Etude de la sertissabilité d'alliage d'aluminium pour la carrosserie automobile

La caractérisation de la pliabilité d'alliage d’aluminium de la série 6xxx a été faite par pliage. Aucun paramètre macroscopique s’est révélé satisfaisant. Les mécanismes d’endommagement locaux ont été observés à l’EBSD et par mesure de déformation locale. Les tôles s’endommagent par la formation d’ondulations sur la peau externe en traction et de microbandes de cisaillement dans les grains. La formation de bandes de localisation de la déformation amenant à la fissuration des tôles a été observée

A Rapid Deformation Texture Model Incorporating Grain Interactions: Application to Aluminium Hot Rolling Textures

Publié suite au congrès ITAP2 Metz 2004International audienceA simple and general new approach to predict deformation texture evolution during large plastic strains is presented. The stress in each grain, first calculated by a Taylor model, is then modified by the stresses of adjacent grains thereby making the local slip systems and lattice rotations neighbour dependent. Examples of texture simulations during hot rolling of aluminium alloys are given. The model predictions are compared with the standard Taylor model predictions and with ODF data of the textures measured during hot plane strain compression

Strain localization and damage mechanisms during bending of AA6016 sheet

International audienceThe bendability of AA6016 sheets is a critical parameter for many automotive applications. In this experimental study the origins of damage and its evolution are characterized using interrupted and in-situ bending tests to correlate microstructural evolution with damage development. Local strains were estimated by optical and scanning microscopy (EBSD). Together with the load-displacement plots, they provided a set of physical parameters characterizing crack initiation. In particular, it is shown that (1) crack initiation occurs at the maximum of the rigidity-displacement curve; (2) cracking is preceded by strain localization in the form of macro-shear bands which induce surface roughening. Local necking then occurs in some surface grains and leads to ductile intergranular crack propagation. The sequence of microscopic changes at the grain scale up to and beyond crack initiation have been characterized and quantified in terms of local grain strains, coarse intragranular slip and shear band evolution over several grains. (C) 2012 Elsevier B.V. All rights reserved

Understanding the role of Cu on the work-hardening and strain-rate sensitivity of 6xxx alloys

Early Career Award plenary sessionInternational audienc

Asymmetry of strain rate sensitivity between up-and down-changes in 6000 series Aluminium alloys of varying Si content

International audienceIncreasing demand for a reduction in fuel emissions in passenger vehicles has generated the need for lighter weight materials to be used in automobile manufacture for body-in-white applications. Aluminium alloys in the 6000-series, containing Mg and Si are ideal candidates for these applications but lack the formability found in commonly used steels, providing a need to more fully understand the factors influencing the formability of these alloys at high strains. Conventionally, a high strain rate sensitivity (SRS) is tied to increased formability because it retards the increase in the local strain rate found in the diffuse neck interior. However, most experimental work neglects that the regions exterior to the neck will undergo a local decrease in the strain rate which causes a corresponding material softening. Observations of an asymmetry between up-change and down-change SRS of these alloys in the natural aged condition show that different mechanisms are controlling the SRS depending on the direction of rate change. Following a characterization of the state of clustering by differential scanning calorimetry, continuous tensile and precision strain rate sensitivity testing results are presented, elucidating the differences between the up-change and down-change SRS tests. It is shown that these differences are due to the activation of different thermal obstacles during the two directions of rate changes. The role of a change in Si content on the mechanical properties is explored and its suspected role on the asymmetric SRS is discussed

Influence of Composition and Pre-Ageing on the Mechanical Properties in Naturally Aged AA6xxx Series Alloys

International audienc

Grain scale modeling of the bendability of AA6xxx Al alloy sheet

International audienceBending sheet metal is a common shaping operation but, at high strains, may lead to failure that is difficult to predict from either standard mechanical tests or models. A recent experimental study of bending AA 6xxx sheet for automotive applications has shown that through-thickness strain localization controls damage development. Here, a new finite element microstructure based model of the standard bending test is introduced to predict strain localization during bending. The sheet metal is modeled as a grain aggregate, each grain having its own flow stress. The model is validated by comparison with a standard model and experimental results through an analysis of the critical plastic strain at the outer surface. It is applied to the bending of industrial AA6xxx sheet alloys and correctly describes the respective influences of sheet thickness, grain size and shape, and work hardening. In particular the model brings out the primary importance of large-strain hardening and the flow stress distribution width. It can be used to give simple guidelines for designing highly bendable sheet metal. (c) 2013 Elsevier B.V. All rights reserved

Understanding the Role of Cu and Clustering on Strain Hardening and Strain Rate Sensitivity of Al-Mg-Si-Cu Alloys

International audienc

Understanding the Role of Cu and Clustering on Strain Hardening and Strain Rate Sensitivity of Al–Mg–Si–Cu Alloys

International audienc