...  
Keyword(s):  
Cold Rolling ◽  
Film Formation ◽  
Mixed Lubrication ◽  
Bulk Deformation ◽  
Metallic Surfaces ◽  
Hydrodynamic Friction ◽  
Plastic Strip ◽  
Coupled Equations ◽  
Inlet Zone ◽  
Raphson Method

A mixed lubrication model for cold rolling was developed by separating, according to common concepts, the domain of calculation into two zones: the inlet zone and the zone of plastic strip bulk deformation. The analysis of the inlet zone mainly focuses on film formation from different lubricants based on the evolution of layers consisting of neat oil on the metallic surfaces. In the zone of plastic strip bulk deformation, contributions of boundary and hydrodynamic friction are modeled incorporating longitudinal and transversal roughness components. Lubricant pressure, which is influenced by the geometry of these roughness structures, is governed by hydrodynamic mechanisms. Additionally, lubricant temperature in the roll bite is predicted by an integrated thermodynamics sub-model. While coupling between the inlet and plastic deformation zones is performed iteratively, the highly non-linear and coupled equations for the latter zone are solved simultaneously by applying a variant of the well-known damped Newton-Raphson method.

Development of Mixed Lubrication Cold Rolling Model

2015 ◽  
Vol 642 ◽  
pp. 190-195
Author(s):  
Yhu Jen Hwu ◽  
Jian Ting Lee ◽  
Yeau Ren Jeng
Keyword(s):  
Cold Rolling ◽  
High Surface ◽  
Work Roll ◽  
Mixed Lubrication ◽  
Rolled Strip ◽  
Base Oil ◽  
Roll Deformation ◽  
Inlet Zone ◽  
Quality Surface ◽  
Roll Bite

Within past 20 years, high surface qualities of cold strip were demanded by automotive industry and electrical engineering. Main purposes of cold rolling processed are to provide high quality surface and generate appropriate roughness for different customs. Emulsion is a common coolant used in cold rolling processes, Properties of base oil in emulsion, concentration, roughness of work roll, rolling speed and reduction are important parameters, which dominate the surface qualities of cold rolled strip. Hence, a powerful cold rolling model which can describe complicate tribological behavior in roll bite is required. In this article, a cold rolling model which integrates roll deformation and mixed lubrication in inlet zone and biting area was developed. The thickness of oil film, fraction of contact area and coefficient of friction in roll bite are calculated.

scholarly journals Film Formation Analysis with Starvation in the Inlet Zone of Cold Rolling Interface at High Roll Speeds

2009 ◽  
Vol 4 (1) ◽  
pp. 36-41 ◽  
Author(s):  
Prahlad Singh ◽  
Raj Kumar Pandey ◽  
Yogendra Nath
Keyword(s):  
Cold Rolling ◽  
Film Formation ◽  
Inlet Zone

Effect of Lubricant Scarcity on the Film Formation in an Inlet Zone During High Speed Cold Rolling Process

2007 ◽  
Author(s):  
Prahlad Singh ◽  
R. K. Pandey ◽  
Yogendra Nath
Keyword(s):  
Cold Rolling ◽  
High Speed ◽  
Heat Dissipation ◽  
Film Formation ◽  
Rolling Process ◽  
Lubricating Oil ◽  
Lubricating Film ◽  
Viscous Heat ◽  
Inlet Zone ◽  
Reduced Temperature

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.

Observations of Liquid Droplet Behavior and Oil Film Formation in O/W Type Emulsion Lubrication

1988 ◽  
Vol 110 (2) ◽  
pp. 348-353 ◽  
Author(s):  
T. Nakahara ◽  
T. Makino ◽  
K. Kyogoku
Keyword(s):  
High Speed ◽  
Liquid Droplet ◽  
Film Formation ◽  
Flat Glass ◽  
Glass Plate ◽  
Rolling Speed ◽  
Liquid Droplets ◽  
Speed Range ◽  
Oil Concentration ◽  
Inlet Zone

The behavior of liquid droplets in O/W type emulsions flowing between a flat glass plate and a metal roller was observed by means of a microscope. The behavior of the droplets introduced into the EHL film was found to be related to the streamlines of the continuous water phase in the vicinity of the inlet zone. It was observed that the oil droplets which penetrated into the EHL zone formed an oily pool (an oily film zone) containing water droplets in the inlet zone close to the EHL zone. This oily pool was a W/O emulsion rich in oil caused by phase inversion. The effects of oil concentration, emulsifier content and rolling speed on the area of the oily pool were investigated, and it was found that the extent of the oily pool was influenced by the rolling speed as well as oil concentration. The EHD film thickness was measured by means of optical interferometry with use of two wavelengths, and the measured results were compared with the calculated ones employing the starvation theory of Wolveridge et al. and the empirical equation of Wymer and Cameron for the region of the oil pool. It was found that course droplets play an important role in film formation by causing the formation of the oily pool in the low speed range. In the high speed range, however, a fine O/W emulsion forms the film.

