Papers by David Delafosse
Materials teaching is part of a paradigm shift currently happening in the design education. It ha... more Materials teaching is part of a paradigm shift currently happening in the design education. It has become crucial to provide design students with an up-to-date knowledge about the latest advance in materials and manufacturing technologies with the aim to prepare them to more effectively cope with the next industry challenges. The introduction of smart materials started to revolutionize the way we design and interact with products. Their dynamic properties are changing our perception and understanding about what a material is in itself (a system), and especially, what it is able to do (its performance). This paper presents a multidisciplinary framework for teaching functional materials based on a 5-layer structure: from the material science basics (1), materials engineering (2), stimuli-responsive phenomena (3), material experience (4) and product experience (5). Among the research outputs, four design-oriented tools are described. Apart from an introductory lecture, descriptive cards provide information on the most common phenomena that describe commercial smart materials application (levels 1-3). The Smart Materials for Sensory Experiences Map (SM4SE) classifies such materials based on their input/output stimuli and puts them into relation with the explorative sensory modalities (levels 3-4). By selecting an application of smart materials, the Dynamic Product Experience tool encourages students to explore, describe and qualitatively rank the dimensions of product experience (usefulness, desirability, credibility, understandability, usability) (level 5). The tools have been tested in a one-week learning experience focused on smart materials teaching
Measurement Science and Technology, 2020
The present paper concerns the oxide layer thickness determination of oxidized metals in the case... more The present paper concerns the oxide layer thickness determination of oxidized metals in the case where an optical interference phenomenon occurs due to multiple reflections inside the oxide layer. The paper focuses on anodized titanium but can be extended to the layer thickness determination of any material composed of a non-absorbing layer over an absorbing substrate. It establishes theoretical formulae to compute the oxide layer thickness from the positions of the local extrema of the material reflectance spectra. In contrast with many publications these formulae take into account the air/oxide and oxide/metal interfaces’ electromagnetic phase-shift. They make also the distinction between TE-, TM- and non-polarized light and are valid for all incidence angles. By applying these formulae to simulated reflectance spectra with known oxide thicknesses, we show that neglecting the interface phase-shift is not appropriate for determining the oxide thickness of samples with thin oxide t...
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific ... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et a ̀ la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Author postprint version – Please cite using: Vucko, F., Bosch, C., & Delafosse, D. (2014). Experimental investigations of internal and
Corrosion Mechanisms in Theory and Practice, 2002
Classical approaches of corrosion fatigue damage according to the different electrochemical corro... more Classical approaches of corrosion fatigue damage according to the different electrochemical corrosion domains are presented through their interests and limits. A peculiar attention is paid on the necessity to integrate corrosion-deformation interactions to these modellings. A non exhaustive review of such interactions in corrosion fatigue is made and trends for further researches are emphasized.
Methodologie, donnees collectees et traitements des specialistes Approche analyse sensorielle ► E... more Methodologie, donnees collectees et traitements des specialistes Approche analyse sensorielle ► Est-ce que presenter un objet fini (coque de telephone) ou un echantillon de matiere change la perception ? Si oui, comment ? ► Experiences-selon un protocole precis :-presenter a 23 utilisateurs 12 echantillons ou 12 objets-les faire placer sur la Nappomatic ®-demander a caracteriser les groupes formes avec des mots libres. ► Traitement des donnees avec des outils standards (a l'exception des mots, donc base uniquement sur les coordonnees x et y)-Clustering assez ressemblant entre les deux types : echantillons versus objets Approche complementaire en analyse sensorielle Croissement des competences Collaboration interdisciplinaire : analyse sensorielle et data science Validation de l'experience ► nombre d'utilisateurs suffisants et resultats fiables ► pas de differences entre les testeurs Analyse du texte produit ► trouver une equivalence via une fonction de similarite entre l...
