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See detailA pendulum test as a tool to evaluate viscous friction parameters in the equine fetlock joint
Noble, Prisca ULg; Lumay, Geoffroy ULg; Coninx, Marc ULg et al

in Veterinary Journal (2011), 188(2), 204-209

An equine fetlock joint pendulum test was studied and the influence of post mortem time and intra-articular lipid solvent on the viscous frictional response examined. Fresh equine digits (group 1, n=6 ... [more ▼]

An equine fetlock joint pendulum test was studied and the influence of post mortem time and intra-articular lipid solvent on the viscous frictional response examined. Fresh equine digits (group 1, n=6 controls; group 2, n=6 lipid solvent) were mounted on a pendulum tribometer. Assuming that pendular joint damping could be modelled by a harmonic oscillator fluid damping (HOFD), damping time (τ), viscous damping coefficient (c) and friction coefficient (μ) were monitored for 5h under experimental conditions (400N; 20°C). In all experiments, pendular joint damping was found to follow an exponential decay function (R(2)=0.99714), which confirmed that joint damping was fluid. The evolution of τ, c and μ was found to be significantly (P<0.05) different in the two groups, with a decrease in τ and an increase in c and μ that was faster and more prominent in digits from group 2. It was concluded that pendular joint damping could be modelled by a HOFD model. The influence of post mortem time on results suggested that, ideally, joint mechanical properties should only be tested on fresh cadavers at the same post mortem time. Moreover, the addition of lipid solvent was found to be responsible for upper viscous friction parameters and for a reduced damping time, which suggested that articular lubricating ability was compromised. This equine pendulum test could be used to test the efficacy of various bio-lubricant treatments. [less ▲]

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See detailTowards the Prediction of Damage Of Peritectic Steels During Continuous Casting Process
Keller, Clément ULg; Schwartz, Renée; Bobadilla, Manuel et al

in AIP Conference Proceedings (2011), 1353

In the Continuous Casting process, products are sometimes rejected or called defective due to the presence of transversal cracks. This type of macroscopic damage is expected to be due to a ductility loss ... [more ▼]

In the Continuous Casting process, products are sometimes rejected or called defective due to the presence of transversal cracks. This type of macroscopic damage is expected to be due to a ductility loss during cooling in the bending and unbending areas of the CC line. In order to study this damage, a 2D model has been developed to predict at the mesoscopic level the intergranular crack event taking into account the creep and diffusion of voids. Already validated for a microalloyed steel, the model is identified and used in this study to predict the crack formation for three different grades of peritectic steels. Results show encouraging predictions of the damage. [less ▲]

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See detailEquilibrium and non Equilibrium study of the Fine Pearlite Formation in two Cast High Speed Steels after solidification and thermal treatment
Tchuindjang, Jérôme Tchoufack ULg; Lecomte-Beckers, Jacqueline ULg

in International Journal of Materials Research (2011)

Two High Speed Steels (HSS) have been studied both having chemical compositions closed one to another. Both HSS grades exhibited similar matrix/carbides microstructure in the industrial as-cast conditions ... [more ▼]

Two High Speed Steels (HSS) have been studied both having chemical compositions closed one to another. Both HSS grades exhibited similar matrix/carbides microstructure in the industrial as-cast conditions, except for M7C3 eutectic carbides only observed in one grade and fine pearlite only found in the other grade. Equilibrium diagrams were obtained from Thermodynamical simulations to enhanced predicted phase transformations whereas Differential Thermal Analysis was performed on both alloys in order to determine their crystallization behaviour in non equilibrium conditions. Light microscopy and Electron microscopy associated with microprobe analyses were done to characterize the microstructure of both alloys. Thermal treatments with related bulk hardness assessments were carried out to enhance conditions for pearlite formation at the end of the casting route. In continuous cooling conditions obtained from DTA simulations, the matrix of both as-cast HSS grades is composed of eutectic carbides, martensite and retained austenite, these phases exhibiting similar chemical compositions. The introduction of an intermediate isothermal stage in the solid state within the DTA cooling sequence leads to the formation of a fine pearlite phase mainly located in the vicinity of M2C eutectic carbides on one HSS grade. The origin of this fine pearlite is discussed in this paper. [less ▲]

