ECL will be in charge of the study of the CIMC regarding tribology (friction, lubrication and wear properties) and surface aspects, including brittleness considerations. The general objective is to define the optimized material (layers organization) for the tribological purpose.
The Laboratoire de Tribologie et Dynamique des Systemes (LTDS), UMR CNRS 5513, at the Ecole Centrale de Lyon (ECL) develops and has a notable expertise in tribology (friction, wear, lubrication and adhesion) and dynamics of systems (vibrations, mechanical parts of machines). Among its principle activities, there are the development of instrumentation in tribology such as various tribometers (including an ultra high vacuum tribometer), surface force and nano-rheology measurements, surface topography measurements, the study of boundary lubrication and friction, the study of dynamic mechanisms (gears), the modelling of granular medium. Working in these fields requires the development of a multidisciplinary scientific approach. These activities concern broad industrial fields, petroleum, automotive, aeronautics, nuclear, chemical, sports The CIMC project, for both the material problematic (mechanical and tribological properties) and the envisaged applications (coatings to improve surface properties or engine parts) fits into our research activities. A full time PhD student will be employed for the project and will be supervised by Professors and Doctors.
WORKPACKAGE TITLE 2.4. Wear, brittleness, surface mechanical properties STARTING DATE (Month #) 0 DURATION (Months) 15 Effort (MM) 15 OBJECTIVES Identify the wear mechanisms of the CIMC and provide relevant experimental data on the surface mechanical properties.
DESCRIPTION OF WORK / TASKS The main drawback in the use of ceramics for tribological applications arises from their brittleness. Thus, their wear behaviour is strongly related to the propagation of fracture in the sub-surface material or in the bulk material generated by the friction conditions. This point could be relevant in the development of ceramic materials for engine parts which may be subjected to high frequency chocks and impact wear. The CIMC concept aims to reduce the material brittleness. A mechanical characterization of the new elaborated CIMC will be conducted. Wear and brittleness of the CIMC will be investigated. Special care will be taken regarding the mechanical surface and sub-surface characterization, as it is directly involved in the contacts.
DELIVERABLES Experimental results : data concerning wear, brittleness and surface mechanical properties of the elaborated CIMC.
MILESTONES AND CRITERIA
INTERRELATION WITH OTHER WORKPACKAGES 3.1. Powder studies 4.3. Surface finish 5.2 Lifetime
WORKPACKAGE TITLE 4.3. Surface finish STARTING DATE (Month #) 21 DURATION (Months) 15 Effort (MM) 15 OBJECTIVES Determine what should be the surface finish regarding stresses in the contact and lubrication efficiency.
DESCRIPTION OF WORK / TASKS The surface finish is an important factor for two reasons. First, it influences the macroscopic stress field in the contact through parameters such as surface roughness or form error, which plays an increasingly important role in the successful operation or failure of contacts. Using the nowadays available techniques of very precise surface roughness measurement, coupled to Multigrid based contact analysis and Multi-Level Multi-Integration analysis of the subsurface stress field will perform detailed stress analysis of contact performance accounting for realistic surface roughness geometry and allow accurate contact performance predictions. The second point concerns lubrication aspects. The control of the surface roughness (tips for load bearing capability or porosity for local lubricant supply) is one the key point in the endurance of a contact, especially in the lubricant boundary film generation. Thus, surface finish of the ceramics is a very important step in the samples manufacturing. These aspects will be simulated in an EHL tribometer in which a ball/plane contact under slide/roll conditions can be observed. An interferometry technique is used to measure the thickness of the oil film according to kinematics conditions. The effect of surface roughness and geometry will be studied.
DELIVERABLES Report : stresses induced by the surface roughness and microscopic form errors and their interaction with the macroscopic stress field. Experimental results : influence of the surface finish on lubrication efficiency
MILESTONES AND CRITERIA
INTERRELATION WITH OTHER WORKPACKAGES 4.2. Alternative elaboration processes 5.2. Lifetime 5.4. Tribological behaviour and coatings properties
WORKPACKAGE TITLE Tribological behaviour and coatings properties STARTING DATE (Month #) 6 DURATION (Months) 18 Effort (MM) 18 OBJECTIVES Determine the tribological behaviour of CIMC and the properties of CIMC coatings.
DESCRIPTION OF WORK / TASKS In engine technology, the macroscopic contacts can be of different types, point contact, line contact or surface contact. Depending on the considered contact, surface roughness and lubrication films induce specific contact pressure on the material asperities and specific tribological behaviour, which will be characterized using friction experiments. This may result in the presence of fractures in the contact, which induce high wear rates, or may lead to solid film formation due to tribochemical reaction between the surfaces in contact, related to the environmental conditions. It will be evaluated by making comparisons with steel surfaces. The mechanical properties of CIMC coatings and their specific tribological behaviour will be investigated, including adhesion considerations.
DELIVERABLES Experimental results : data concerning the tribological behaviour of the CIMC and CIMC coatings properties.
MILESTONES AND CRITERIA
INTERRELATION WITH OTHER WORKPACKGES 6.1. CIMC coatings 6.2. CIMC engine valve
BUDGET (in Euros, for a 3 year period)
1 full time PhD student : 110 000
Travel costs : 6 500
Consumables : 33 000
Equipment : 40 000
Computer : 10 000
20 % overheads : 39 900
Total : 239 400
The participants of the proposal are Dr S. Bec, Dr A. Tonck, Dr D. Mazuyer, Prof. A.T. Lubrecht and Prof. J.M. Georges
A. Brandt, A.A. Lubrecht, "Multilevel matrix multiplication and fast solution of integral equations", Journal of Computational Physics, 90, nÝ2, pp.348-370, 1990.
A.A. Lubrecht, E. Ioannides, "A fast solution to the dry contact problem and the associated sub-surface stress field, using multilevel techniques", ASME JOT, 113, pp 128-133, 1991.
C.H. Venner, F. Couhier, A.A. Lubrecht and J. Greenwood, "Amplitude reduction of waviness in transient EHL line contacts", Proc. 1996 Leeds Lyon Tribology Conference, Elsevier, Tribology Series 32, Ed. Dowson et al. pp 103-112, 1996.
S. Bec, A. Tonck, J.M. Georges, E. Georges, J.L. Loubet, "Improvements in the indentation method with a surface force apparatus", Phil. Mag. A. vol 74, pp 1061-1072, 1996.
J.M. Georges, "Some surface science aspects of tribology", in "New Directions in Tribology", Edit I. M. Hutchings, Mech. Eng. Publ., 1997, pp 67-84.
S. Bec, A. Tonck, J.M. Georges, R.C. Coy, J.C. Bell, G.W. Roper, "Relationship between mechanical properties and structures of zinc dithiophosphate anti-wear films", accepted for publication in Proceedings of the Royal Society series A.
D. Mazuyer, E. Varenne, A.A. Lubrecht, J.M. Georges, B. Constant, "Shearing of adsorbed polymer layers in an elastohydrodynamic contact in pure sliding, to be published in Lubrication at the Frontier : The role of the interface and surface layers in the thin film and boundary regime, Proc. 1998 Leeds Lyon Tribology Conference, Elsevier, Tribology Series 34, Ed. Dowson et al.