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Pure iron nanopowders have been sintered using the spark plasma sintering technique. Fully dense materials can be achieved by a simple route. The influence of process parameters on density and hardness has been studied. The samples exhibit high hardness characteristic of nanostructured iron. This is confirmed by grain size measurements by X-ray diffraction and TEM. Moreover, when submitted to compression, the sinter exhibits high maximal strength with non-negligible ductility.

The fracture process of commercially pure titanium was visualized in model materials containing artificial holes. These model materials were fabricated using a femtosecond laser coupled with a diffusion bonding technique to obtain voids in the interior of titanium samples. Changes in void dimensions during in-situ straining were recorded in three dimensions using x-ray computed tomography. Void growth obtained experimentally was compared with the Rice and Tracey model which predicted well the average void growth. A large scatter in void growth data was explained by differences in grain orientation which was confirmed by crystal plasticity simulations. It was also shown that grain orientation has a stronger effect on void growth than intervoid spacing and material strength. Intervoid spacing, however, appears to control whether the intervoid ligament failure is ductile or brittle.

Bulk and cellular cordierite ceramics were prepared from a non-stoichiometric powder consisting of corundum, talc (triclinic), α-quartz, K-feldspar, kaolinite, mullite and a small amount of a glass phase. The optimal sintering processing route was evaluated to obtain good mechanical properties. A high flexural strength of 120 MPa and a Young’s modulus of 99 GPa were achieved. The ceramic foams were fabricated by impregnation of polymer preforms with the optimized stock suspension. The mechanical properties of ceramic foams were studied by impulse excitation and compression tests. The Gibson–Ashby model predicted the ceramic foam’s effective modulus and its elastic limit strength well, as measured experimentally. In addition, the actual three-dimensional (3-D) structure obtained from X-ray computed tomography (CT) coupled with the finite element method (FEM) was used to calculate the Young’s modulus and the elasticity limit of the ceramic foam; however, this did not produce aby better agreement between the calculated values and the experimental results. The discrepancy between the Gibson–Ashby model and FEM could probably be attributed to the accuracy and small volume of representative reconstructed 3-D cellular structure. Taking account of the effect of the internal hollow structure on the stress localization in the ceramic struts, the CT–FE modeling provides a good measure of the adaptability and predictability of actual ceramic foam structures for realistic damage modeling.

A new type of architectured materials, namely « monofilament entangled materials », were studied in order to have a better understanding of their behavior under compressive loading and damping. The materials studied in this paper were made of an entanglement of a single steel wire. Their complex internal architecture was investigated using X-ray computed tomography. The evolution of the number of contacts per unit of volume, as well as of the density profile, were followed during the compression test in order to compare it to the mechanical results. Dynamical Mechanical Analysis (DMA) was performed to characterize the evolution of the loss factor of this material with the frequency and the volume fraction. It was shown that this material present an interesting strength/loss factor ratio. A discrete element model was proposed to model the mechanical properties of this material.

International audience; Spark plasma sintering has been used for decades in order to consolidate a wide variety of materials and permitting to obtain fully dense specimens. This technique has been mainly applied to ceramics. This paper concentrates on an unusual use of spark plasma sintering system: obtaining innovative materials especially architectured ones. Different applications are presented. Firstly, the SPS technique has been used to elaborate nanometers grain size materials or containing nanoscale microstructure. This is possible since the sintering temperature and the holding time are far lower in the SPS compared to other techniques. Then SPS has been used to realize diffusion bonding. In that case again, bonding can be realized at low temperature and for short time. It permits for example to realize bonding between two copper layers which is of a great importance for microelectronic applications. It is worth noting that this bonding can have the same mechanical strength as pure copper even for diffusion time of a few minutes. Secondly, bonding has been also carried out between a metallic layer and a ceramic one. This could lead to design of new layered materials combining interesting properties in terms of mechanical strength but also in terms of electrical resistance. The SPS machine has also been used to obtain porous materials (cobalt alloys or copper) with an adapted microstructure (porosity, tortuosity,). These structures could open new perspectives for biomedical or for microelectronic applications. All these examples lead to a better understanding of the physical processes which happen during spark plasma sintering.

National audience; L’essai de double-torsion est utilisé pour caractériser la propagation de fissure dans les céramiques. Ce test ayant été peu étudié d’un point de vue mécanique dans la littérature, un prototype a été fabriqué pour réaliser un test in situ dans un tomographe sur une céramique poreuse. Les scans ainsi obtenus au cours du chargement mécanique sont associés à des techniques de corrélation d’images 3Dpour obtenir des informations quantitatives sur la cinématique globale et la forme du front de fissure.

International audience; The mechanical behavior of alloys resulting from a mixture of a AA6061 base alloy with different alloys from the Al-Si and Al-Mg series used as filler alloys during welding has been investigated under conditions close to welding. The specimens have been subjected to constrained solidification carried out at a high cooling rate of 80 K/s. In the test developed in this study, the central part of the specimen is initially melted. During solidification, this zone suffers strains only generated by thermal contraction and solidification shrinkage, which can possibly lead to the formation of hot cracks. The hot cracking sensitivity of the various alloys has been determined thanks to X-ray microtomography observations which have allowed imaging the zone solidified under constrained conditions and measuring the volume fraction and the number of open cracks as a function of Si and Mg contents. The variation of stress induced by deformation of the solid during constrained solidification has been also measured as a function of solid fraction. The results show that: (1) stress developed within the solidifying alloy exhibits the same variation whatever the Si and Mg contents. Stress starts increasing at the coherency of the solid skeleton and increases much more sharply when coalescence occurs. (2) the alloys with Si and Mg contents exceeding 3 and 2 wt% respectively are less sensitive to hot tearing in comparison with the base alloy; (3)Al-Mg filler alloys seem to be the best solution to reduce hot cracking in 6061 welded joints.