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See detailNew Trends in Hot Strip Mill Roughing Mills: Characterization of High Chromium Steel and Semi-HSS Grades
Lecomte-Beckers, Jacqueline ULg; Sinnaeve, Mario; Tchuindjang, Jérôme Tchoufack ULg

in Proceedings of the Iron & Steel Technology Conference (AISTech 2011) (2011)

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill (HSM) are compared. The first grade known as High Chromium Steel (HCS) is presently the most widely used alloy for such an ... [more ▼]

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill (HSM) are compared. The first grade known as High Chromium Steel (HCS) is presently the most widely used alloy for such an application, while the second one known as semi-High-speed Steel (semi-HSS) is the new grade developed to improve the overall performance of the work roll in the roughing stands of the HSM. In the present paper, the new semi-HSS grade is studied starting from three chemical compositions closed one to another, the variation in the alloying elements is intended to assess, on one hand the effect of a small increase of the carbon content, and on the other hand the influence of the addition of a strong MC carbide forming element. The comparison of HCS and semi-HSS grades involves many fields. Regarding the metallurgical aspect, such a comparison led to the enhancement of the solidification range, the crystallization behavior and the microstructure in the as-cast condition for both grades. Furthermore, corrosion behavior and performances of the work rolls in service are compared. Various techniques are used in order to characterize both grades, such as Differential Thermal Analysis (to determine phase transformations temperatures, the crystallization behavior and the interval of solidification), hardness measurements, optical microscopy, scanning electron microscopy associated with energy dispersive X-ray spectroscopy (to determine the nature and the composition of phases, especially matrix and carbides). Finally micro-macro relations between the nature of the microstructure and the properties of HCS and semi-HSS rolls grades in service conditions could be established. [less ▲]

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See detailRECENT TRENDS IN HOT STRIP ROUGHING MILLS: HIGH CHROMIUM STEEL VERSUS SEMI-HSS
Lecomte-Beckers, Jacqueline ULg; Tchuindjang, Jérôme Tchoufack ULg; Sinnaeve, Mario et al

in Procceedings of the 47th Rolling Seminar - Processes, Rolled and Coated Products (2010, October)

compared. The first grade known as High Chromium Steel (HCS) is presently the most widely used alloy for such an application, while the second one known as semi-High Speed Steel (semi-HSS) is the new ... [more ▼]

compared. The first grade known as High Chromium Steel (HCS) is presently the most widely used alloy for such an application, while the second one known as semi-High Speed Steel (semi-HSS) is the new grade developed to improve the overall performance of the work roll in the roughing stands of the HSM. In the present paper, the new semi-HSS grade is studied starting from three chemical compositions closed one to another, the variation in the alloying elements is intended to assess, on one hand the effect of a small increase of the carbon content, and on the other hand the influence of the addition of a strong MC carbide forming element. Furthermore, corrosion behavior and performances of the work rolls in service are compared. Various techniques are used in order to characterize both grades, such as Differential Thermal Analysis (to determine phase transformations temperatures, the crystallization behavior and the interval of solidification), hardness measurements, optical microscopy, scanning electron microscopy associated with energy dispersive X ray spectroscopy (to determine the nature and the composition of phases, especially matrix and carbides). Finally micro-macro relations between the nature of the microstructure and the properties of High Chromium Steel and semi-HSS rolls grades in service conditions could be established. [less ▲]

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See detailComparison between a high chromium steel and a semi HSS grades used as work rolls in the roughing stands of a hot strip mill
Tchuindjang, Jérôme Tchoufack ULg; Lecomte-Beckers, Jacqueline ULg

in Proceedings of The 10th International Conference on Steel Rolling (10th ICSR) (2010, September)

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill (HSM) were compared. The first grade known as High Chromium Steel (HCS) is actually the alloy widely used for such an ... [more ▼]

