WEMESURF course, 21-25 June 2010, Paris
Practical work in ZéBuLoN
Fretting crack investigation, Lingtao Sun
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The fretting phenomenon occurs when two solid surfaces in
contact are subjected to high pressure and an oscillatory relative
movement of small amplitude. Fretting is an important phenomenon in
industrial sectors such as energy, aerospace, and railway transport,
because it decreases the fatigue strength of materials. This can cause
initiation and subsequent propagation of cracks in the vicinity of the
contact zone. If the cracks reach a critical size in presence of fatigue
loading, this may eventually lead to the complete failure of the
mechanical structure. In this mini project we will compute the stress and strain fields due to a fretting contact and use them to calculate the stress intensity factors arising at the crack tip. Different crack length will be studied and the life time of the crack propagation will be estimated. | 
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Rail-wheel contact, Saber El-Arem
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| The purpose is to model the contact between the wheel of a locomotive and a piece of rail by a cylinder and a plate. The first case studied deals with the locomotive standing in the train station. The contact between wheel and rail is loaded by the weight of the locomotive only. When the locomotive starts to pull the wagons the whole traction is transmitted through the wheel/rail contact. The maximum traction can be limited by the power of the engine, by the friction pair wheel/rail or the material properties of wheel and rail. Typical questions solved in the project are: (1) Can a contact slide and stick at the same time ? (2) What is the stress level near wheel/rail contact, compared to the material resistance ? (3) What is the respective level of normal and tangential load. (4) Is there a mesh size effect ? | 
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Coating indentation test, Vladislav A. Yastrebov
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| The mechanical behaviour of coatings can be evaluated by using indentation tests on the coated surface. This is the subject of this mini-project. The aim of the study is then the definition of the suitable conditions to avoid the bias in the characterisation of the characteristics of the coating. The main question is: what is the minimal thickness that allows the user to reach the intrinsic properties of the layer ? A rigid sphere and a coated half space are considered. The coating behaviour is elasto-plastic with a nonlinear kinematic hardening. We propose an analysis of the maximum and residual stresses in the half space during the indentation test, and the characterisation of the global load-displacement curves. | 
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Composite surface frictional contact, Siarhei Dubouski
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| A reduction in wear and friction can be achieved through surface engineering, by a combination of surface texturing and the application of a coating layer of solid lubricant. The textured surface behaves as a composite surface with a global behaviour that can be determined from the local coefficients of friction and the mechanical properties of the metal and the lubricant. These composite surfaces are simulated here using 2D plane strain meshes, with elastic materials. Sliding friction is taken into account using Coulomb friction. The following questions are addressed: (1) How depth and length of the dimples do influence the global coefficient of friction of composite surfaces ? (2) What is the position of the FE results with respect to simplified analytical friction curves ? | 
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Contact between an asperity and a plane, Julian Durand
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| The purpose of this study is to see the evolution of the contact area with the applied load. Thus, we will simulate the contact between an asperity and a smooth and rigid surface. Two problems will be investigated in order to see differences on the contact area between a purely elastic asperity and an elastoplastic asperity. | 
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