Development of synchrotron tomography at the end of the 20th century and the following improvements in radiation source, X-ray detectors as well as X-ray optics boosted the application of the tomographic technique in materials science. It became possible for the first time to reveal the three dimensional structure of heterogeneous materials with sub-micrometer spatial resolution, the length scale where the basic mechanisms of plastic deformation and damage are taking place and determine the macroscopic behavior of engineering components. The present chapter introduces the basic features of the tomographic method developed at synchrotron sources, related mainly to the high flux and lateral coherence of the beam. These allow performing high resolution tomographic scans within a reasonable time, but also to use the optical phase of the transmitted X-ray beam to increase the sensitivity by revealing the spatial distribution of electron density. After the introduction of the technique several application examples in the field of materials science are presented.

The damage process leading to fracture during tensile testing of a biomedical grade Co–29Cr–6Mo–0.14N alloy was analyzed on the basis of three-dimensional damage observation using X-ray tomography and electron backscattered diffraction of the fractured specimen. Initial cracking occurred at grain and annealing twin boundaries, where strain concentrates due to impingement of e-hcp plates formed through strain-induced martensitic transformation (SIMT). Cracks propagated along the interface between the γ-fcc matrix and SIMTed e-hcp on {1 1 1}, resulting in the occurrence of a quasi-cleavage fracture.

The aim of the paper is to show the potential of the X-ray tomography to quantitatively measure volume changes in granular materials during silo flow in a rectangular model bin. The experiments were carried out with initially dense sand. The bin walls were smooth or very rough. In the first step, continuous X-ray radiographs were conducted. The results of volume changes were presented in form of 1D cross-sectional plots and 2D images. They were directly compared with corresponding experimental results obtained with a Particle Image Velocimetry (PIV) method allowing for measuring displacements on the solid surface. Measurement errors in both methods were discussed.

International audience; X-ray tomography is a non-destructive technique which allows reconstruction of the internal geometry of opaque and massive materials in three dimensions (3D). This chapter first discusses the capabilities of this technique in the field of the mechanics of composite reinforcements. It then describes methods of analysing reconstructed data at different characteristic length scales. The chapter also includes an example of the use of such analyses to develop a numerical model of the mechanical behaviour of a woven composite reinforcement.

The high manganese TWIP (twinning induced plasticity) steels exhibit very high mechanical properties compared to others grades. Indeed they have a mechanical strength that can attain 1.5 GPa and fracture strain that can go up to 60%. However the governing damage mechanisms that maximize their ductility are not well understood. To have a better understanding of these mechanisms, in situ tensile tests have been carried out at the European Synchrotron Radiation Facility. During tensile test no necking can be observed which has already been observed on this type of steel. Moreover, the number of cavities in a given volume do not deeply evolve during the deformation meaning that nucleation of voids is weak in the TWIP steel considered. This leads to a maximal number at fracture very low compared to other steels (interstitial free steel, dual phase….). Morever, the growth of cavities according to local strain seems to be equivalent to other austenitic or ferritic steels. At last, shear bands can be observed in the sample which seems to be correlated with some of the cavities.

Three-dimensional (3D) images of casting defects present in broken and nonbroken fatigue samples of a cast Al alloy (A380-ISO: AlSi8Cu3Fe) have been obtained using laboratory X-ray tomography. The 3D images have been processed to obtain various parameters (size, distance from the surface, projected area, etc.), for all the defects present in the gage length. 3D finite element meshes have also been generated from the tomographic images in order to compute the stress field at the vicinity of each defect. Correlations between the fatigue properties of the investigated samples and the above mentioned parameters are analyzed in order to elucidate which one seem to be predominant for the studied material.

International audience; The microstructures, cold-rolling abilities, and mechanical properties of a Ti-6Al-4V alloy with a alpha' microstructure were examined, and compared with these properties in alloys with the (alpha+beta) microstructure. The microstructure of a Ti-6Al-4V alloy solution treated at 1373 K followed by quenching (referred to as 1373 K STQ in the following) exhibits the acicular alpha' martensite microstructure. The alloy exhibits the (equilibrium alpha+alpha' martensite) bimodal microstructure when 1223 K solution treatment is carried out followed by quenching (referred to as 1223 K STQ). In contrast, Ti-6Al-4V alloys heat treated at 1373 K or 1223 K, followed by furnace cooling (referred to as 1373 K ST-FC and 1223 K ST-FC), exhibit a lamellar (alpha+beta) microstructure and an equiaxed (alpha+beta) microstructure, respectively. The strength of the STQ specimens was found to be higher than that of the ST-FC specimens. The 1223 K STQ specimen had excellent cold-rolling ability (more than 40% reduction) and higher tensile ductility than those of the ST-FC specimens. The excellent ductility of 1223 K STQ is thought to be due to the constituent phase of the single HCP phase (alpha' and alpha) and the fine equiaxed bimodal morphology. The compositional distribution of the V content enrichment and the decrease in the Al content in the alpha' martensitic region during solution treatment at 1223 K should contribute to the excellent ductility. This work therefore suggests a useful method for improving room-temperature ductility by using industrial Ti-6Al-4V alloys with the alpha' martensite microstructure. (C) 2010 Elsevier B.V. All rights reserved.

Colloidal crystals were grown on flat or patterned glass slides. The structure of the grains and their defects was first visualized by 3D confocal microscopy and then characterized using simple geometric measurements. Crystals grown on a flat surface maintained a layered structure induced by the closed-packed planes. In the case of the [110] •5 grain boundary, the presence of particles in interlayer position was established.