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill (HSM) were compared. The first grade known as High Chromium Steel (HCS) is actually the alloy widely used for such an application, while the second one known as semi-High Speed Steel (semi-HSS) is the new grade developed to improve overall properties of the work roll in the roughing stands of the HSM. In the present work, the new semi-HSS grade is studied starting from 3 chemical compositions closed one to another, the variation in the alloying elements being intended to assess, on one hand the effect of a light increase of the carbon content, and on the other hand the influence of the addition of a strong MC carbide forming element. The comparison of HCS and semi-HSS grades involved many fields. Regarding the metallurgical aspect, such a comparison led to the enhancement of the solidification range, the crystallization behavior and the microstructure in the as-cast condition for both grades. Heat treatment behavior of both grades was also investigated and optimal parameters leading to the homogenization of the alloy composition within the deepness of the roll were found. Furthermore, hot corrosion behavior and performances of the work rolls in service were compared. Various techniques were used in order to characterize both grades, such as Differential Thermal Analysis (to determine phase transformations temperatures, the crystallization behavior and the interval of solidification), hardness measurements, optical microscopy, scanning electron microscopy associated with energy dispersive X ray spectroscopy (to determine the nature and the composition of phases, especially matrix and carbides). Finally micro-macro relations between the nature of the microstructure and the properties of HCS and semi-HSS rolls grades in service conditions could be established. [less ▲]

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See detailStability of steel thixoforging process
Pierret, Jean-Christophe ULg; Rassili, Ahmed ULg; Vaneetveld, Grégory ULg et al

in Transactions of Nonferrous Metals Society of China (2010), 20(Special 3), 937-942

Whereas thixoforming of aluminum and other low melting point alloys is now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the research level. High temperature ... [more ▼]

Whereas thixoforming of aluminum and other low melting point alloys is now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the research level. High temperature issues, die wearing and production rate are problems that must be solved and are more and more investigated. This work focus on the study of a thixoforming line stability in the aim of industrialization of the process. The line is fully automated in order to maximize the repeatability of the experiments. Studied parameters are the heating cycle, the slug temperature, the tool temperature and the forming speed. For each of them we will give an order of magnitude of the expected variations in a steady-state process as well as the effects of these variations on the process itself (forming load and parts quality). Three different tools, and so three slugs and parts geometries, have been used in the experiments and are presented. Some mathematical simulations have been realized on the finite elements code Forge2008© with a semi-solid constitutive law and are also compared to the experiments. So the capacity of the model to represent the process stability is discussed as well. [less ▲]

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See detailX38CrMoV5 hot-work tool steel as tool material for thixoforging of steel, numerical and experimental evaluation
Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg; Vaneetveld, Grégory ULg et al

in Transactions of Nonferrous Metals Society of China (2010), 20(Special 3), 713-718

Whereas thixoforming of low melting point alloys as aluminum or magnesium is now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the research level. High working ... [more ▼]

Whereas thixoforming of low melting point alloys as aluminum or magnesium is now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the research level. High working temperature, die wearing and production rate are problems that must be solved and are under investigation. The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during the steel thixoforging process in order to determine if classical hot-work tool steel could be an appropriate tool material. This evaluation has been realized thanks to experimental trials and to simulations on the finite elements code Forge2008©. The effect of the loadings on the tool’s failure modes are highlighted and compared to the ones observed in classical hot forging. Beyond this, the failure modes of hot-work tool steel, the X38CrMoV5 or H11, is presented. [less ▲]

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See detailConception of tooling adapted to the thixoforging of high solid fraction hot-crack-sensitive aluminium alloys
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg et al

in Transactions of Nonferrous Metals Society of China (2010), 20(9), 1712-1718

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<fs<1), which involves the processing of alloys in the semi-solid state. Tooling has to be adapted to this particular ... [more ▼]

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<fs<1), which involves the processing of alloys in the semi-solid state. Tooling has to be adapted to this particular process to benefit of shear thinning and thixotropic behaviour of such semisolid material. Tooling parameters, as the forming speed and tool temperature, have to be accurately controlled because of their influence on thermal exchanges between material flow and tool. These thermal exchanges influence the high-cracking tendency and the rheology of the semisolid material during forming which affect parts properties. This paper shows, thanks to extrusion tests, how thermal exchanges influence surface quality of thixoforged parts made in 7075 aluminium alloys at high solid fraction by modifying process parameters like forming speed, tool temperature and tool thermal protector. A direct application is the evaluation of surface quality of thixoforged thin wall parts made in 7075 aluminium alloys. [less ▲]

