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Hagondange, France

Courbon C.,CNRS Tribology and Dynamic Systems Laboratory | Courbon C.,CNRS Contacts and Structural Mechanics Laboratory | Mabrouki T.,CNRS Contacts and Structural Mechanics Laboratory | Rech J.,CNRS Tribology and Dynamic Systems Laboratory | And 2 more authors.
Advanced Materials Research | Year: 2011

The present work proposes to enhance the thermal interface denition in Finite Element (FE) simulations of machining. A user subroutine has been developed in Abaqus/Explicit © to implement a new experimentally-based heat partition model extracted from tribological tests. A 2D Arbitrary-Lagragian- Eulerian (ALE) approach is employed to simulate dry orthogonal cutting of AISI 1045 steel with coated carbide inserts. Simulation results are compared to experimental ones over a whole range of cutting speeds and feed rates in terms of average cutting forces, chip thickness, tool chip contact length and heat flux. This study emphasizes that heat transfer and temperature distribution in the cutting tool are drastically in uenced by the thermal formulation used at the interface. Consistency of the numerical results such as heat flux transmitted to the tool, peak temperature as well as hot spot location can be denitively improved. © (2011) Trans Tech Publication.

Bonnet C.,Jean Monnet University | Rech J.,Jean Monnet University | Hamdi H.,Jean Monnet University | D'Eramo E.,ASCOMETAL CREAS
International Journal of Machining and Machinability of Materials | Year: 2011

The numerical modelling of cutting processes remains an issue for scientists. A better understanding of friction modelling is required to lead to more realistic finite element models (FEMs). This work proposes to evaluate the performance of a new friction model depending on the local sliding velocity. This model has been applied to the investigation of an AISI1045 steel in dry orthogonal cutting. The friction model has been implemented in a FEM based on the Arbitrary Lagrangian-Eulerian (ALE) approach. A large spectrum of cutting velocities and feed rates has been investigated. In parallel, experimental orthogonal cutting test have been performed in order to evaluate the accuracy of the model for each cutting condition. The model has shown a very good agreement with experimental results. Copyright © 2011 Inderscience Enterprises Ltd.

The fatigue resistance of car components such as crankshafts or diesel injection rails is mainly related to fatigue at geometrical singularities. Its understanding requires the simulations of the different steps of the industrial process resulting in residual stresses generation and their evolutions in service. First concerning crankshaft fatigue damage, a complete analytical model of residual stresses generation and shakedown in fatigue is presented. Then a fatigue criterion is established and validated for this application. Finally, for the high pressure diesel injection rail, this approach can be generalized to the holes intersection singularities.

Michaud H.,ASCOMETAL CREAS | Sprauel J.-M.,EA MS | Braham C.,CNRS Process and Engineering in Mechanics and Materials Laboratory
Materials Science Forum | Year: 2011

ASCOMETAL produces alloy steels used for spring (leaf or coil), where the weak fatigue points are on the surface which is reinforced by shot-peening. So, the fatigue optimization with the steel grade needs a perfect knowledge of the material answer after shot-peening. For that reason, an analytical model has been developed where low cycle fatigue behaviour and all the usual process parameters are integrated (especially the impact position, and the covering-rate). Moreover, through a Monte-Carlos approach, the model permits to analyse the effect of scattering elements like impact speeds, ball sizes, or material fatigue behaviour. With this model several key process parameters have been analysed and validated with residual stress profiles evaluated by X-ray diffraction. So, for spring leaf, the effect of an applied load during shot-peening or shakedown during bending fatigue is described.

Becker E.,CNRS Laboratory of Design, Manufacturing and Control | Favier V.,CNRS Process and Engineering in Mechanics and Materials Laboratory | Bigot R.,CNRS Laboratory of Design, Manufacturing and Control | Cezard P.,ASCOMETAL CREAS | Langlois L.,CNRS Laboratory of Design, Manufacturing and Control
Journal of Materials Processing Technology | Year: 2010

Semi-solid forming is an effective near-net-shape forming process to produce components with complex geometry and in fewer forming steps. It benefits from the complex thixotropic behaviour of semi-solids. However, the consequences of such behaviour on the flow during thixoforming, is still neither completely characterized and nor fully understood, especially for high melting point alloys. The study described in this paper investigates thixoextrusion for C38 low carbon steel material using dies at temperatures much lower than the slug temperature. Four different process parameters were studied: the initial slug temperature, the die temperature, the ram speed and the presence of a ceramic layer at the tool/material interface. The extruded parts were found to have an exact shape and a good surface state only if the temperature was below a certain value. This critical temperature is not an intrinsic material property since its value depends on die temperature and the presence of the Ceraspray© layer. Two kinds of flow were highlighted: a homogeneous flow controlled by the behaviour of the solid skeleton characterized by a positive strain rate sensitivity, and a non homogeneous flow (macro liquid/solid phase separation) dominated by the flow of the free liquid. With decreasing ram speed, heat losses increase so that the overall consistency of the material improves, leading to apparent negative strain rate sensitivity. Finally, some ways to optimise thixoforming are proposed. © 2010 Elsevier B.V.

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