International audience; Agroforestry systems are fundamental features of the rural landscape of the Indian state of Kerala. Yet these mixed species systems are increasingly being replaced by monocultures. This paper explores how public policies on land tenure, agriculture, forestry and tree growing on private lands have interacted with farmer preferences in shaping land use dynamics and agroforestry practices. It argues that not only is there no specific policy for agroforestry in Kerala, but also that the existing sectoral policies of land tenure, agriculture, and forestry contributed to promoting plantation crops, even among marginal farmers. Forest policies, which impose restrictions on timber extraction from farmers' fields under the garb of protecting natural forests, have often acted as a disincentive to maintaining tree-based mixed production systems on farmlands. The paper argues that public policies interact with farmers' preferences in determining land use practices.

This paper presents results obtained using in situ tensile experiments allowing the observation of damage nucleation, growth and coalescence. Three different aluminium alloys (2024, 7449 and 5754) exhibiting various mechanical properties were chosen to produce a wide data base. Smooth and notched axisymetric samples were cut out of the raw materials to introduce different levels of initial stress triaxiality using the geometry of the samples. In the different cases, the damage steps (initiation, growth and coalescence) were clearly visualised during interrupted and continuous in situ tensile tests in synchrotron X-ray tomography. The imaging was performed with a voxel size of 1.6 μm. The X-ray tomography method also gives a precise image of the outer shape of the sample and its change during deformation can then be analysed. This allows to calculate precisely the true strain vs true stress curve and also an approximation of the stress triaxiality using the Bridgman formula. The results show that damage can be visualised but also quantified precisely in the different cases in terms of nucleation and growth, coalescence being also evident in the results but still hard to quantify so far. Finally, a previously developed model for damage growth during ductile straining based on the Rice and Tracey approach can be fitted to the results.

This study is part of a broader research project on the prediction of formability limits in bending on radius of the order of the sheet thickness, based on ductile damage. As a first step, ductile damage in DP980 steel sheet was investigated by means of micro‐tomography and mechanical testing, including tensile and simple shear tests. The local strain in tension was measured with a digital image correlation device up to rupture, on macroscopic samples of standard dimensions. Moreover, interrupted tensile tests on smaller specimen were also performed, in order to analyze the void distribution by X‐ray micro‐tomography. The final aim is to perform numerical simulation of the tests, with Gurson‐Tvergaard‐Needleman model, to take into account the influence of ductile damage on the mechanical behavior. A fair description of the void volume fraction was obtained as well as the stress level, in the case of small‐size specimen.

The mechanical properties and deformation behavior of Ti–V–(Al, Sn) alloys with a α′ martensite microstructure are examined in this work. In as-quenched Ti–V–Al alloys consisting of α′ martensite microstructure with compositions near α − (α + β), the cold-rolling ability drastically decreases from a reduction of more than 75% to less than 40% with an increase in Al content. While, excellent cold-rolling ability (more than 75% reduction) is seen in the constituent phases of α′ in the compositional region near β − (α + β), and α″ and β. On the other hand, in as-quenched Ti–V–Sn alloys, excellent cold-rolling ability with a reduction of more than 80% that is independent of phase constituents is seen. In α′ martensite Ti–V–Al–Sn alloy with compositions in α − (α + β) that is tensile-deformed at a strain of 5%, a homogenous deformation substructure with straight dislocations is seen in alloy that with a low Al content. In contrast, the dislocation substructure begins to exhibit a planar configuration with increasing Al content. This change in deformation substructure due to increasing Al content is considered to cause the low ductility in α′ martensite Ti alloy that contains high Al. On the other hand, in α′ martensite Ti–V–Al alloy with a composition near β − (α + β), plastic deformation is found to be proceeded via the activation of the basal 〈 a 〉 slip and the { 10 1 ¯ 1 } twin with a homogenous deformation substructure. As a consequence, this deformation mode is considered to cause the high ductility in the α′ phase as compared with the equilibrium (α + β) phase.

In-situ tensile tests have been carried out during X-ray microtomography imaging of dual-phase steels. Void nucleation has been quantified as a function of strain and triaxiality using the obtained 3D images. The Argon's criterion of decohesion has then been used in a model for nucleation in the case where martensite plays the role of inclusions. This criterion has been modified to include the local stress field and the effect of kinematic hardening present in such an heterogeneous material.

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This paper describes how volumic images of a composite material could be used to measure 3D displacement fields, and assess mechanical properties. The exemple of a tensile test performed on a sample made of an energetic material is chosen. Different tools are used, namely, X-ray microtomography of an in situ experiment, image acquisi- tion and processing, volume correlation to measure 3D displacement fields. The principle of an integrated approach is finally introduced.

International audience; Demand for vulnerability assessments is growing in policy-making circles, to support the choice of appropriate measures and policies to reduce the vulnerability of water users and resources. Through the SHIVA ANR project, we are seeking a method to assess and map the vulnerability of farmers in southern India to both climate and socioeconomic changes, and secondly, to assess the costs and benefits associated with trends in farmers’ vulnerability in the medium and long term. The project is focusing on southern India’s hard rock area, as in this geological context, both surface and ground water resources are naturally limited. We are also focusing on farming populations as these are the main water users in the area and rely exclusively on groundwater. The area covers southern India’s semi-arid zone, where the rainfall gradient ranges from 600 mm to 1100 mm. Vulnerability is expected to vary according to local climatic conditions but also the socioeconomic characteristics of farming households. The SHIVA research team has been divided into six thematic groups in order to address the different scientific issues: downscaling the regional climate scenario, farm area projections, vulnerability assessments and quantification, vulnerability mapping, hydrological modelling and upscaling, and vulnerability impact assessments. Our approach is multidisciplinary to cater for the numerous inherent themes, and integrated to cater for vulnerability as a dynamic and multidimensional concept. The project’s first results after 10 months of research are presented below.