Mechanics - Microstructure - Corrosion Coupling, 2019
Abstract: Many mechanisms have been proposed to describe the different hydrogen embrittlement pro... more Abstract: Many mechanisms have been proposed to describe the different hydrogen embrittlement processes. The materials' variability and their properties, their conditions of use and the nature of the surrounding environment make it difficult to establish a single fundamental theory or approach to describe hydrogen embrittlement (HE). Experimental validations of these mechanisms are often based on a set of conditions (metallurgy, mechanical loading, surface hydrogen activity, volume concentration, etc.) which are favorable to the emergence of a particular mechanism, making it difficult to get an overview of the various interaction modes between the adsorbed hydrogen or hydrogen in solid solution and the crystal defects. Kirchheim points out that from a thermodynamic point of view, all the approaches proposed in the literature are based on a decrease of the defect formation or emission energy (dislocations, vacancies, microcavities), of the cohesion and surface energies, or the energy associated with the displacement of defects such as dislocations, in the presence of adsorbed or absorbed hydrogen. The brittle fracture of deformable crystal materials subjected to quasi-static monotonic loading arises from a competition between, on the one hand, the accumulation rate of elastic energy at the crack tip until a critical value intrinsic to the material is reached (the critical elastic energy release rate, related to the fracture toughness and to Young's modulus) and, on the other hand, the dynamics of crystal defect creation/multiplication that blunt the existing cracks or their nuclei, or screen the loading applied to them. Understanding the hydrogen-induced damage and fracture requires taking into account the effects of hydrogen on the crystal cohesion as well as the plasticity or the phase transformations at the crack tip. In the presence of intrinsically brittle interfaces, heterogeneities or phases, hydrogen can affect the material's cohesion through (co-)segregation effects, through the accumulation of deformation incompatibilities or induced precipitation. If, from a formal point of view, these mechanisms belong to the two preceding categories (intrinsic embrittlement or plasticity modification), from a practical point of view, their study and modeling have led to specific developments. We thus find four major classes of hydrogen-assisted damage mechanisms in the literature: brittle fracture through the reduction of the material's cohesion, damage due to the formation of vacancies and their condensation, fracture due to the local increase of plasticity (“direct”, through localized shear; or “indirect”, through the accumulation of internal stresses near the interfaces) and fracture through the formation of a brittle phase (hydride). The first model is based on the idea of the decrease in the interfaces' cohesion energy (lattice, grain boundaries, inter-phase, etc.) caused by the segregation of hydrogen, which promotes the formation and propagation of cracks. The second model is based on the formation of new defects such as vacancies followed by microcavities in the presence of hydrogen. The multiplication and localization of these defects can lead to the initiation and propagation of cracks. The third approach of HE is based on the emission of dislocations favored by the presence of hydrogen (decrease of elastic interactions and line tension) which can induce the initiation of a crack and the localization of the plastic deformation in front of the crack tip. Finally, the fourth model is based on the formation of a brittle hydrogen-rich hydride phase. In order to better understand the different aspects of the hydrogen-material interaction as well as its harmful effects, we will describe in more detail the four HE models and the various associated mechanisms.
Thin Solid Films, 2020
The oxide thickness of anodized titanium samples has been determined through ellipsometry, reflec... more The oxide thickness of anodized titanium samples has been determined through ellipsometry, reflectance spectra extrema positions and electronic imaging. The reflectance spectra extrema position technique is applicable in the case were the oxide layer is thin enough to generate an interference phenomenon inside the oxide layer. When reflected at the air/oxide and oxide/metal interfaces, the electromagnetic field undergoes a phase-shift, which is often neglected in the literature. By comparing the oxide thickness obtained through the different techniques, it is shown that this phase-shift is not negligible for thin oxide layers. The relative error on the oxide thickness is for example of about 50% for a 17 nm thick oxide layer. By studying the discrepancy observed in the literature for the titanium and oxide layer refractive indexes, which is of about 13% in the wavelength range (350-600 nm), the error induced when neglecting the electromagnetic phase-shift is higher than the error induced by the uncertainty on the refractive indexes for oxide thicknesses below about 50 nm.
Sciences du Design, 2015
Le design se pratique en projet de conception d'objets. Le plus souvent, ce n'est pas le seul mét... more Le design se pratique en projet de conception d'objets. Le plus souvent, ce n'est pas le seul métier ou discipline à intervenir. Dans tout projet de conception/design, l'utilisation et la manipulation d'information sont vitales. Le support de l'information doit accompagner le dialogue entre les métiers. Si le dessin technique permet l'échange entre les métiers de la conception et ceux de la réalisation, il nécessite un apprentissage. Le dessin technique est un objet intermédiaire de conception codifié, il suppose d'être appris pour être compris. Le design possède de nombreux supports d'information propice à l'échange « naturelle » entre les métiers (croquis, dessin, rough, maquette d'étude, maquette d'aspect). Pourtant, dans ces cas, a contrario du dessin technique, un certain flou d'interprétation peut exister favorisant des quiproquos. Expliciter les outils de (re)présentation du design devient un sujet d'une recherche interdisciplinaire par le design. Le design sensoriel a hybridé les outils de l'évaluation sensorielle en les orientant projet de conception. Quelques outils méthodologiques illustrent ce que peut être une recherche par le design.
