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The viscoplastic behavior of polycrystalline Mg2SiO4 wadsleyite aggregates, a major high pressure phase of the mantle transition zone of the Earth (depth range: 410--520 km), is obtained by properly bridging several scale transition models. At the very fine nanometric scale corresponding to the dislocation core structure, the behavior of thermally activated plastic slip is modeled for strain-rates relevant for laboratory experimental conditions, at high pressure and for a wide range of temperatures, based on the Peierls--Nabarro--Galerkin model. Corresponding single slip reference resolved shear stresses and associated constitutive equations are deduced from Orowan's equation in order to describe the average viscoplastic behavior at the grain scale, for the easiest slip systems. These data have been implemented in two grain-polycrystal scale transition models, a mean-field one (the recent Fully-Optimized Second-Order Viscoplastic Self-Consistent scheme of [1]) allowing rapid evaluation of the effective viscosity of polycrystalline aggregates, and a full-field (FFT based [2, 3]) method allowing investigating stress and strain-rate localization in typical microstructures and heterogeneous activation of slip systems within grains. Calculations have been performed at pressure and temperatures relevant for in-situ conditions. Results are in very good agreement with available mechanical tests conducted at strain-rates typical for laboratory experiments. [ABSTRACT FROM AUTHOR]

Nanostructured and architectured copper niobium composite wires are excellent candidates for the generation of intense pulsed magnetic fields (> 90T) as they combine both high strength and high electrical conductivity. Multi-scaled Cu–Nb wires are fabricated by accumulative drawing and bundling (a severe plastic deformation technique), leading to a multiscale, architectured, and nanostructured microstructure exhibiting a strong fiber crystallographic texture and elongated grain shapes along the wire axis. This paper presents a comprehensive study of the effective elastic behavior of this composite material by three multi-scale models accounting for different microstructural contents: two mean-field models and a full-field finite element model. As the specimens exhibit many characteristic scales, several scale transition steps are carried out iteratively from the grain scale to the macro-scale. The general agreement among the model responses allows suggesting the best strategy to estimate the effective behavior of Cu–Nb wires and save computational time. The importance of crystallographical and morphological textures in various cases is discussed. Finally, the models are validated by available experimental data with a good agreement. [ABSTRACT FROM AUTHOR]

A new method of determining the deviatoric elastic strain and lattice orientation from Laue microdiffraction images is presented. Standard data treatment methods can suffer from the difficulty of precisely pinpointing the positions of diffraction peaks on two-dimensional Laue images. In a previous article, digital image correlation (DIC) was introduced for the treatment of Laue images, leading to the so-called Laue-DIC method. This performed better than the standard method in terms of the deviatoric elastic strain increment and relative rotation from one lattice to another, particularly when the shape of the Laue spots departs from regular ellipsoids. The present work intends to push forward the Laue-DIC method, aiming to determine the deviatoric elastic strain and lattice orientation, as well as the calibration parameters. The performance of this new method, named enhanced Laue-DIC, is assessed by modeling the spot displacements and accounting for random fluctuations relevant for typical experimental conditions. When the enhanced Laue-DIC method is applied to the case of an in situ deformed Si crystal, the obtained standard deviation of local stress is of the order of 1-2 MPa, while the calibration parameters are optimized to high accuracy. [ABSTRACT FROM AUTHOR]