Film Formation and Flow Characteristics at the Inlet of a Starved Contact—Theoretical Study

1983 ◽  
Vol 105 (2) ◽  
pp. 178-185 ◽  
Author(s):  
D. Bonneau ◽  
J. Frene
Keyword(s):  
Surface Tension ◽  
Film Formation ◽  
Flow Characteristics ◽  
Integral Equation Method ◽  
Surface Velocity ◽  
Stress Distributions ◽  
New Interpretation ◽  
Inlet Zone ◽  
Hydrodynamic Effects ◽  
Effect Of Surface

The conditions of film formation are examined theoretically when starvation occurs. The analysis is for two-dimensional Newtonian flow and includes surface tension effects. Using an integral equation method, stream function solutions, velocity fields, pressure and shear stress distributions are calculated along and across the inlet zone of a sliding contact. The effect of surface tension and feeding thickness on the meniscus shape and on pressure buildup is studied in correlation with hydrodynamic effects. In all cases, pressure value lower than the gas pressure acting on the free boundary is found along the sliding surface. This depression value increases with an increase in viscosity or surface velocity. Owing to these results, a new interpretation of some published experimental data on starved contacts is proposed.

Effect of Liquid-Solid Lubricant on Mixed Lubrication in Line Contact

2011 ◽  
Vol 148-149 ◽  
pp. 778-784
Author(s):  
Rattapasakorn Sountaree ◽  
Panichakorn Jesda ◽  
Mongkolwongrojn Mongkol
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Solid Lubricant ◽  
Reynolds Equation ◽  
Contact Region ◽  
Mixed Lubrication ◽  
Line Contact ◽  
Load Carrying ◽  
Roughness Amplitude ◽  
Raphson Method

This paper presents the performance characteristics of two surfaces in line contact under isothermal mixed lubrication with non-Newtonian liquid–solid lubricant base on Power law viscosity model. The time dependent Reynolds equation, elastic equation and viscosity equation were formulated for compressible fluid. Newton-Raphson method and multigrid technique were implemented to obtain film thickness profiles, friction coefficient and load carrying in the contact region at various roughness amplitudes, applied loads, speeds and the concentration of solid lubricant. The simulation results showed that roughness amplitude has a significant effect on the film pressure, film thickness and surface contact pressure in the contact region. The film thickness decrease but friction coefficient and asperities load rapidly increases when surface roughness amplitude increases or surface speed decreases. When the concentration of solid lubricant increased, friction coefficient and asperities load decrease but traction and film thickness increase.

Soft micro-elastohydrodynamic lubrication and friction at rough conformal contacts

2016 ◽  
Vol 231 (3) ◽  
pp. 302-315 ◽  
Author(s):  
B Wennehorst ◽  
GWG Poll
Keyword(s):  
Solid Body ◽  
Film Formation ◽  
Normal Load ◽  
Elastohydrodynamic Lubrication ◽  
Elastic Solid ◽  
Hydrodynamic Pressure ◽  
Mixed Lubrication ◽  
Fluid Film ◽  
Shear Stresses ◽  
Asperity Contacts

Conformal surfaces in parallel sliding lack a macroscopic hydrodynamic pressure and fluid film formation mechanism. However, such a mechanism still exists on a microscopic level due to roughness. It is common to translate roughness into a variation of fluid film thickness which in turn yields a hydrodynamic pressure distribution resulting in a net hydrodynamic lift. Reynolds equation and a suitable cavitation algorithm suffice to describe this effect mathematically. In case one surface consists of a compliant material with low modulus of elasticity, the deformation of asperities due to pressures and shear stresses in the fluid cannot be neglected—in fact, besides cavitation, it significantly contributes to the net hydrodynamic lift. Therefore, a coupling between fluid dynamics and elastic solid body deformations needs to be introduced. An additional complication arises when the hydrodynamic lift and the subsequent separation of the mean lines of the contacting rough surfaces is not enough to prevent asperity contacts completely. This situation is known as mixed lubrication where part of the normal load is transmitted at asperity contacts. These contacts are commonly treated as solid body contacts with a Coulomb-like friction law or more sophisticated solid friction models. However, when considering asperities as contraformal Hertzian contacts, elastic deformation may allow for the existence of thin micro-elastohydrodynamic lubricant films preventing direct solid body contact even at speeds which otherwise would be regarded as deep within the mixed lubrication regime close to boundary lubrication. These films may not be able to prevent wear completely, but may reduce friction significantly in comparison to dry friction. In this paper, the existence of such effects is demonstrated both by simulation and by experiments with elastomeric radial lip seals.