Matériaux & Techniques, 2003
The effect of hydrogen on tensile tests of nickel and binary nickel – 16 wt. % chromium alloy is ... more The effect of hydrogen on tensile tests of nickel and binary nickel – 16 wt. % chromium alloy is analysed in terms of solute drag phenomenon. Static Strain Ageing experiments are used to measure the saturated dislocation pinning force as a function of the H concentration. First order hydrogen-dislocation interactions cause a shielding of the pair interactions between edge dislocations. The influence of this screening effect is analytically evaluated on the self-energy and line tension of curved dislocations, the critical force for the expansion of a dislocation loop and the dissociation mechanism. These results are used to interpret experimental results on the plastic flow of hydrogen-charged nickel single crystals oriented for easy glide.This study illustrates the mechanisms of H-dislocation interactions and their consequences on the different contributions of hydrogen to the flow stress of nickel.
Ceramics International, 2017
Consolidation processes aimed at manufacturing cellular solids from bioglasses often result in a ... more Consolidation processes aimed at manufacturing cellular solids from bioglasses often result in a glass-ceramic microstructure, whose response to aqueous environment affects their performance. In this study, we evaluated the microstructure and the effect of crystallization on the dissolution mechanism of a Bioglass®-based glassceramic scaffold, produced with a powder metallurgy inspired technology. All the experiments are conducted in a controlled aqueous environment in order to avoid nucleation of different species or unknown chemical interactions between simulated body fluids and bioglass-ceramic material. The presence of a residual silica glass embedding different phases of not fully crystallized particles is highlighted, showing a complex multiscale structure elucidated via Focused Ion Beam (FIB) preparation and Scanning Transmission Electron Microscopy (STEM) observation. Crystalline and amorphous phases dissolved both in water, with different kinetics. The dissolution appears to be a surface phenomenon, which reduces the section of the foam struts without instability of the glass-ceramic material. Amorphization of crystalline phase is observed during immersion of the glass-ceramic material in stirring conditions at room temperature from the ions dissolved in water.
IEEE Transactions on Haptics, 2016
The tactile perception of a surface texture is mediated by factors such as material, topography a... more The tactile perception of a surface texture is mediated by factors such as material, topography and vibrations induced by the sliding contact. In this paper, sensory characterizations are developed together with topographical and tribo-tactile characterizations to relate perceived features with objective measurements of tribological and dynamic signals. Two sets of surface samples are used in this study: the first set is made of a commercial floor covering tiles that aim at counter-typing natural wood flooring, with both a visual and a tactile texture mimicking wood. A second set is custom-made by replicating the first set using a plain purple polyurethane resin. The comparison between tribo-tactile signals and sensory analysis allowed the identification of objective indices for textures with slight topographical differences. Even though the topography of the replicated samples is the same as their corresponding commercial products, the fact that the material is different, induces differences in the contact and vibrational parameters. This in turn modifies the discrimination performances during the sensory experiment. Tactile characteristics collected during sensory procedures are found to be in agreement with objective indices such as friction coefficients and induced vibrations.
Cracks were detected on nickel-aluminium bronze tubes used in saline water. In order to gain insi... more Cracks were detected on nickel-aluminium bronze tubes used in saline water. In order to gain insight to the mechanisms by which service damage develops, we investigated the environmental and metallurgical conditions under which stress corrosion cracking of CuAl9Ni3Fe2 occurs. We conducted slow strain rate tensile (SSRT) tests in synthetic sea water. At open-circuit potential, at pH under 4, general corrosion occurs. At higher pH, cracking proceeds by dissolution of the more anodic phase and fracture mode depends on phases nature and repartition. When the second phase is martensitic, back-scattered SEM observations show that dealloying of the martensite is associated to the crack growth. At pH 10 or in synthetic sea water, we also observe local transgranular cracking of the $alpha$ phase.