A better understanding of the effective mechanical behavior of polycrystalline materials requires an accurate knowledge of the behavior at a scale smaller than the grain size. The X-ray Laue microdiffraction technique available at beamline BM32 at the European Synchrotron Radiation Facility is ideally suited for probing elastic strains (and associated stresses) in deformed polycrystalline materials with a spatial resolution smaller than a micrometer. However, the standard technique used to evaluate local stresses from the distortion of Laue patterns lacks accuracy for many micromechanical applications, mostly due to (i) the fitting of Laue spots by analytical functions, and (ii) the necessary comparison of the measured pattern with the theoretical one from an unstrained reference specimen. In the present paper, a new method for the analysis of Laue images is presented. A Digital Image Correlation (DIC) technique, which is essentially insensitive to the shape of Laue spots, is applied to measure the relative distortion of Laue patterns acquired at two different positions on the specimen. The new method is tested on an in situ deformed Si single-crystal, for which the prescribed stress distribution has been calculated by finite-element analysis. It is shown that the new Laue-DIC method allows determination of local stresses with a strain resolution of the order of 10−5. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the flow of ice in glaciers and polar ice sheets is of increasing relevance in a time of potentially significant climate change. The flow of ice has hitherto received relatively little attention from the structural geological community. This paper aims to provide an overview of methods and results of ice deformation modeling from the single crystal to the polycrystal scale, and beyond to the scale of polar ice sheets. All through these scales, various models have been developed to understand, describe and predict the processes that operate during deformation of ice, with the aim to correctly represent ice rheology and self-induced anisotropy. Most of the modeling tools presented in this paper originate from the material science community, and are currently used and further developed for other materials and environments. We will show that this community has deeply integrated ice as a very useful “model” material to develop and validate approaches in conditions of a highly anisotropic behavior. This review, by no means exhaustive, aims at providing an overview of methods at different scales and levels of complexity. [Copyright &y& Elsevier]

Abstract: Understanding the mechanical behavior of nano-structured thin films in relation to their microstructure, in particular to the grain size, is of utmost importance for the development of technological applications. Model nanometric W/Cu multilayers exhibiting different microstructures and supported by a (thin) polyimide substrate are elaborated. The films mechanical response is characterized experimentally by tensile tests carried out in-situ in an X-ray diffractometer installed at a synchrotron beam line. The orientation dependence of elastic strains and stresses is determined by an appropriate micromechanical model accounting for the material microstructure, and based on homogenization schemes. While a good agreement is globally found, the model better reproduces the experimental results of the W component than those of Cu, due probably to the elastic anisotropy of Cu grains. [Copyright &y& Elsevier]

Abstract: The slip system activity in individual grains of a plastically deformed Zircaloy-2 specimen was determined by micro-diffraction X-ray line profile analysis measurements at the ID22 beam line of the European Synchrotron Radiation Facility synchrotron in Grenoble, France. The grain to grain orientation map was determined by electron back scattering diffraction (EBSD) and this was used for orienting individual grains to produce specific Bragg reflections. Anisotropic X-ray line broadening was evaluated in terms of dislocation densities, the average sub-grain size and slip activity. Slip line traces were evaluated in the EBSD micrographs in correlation with the grain orientation. The X-ray and EBSD correlation indicated that 〈a〉-type dislocations with considerable prismatic slip activity dominated plastic deformation in this alloy and that, with increasing dislocation density, the fractions of 〈a〉- and 〈c〉-type dislocations increased. [Copyright &y& Elsevier]

Abstract: The elastic behavior of supported gold thin films has been studied using a framework in which the elastic interaction between grains and the actual structure of the film (i.e. preferential grain orientation and grain shape) are taken into account. Experiments were carried out using synchrotron X-ray diffraction combined with in-situ tensile testing and thereafter, no assumptions on the residual stress state and on the stress-free lattice parameter a 0 have to be made. Modeling of grain elastic interactions is based on the extension of Eshelby–Kröner model, which allows for estimating the elastic behavior of polycrystals considering the texture and the shape of the crystallites. Flat-disc shaped grains arrangement is shown to yield the best representation of the elastic behavior of the fiber-textured gold thin films composed of columnar grains. This non-intuitive representation results from free-surface effect. [Copyright &y& Elsevier]

Abstract: In polycrystalline aggregates deforming by crystal plasticity, the local shears on each slip system can be significantly affected by the intergranular interaction. Therefore, in the framework of mean-field approaches, the intragrain strain heterogeneity must be taken into account when dealing with microstructure evolution associated with strain hardening. For that goal, a novel treatment is proposed and applied to a two-dimensional linearly viscous polycrystal. The results of the implementation of this new hardening treatment within the self-consistent scheme are compared to those of a fast Fourier transform-based full-field computation, considered as a reference solution. It is shown that the evolution with strain of the grain average reference resolved shear stress (RRSS) is well reproduced by the proposed scheme. The overall stress response of the polycrystal is slightly underestimated, due to some intrinsic heterogeneity of the distribution of RRSS. [Copyright &y& Elsevier]

