scholarly journals Analyse de la dégradation thermique du Poly(éther éther cétone)

2017 ◽  
Vol 105 (4) ◽  
pp. 403 ◽  
Author(s):  
Emilie Courvoisier ◽  
Yoann Bicaba ◽  
Xavier Colin
Keyword(s):  
Micro Indentation ◽  
Module D’Young

La dégradation thermique du PEEK a été étudiée à l’état caoutchoutique dans de larges intervalles de température (entre 180 et 320 °C) et de pression partielle d’oxygène (entre 0,21 et 50 bars). Tout d’abord, les mécanismes de vieillissement thermique ont été analysés et élucidés par spectroscopie IRTF et par calorimétrie différentielle (DSC) sur des films de PEEK suffisamment minces (entre 10 et 60 μm d’épaisseur) pour s’affranchir totalement des effets de la diffusion d’oxygène. L’oxydation se produit sur les cycles aromatiques provoquant la croissance de cinq nouvelles bandes d’absorption IR centrées à 3650, 3525, 1780, 1740 et 1718 cm-1 et attribuées aux vibrations d’élongation des liaisons O–H du phénol et de l’acide benzoïque, et des liaisons C–O de l’anhydride benzoïque, du benzoate de phényle et de la fluorénone respectivement. De plus, l’oxydation conduit à une large prédominance de la réticulation sur les coupures de chaîne (augmentation de Tg) empêchant le recuit du PEEK, en particulier lorsque la température d’exposition est supérieure au pied du pic de fusion. Enfin, les conséquences de l’oxydation sur les propriétés élastiques ont été analysées et élucidées par micro-indentation sur des sections droites préalablement polies de plaquettes de PEEK de 3 mm d’épaisseur. Les variations du module d’Young et du taux de cristallinité se corrèlent parfaitement, vérifiant ainsi la relation de Tobolsky.

scholarly journals Analyse de la dégradation thermique du Poly(éther imide)

2017 ◽  
Vol 105 (4) ◽  
pp. 402
Author(s):  
Emilie Courvoisier ◽  
Yoann Bicaba ◽  
Xavier Colin
Keyword(s):  
Bisphenol A ◽  
Micro Indentation ◽  
Module D’Young

La dégradation thermique du PEI a été étudiée dans de larges intervalles de température (entre 180 et 250 °C) et de pression partielle d’oxygène (entre 0,21 et 50 bars). Tout d’abord, les mécanismes de vieillissement thermique ont été analysés et élucidés par spectroscopie IRTF et par calorimétrie différentielle (DSC) sur des films de PEI suffisamment minces (entre 10 et 60 μm d’épaisseur) pour s’affranchir totalement des effets de la diffusion d’oxygène. Comme attendu, et par analogie avec d’autres polymères aromatiques de structure chimique similaire, l’oxydation se produit préférentiellement sur les groupes méthyle de l’unité isopropylidène du motif bisphenol A, causant la disparition de leur bande d’absorption IR caractéristique à 2970 cm−1 et la croissance d’une nouvelle bande d’absorption IR centrée à 3350 cm−1 et attribuée aux groupes alcool. De plus, l’oxydation conduit successivement à une prédominance relative des coupures de chaîne (diminution de Tg) et de la réticulation (augmentation de Tg). Enfin, les conséquences de l’oxydation sur les propriétés élastiques ont été analysées et élucidées par micro-indentation sur des sections droites préalablement polies de plaquettes de PEI de 3 mm d’épaisseur. Cependant, l’augmentation du module d’Young dans la couche superficielle oxydée est principalement due à un vieillissement physique.

Electron microscope studies of the plastic deformation of ternary alloys based on GaAs

1990 ◽  
Vol 48 (4) ◽  
pp. 1120-1120
Author(s):  
R. Haswell ◽  
U. Bangert ◽  
P. Charsley
Keyword(s):  
Plastic Deformation ◽  
Electron Microscope ◽  
Room Temperature ◽  
Stacking Faults ◽  
The Other ◽  
Ternary Alloys ◽  
Dislocation Mobility ◽  
Semiconducting Materials ◽  
Micro Indentation

A knowledge of the behaviour of dislocations in semiconducting materials is essential to the understanding of devices which use them . This work is concerned with dislocations in alloys related to the semiconductor GaAs . Previous work on GaAs has shown that microtwinning occurs on one of the <110> rosette arms after indentation in preference to the other . We have shown that the effect of replacing some of the Ga atoms by Al results in microtwinning in both of the rosette arms.In the work to be reported dislocations in specimens of different compositions of Gax Al(1-x) As and Gax In(1-x) As have been studied by using micro indentation on a (001) face at room temperature . A range of electron microscope techniques have been used to investigate the type of dislocations and stacking faults/microtwins in the rosette arms , which are parallel to the [110] and [10] , as a function of composition for both alloys . Under certain conditions microtwinning occurs in both directions . This will be discussed in terms of the dislocation mobility.