We study the subcritical stress corrosion crack propagation of 316L austenitic stainless steel in... more We study the subcritical stress corrosion crack propagation of 316L austenitic stainless steel in boiling magnesium chloride, i.e. below the conventional K1SCC. Interrupted slow strain rate tensile tests were conducted on 316L micro-notched tensile specimens in 117°C boiling MgCl2 medium. Finite elements calculations are performed to evaluate the corresponding Mode I Stress Intensity Factor, as well as the enhanced plastic strain rate at the notch root. Crack initiation and propagation are only observed for shorter notches. Cracks are seen to branch preferentially at grain boundaries, and appear to approximately follow the directions of maximum plastic strain rate. Applied K1 ranges from 9 to 16 MPa.m1/2 and average crack growth rates are between 1.6x10-9 s-1 and 8x10-9 s-1. FE simulations show the local effect of the notch on enhancing the strain rate, with amplification factors ranging from 8 to 34, this effect vanishing 300 µm away from the notch.
Current Nanoscience, 2015
ABSTRACT Anodizing of aluminum generates a nanoporous alumina layer comprising cylindrical nanopo... more ABSTRACT Anodizing of aluminum generates a nanoporous alumina layer comprising cylindrical nanopores extending essentially perpendicular to the substrate. Visual observation of such nanoporous layers shows a colored specular reflectance consistent with reflectance spectrum measurements. Such structural colors raise interest in particular for producing non-fading colors. However the optical behavior is complex and requires specific characterization setups and modelling approaches. A morphological and optical characterization of nanoporous anodic alumina has been performed and enabled to draw the chromatic paths. Moreover, the optical behavior has been compared to numerical simulations of optical properties using the Fourier Modal Method, thus demonstrating the impact of short-range order and long-range disorder on the formation of structural colors in these partially ordered nanostructures.
Acta Materialia, 2015
ABSTRACT Various forms of the plastic deformation in single crystals are studied in pure and hydr... more ABSTRACT Various forms of the plastic deformation in single crystals are studied in pure and hydrogen-containing nickel and nickel alloys oriented for single slip [1 3 5] and strained in the stage III regime (shear strain, γ = 0.8). The heterogeneity of deformation is investigated at two distinct scales: slip bands and dislocation structures, using atomic force microscopy (AFM) and transmission electronic microscopy (TEM). Size and distribution of slip band thicknesses and geometrically necessary boundary (GNB) spacing are comparable. GNB structures both screen the long-range stress fields and decrease the mean free path of mobile dislocations, whereas equiaxed cells only impede dislocation motion through their role as obstacles. Consequently, GNB formation localizes deformation in specific slip bands. Additionally, the observed similarity between GNB spacing and equiaxed cell size suggests a correlation between these microstructural features. The impact of solid solution atoms on the inter-wall spacing is established for chromium and hydrogen. Both decrease the GNB spacing because of a decrease of the cross-slip probability and stacking fault energy, combined to a shielding effect for the later. The effect of GNB spacing on strain hardening is discussed in terms of the length scale associated with GNBs and the effect of solute content.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt età la diffusion de documents scientifiques de niveau recherche, publiés ou non, emanant desétablissements d'enseignement et de recherche français ouétrangers, des laboratoires publics ou privés.
The analysis of users' experience is indispensable in order to catch the subjectivity. For this r... more The analysis of users' experience is indispensable in order to catch the subjectivity. For this reason the industrial designer needs to take into account these new qualitative properties, and translate them in a concrete way during the creative process. Firstly the sensory information acquired need to be coached by the material experience. The user is able to construct his relation with the product primarily interfacing himself with the skin of the object by touch and sight, and after that explore its functionality. The work aims to improve the development of emotional and feeling investigation by the use of an holistic approach that take into account all the product's aspects. To realise this investigation has been chosen to apply the technique offered by Sensory Metrology discipline and two methods derived from the Classical Sensory Evaluation. In this paper the test experiences done in order to read users' subjectivity have been described. The different proofs have been structured in three different moments. Results have shown the possibility to use the sensorial sphere as a constructive matter to achieve user's affection to the products always from an holistic point of view.
Uploads
Papers by David Delafosse