Compréhension et modélisation du régime mixte : synthèse des avancées et perspectives d'applications industrielles : Frottement et lubrification en mise en forme = Understanding and modelling the mixed lubrication regime: summary of achievements and perspectives of industrial applications

Free access articleInternational audienceL'ensemble des travaux décrits précédemment, et résumés ici, a d'ores et déjà fait l'objet de mises en application diverses, qui sont décrites dans cette courte conclusion: explication d'observations sur sites de production, modèles de connaissance, nouvelles idées de formulation de lubrifiants, qui ne demandent qu'à être testées. Bien sûr, l'ensemble des besoins de connaissances et de nouveaux outils n'a pas été satisfait, et quelques pistes de travaux futurs sont dégagées = The works described previously, and summarized here, have already been applied under various forms, to be described hereafter: explanation of industrial observations, knowledge models, new ideas for lubricant formulation, which now have to be tested. Of course, not all the needs of industry have been fulfilled, so that perspectives for further research are highlighted

Numerical Simulations of Asperity Crushing—Application to cold rolling

peer reviewedAsperity flattening has a huge influence on friction and wear in metal forming processes. Nevertheless, phenomena that occur at the microscopic scale are still not well understood. Since no experiments can be easily performed in real forming conditions, numerical models are essential to achieve a better knowledge of what happens in these contact regions. In this paper, two finite elements models are presented. The first one represents the flattening of a serrated asperity field in plane strain conditions. The results are compared to the experiments conducted by Sutcliffe [1]. The second one is a tri-dimensional asperity model flattened by a rigid plane. The boundary conditions applied to this model correspond to the ones encountered in a real cold rolling case. The results are compared to the relative contact area computed by a strip rolling model using the analytical laws proposed by Wilson & Sheu [2] and Marsault [3]

Lubrication with Emulsions

International audienceBecause oil has a different density than water, buoyancy causes the phases to separate, i.e., emulsions are inherently unstable. To add stability, emulsions are aggressively agitated to achieve very small droplet sizes and tight distributions, or emulsifiers are added to the system. Emulsifiers are usually surfactants, although some formulations use macromolecules, fine particles, and/or simple electrolytes as emulsifiers. An emulsifier is a long molecule with a polar end. One end of the molecule is soluble in oil, while the other prefers water ..

Metalub – A Slab Method software for the numerical simulation of mixed lubrication regime. Application to cold rolling

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Numerical simulations of asperity crushing using boundary conditions encountered in cold-rolling

Asperity flattening has a huge influence on friction and wear in metal forming processes. Nevertheless, phenomena that occur at the microscopic scale are still not well understood. Since no experiment can be easily performed in real forming conditions, numerical models are essential to achieve a better knowledge of what happens in these contact regions. In this paper, two finite elements models are presented. The first one represents the flattening of a serrated asperity field in plane-strain conditions. The results are compared to the experiments published by Sutcliffe [1]. The second one is a tri-dimensional asperity model flattened by a rigid plane. The boundary conditions applied to this model correspond to the ones encountered in a real cold-rolling case. The results are compared to the relative contact area computed by a strip rolling model using the analytical laws proposed by Wilson & Sheu [2] and Marsault [3]

Three-dimensional Modelling of Asperity Crushing

Asperity flattening has a huge influence on friction and wear in metal forming processes. Nevertheless, phenomena that occur at the microscopic scale are still not well understood. Since no experiment can be easily performed in real forming conditions, numerical models are essential to achieve a better knowledge of what happens in these contact regions. In this paper, a threedimensional model of a rough strip flattened by a rigid rough tool is presented. The boundary conditions applied to this model correspond to the ones encountered in a real cold-rolling case. The results are compared to experimental measurements from the pilot mill of ArcelorMittal Maizières R&D

METALUB – A Slab Method Software for the Numerical Simulation of Mixed Lubrication Regime in Cold Strip Rolling

A cold rolling model taking into account mixed lubrication regime has been developed and included into a simulation software named MetaLub. The main objective is to enhance the performances of rolling mills from a lubrication point of view. It means that lubricant rheology but also roll diameters and roughness, etc., can be optimised to improve stability and efficiency of the rolling tool. The main features of MetaLub, are briefly presented in this paper. Then, two studies of the influence of rolling speed and negative forward slip are discussed. The obtained numerical results are presented and compared to some experimental data from literature and from ArcelorMittal facilities in order to validate the model and to show its capacity to understand and help to improve industrial rolling conditions

An advanced model of lubricated cold rolling with its comprehensive pilot mill validation

peer reviewedThe increasing demand for thinner and harder steel strips requires the introduction of flexible lubrication systems that continuously adapt the lubrication conditions in existing rolling mills to not saturate the stand capacity by excessive friction. To design these systems, this article introduces one of the most advanced models of lubricated cold rolling since it combines the following features in a single model: elasto-thermo-viscoplasticity of the strip, mixed lubrication by a thermo-piezoviscous lubricant, full-flooded lubrication or starvation, and a complete formulation of non-circular roll flattening. This model is then validated by a new semi-industrial data set, which is one of the most comprehensive ones since it includes: roughness measurements of the rolls and the strips, hardening laws of the strips by plane-strain compression tests, thermo-piezoviscous material laws of the lubricants and a large design space to isolate the influence of individual operating parameters. The results indicate that the changes of the rolling force and the forward slip with the rolling speed and the reduction can be quantitatively predicted except for the decreasing forward slip with the reduction. These predictions require to calibrate the coefficients of boundary friction, thermoplasticity and viscoplasticity for each rolled product as well as the inlet film thickness at each rolling speed, if starvation occurs. Once calibrated, the model therefore allows to predict the influences of various operating conditions, e.g. by how much the rolling force can be reduced if more lubricant becomes available at the entry of the roll bite

Micro-plasto-hydrodynamic lubrication: a fundamental mechanism in cold rolling

peer reviewedMicro Plasto-Hydrodynamic (MPH) lubrication is a general mechanism in metal forming that consists in a re-lubrication of tool-piece solid contacts by an outflow of lubricant from pressurized “pockets” promoted by the plastic deformation. MPH lubrication is one of the main sources of friction variation (e.g. uncontrolled friction) in metal forming processes like strip drawing or cold rolling. This paper presents experimental results giving evidence of the MPH lubrication mechanism in cold rolling and a new lubrication model that predicts for strip drawing conditions MPH lubrication initiation and lubricant extension along the solid contacts initially in boundary condition. This MPH model could be implemented in a cold rolling model soon to help in high strength steels developments on cold rolling mills