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See detailContrôle de la porosité résiduelle dans les pièces en acier inoxydable fabriquées par rapid manufacturing selon la technologie 3D printing.
Verlee, Bruno; Dormal, Thierry ULg; Lecomte-Beckers, Jacqueline ULg

Conference (2010, June 15)

Additive technologies offer the possibilities to build complex geometries with integrated functionalities, specific to target application. 3D-printing of metallic powder is an additive technology ... [more ▼]

Additive technologies offer the possibilities to build complex geometries with integrated functionalities, specific to target application. 3D-printing of metallic powder is an additive technology proceeding in 2 steps: a green part is first built layer by layer by printing a liquid binder on the powder bed, and then green part is debinded and sintered. As sintering occurs separately of shaping process, 3D-printing is one of the only additive techniques able to produce porous parts, as filters or other fluid permeable components. Different porous characteristics can be obtained by playing on process parameters. [less ▲]

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See detailA pendulum test as a tool to evaluate viscous friction parameters in the equine fetlock joint
Noble, Prisca ULg; Lumay, Geoffroy ULg; Coninx, Marc ULg et al

Poster (2010, April)

This study describes an equine fetlock joint pendulum test, and investigates the influence of post mortem time and intra-articular lipid solvent on the viscous frictional response. Fresh equine digits ... [more ▼]

This study describes an equine fetlock joint pendulum test, and investigates the influence of post mortem time and intra-articular lipid solvent on the viscous frictional response. Fresh equine digits (control group 1 (n = 6); lipid solvent group 2 (n = 6)) were mounted in a pendulum tribometer. Assuming that pendular joint damping could be modelled by a harmonic oscillator fluid damping (HOFD), damping time (t), viscous damping coefficient (c ) and friction coefficient (µ) were then followed for 5 hours under experimental conditions (400 N; 20 °C). In all experiments, pendular joint damping was found to follow an exponential decay function (R² = 0.99714), which confirms that joint damping is fluid. The evolution of t, c and µ was found to be significantly (P <0.05) different in the two groups. Indeed, t decreased and c and µ increased more rapidly and strongly in the group 2. It was concluded that pendular joint damping can be modelled by an HOFD model. The influence of post mortem time on results suggests that, ideally, joint mechanical properties should only be tested on fresh cadavers at the same post mortem time. Finally, the addition of lipid solvent was found to be responsible for upper viscous friction parameters and for a reduced damping time, which suggests that articular lubricating ability was compromised. This equine pendulum test could be used to test the efficacy of various bio-lubricant treatments. [less ▲]

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See detailAn equine joint friction test model using a cartilage-on-cartilage arrangement.
Noble, Prisca ULg; Collin, Bernard ULg; Lecomte-Beckers, Jacqueline ULg et al

in Veterinary Journal (2010)

This study describes an equine joint friction test using a cartilage-on-cartilage arrangement and investigates the influence of age and load on the frictional response. Osteochondral plugs were extracted ... [more ▼]

This study describes an equine joint friction test using a cartilage-on-cartilage arrangement and investigates the influence of age and load on the frictional response. Osteochondral plugs were extracted from equine shoulder joints (2-5 years, n=12; 10-14 years, n=15), and mounted in a pin-on-disc tribometer. The frictional response was then measured under constant conditions (2N; 20 degrees C; 5 mm/s), and with increasing load (2N, 5N, 10N). In all experiments, the friction coefficient of young cartilage was significantly (P<0.001) smaller than obtained from old cartilage, while the application of a greater load resulted in a significant (P<0.001) decrease in friction coefficient only in old cartilage. It was concluded that cartilage ageing was responsible for an increase in friction coefficient under these experimental conditions. Moreover, where young cartilage lubrication remained stable, cartilage ageing may have been responsible for lubrication regime change. The cartilage-on-cartilage model could be used to better understand lubrication regime disturbances in healthy and diseased equine joints, and to test the efficacy of various bio-lubricant treatments. [less ▲]