International audience; Demand for vulnerability assessments is growing in policy-making circles, to support the choice of appropriate measures and policies to reduce the vulnerability of water users and resources. Through the SHIVA ANR project, we are seeking a method to assess and map the vulnerability of farmers in southern India to both climate and socioeconomic changes, and secondly, to assess the costs and benefits associated with trends farmers' vulnerability in the medium and long-term. The project is focusing on southern India 's hard rock area, as in the geological context, both surface and ground water resources are naturally limited. We are also focusing on farming populations as these are the main water users in the area and rely exclusively on groundwater. The area covers southern India's semi-arid zone, where the rainfall gradient ranges from 600 mm to 1100 mm. Vulnerability is expected to vary according to local climatic conditions but also the socioeconomic characteristics of farming households. The SHIVA research team has been divided into six thematic groups in order to address the different scientific issues : downscaling the regional climate scenario, farm area projections, vulnerability assessments and quantification, vulnerability mapping, hydrological modelling and upscaling, and vulnerability impact assessements. Our approach is multidisciplinary to cater for for numerous inherent themes, and integrated to cater for vulnerability as a dynamic and multidimensional concept. The project 's first results after 10 months of research are presented below.

cited By 4; International audience; Among the possible forming processes for structural composite parts, the Liquid Composite Moulding ones are widely used. For such kind of forming process, a resin injection phase occurs after the forming of a dry fibrous reinforcement skeleton. Several parameters can affect the quality of the manufactured part. It has been experimentally proved that the deformation of the fibrous reinforcement has a significant influence on its permeability. In order to evaluate that parameter, it is necessary to have a realistic deformed solid skeleton. During the pre-forming stage, the fibrous reinforcement can be subjected to different kind of loading: yarn tension and in-plane shear to obtain the correct part shape, but also transverse compression. The aim of this paper is to analyze the influence of that last loading mode on the global state of the solid skeleton. For that purpose, two aspects are explored. First, numerical simulations are performed at the mesoscopic scale: a finite element model of the smallest pattern of the woven textile is realized in which each yarn is modelled used 3D elements. The constitutive behaviour of the yarn must exhibit the specificities of a fibrous material. Secondly, experimental characterization of the yarn material is realized. For that, a new experimental setup is used which allow to investigate the relation between longitudinal tension and transverse compression stiffness of the yarn. This allows determining the material parameters used in the yarn constitutive equation. The other material parameters are determined using a tensile test and an in-plane shear test. X-ray tomography gives geometrical validations of the model. © 2010 Springer-Verlag France.

X-ray tomography has been applied for the estimation of iron ore sinter porosity. Procedures to distinguish open and closed pores and to estimate the volume and the equivalent diameter of each pore were developed, providing the possibility to calculate the amount of porosity considering open and closed pores separately. The effect of the sinter mixture composition on the porosity parameters was investigated, and a comparison with a mercury intrusion measurement is also presented. Reducibility tests were performed for the samples, the porosity of which had been previously identified by tomography. The fact that samples with a premeasured porosity could be analysed with other characterisation methods opens new possibilities to understand the effect of the porosity on the properties of the sinter.

In this study, Spark Plasma Sintering has been used to sinter pure iron with an initial crystallite size around 100 nm. The process parameters for sintering pure iron have been optimized in order to obtain fully dense materials and avoid excessive grain growth. Archimede's method has been used to calculate the relative density of the sintered samples. It appears that almost fully dense materials can be obtained (95%). X Ray diffraction applied to the sintered samples shows the presence of iron and of the wustite oxide FeO (around 6% wt) formed during the sintering process. Peak enlargement measurements show that the grain size after sintering is around 200nm. This is confirmed by TEM observations showing a dual distribution of grain size. Finally, mechanical characterization has been carried out. The sintered compact exhibits a very high hardness of about 400 Hv. Compression test reveals a very high maximal stress of about 1.2 GPa and that the ductility in compression is non negligible. Using the Hall and Petch law, the calculated grain size should be around 450 nm which is in accordance with direct observations.