Abstract: The effective behavior and the distribution of local mechanical fields of linearly viscous 2-D polycrystals under antiplane shear is investigated. Several microstructures are considered, and a full-field approach based on the Fast Fourier Transform technique is applied. First, the accuracy of this technique is evaluated on a strictly isotropic 2-phase microstructure. Voronoi tessellation is then used to generate artificial microstructures, and a real (fully recrystallized) polycrystalline microstructure is obtained by electron back-scattering diffraction. Ensemble averages over several configurations using eight crystalline orientations (phases) are performed. Although a slight anisotropy is obtained for the effective behavior of each individual configuration, statistically, the results are in very good agreement with the available analytical isotropic solution. At phase level, a marked asymmetry is obtained for the distribution of local stresses. The intraphase first- and second-order moments of the stress field, calculated for both microstructures are compared with corresponding self-consistent predictions. [Copyright &y& Elsevier]

Insight into upper-mantle processes can be gained by linking flow-induced mineral alignment to regional deformation and seismic anisotropy patterns. Through a series of linked micro–macro scale numerical experiments, we explore the rheologic effects of crystal preferred orientation (CPO) and evaluate the magnitude of possible impacts on the pattern of flow and associated seismic signals for mantle that includes a cooling, thickening young oceanic lithosphere. The CPO and associated anisotropic rheology, computed by a micromechanical polycrystal model, are coupled with a large scale flow model (Eulerian Finite Element method) via a local viscosity tensor field, which quantifies the stress:strain rate response of a textured polycrystal. CPO is computed along streamlines throughout the model space and the corresponding viscosity tensor field at each element defines the local properties for the next iteration of the flow field. Stable flow and CPO distributions were obtained after several iterations for the two dislocation glide cases tested: linear and nonlinear stress:strain rate polycrystal behaviour. The textured olivine polycrystals are found to have anisotropic viscosity tensors in a significant portion of the model space. This directional dependence in strength impacts the pattern of upper-mantle flow. For background asthenosphere viscosity of ∼1020 Pa s and a rigid lithosphere, the modification of the corner flow pattern is not drastic but the change could have geologic implications. Feedback in the development of CPO occurs, particularly in the region immediately below the base of the lithosphere. Stronger fabric is predicted below the flanks of a spreading centre for fully coupled, power-law polycrystals than was determined using prior linear, intermediate coupling polycrystal models. The predicted SKS splitting is modestly different (∼0.5 s) between the intermediate and fully coupled cases for oceanic plates less than 20 Myr old. The magnitude of azimuthal anisotropy for surface waves, on the other hand, is predicted to be twice as large for fully coupled power-law flow/polycrystals than for linear, intermediate coupled flow/polycrystal models. [ABSTRACT FROM AUTHOR]

We show in this paper by using a two-scale transition model that the elastic anisotropy of a thin film specimen can be tuned by appropriate stacking design. The anisotropic behaviour is illustrated for two monophase thin films, namely W which is perfectly elastically isotropic and Au which is strongly elastically anisotropic, and for a nanometric W/Au multilayers. The experimental measurements show that the model capture the elastic anisotropy rather well even for a nanometric multilayer stacking (period of 12 nm) and that the elastic anisotropy of W/Au multilayer is more pronounced than the ones of the two components for a fraction of 50%. This enhanced anisotropy is discussed in view of the multilayer microstructure. [ABSTRACT FROM AUTHOR]

During the deformation of low carbon steel by cold-rolling, dislocations are created and stored in grains depending on local crystallographic orientation, deformation, and deformation gradient. Orientation dependent dislocation densities have been estimated from the broadening of X-ray diffraction lines measured on a synchrotron beamline. Different cold-rolling levels (from 30% to 95% thickness reduction) have been considered. It is shown that the present measurements are consistent with the hypothesis of the sole consideration of screw dislocations for the analysis of the data. The presented evolutions show that the dislocation density first increases within the α fiber (={hkl}<110>) and then within the γ fiber (={111}). A comparison with EBSD measurements is done and confirms that the storage of dislocations during the deformation process is orientation dependent and that this dependence is correlated to the cold-rolling level. If we assume that this dislocation density acts as a driving force during recrystallization, these observations can explain the fact that the recrystallization mechanisms are generally different after moderate or large strains. [ABSTRACT FROM AUTHOR]