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See detailFissuration de dépôts durs à base de Ni et de Co en Laser Cladding
Montrieux, Henri-Michel ULg; Lecomte-Beckers, Jacqueline ULg

Report (2010)

Le rapport concerne l'étude de la fissuration de dépôts durs en Ni-Cr-Fe-B-Si réalisés par Laser Cladding. Il est montré que la fissuration est provoquée par la présence de contraintes mécaniques ... [more ▼]

Le rapport concerne l'étude de la fissuration de dépôts durs en Ni-Cr-Fe-B-Si réalisés par Laser Cladding. Il est montré que la fissuration est provoquée par la présence de contraintes mécaniques résiduelles d'origine thermique et on se trouve face à un phénomène de fissuration à froid. Le travail comporte également la comparaison de 4 nuances de poudre différentes utilisées en Laser Cladding au niveau du coefficient de dilatation thermique et des microstructures. La présence de composés céramiques (borure ou carbure) de nature pro-eutectique a pour effet de diminuer le coefficient de dilatation mais d'augmenter la fragilité. Le rôle du coefficient de dilatation thermique dans la fissuration semble être moins important que la nature de la microstructure en elle-même. Le choix de nuances présentant une structure hypo-eutectique et une haute dureté semble être pertinent en ce qui concerne l'établissement d'un compromis entre la dureté et la résilience de ces matériaux particuliers. [less ▲]

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See detailL'articulation synoviale : un systeme tribologique parfait
Noble, Prisca ULg; Collin, Bernard ULg; Lecomte-Beckers, Jacqueline ULg et al

in Annales de Médecine Vétérinaire (2010), 154(2), 83-93

The synovial joint, by load bearing and by minimal wear and minimal friction conferring, is considered as a perfect tribological system. During these last years, researchs in articular biomechanics have ... [more ▼]

The synovial joint, by load bearing and by minimal wear and minimal friction conferring, is considered as a perfect tribological system. During these last years, researchs in articular biomechanics have been performed to study how the joint friction coefficient, a dimensionless measure which represents the ratio between the frictional force on the normal force, was close to zero. Today, there is still no consensual explanation and the articular prosthesis partially imitates the biological mechanics. This review describes the composition and the general properties of the synovial joint components. Additionally, different theorical models, on the tribology of the articular triplex cartilage-synovial fluid-cartilage, are explained. [less ▲]

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See detailFriction coefficients evaluation for steel thixoforging
Pierret, Jean-Christophe ULg; Rassili, Ahmed ULg; Vaneetveld, Grégory ULg et al

in Proceedings of The 13th Esaform Conference on Material Forming (2010) - semi-solid processing (2010)

Since the first works on thixoforming, lot of studies have been performed all over the world and the behaviour of the globular semi-solid slurry is now quite well understood. This knowledge had lead to an ... [more ▼]

Since the first works on thixoforming, lot of studies have been performed all over the world and the behaviour of the globular semi-solid slurry is now quite well understood. This knowledge had lead to an industrialisation of the technology for low melting point alloys as aluminium or magnesium. For high melting point alloys as steel, this industrialisation is still a wish but seems closer each year. In the aim of this development of the process, it is important to be able to accurately represent the behaviour of the slurry during thixoforming. In this goal, lot of constitutive models has been proposed during the last years. However, until now there isn’t any study about the friction in the case of thixoforming. This knowledge is needed as friction has an important effect on the flow of the slurry during the shaping. The aim of this work is so to propose a quantification of the friction coefficients for the thixoforming technology thanks to experiments on a dedicated tool and comparison with simulations run on the finite elements code Forge2008©. The friction law is a Coulomb limited Tresca one. [less ▲]

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See detailMaterials for advanced power engineering 2010 : Proceedings of the 9th Liège conference
Lecomte-Beckers, Jacqueline ULg; Contrepois, Quentin ULg; Kuhn, F. et al

Book published by Schriften des Forschungszentrum Julich, Reihe energietechnik/Energy Technology Forschungszentrum Julich (2010)

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See detailBenefits of thixoforging hot-crack-sensitive aluminium alloys at high solid fraction
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg et al

in International Journal of Material Forming (2010), 2

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