ISI Document Delivery No.: 627FH Times Cited: 1 Cited Reference Count: 59 Cited References: AALTONEN J, 2001, EUR J ENV ENG GEOPHY, V6, P33 Acevedo-Opazo C, 2008, PRECIS AGRIC, V9, P285, DOI 10.1007/s11119-008-9073-1 ALVES F, 2006, 6 INT TERR C, P280 ANGLADE I, 1991, ETUDE BIOCLIMATIQUE ARCHER E, 1989, South African Journal for Enology and Viticulture, V10, P49 ATTIA F, 2007, THESIS INPT TOULOUSE Benderitter Y., 1999, EUR J ENV ENG GEOPHY, V4, P37 Besson A, 2004, SOIL TILL RES, V79, P239, DOI 10.1016/j.still.2004.07.012 BINLEY A, 2002, J HYDROL, V7, P51 BOCOCK KL, 1982, EUR J SOIL SCI, V33, P155 BOUTRAUD JC, 1984, SCI SOL, V4, P295 CAMPBELL RB, 1948, SOIL SCI SOC AM PRO, V13, P66 CAVAILLE A, 1973, CARTE GEOLOGIQUE DET CELETTE F, 2008, EUR J AGR, DOI DOI 10.1016/J.EJA Courjault-Rade P, 2005, J INT SCI VIGNE VIN, V39, P95 CREASY GL, 1993, AM J ENOL VITICULT, V44, P193 DAILY W, 1992, WATER RESOUR RES, V28, P1429, DOI 10.1029/91WR03087 EDWARDS LS, 1977, GEOPHYSICS, V66, P78 Goulet E, 2004, J INT SCI VIGNE VIN, V38, P231 Goulet E, 2006, J INT SCI VIGNE VIN, V40, P57 GRIFFITHS DH, 1993, J APPL GEOPHYS, V29, P211, DOI 10.1016/0926-9851(93)90005-J Haynes SJ, 1999, GEOSCI CAN, V26, P189 *INF, 2009, DONN ARCH DONN STAT Intrigliolo DS, 2009, AGR WATER MANAGE, V96, P282, DOI 10.1016/j.agwat.2008.08.001 Jackson RS, 2008, FOOD SCI TECHNOL-INT, P1 KEAREY P, 2002, INTRO GEOPHYS EAPLOR Keller G.V., 1966, ELECT METHODS GEOPHY Lamb D.W., 2002, ACTA HORTIC, V640, P15 LAVIGNAC G, 2001, CEPAGES SUD OUEST 20 LOKE MH, 2001, USGS WORKSH 2 D 3 D Loke MH, 1996, GEOPHYS PROSPECT, V44, P131, DOI 10.1111/j.1365-2478.1996.tb00142.x Loke MN., 1997, RES2DINV SOFTWARE US Michot D, 2003, WATER RESOUR RES, V39, DOI 10.1029/2002WR001581 MORAIS R, 2007, COMPUT ELECTRON AGR, V62, P94 MORARI F, 2009, COMP ELECT AGR Morlat R., 1992, Journal International des Sciences de la Vigne et du Vin, V26, P197 Morlat R, 2003, AM J ENOL VITICULT, V54, P1 Morlat R., 2001, TERROIRS VITICOLES E Bodin F, 2006, PLANT SOIL, V281, P37, DOI 10.1007/s11104-005-3768-0 Ojeda H, 2002, AM J ENOL VITICULT, V53, P261 PALACKY GJ, 1987, ELECTROMAGNETIC METH, V1, P53 Panissod C, 2001, GEOPHYS PROSPECT, V49, P570, DOI 10.1046/j.1365-2478.2001.00277.x Pellegrino A, 2004, PLANT SOIL, V266, P129 POMEROL C, 1990, TERROIRS VINS FRANCE Rein A, 2004, J HYDROL, V285, P215, DOI 10.1016/j.jhydrol.2003.08.015 Samouelian A, 2005, SOIL TILL RES, V83, P173, DOI 10.1016/j.still.2004.10.004 SHAFFER R, 2004, 8882 EM OR STAT U SHULTZ HR, 2003, PLANT CELL ENVIRON, V26, P1393 Stoll M, 2007, J INT SCI VIGNE VIN, V41, P77 TABBAGH A, 2002, EUR J ENV ENG GEOPHY, V7, P229 Tardieu F, 1998, J EXP BOT, V49, P419, DOI 10.1093/jexbot/49.suppl_1.419 TIMLIN D, 2008, RESPONSES CROPS LTD, P105 TISSEYYE B, 2007, INT J WINE VINE RES, V41, P63 Van Leeuwen Cornelis, 2006, Journal of Wine Research, V17, P1, DOI 10.1080/09571260600633135 van Leeuwen C, 2004, AM J ENOL VITICULT, V55, P207 Van Leeuwen C, 2009, J INT SCI VIGNE VIN, V43, P121 Vouillamoz JF, 2006, HEREDITY, V97, P102, DOI 10.1038/sj.hdy.6800842 Wheeler S.J., 2003, FOOD AGR ENV, V1, P190 Zhou QY, 2001, WATER RESOUR RES, V37, P273, DOI 10.1029/2000WR900284 Courjault-Rade, P. Llubes, M. Darrozes, J. Munoz, M. Maire, E. Hirissou, N. 1 VIGNE ET VIN PUBLICATIONS INT VILLENAVE D ORNON J INT SCI VIGNE VIN; Aims: The aim of this 2D electrical resistivity tomography (ERT) survey performed on a vineyard plot of the Gaillac appellation was to investigate spatial and temporal variations in subsurface water supply in relation with pedo-geological and morphological features. Methods and results: The ERT surveys were carried out under two contrasted - dry and humid - climatic conditions. All the resistivity profiles showed the superposition of two layers: a lower layer characterized by very low resistivity values (< 40 Omega.m) corresponding to a marly molassic subsoil overlaid by an upper layer characterized by moderate to high resistivity values (300 Omega.m to 1500 Omega.m) corresponding to a silty-sandy and gravely-pebbly soil sequence. The resistivity values of the molassic subsoil stayed very low independently of water supply conditions whereas those of the soil sequence decreased by a factor 2 (300/750 Omega.m versus 750/1500 Omega.m) when the plot was close to field capacity. Conclusion: The ERT results coupled with pedological and morphological data strongly suggest that the water flow is preferentially restricted at the molassic subsoil/soil sequence interface, short-lived and of low amplitude. Significance and impact of the study: Consequently, the water supply regime, which points out a potential risk of drought stress for vine crops, implies a minimization strategy when choosing vegetal material and viticultural management operations

International audience; In situ tensile tests have been carried out during X-ray microtomography imaging of dual phase steels. Void nucleation has been quantified as a function of strain and triaxiality using the obtained three-dimensional images. The Argon criterion of decohesion has been used in a model for nucleation in the case where martensite plays the role of inclusions. This criterion has been modified to include the local stress field and the effect of kinematic hardening present in such a heterogeneous material.

This paper aims at illustrating the potential of X-ray tomography for studying the mechanical behaviour of materials through in situ experiments. Typical experimental tomography set ups which use laboratory and synchrotron X ray sources are described; advantages and limitations of both types of sources are presented. Dedicated experimental devices which allow deformation and/or temperature changes to be applied to various types of materials are described. Examples of results of in situ mechanical experiments are presented and discussed; they include monotonic tensile testing of steel fiber entanglements, high temperature compression and room temperature fatigue of Al alloys. Examples of quantitative assessment of localisation of deformation in the interior of optically opaque samples under mechanical loading are also described.