Abstract: A digital image correlation (DIC) technique has been adapted to polycrystalline ice specimens in order to characterize the development of strain heterogeneities at an intragranular scale during transient creep deformation (compression tests). Specimens exhibit a columnar microstructure so that plastic deformation is essentially two-dimensional, with few in-depth gradients, and therefore surface DIC analyses are representative of the whole specimen volume. Local misorientations at the intragranular scale were also extracted from microstructure analyses carried out with an automatic texture analyzer before and after deformation. Highly localized strain patterns are evidenced by the DIC technique. Local equivalent strain can reach values as much as an order of magnitude larger than the macroscopic average. The structure of the strain pattern does not evolve with strain in the transient creep regime. Almost no correlation between the measured local strain and the Schmid factor of the slip plane of the underlying grain is observed, highlighting the importance of the mechanical interactions between neighboring grains resulting from the very large viscoplastic anisotropy of ice crystals. Finally, the experimental microstructure was introduced in a full-field fast Fourier transform polycrystal model; simulated strain fields are a good match with experimental ones. [Copyright &y& Elsevier]

The correspondence principle is customarily used with the Laplace-Carson transform technique to tackle the homogenization of linear viscoelastic heterogeneous media. The main drawback of this method lies in the fact that the whole stress and strain histories have to be considered to compute the mechanical response of the material during a given macroscopic loading. Following a remark of Mandel (1966 Mécanique des Milieux Continus (Paris, France: Gauthier-Villars)), Ricaud and Masson (2009 Int. J. Solids Struct. 46 1599-1606) have shown the equivalence between the collocation method used to invert Laplace-Carson transforms and an internal variables formulation. In this paper, this newmethod is developed for the case of polycrystalline materials with general anisotropic properties for local and macroscopic behavior. Applications are provided for the case of constitutive relations accounting for glide of dislocations on particular slip systems. It is shown that the method yields accurate results that perfectly match the standard collocation method and reference full-field results obtained with a FFT numerical scheme. The formulation is then extended to the case of time- and strain-dependent viscous properties, leading to the incremental collocation method (ICM) that can be solved efficiently by a step-by-step procedure. Specifically, the introduction of isotropic and kinematic hardening at the slip system scale is considered. [ABSTRACT FROM AUTHOR]

Abstract: Homogenization estimates based on the self-consistent scheme are customarily used to describe the plastic yielding of polycrystals. Such estimates of the initial micro yield surface of a polycrystal depend on the morphologic and crystallographic textures, the slip system geometry, the corresponding critical resolved shear stresses and the single crystal elastic anisotropy. The usual approach relies on a rather crude description of the stress field induced by the local elastic anisotropy. This deficiency is addressed and a new concept, i.e. a “probability” yield surface is proposed. Based on a statistical description of the local fields, the latter makes use of the average and the standard deviation of the resolved shear stress on the different slip systems within a given crystalline orientation. By comparing the homogenization estimates with full-field results, it is shown that the self-consistent scheme does not present intrinsic shortcomings regarding the prediction of the micro yield stress of polycrystals with anisotropic elastic constitutive behaviour. On the contrary, it delivers realistic estimates if the local field fluctuations are taken into account in the yield criterion. The quantitative results obtained for cubic elasticity show a strong influence of the intragranular stress heterogeneity on the estimate of the micro yield stress. [Copyright &y& Elsevier]

