Papers by Author: Jean Lu Lebrun

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Authors: G. Mohamed, Brigitte Bacroix, Jean Lu Lebrun
Authors: Guenael Germain, Franck Morel, Jean Lu Lebrun, Anne Morel, Bertrand Huneau
Abstract: The use of Laser Assisted Machining (LAM) can improve different aspects of the machinability of high strength materials. A study was undertaken to determine the optimum cutting parameters and to quantify their influence on fatigue strength according to the type of microstructure created. Two different materials were studied: a bearing steel (100Cr6 / AISI 52100) and an aeronautical titanium alloy (Ti6Al4V). In the bearing steel a significant increase of the fatigue resistance was observed due to the transformation of the surface layer into martensite. For the titanium alloy, a slight reduction in the fatigue strength was found as in this case the microstructure and residual stress state of the surface layer was less beneficial. The surface roughness has also been measured and no significant variation has been observed for different laser powers in each material.
Authors: L. Arnault, S. Branchu, Manuel François, Ronald Guillén, Karim Inal, Jean Lu Lebrun, C. Vial
Authors: Fabien Lefebvre, M. Francois, J. Cacot, C. Hemery, P. Le-Bec, E. Baumhauer, Denis Bouscaud, T. Bergey, D. Blaize, D. Gloaguen, Jean Lu Lebrun, A. Cosson, Regis Kubler, Y. Cheynet, E. Daniel, H. Michaud, J.C. Monvoisin, P. Blanchet, P. Allain, Y Mrini, Jean Michel Sprauel, Philippe Goudeau, P. Barbarin, C. Charles, J.M. Le Roux, Wilfrid Seiler, C. Fischer, L. Desmas, A. Ouakka, M.J. Moya, Y. Bordiec
Abstract: The GFAC (French Association for residual stress analysis) decided in 2007 to work on external reference samples for residual stress analysis by X-ray diffraction as defined in the XPA 09-285 and EN 15305-2009 standards. Seven materials are studied: ferritic steel, martensitic steel, aluminium alloy, titanium alloy, 2 types of Nickel-Chromium alloy and tungsten thin layers deposited on silicon wafers. The purpose of this external round robin campaign is threefold: (i) to give possibilities for each laboratory involved in the campaign test to obtain external reference samples for each material tested, (ii) to validate a common procedure for qualification of external samples and (iii) to commercialise validated external reference samples through the GFAC association. A common approach of X-Ray diffraction parameters, samples geometry and standard procedure has been chosen and adopted by each laboratory involved in these tests. No indication in terms of residual stress calculation method is given; the choice of the method (centroid, middle point, maximum of peak, fitting…) is the choice of the laboratory according to their X-ray diffraction set-ups, softwares and experience. Once all samples are analysed, values given by each laboratory are compared and analysed.
Authors: Raphaël Pesci, Karim Inal, Marcel Berveiller, Jean Lu Lebrun
Authors: Maria José Marques, A. Morão Dias, C. Gautier-Picard, Jean Lu Lebrun
Authors: Malek Habak, Jean Lu Lebrun, Stefan Waldmann, Patrick Robert, Cyril Fischer
Abstract: In this paper, the effect of a high pressure water jet, directed into the tool chip interface, on surface residual stresses and chip shape, in face turning of AISI 316L stainless steel has been investigated. Tests have been carried out with a standard cutting tool. This tool is not specifically meant for the machining of this type of material. The cutting speeds used were 80 m/min and 150 m/min, with a constant feed rate of 0.1 mm/rev and a constant cutting depth of 0.1 mm. Three jet pressures were used: 20, 50 and 80 MPa. Residual stress profiles have been analysed using the X-ray diffraction method in both longitudinal and transversal directions. The results show that by using a high pressure jet directed into the tool-chip interface, it is possible to create a well fragmented chip in contrast to the continuous chip formed using dry turning. It is also possible to control the chip shape and increase tool life. When the jet pressure is increased the residual stress at the surface decreases however it is increased by an increase in cutting speed. It can be concluded that surface residual stresses can be reduced by the introduction of a high pressure water jet. A reduction in the residual stress value by about 20 to 40 % can be observed when using high pressure water jet assisted turning compared to dry turning. Also, it has been observed that the jet pressure does not have a great influence on the depth affected by residual stress and by hardening.
Authors: J.C.P. Pina, A. Morão Dias, Jean Lu Lebrun
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