International audience; Heterogeneous materials usually break through a process of microcracking that eventually leads to final rupture after accumulation and coalescence of many microcracks. The statistical properties of microcracking rupture have been known to resemble critical point statistics, with many of the physical quantities obeying power law distributions. However, there is no clear understanding of the origin of these distributions and of the specific values observed for the power law exponents. In this paper, we review the special case of polymeric foams that have the advantage of containing a single material component, the polymer, as opposed to usual heterogeneous materials such as composites. First, we review briefly the typical features of the polymeric foam mechanical response up to rupture that have been studied a lot previously. Then, we focus on a less-well-known aspect: the rupture dynamics of polymeric foams. We show that not only polymeric foams behave like other heterogeneous materials, i.e. they display power law statistics, but also, we are able to test the effect on the power laws of the following properties: the foam heterogeneity by changing its density, the foam mechanical response by changing its temperature and the mechanical history by comparing creep tests and tensile tests.

This paper investigates the behaviour of colloidal suspensions of alumina particles during directional solidification, by in situ high-resolution observations using X-ray radiography and tomography. This second part is focussed on the evolution of ice crystals during steady state growth (in terms of interface velocity) and on the particles redistribution taking place in this regime. In particular, it is shown that diffusion cannot determine the concentration profile and the particles redistribution in this regime of interface velocities (20-40 microns/s); constitutional supercooling arguments cannot be invoked to interpret particles redistribution. Particles are redistributed by a direct interaction with the moving solidification interface. Several parameters controlling the particles redistribution were identified, namely the interface velocity, the particle size, the shape of the ice crystals and the orientation relationships between the crystals and the temperature gradient., 19 pages, 15 figures

This paper investigates by in situ high-resolution X-ray radiography and tomography the behaviour of colloidal suspensions of alumina particles during directional solidification by freezing. The combination of these techniques provided both qualitative and quantitative information about the propagation kinetic of the solid/liquid interface, the particles redistribution between the crystals and a particle enriched phase and the 3D organisation of the ice crystals. In this first part of two companion papers, the precursor phenomena leading to directional crystallisation during the first instants of solidification is studied. Mullins-Sekerka instabilities are not necessary to explain the dynamic evolution of the interface pattern. Particle redistribution during these first instants is dependent on the type of crystals growing into the suspension. The insights gained into the mechanisms of solidification of colloidal suspensions may be valuable for the materials processing routes derived for this type of directional solidification (freeze-casting), and of general interest for those interested in the interactions between solidification fronts and inert particles., 19 pages, 12 figures

Colloidal particles are often seen as big atoms that can be directly observed in real space. They are therefore playing an increasingly important role as model systems to study processes of interest in condensed matter physics such as melting, freezing and glass transitions. The solidification of colloidal suspensions has long been a puzzling phenomenon with many unexplained features. Here we demonstrate and rationalize the existence of instability and metastability domains in cellular solidification of colloidal suspensions, by direct in situ high-resolution X-ray radiography and tomography observations. We explain such interface instabilities by a partial Brownian diffusion of the particles leading to constitutional supercooling situations. Processing under unstable conditions leads to localized and global kinetic instabilities of the solid/liquid interface, affecting the crystals morphology and particle redistribution behaviour., Comment: 18 pages, 6 figures

This paper summarizes different results obtained by the authors applying X-ray tomography to the study of cellular materials (metals, ceramics and polymers). From the 3D images, three different kinds of analysis are carried out. The first is image processing to retrieve the morphological characteristics (density, size, tortuosity) of the studied materials. The second is the analysis of the deformation modes using in situ or ex situ mechanical tests (tension, compression, fatigue). The third is devoted to FE calculations in which models are produced to represent as exactly as possible the architecture of these materials as seen in tomography. These different points are successively presented and exemplified in the present paper.

A combined experimental and analytical approach is used to study damage initiation and evolution in three-dimensional second phase particle fields. A three-dimensional formulation of a damage percolation model is developed to predict damage nucleation and propagation through random-clustered second phase particle fields. The proposed approach is capable of capturing the three-dimensional character of damage phenomena and the three stages of ductile fracture, namely, void nucleation, growth, and coalescence, at the level of discrete particles. An in situ tensile test with X-ray tomography is utilized to quantify material damage during deformation in terms of the number of nucleated voids and porosity. The results of this experiment are used for both the development of a clustering-sensitive nucleation criterion and the validation of the damage percolation predictions. The evolution of damage in aluminum alloy AA5182 has been successfully predicted to match that in the in situ tensile specimen. Two forms of second phase particle field input data were considered: (1) that measured directly with X-ray tomography and (2) fields reconstructed statistically from two-dimensional orthogonal sections. It is demonstrated that the adoption of a cluster-sensitive void nucleation criterion, as opposed to a cluster-insensitive nucleation criterion, has a significant effect in promoting predicted void nucleation to occur within particle clusters. This behavior leads to confinement of void coalescence to within clusters for most of the duration of deformation followed by later development of a macrocrack through intracluster coalescence. The measured and reconstructed second phase particle fields lead to similar rates of predicted damage accumulation and can be used interchangeably in damage percolation simulations.

Les plages du littoral de Kénitra ont connu des modifications au cours de ces quatre dernières décennies. La mise en valeur économique de certaines plages par des aménagements touristiques et l’extraction massive de sables pour les travaux d’aménagements urbains sont à l’origine d’une déstabilisation des échanges transversaux de sédiments. Ils sont accentués par la succession de périodes de sécheresse et par la multiplication de construction de barrages sur le bassin versant du Sebou. Le préambule à une meilleure gestion de ces plages est la compréhension de leur comportement passé vis-à-vis des contraintes naturelles et anthropiques. Cette démarche s’appuie essentiellement sur les missions aériennes de 1963 et de 1993. Le Modèle Numérique de Terrain (MNT), d’une précision de ± 10 cm en altitude issu de ces missions et le suivi du positionnement du trait de côte par un système d’analyse numérique (DSAS), ont permis d’estimer les taux de changement.Mots-clés : Littoral, basin versant de Sebou, Maroc, photographies aériennes,MNT, DSAS.