The derivation of the overall behaviour of nonlinear viscoelastic (or rate-dependent elastoplastic) heterogeneous materials requires a linearisation of the constitutive equations around uniform per phase stress (or strain) histories. The resulting Linear Comparison Material (LCM) has to be linear thermoviscoelastic to fully retain the viscoelastic nature of phase interactions. Instead of the exact treatment of this LCM (i.e., correspondence principle and inverse Laplace transforms) as proposed by the “classical” affine formulation, an approximate treatment is proposed here. First considering Maxwellian behaviour, comparisons for a single phase as well as for two-phase materials (with “parallel” and disordered morphologies) show that the “direct inversion method” of Laplace transforms, initially proposed by Schapery (1962), has to be adapted to fit correctly exact responses to creep loading while a more general method is proposed for other loading paths. When applied to nonlinear viscoelastic heterogeneous materials, this approximate inversion method gives rise to a new formulation which is consistent with the classical affine one for the steady-state regimes. In the transient regime, it leads to a significantly more efficient numerical resolution, the LCM associated to the step by step procedure being no more thermoviscoelastic but thermoelastic. Various comparisons for nonlinear viscoelastic polycrystals responses to creep as well as relaxation loadings show that this “quasi-elastic” formulation yields results very close to classical affine ones, even for high contrasts. [Copyright &y& Elsevier]

Neutron scattering provides a volume measurement of the elastic strain distribution in polycrystals. Phase average elastic strains have been measured on a plastically deformed specimen of Zircaloy-4, and an excellent agreement was obtained with the prediction of the affine self-consistent scheme for nonlinear elasto-viscoplasticity. [Copyright &y& Elsevier]

Zirconium alloys present a large variability of their mechanical behaviour with respect not only to their chemical composition but also to their microstructure. We analyze here the creep behaviour at 400 °C of two Zr–Nb1%–O alloys presenting identical chemical composition, crystallographic texture, grain size and grain shape. Both alloys only differ by the thermal cycles imposed during the fabrication process, either below (alloy A) or alternatively above and below (alloy B) the monotectoı¨d transition. This sole difference gives rise to creep rates varying by a factor of about 4 between the two alloys. From a microstructural point of view, alloys A and B differ by the precipitates distribution and the thermodynamical state (alloy B is in a metastable equilibrium state). Our experimental analysis based on mechanical tests, transmission electron microscopy (TEM) observations and phase analysis by X-ray diffraction strongly suggests an hardening effect of Nb in solid solution to explain the differences between alloys A and B. This result is confirmed by TEM X-ray spectrometry which gives a weight content of Nb in solid solution differing by about 0.1% between the two alloys. A predictive micromechanical model, based on the self-consistent affine scheme, is then applied. This model well captures the anisotropy of the specimens, and describes accurately both transient and secondary creep regimes. As a result of the identification procedure, identical hardening laws are obtained for the two alloys at the grain scale, and the saturating reference stress for prismatic slip is found to be higher for alloy B by about 30 MPa with respect to alloy A. [Copyright &y& Elsevier]

At near-grounded glacier termini, calving can lead to the capsize of kilometre-scale (i.e. gigatons) unstable icebergs. The transient contact force applied by the capsizing iceberg on the glacier front generates seismic waves that propagate over teleseismic distances. The inversion of this seismic signal is of great interest to get insight into actual and past capsize dynamics. However, the iceberg size, which is of interest for geophysical and climatic studies, cannot be recovered from the seismic amplitude alone. This is because the capsize is a complex process involving interactions between the iceberg, the glacier and the surrounding water. This paper presents a first step towards the construction of a complete model, and is focused on the capsize in the open ocean without glacier front nor ice-mélange. The capsize dynamics of an iceberg in the open ocean is captured by computational fluid dynamics (CFD) simulations, which allows assessing the complexity of the fluid motion around a capsizing iceberg and how far the ocean is affected by iceberg rotation. Expressing the results in terms of appropriate dimensionless variables, we show that laboratory scale and field scale capsizes can be directly compared. The capsize dynamics is found to be highly sensitive to the iceberg aspect ratio and to the water and ice densities. However, dealing at the same time with the fluid dynamics and the contact between the iceberg and the deformable glacier front requires highly complex coupling that often goes beyond actual capabilities of fluid-structure interaction softwares. Therefore, we developed a semi-analytical simplified fluid-structure model (SAFIM) that can be implemented in solid mechanics computations dealing with contact dynamics of deformable solids. This model accounts for hydrodynamic forces through calibrated drag and added-mass effects, and is calibrated against the reference CFD simulations. We show that SAFIM significantly improves the accuracy of the iceberg motion compared with existing simplified models. Various types of drag forces are discussed. The one that provides the best results is an integrated pressure-drag proportional to the square of the normal local velocity at the iceberg's surface, with the drag coefficient depending linearly on the iceberg's aspect ratio. A new formulation based on simplified added-masses or computed added-mass proposed in the literature, is also discussed. We study in particular the change of hydrodynamic-induced forces and moments acting on the capsizing iceberg. The error of the simulated horizontal force ranges between 5 and 25 per cent for different aspect ratios. The added-masses affect the initiation period of the capsize, the duration of the whole capsize being better simulated when added-masses are accounted for. The drag force mainly affects the amplitude of the fluid forces and this amplitude is best predicted without added-masses. [ABSTRACT FROM AUTHOR]