Elastohydrodynamic Lubrication: A Gateway to Interfacial Mechanics—Review and Prospect

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Dong Zhu ◽  
Q. Jane Wang
Keyword(s):  
Hydrodynamic Lubrication ◽  
Film Formation ◽  
Elastohydrodynamic Lubrication ◽  
Numerical Approach ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Interfacial Mechanics ◽  
Special Cases ◽  
Dry Contact ◽  
Film Lubrication

Elastohydrodynamic Lubrication (EHL) is commonly known as a mode of fluid-film lubrication in which the mechanism of hydrodynamic film formation is enhanced by surface elastic deformation and lubricant viscosity increase due to high pressure. It has been an active and challenging field of research since the 1950s. Significant breakthroughs achieved in the last 10–15 years are largely in the area of mixed EHL, in which surface asperity contact and hydrodynamic lubricant film coexist. Mixed EHL is of the utmost importance not only because most power-transmitting components operate in this regime, but also due to its theoretical universality that dry contact and full-film lubrication are in fact its special cases under extreme conditions. In principle, mixed EHL has included the basic physical elements for modeling contact, or hydrodynamic lubrication, or both together. The unified mixed lubrication models that have recently been developed are now capable of simulating the entire transition of interfacial status from full-film and mixed lubrication down to dry contact with an integrated mathematic formulation and numerical approach. This has indeed bridged the two branches of engineering science, contact mechanics, and hydrodynamic lubrication theory, which have been traditionally separate since the 1880s mainly due to the lack of powerful analytical and numerical tools. The recent advancement in mixed EHL begins to bring contact and lubrication together, and thus an evolving concept of “Interfacial Mechanics” can be proposed in order to describe interfacial phenomena more precisely and collaborate with research in other related fields, such as interfacial physics and chemistry, more closely. This review paper briefly presents snapshots of the history of EHL research, and also expresses the authors’ opinions about its further development as a gateway to interfacial mechanics.

Flattening of Random Rough Surfaces in Metal-Forming Processes

1999 ◽  
Vol 121 (3) ◽  
pp. 433-440 ◽  
Author(s):  
M. P. F. Sutcliffe
Keyword(s):  
Surface Modification ◽  
Cold Rolling ◽  
Spectral Density ◽  
Metal Forming ◽  
Short Wavelength ◽  
Rough Surfaces ◽  
Bulk Deformation ◽  
Long Wavelength ◽  
Power Spectral ◽  
Random Rough Surfaces

Flattening of random rough surfaces on a workpiece undergoing bulk deformation has beenanalyzed using a model of the surface consisting of just two wavelength components. Asperities are flattened at a rate which depends on the ratio of the initial r.m.s. amplitudes of the long and short wavelength components. The flattening behavior of the long wavelength asperities only becomes important when the amplitude of the long wavelength asperitiesis much greater than that of the shorter wavelength asperities. The surface modification was investigated experimentally by cold rolling of aluminium strips. The power spectral density of the roughness was used to extract appropriate amplitudes for the short and longwavelength components of roughness. The change in roughness amplitudes showed excellent agreement with theory.

Effect of Surface Topography on Mixed Lubrication Film Under Transient Conditions

2009 ◽  
Author(s):  
Ivan Krupka ◽  
Martin Hartl ◽  
Petr Svoboda
Keyword(s):  
Surface Topography ◽  
Film Formation ◽  
Surface Damage ◽  
Mixed Lubrication ◽  
Real Surface ◽  
Transient Conditions ◽  
Lubrication Film ◽  
Lubricated Contacts ◽  
Start Up ◽  
Ball Surface

Surface topography plays an important role in the efficiency of lubricated contacts formed between highly loaded machine parts. Gears, rolling bearings, cam and followers etc. subjected to high loads and/or slow speeds are operated under mixed lubrication when lubrication film is not able to completely separate rubbing surfaces. Such an effect becomes even more serious under transient conditions that bring the risk of the surface damage because of asperities interactions. This paper focuses on the effects of both artificially produced and real roughness features on mixed lubrication film formation during start up motion of non-conformal contacts operated under rolling/sliding conditions. The observation of the effects of surface dents artificially produced on the ball surface helped to understand better the behavior of real surface topography. It was found that the presence of shallow surface features can help to separate mixed lubricated rubbing surfaces more efficiently than it could be suggested from the results obtained with smooth surfaces.

Sign in / Sign up

Export Citation Format

Share Document