X-ray tomography was applied to the investigation of the structure of sinter mixture granules. Different components such as ore, concentrate, coke breeze and limestone were identified and their sizes and spatial distribution estimated. Classification of the granule structure by the thickness of the adhering fines layer in a proportion to the whole granule radius has been estimated. Excessive amount of fines (concentrate) in a mixture leads to the increasing presence of granules with an adhering fines layer thicker than a half of the granule radius. Abnormal structures of granules have been observed in some cases such as microgranules embedded in the adhering layer of bigger granules, granules formed as the result of two or more granules coalescence or granules formed without a nucleus particle with a structure similar to pellets.

Symposium on Architectured Multifunctional Materials held at the 2009 MRS Spring Meeting -- APR 14-16, 2009 -- San Francisco, CA, WOS: 000273973000005, Bio-inspired architectures, especially metallic foams, have been receiving an increasing interest for the last 10 years due to their unusual mechanical properties. Among commonly dealt foamed metals, like aluminum and steel, titanium possesses a distinctive place because of its high strength-to-weight ratio, excellent corrosion resistance and biocompatibility. In this study, Ti foams were produced by a very simple and common method, sintering under inert atmosphere with fugitive space holder. Removal of the space holder was conducted by dissolution in hot deionized water which makes it possible to minimize contamination of Ti. Sintering of remaining Ti skeleton at 1300 degrees C offered a wide range of properties and cost savings. The effects of the processing parameters such as sintering temperature and powder characteristics on the 3D foam architecture were investigated by using X-ray microtomography (mu-CT). Use of bimodal Ti powders caused a decrease in final theoretical density when compared to the ones prepared with the same amount of space holder but with monomodal Ti powders. It was also observed that the use of bimodal Ti powders decreased compressive strength at a fixed relative density, by introducing pores into the cell walls., Mat Res Soc, INSA Lyon Mateis; Scientific Research Commission of Anadolu University [040231], The authors would like to thank Jerome Adrien from INSA Lyon Mateis and the Scientific Research Commission of Anadolu University for financing this work under the contract number of 040231.

Difficile a definir, souvent percu comme genant dans les zones de grande culture, l’arbre hors foret n’en est pas moins un element omnipresent dans les paysages francais. Tellement present que l’on ne lui accorde pas toujours la place qu’il merite. La diversite des structures arborees peut fournir cependant de nombreuses ressources en termes economiques. En outre, ces structures sont de plus en plus reconnues pour leurs fonctions ecologiques. L’arbre hors foret constitue egalement un important marqueur socio-culturel et un atout a developper pour l’amelioration des productions agricoles. Les paysages d’arbres hors foret (AHF), souvent mis en avant pour valoriser des produits de terroir, sont pourtant encore insuffisamment pris en compte par les pouvoirs p ublics en termes d’amenagement du territoire, et le volontarisme des politiques locales de preserver les arbres hors foret est confronte au manque de reconnaissance juridique et de statut de ces « arbres champetres ».

The aim of this paper is to report the very first in situ observations of the deformation behaviour of an Al-Cu alloy in the semisolid state by using ultrafast, high-resolution X-ray microtomography. It is shown that this deformation is non-homogeneous and involves an accumulation of liquid at an intergranular surface nearly perpendicular to the strain axis. Once the liquid is no longer able to feed such a region, micropores form and grow at this surface, finally leading to a crack. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

International audience; This study has been devoted to a volumetric exploration of the meso-structure of a two-dimensional SiCf-SiC composite with cross-weave fibers using X-ray tomography. A series of projection images have been used to reconstruct the three-dimensional composite's architecture and a quantitative analysis of the morphology of the porosity network has been carried out in order to characterize the fiber-tissue structure. The suitability of X-ray tomography for characterizing this structural material at a meso-scale level is critically assessed.

International audience; A beta-quenched titanium alloy was studied by means of microtomography. This technique provides three dimensional (3D) representations of the microstructure. It appears that the colonies have non-convex shapes and form an intricate aggregate. An algorithm of 3D image segmentation based on the orientation of the lamellae is presented. Its results are in agreement with those derived from a manual segmentation method, and allow the colonies to be examined individually. Further perspectives on the basis of this experiment are outlined.

International audience; Syntactic foams (glass hollow spheres embedded in an epoxy matrix) were produced on purpose to be used as test materials for the present study. Two kinds of spheres (MS1 and MS2) were adjoined to a same polymer matrix, MS1 with a volume fraction of 55 and MS2 with 30 and 55%. The samples were analysed by X-ray tomography using synchrotron radiation. The three-dimensional images were used to observe the qualitative differences between the three samples. Three-dimensional image processing was then carried out to quantify the differences. The images were used to retrieve the fraction of the different phases which was in fairly good agreement with the expected values. The external and internal diameter of the spheres and their thickness were also measured. The MS1 spheres are smaller, thicker and their size distribution is less homogeneous compared to the MS2. The size distribution of the spheres before blowing was retrieved and evidenced to be similar for the two kinds of spheres. The thickness depends only weakly on the diameter of the spheres.

International audience; A study was conducted to examine and formulate the effect of the microstructure of metal hollow spheres structures (MHSS) on their fatigue properties. Standard compression/compression fatigue tests were conducted to measure the macroscopic properties of microstructures with different structural parameters. The stress concentration inside the complex microstructure was measured to develop a model that shows properties of the materials. X-ray tomographic images were obtained to study their three-dimensional (3D) architecture. The tomography was also used to determine the morphological parameters. The 3D images were processed and analyzed using a granulometry procedure based on sequential opening operations. A hydraulic fatigue machine (MTS) at a frequency of 10 Hz was used to perform all the fatigue tests. Results show that the ratio of the fatigue limit to the yield stress is about 0.5 in each condition, providing a useful design rule for microstructure.

