ASCOMETAL CREAS

Tremblay-en-France, France

ASCOMETAL CREAS

Tremblay-en-France, France
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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.


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.


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.


Leiro A.,Lulea University of Technology | Vuorinen E.,Lulea University of Technology | Sundin K.G.,Lulea University of Technology | Prakash B.,Lulea University of Technology | And 5 more authors.
Wear | Year: 2013

Specially designed steels with carbon contents from 0.6 to 1.0. wt% were isothermally transformed at very low temperatures, between 220 and 270. °C, in order to obtain a nano-structured bainitic microstructure. It is shown that the wear resistance in dry rolling-sliding of these nano-structured steels is significantly superior to that of bainitic steels transformed at higher temperatures with similar hardness values. In addition to the highly refined microstructure, the transformation under strain to martensite (TRIP effect), contributes to the plasticity of the nano-scaled steels, increasing surface hardness during testing, thus reducing the wear rate. © 2012 Elsevier B.V.


Courbon C.,École Centrale Lyon | Courbon C.,INSA Lyon | Mabrouki T.,INSA Lyon | Rech J.,Jean Monnet University | And 3 more authors.
Procedia CIRP | Year: 2013

Whether analytical or numerical, models of a machining operation require important input data such as friction laws or material constitutive models to reach accurate results. Recent experimental studies provided a better fundamental understanding of the cutting process especially regarding the thermo-mechanical conditions associated to the chip formation. However, in most of the numerical works, the deformation behaviour of materials is still represented by a simple empirical equation. This contribution therefore aims at improving the physical meaning of a FE cutting model by the use of an advanced constitutive equation. After an emphasis on the microstructural evolutions occurring in cutting, a dynamic compression test campaign is conducted to assess the material behaviour at high strains. A "metallurgy based" constitutive model, taking into account a dynamic recrystallization process, is identified. It clearly leads to a better description of the thermo-mechanical behaviour than the commonly used Johnson & Cook's model, also identified based on these experiments. Finally, the latter are implemented in a FE code (Abaqus/Explicit©) via a VUMAT© subroutine. An ALE 2D orthogonal cutting model is then involved to assess their performance as well as the effect of the dynamic recrystallization in machining. Numerical results are compared to experimental data in orthogonal cutting conditions as well as identifications of Johnson & Cook's model conducted in the literature. Copyright © 2013 Elsevier B.V.


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.


Michaud H.,ASCOMETAL C.R.E.A.S | 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.


Courbon C.,École Centrale Lyon | Courbon C.,University of Lyon | Mabrouki T.,University of Lyon | Rech J.,National School of Engineering, Saint-Etienne | And 2 more authors.
Applied Thermal Engineering | Year: 2013

This paper questions the perfect thermal contact conditions usually assumed at the tool-chip interface in machining. Dry orthogonal cutting tests are first conducted on a AISI 1045 steel with TiN coated carbide tools. Tool-chip contact zones are analysed by SEM-EDS and sticking and sliding parts are dissociated. A formation mechanism of a Thermal Contact Resistance (TCR) is proposed from the real contact area extracted. A Finite Element (FE) model based on the Arbitrary-Lagrangian-Eulerian (ALE) approach is then employed to investigate the influence of such thermal contact conditions on the cutting process. Evolution of the main cutting outputs such as average cutting forces, average chip thickness, tool-chip contact length and thermal fields is assessed. It is demonstrated, on one side, that average cutting forces, chip thickness and tool-chip contact length are shown to be insensitive to a TCR. On the other side, heat flux transmitted to the tool, temperature distribution on the tool rake face as well as continuity of temperature across the tool-chip interface are clearly affected depending on its amplitude. This study emphasizes that the existence of a TCR at the tool-chip interface can completely modify local heat partition compared to a perfect thermal contact. The possible occurence of an imperfect contact in machining should be highly considered and modelled based on thermal exchange considerations. Local heat transfer models at the interface are still required to reach more reliable and physically based simulations. © 2012 Elsevier Ltd. All rights reserved.


Courbon C.,University of Lyon | Mabrouki T.,University of Lyon | Rech J.,University of Lyon | Mazuyer D.,University of Lyon | And 2 more authors.
International Journal of Machine Tools and Manufacture | Year: 2014

The main objective of this paper is to clarify the deformation mechanisms of ferritic-pearlitic steels in metal cutting and correlate them to the associated thermo-mechanical loadings. Dry orthogonal cutting tests have been performed on a normalised AISI 1045 steel with coated carbide tools. Experimental evidences of a drastic grain refinement process in the main deformation zones are advanced on the basis of optical microscope, Field Emission Scanning Electron Microscope (FESEM) and Electron BackScattered Diffraction (EBSD). Microstructural evolutions leading to a grain size down to 200 nm and fragmented cementite are especially emphasized. A numerical approach is further employed to target and quantify the loadings applied to the machined material and extract further information on the Secondary Shear Zone (SSZ). Strains amplitude appears to be the driving parameter of these evolutions via a dynamic recrystallisation process promoted by an intense and localised heat generation. The present contribution highlights that in-depth and microscale investigations of chip formation including microstructural aspects are still required. © 2013 Elsevier Ltd.


Sourmail T.,Ascometal CREAS | Smanio V.,Ascometal CREAS | Auclair G.,Ascometal CREAS
ASTM Special Technical Publication | Year: 2015

This investigation is concerned with quantifying the role of alloying elements in the bainite formation kinetics in 100Cr6 and similar steel grades. Using industrial or laboratory casts, we quantified the influence of Mn, Cr, Si, Mo, C, and Co. For this, dilatometry measurements were carried out at various temperatures between 200°C and 350°C. The influence of the different elements is discussed and compared with that expected from the impact of these elements on the austenite-to-ferrite transformation driving force. It is shown that additions of Co, while indeed having a beneficial influence, can easily be avoided with small adjustments to the austenitizing conditions. The results are used to propose a modified version of the standard 100CrMo7 with a 38 % reduced bainitic reaction duration. Copyright © 2014 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.

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