Détermination du module d'Young dans des films minces de tungstène par diffraction des rayons X

2002 ◽  
Vol 12 (6) ◽  
pp. 147-154
Author(s):  
P. Villain ◽  
P. Goudeau ◽  
P.-O. Renault ◽  
K. F. Badawi
Keyword(s):  
Module D’Young

A Study of Microindentation Hardness Tests by Mechanism-based Strain Gradient Plasticity

2000 ◽  
Vol 15 (8) ◽  
pp. 1786-1796 ◽  
Author(s):  
Y. Huang ◽  
Z. Xue ◽  
H. Gao ◽  
W. D. Nix ◽  
Z. C. Xia
Keyword(s):  
Strain Gradient ◽  
Size Dependence ◽  
Plasticity Theory ◽  
Strain Gradient Plasticity ◽  
Gradient Plasticity ◽  
Hierarchical Framework ◽  
Microindentation Hardness ◽  
Dislocation Hardening ◽  
Hardness Tests ◽  
Micro Indentation

We recently proposed a theory of mechanism-based strain gradient (MSG) plasticity to account for the size dependence of plastic deformation at micron- and submicronlength scales. The MSG plasticity theory connects micron-scale plasticity to dislocation theories via a multiscale, hierarchical framework linking Taylor's dislocation hardening model to strain gradient plasticity. Here we show that the theory of MSG plasticity, when used to study micro-indentation, indeed reproduces the linear dependence observed in experiments, thus providing an important self-consistent check of the theory. The effects of pileup, sink-in, and the radius of indenter tip have been taken into account in the indentation model. In accomplishing this objective, we have generalized the MSG plasticity theory to include the elastic deformation in the hierarchical framework.

scholarly journals In situ SEM micro-indentation of single wood pulp fibres in transverse direction

2010 ◽  
Vol 59 (5) ◽  
pp. 345-349 ◽  
Author(s):  
R.-B. Adusumalli ◽  
R. Raghavan ◽  
P. Schwaller ◽  
T. Zimmermann ◽  
J. Michler
Keyword(s):  
Transverse Direction ◽  
Wood Pulp ◽  
Pulp Fibres ◽  
Micro Indentation

Determining Elastic-Plastic Properties of Al6061-T6 from Micro-Indentation Technique

2013 ◽  
Vol 592-593 ◽  
pp. 610-613
Author(s):  
Sina Amiri ◽  
Nora Lecis ◽  
Andrea Manes ◽  
Davide Mombelli ◽  
Marco Giglio
Keyword(s):  
Manufacturing Process ◽  
Optimization Procedure ◽  
Test System ◽  
Standard Test ◽  
Material Behavior ◽  
Plastic Properties ◽  
Representative Strain ◽  
Elastic Plastic ◽  
Dimensionless Analysis ◽  
Micro Indentation

Different approaches have been proposed in order to determine the material behavior of ductile materials. Since, the mechanical properties of a mechanical component are modified during manufacturing process due to plastic deformation, heat treatment and etc, a non-destructive indentation experimental procedure addressed to predict the elastic-plastic properties of material after manufacturing process is of interest. This is especially true for small size components where it is complex to extract specimens to test on standard test system. Based on dimensionless analysis and the concept of a representative strain, different approaches have been proposed to determine the material properties of power law materials by using indentation process. In this work, the Johnson-Cook (JC) constitutive model of the aluminum alloy Al6061-T6 is characterized by means of a well-defined optimization procedure based on micro-indentation testing and high fidelity finite element models and an optimization procedure but without the concept of dimensionless analysis and a representative strain. This methodology allows determining a set of JC constants for Al6061-T6. The obtained results have good agreement with parameters calibrated by means of universal standard tests and reverse engineering approach.

Ultraprecision Ductile-Regime Cutting of Brittle Materials

2007 ◽  
Vol 339 ◽  
pp. 395-399 ◽  
Author(s):  
Ming Zhou ◽  
X.D. Liu ◽  
S.N. Huang
Keyword(s):  
Ultrasonic Vibration ◽  
Soda Lime ◽  
Depth Of Cut ◽  
Soda Lime Glass ◽  
Diamond Cutting ◽  
Vibration Cutting ◽  
Ductile Regime Machining ◽  
Critical Depth Of Cut ◽  
Micro Deformation ◽  
Micro Indentation

Soda-lime glass is a typical brittle material, which is difficult to realize ductile-regime machining by using conventional cutting technology due to the extremely small critical depth of cut. In this work, the micro-deformation characteristics of this kind of materials were analyzed by micro indentation. Ultrasonic vibration assisted diamond cutting was performed in order to investigate the effect of tool vibration on material removal process and surface quality. The profiles of cut surfaces were measured and compared with those obtained by conventional diamond cutting. Real depths of cut in ultrasonic vibration cutting correspond well with the nominal ones. The change in the tribology of the cutting process as well as the alteration of the deformation mechanism of the work material might be responsible for the reduction in tool wear in vibration cutting.

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