Nanostructured and architectured copper niobium composite wires are excellent candidates for the generation of intense pulsed magnetic fields (∼ 100 T) as they combine both high strength and high electrical conductivity. Multi-scaled Cu-Nb wires are fabricated by accumulative drawing and bundling (a severe plastic deformation technique), leading to a multiscale, architectured, and nanostructured microstructure exhibiting a strong fiber crystallographic texture and elongated grain shape along the wire axis. This paper presents a comprehensive study of the effective elasto-plastic behavior of this composite material by using two different approaches to model the microstructural features: full-field finite elements and mean-field modeling. As the material exhibits several characteristic scales, an original hierarchical strategy is proposed based on iterative scale transition steps from the nanometric grain scale to the millimetric macro-scale. The best modeling strategy is selected to estimate reliably the effective elasto-plastic behavior of Cu-Nb wires with minimum computational time. Finally, for the first time, the models are confronted to tensile tests and in-situ neutron diffraction experimental data with a good agreement. • A hierarchical homogenization strategy is proposed to describe the elastoplastic behavior of architectured and nanostructured Cu-Nb. • The mean field effective model is identified by means of full field finite element simulations. • The model accounts for the double <100> - <111> fiber texture in Copper and the <110> fiber texture in Niobium. • Elastic strains were measured in the individual copper and niobium texture components by neutron diffraction during in situ tensile testing. • Experiments and theory show consistently that plastic activity occurs in <100> oriented grains at a higher applied macroscopic stress than in <111> grains in tensile loading along the wire direction. [ABSTRACT FROM AUTHOR]

A new method based on time‐resolved X‐ray diffraction is proposed in order to measure the elastic strain and stress during ultrasonic fatigue loading experiments. Pure Cu was chosen as an example material for the experiments using a 20 kHz ultrasonic fatigue machine mounted on the six‐circle diffractometer available at the DiffAbs beamline on the SOLEIL synchrotron facility in France. A two‐dimensional hybrid pixel X‐ray detector (XPAD3.2) was triggered by the strain gage signal in a synchronous data acquisition scheme (pump–probe‐like). The method enables studying loading cycles with a period of 50 µs, achieving a temporal resolution of 1 µs. This allows a precise reconstruction of the diffraction patterns during the loading cycles. From the diffraction patterns, the position of the peaks, their shifts and their respective broadening can be deduced. The diffraction peak shift allows the elastic lattice strain to be estimated with a resolution of ∼10−5. Stress is calculated by the self‐consistent scale‐transition model through which the elastic response of the material is estimated. The amplitudes of the cyclic stresses range from 40 to 120 MPa and vary linearly with respect to the displacement applied by the ultrasonic machine. Moreover, the experimental results highlight an increase of the diffraction peak broadening with the number of applied cycles. [ABSTRACT FROM AUTHOR]

