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See detailMicro-plasto-hydrodynamic lubrication: a fundamental mechanism in cold rolling
Laugier, Maxime; Boman, Romain ULg; Legrand, Nicolas et al

in Advanced Materials Research (2014), 966-967

Micro 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” ... [more ▼]

Micro 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. [less ▲]

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See detailModélisation des conditions d’apparition du micro-hydrodynamisme via la méthode des éléments finis dans la perspective d’intégrer ce phénomène dans un modèle numérique de laminage à froid.
Carretta, Yves ULg

Doctoral thesis (2014)

This dissertation presents a finite element numerical model able to predict the occurrence of Micro-Plasto-Hydrodynamic (MPH) lubrication. This phenomenon, which was first introduced by Mizuno and Okamoto ... [more ▼]

This dissertation presents a finite element numerical model able to predict the occurrence of Micro-Plasto-Hydrodynamic (MPH) lubrication. This phenomenon, which was first introduced by Mizuno and Okamoto, appears in the mixed lubrication regime. It consists in lubricant flows at the microscopic scale leading to a lubrication of the tool-piece solid contacts and therefore to a local friction drop. For instance, Laugier et al. have observed a friction decrease while rolling High Strength Steels for different strip thickness reductions. The only physical explanation to this trend is the MPH lubrication. Despite the huge influence of MPH lubrication on friction in metal forming processes, only a few numerical models can be found in the literature. Moreover, these models rely on several restrictive assumptions which prevent them from delivering predictive results. This work consists in the development of the first finite element model capable of predicting the appearance of the MPH lubrication. This model is used to numerically reproduce the experiments of Bech who studied this phenomenon, in plane strip drawing, by observing the behaviour of macroscopic pyramidal lubricant cavities through a transparent die. In the proposed approach, plane strip drawing is modelled in 2D with Metafor, an in-house nonlinear FE code. This model allows us to compare the lubricant pressure to the solid-solid contact pressure profile between the upper die and the strip material. Once the lubricant pressure exceeds the solid-to-solid contact pressure, the condition allowing a lubricant flow from the pocket to the neighbouring plateaus is fulfilled. The presented FE model is able to predict backward and forward escapes of the lubricant from the pocket. As in the experiments of Bech, several parametric studies have been carried out. The numerical results show that the model reproduces the trends observed experimentally. [less ▲]

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See detailNumerical simulations of asperity crushing using boundary conditions encountered in cold-rolling
Carretta, Yves ULg; Boman, Romain ULg; Legrand, Nicolas et al

in Key Engineering Materials [=KEM] (2013), 554-557

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 ... [more ▼]

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]. [less ▲]

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See detailThree-dimensional Modelling of Asperity Crushing
Carretta, Yves ULg; Boman, Romain ULg; Legrand, Nicolas et al

Conference (2012, October)

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 ... [more ▼]

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. [less ▲]

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See detailMixed Lubrication Regime in Cold Strip Rolling
Carretta, Yves ULg; Boman, Romain ULg; Legrand, Nicolas et al

in 2nd Annual ArcelorMittal CFD and Thermomechanics Days 2012 (2012, January)

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See detailMETALUB – A Slab Method Software for the Numerical Simulation of Mixed Lubrication Regime in Cold Strip Rolling
Carretta, Yves ULg; Boman, Romain ULg; Stephany, Antoine et al

in Proceedings of the Institution of Mechanical Engineers - Part J - Journal of Engineering Tribology (2011), 225(9), 894-904

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 ... [more ▼]

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. [less ▲]

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See detailThermomechanical simulation of roll forming process based on the coupling of two independent solvers
Carretta, Yves ULg; Boman, Romain ULg; Stephany, Antoine et al

in Proceedings of the IV International Conference on Computational Methods for Coupled Problems in Science and Engineering COUPLED PROBLEMS 2011 (2011, June)

This paper deals with an industrial application of a coupling procedure involving two different computer programs : MetaLub and ThermRoll. The first one models the mechanical phenomena occurring in the ... [more ▼]

This paper deals with an industrial application of a coupling procedure involving two different computer programs : MetaLub and ThermRoll. The first one models the mechanical phenomena occurring in the roll-bite during cold rolling such as elasto-plastic strip strains, elastic-roll deformations, asperity flattening and lubricant flow. The second one uses the previous results to compute the steady-state temperature field of the work-roll and the strip. These two codes are briefly described and a model of an industrial stand demonstrates the importance of the thermomechanical coupling in order to get a better understanding of the process. [less ▲]

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See detailNumerical Simulations of Asperity Crushing - Application to Cold Rolling
Carretta, Yves ULg; Legrand, Nicolas; Laugier, Maxime et al

in Proceedings of ESAFORM : Belfast, 27-29th april 2011 (2011)

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 experiments ... [more ▼]

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 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]. [less ▲]

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See detailMetalub – A Slab Method software for the numerical simulation of mixed lubrication regime. Application to cold rolling
Carretta, Yves ULg; Stephany, Antoine; Legrand, Nicolas et al

in ICTMP 2010 - International Conference on Tribology in Manufacturing processes (2010)

Detailed reference viewed: 55 (16 ULg)