A methodology for determining long-term denudation rates from morphologic markers in a Digital Elevation Model (DEM) is checked by a comparative study of two drainage basins in the PrecordiUera of the Central Andes. In both cases the initial configuration of an incised pediment surface has been restored by using two different methods: the Black Top Hat (BTH) function and the Inverse Distance Weighting (IDW) interpolation. Where vertical incision and hillslope erosion are recorded, the IDW appears to be the most adequate to reconstitute the pediment surfaces. Conversely, where only vertical incision is observed, the BTH describes more precisely the former pediment surfaces and it is easier to solve. By subtracting the DEM from the reconstructed marker we calculated an eroded volume, and estimated its uncertainty by considering Root Mean Square Error (RMSE) and DEM grid error. For the last ~10 Myr we obtained long-term denudation rates of 7.33±1.6 m/Myr in the San Andrés drainage basin and 13.59±1.9 m/Myr in the El Salado drainage basin. These estimations are largely in agreement with other reported estimates of long-term denudation rates in the Atacama Desert. Comparison with long-term denudation rates reported in a wide range of climatic regimes suggests that our estimates cannot be explained by the current rainfall in the PrecordiUera. However they could be explained by a rainfall similar to that reported 40 km to the east in the Puna. This suggests that during the time span concerned the geomorphologic evolution of the study area, this evolution is dominated by an orographically controlled rainfall pattern. The preserved pediment surface and the small long term denudation rates determined in this study also indicate that the PrecordiUera was never reached by humid tropical air masses and precipitation as currently observed in the Altiplano during the summer months Una metodología para determinar tasas de denudación de largo tiempo a partir de marcadores geomorfológicos obtenidos desde un Modelo Digital de Elevación (MDE), ha sido comprobada considerando un estudio comparativo de dos cuencas vertientes de la precordillera de los Andes Centrales. Para ambas cuencas, la configuración inicial de una superficie de pedimentación afectada por incisión, ha sido reconstruida usando dos métodos diferentes: la función 'Top Hat' por Cierre (THC) y la Interpolación Ponderada por el Inverso de la Distancia (IPID). Cuando se observa tanto incisión vertical como erosión de laderas, la IPID es más apropiada para reconstruir las superficies de pedimentación. Por el contrario, donde solo se observa incisión vertical, la THC describe con mayor precisión las superficies de pedimentación, y es de más fácil implementation. En este trabajo, se calculó un volumen erosionado por medio de la sustracción del MDE del marcador geomorfológico reconstruido, y se estimó su incertitud al considerar un Error Cuadrático Medio y un MDE representando una grilla de errores. Para los últimos 10 Myr se obtuvo tasas de denudación de largo tiempo de 7,33±1,6 m/Myr en la cuenca vertiente de San Andrés y de 13,59±1,9 m/Myr en la cuenca vertiente de El Salado. Estas estimaciones son similares a otras estimaciones de tasas de denudación de largo tiempo publicadas para el Desierto de Atacama. La comparación con valores de tasas de denudación de largo tiempo reportadas para un amplio rango de regímenes climáticos sugiere que estas estimaciones no pueden ser explicadas por las actuales tasas de precipitación de la Precordillera. Sin embargo, podrían ser explicadas por tasas de precipitación similares a aquellas actualmente imperantes 40 km al este, en la Puna. Esto sugiere que durante el lapso de tiempo concerniente a la evolución geomorfológica del área de estudio, esta evolución es dominada por el control orográfico de las precipitaciones. La preservación de superficies de pedimentación y los bajos valores de las tasas de denudación de largo tiempo determinadas en este estudio indican, por otra parte, que la Precordillera no fue afectada por precipitaciones y masas de aire húmedas tropicales como las que actualmente se observan en el Altiplano durante los meses de verano

International audience; The aim of this study is to determine the radiative properties, which are the extinction coefficient, the scattering albedo and the scattering phase function, of highly porous open-cell aluminium foam, using more-or-less simple predictive models, and to compare all these models. The radiative properties are predicted using geometric optics laws to model the interaction of radiation with the particles forming the foam. Moreover, the particles forming the foam are large compared with the considered wavelength and are supposed to be sufficiently distant from each other to scatter radiation independently. Thus, the radiative characteristics of the foam can be determined by adding the contributions of each particle. A particular attention is paid on microstructure analysis and modelling. We considered different kinds of cell shapes and struts cross-section, using microscopic and tomographic analysis. Furthermore, a new phase function modelling is presented. Finally, we compare the results of each method with the radiative properties obtained from experimental measurements of directional and hemispherical transmittances and hemispherical reflectance.

Closed-cell cellular materials exhibit several interesting properties. These properties are, however, very difficult to simulate and understand from the knowledge of the cellular microstructure. This problem is mostly due to the highly complex organization of the cells and to their very fine walls. X-ray tomography can produce three-dimensional (3-D) images of the structure, enabling one to visualize locally the damage of the cell walls that would result in the structure collapsing. These data could be used for meshing with continuum elements of the structure for finite element (FE) calculations. But when the density is very low, the walls are fine and the meshes based on continuum elements are not suitable to represent accurately the structure while preserving the representativeness of the model in terms of cell size. This paper presents a shell FE model obtained from tomographic 3-D images that allows bigger volumes of low-density closed-cell cellular materials to be calculated. The model is enriched by direct thickness measurement on the tomographic images. The values measured are ascribed to the shell elements. To validate and use the model, a structure composed of stainless steel hollow spheres is firstly compressed and scanned to observe local deformations. The tomographic data are also meshed with shells for a FE calculation. The convergence of the model is checked and its performance is compared with a continuum model. The global behavior is compared with the measures of the compression test. At the local scale, the model allows the local stress and strain field to be calculated. The calculated deformed shape is compared with the deformed tomographic images.