Nanostructured and architectured copper niobium composite wires are excellent candidates for the generation of intense pulsed magnetic fields (> 90T) as they combine both high electrical conductivity and high strength. Multi-scaled Cu-Nb wires can be fabricated by accumulative drawing and bundling (a severe plastic deformation technique), leading to a multiscale, architectured and nanostructured microstructure providing a unique set of properties. This work presents a comprehensive multiscale study to predict the anisotropic effective electrical conductivity based on material nanostructure and architecture. Two homogenization methods are applied: a mean-field theory and a full-field approach. The size effect associated with the microstructure refinement is taken into account in the definition of the conductivity of each component in the composites. The multiscale character of the material is then accounted for through an iterative process. Both methods show excellent agreement with each other. The results are further compared, for the first time, with experimental data obtained by the four-point probe technique, and also show excellent agreement. Finally, the qualitative and quantitative understanding provided by these models demonstrates that the microstructure of Cu-Nb wires has a significant effect on the electrical conductivity. [ABSTRACT FROM AUTHOR]

Laue microdiffraction, available at several synchrotron radiation facilities, is well suited for measuring the intragranular stress field in deformed materials thanks to the achievable submicrometer beam size. The traditional method for extracting elastic strain (and hence stress) and lattice orientation from a microdiffraction image relies on fitting each Laue spot with an analytical function to estimate the peak position on the detector screen. The method is thus limited to spots exhibiting ellipsoidal shapes, thereby impeding the study of specimens plastically deformed. To overcome this difficulty, the so-called Laue-DIC method introduces digital image correlation (DIC) for the evaluation of the relative positions of spots, which can thus be of any shape. This paper is dedicated to evaluating the accuracy of this Laue-DIC method. First, a simple image noise model is established and verified on the data acquired at beamline BM32 of the European Synchrotron Radiation Facility. Then, the effect of image noise on errors on spot displacement measured by DIC is evaluated by Monte Carlo simulation. Finally, the combined effect of the image noise, calibration errors and the number of Laue spots used for data treatment is investigated. Results in terms of the uncertainty of stress measurement are provided, and various error regimes are identified. [ABSTRACT FROM AUTHOR]

Multiscale models involving crystal plasticity are essential to predict the elastoplastic behavior of structural materials with respect to their microstructure. However, those models are often limited by a poor knowledge of the local constitutive behavior. This article reports a method to measure the mechanical behavior directly, at the micrometre scale, in bulk crystalline materials. Local strain and stress states were evaluated at the surface of a bent stainless steel crystal by combining total strain measurements - performed with the digital image correlation technique on optical images - with elastic strain measurements obtained by Laue microdiffraction. A local constitutive relation was measured, in an efficient nondestructive way, without the need for full-field simulations. The method was validated by a comparison between the measured local behavior and the macroscopic behavior of the single crystal. [ABSTRACT FROM AUTHOR]

The aim of this paper is to develop a model allowing a fast first approximate estimation of the elastic–plastic stress wave propagation caused by a laser impact and the resulting residual stress field. We start by modeling the stress wave propagation, adopting a 1D uniaxial modeling, reducing the behavior of the specimen to the axis of the laser impact, excluding any edge effects caused by the edges of the laser spot. The plastic strain field resulting from this propagation can in turn be used to compute the residual stresses, by making use of an analytic modeling in the case of an infinite planar plate. The accuracy of the 1D model is assessed by comparing it to finite elements simulations, acting as a reference solution, for several materials and laser spot diameters. The results show that the stress wave propagation from the 1D model is close to identical to the reference solution. The residual plastic and stress fields from the finite elements model present a uniaxial distribution on a large portion of the laser spot, except for the very edge and spot center. The comparison between the 1D model and the reference solution shows a good match, indicating that the 1D model can be used for a fast approximation the mechanical fields created by a laser impact for laser spot diameters larger than 2 mm. • The stress wave induced by laser shock in elasto-plastic specimens is studied. • A fast uniaxial solver is developed for the stress wave propagation problem. • An analytical model is used for estimating the associated residual stress field. • Results match main parts of 3D fields from FE simulations, for shorter CPU times. • The estimation applies to VISAR/LSP configurations, for spot sizes of a few mm. [ABSTRACT FROM AUTHOR]

Titanium Matrix Composites (TMC's) containing various volume fractions of (TiB+TiC) particles have been deposited from powder feedstocks consisting of a blend of pre-alloyed (Ti-6Al-4V+B 4 C) powders, using the direct metal deposition (DMD) laser process and the in-situ chemical reaction 5Ti+B 4 C→4TiB+TiC. Process optimization has allowed to obtain a homogeneous distribution of tiny TiB whiskers within the Ti-6Al-4V α/β matrix, with a full solubilization of C for low B 4 C contents (0.5 wt% and 1.5 wt%), and the formation of a small amount of globular TiC particles at higher B 4 C content (3%). Comparisons with Ti-6Al-4V DMD walls revealed a substantial grain refinement on TMC's due to enhanced grain nucleation on TiB whiskers, even for low B 4 C contents. Last, mechanical investigations indicated an increase of 10–15% of Vickers hardness, and a constant 10% increase of Young modulus on a large temperature range (20–600 °C) for all B 4 C content. [ABSTRACT FROM AUTHOR]

Determining the accuracy of elastic strain measurements in plastically deformed alloys is an experimental challenge. To develop a novel cross-validation procedure, a controlled elasto-plastic strain gradient was created in a stainless steel single crystal by four point bending deformation. The corresponding elastic strain field was probed, with an intragranular spatial resolution, in-situ by Laue microdiffraction and ex-situ by High Resolution EBSD. Good agreement is found for the two independent measurements and the predictions of a mechanical model, at plastic strains below 0.5 %. The accuracy of the measurements is estimated at 3.2 × 10. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the effect of microstructure heterogeneity upon elasto-plastic wave propagation generated during laser shot peening. We consider a simplified elasto-plastic laminate specimen subjected to uniaxial strain. The microstructure is composed of two phases alternating periodically and perfectly bonded together. The associated PDE system is solved using a high-resolution Godunov scheme, allowing to study the wave propagation in the heterogeneous structure. It is found that, even for a small mechanical contrast between the two phases, the considered laminate microstructure has a significant effect on the distribution of plastic strain. In addition, an elasto-plastic homogenization of the laminate has been carried out, and the resulting Homogeneous Equivalent Medium (HEM) has been used to decrease the computation time of the wave propagation. The HEM-based model is able to reproduce accurately the full-field solution in terms of distribution of mean plastic strain within the specimen and its fluctuation between the two phases. [ABSTRACT FROM AUTHOR]

Background Despite advances in cancer therapy, mortality is still high except in early-stage tumors, and screening remains a challenge. The randomized National Lung Screening Trial (NLST), comparing annual low-dose computed tomography (LDCT) and chest X-rays, revealed a 20% decrease in lung-cancer-specific mortality. These results raised numerous questions. The French intergroup for thoracic oncology and the French-speaking oncology group convened an expert group to provide a coherent outlook on screening modalities in France. Methods A literature review was carried out and transmitted to the expert group, which was divided into three workshops to tackle specific questions, with responses presented in a plenary session. A writing committee drafted this article. Results The multidisciplinary group favored individual screening in France, when carried out as outlined in this article and after informing subjects of the benefits and risks. The target population involves subjects aged 55–74 years, who are smokers or have a 30 pack-year smoking history. Subjects should be informed about the benefits of quitting. Screening should involve LDCT scanning with specific modalities. Criteria for CT positivity and management algorithms for positive examinations are given. Conclusions Individual screening requires rigorous assessment and precise research in order to potentially develop a lung-cancer screening policy. [ABSTRACT FROM AUTHOR]

Concurrent chemoradiotherapy (CHRT) is the standard of care for unresectable locally advanced stage III non-small cell lung cancer. However, the optimal combination remains unclear. The aim of this study was to evaluate the efficacy of 2 induction chemotherapy cycles (days 1 and 22) with docetaxel 75 mg/m2 and cisplatin 75 mg/m2 followed by concurrent chemotherapy (weekly docetaxel-cisplatin, 20 mg/m2) and 3-D conformal radiotherapy for 6 weeks (66 Gy/5 fractions per week/2 Gy per fraction). The primary endpoint was the response rate. Secondary objectives were toxicity, time to progression, and overall survival. Forty-four patients were included and 40 were eligible. The mean age was 60.5 years (range 40.7-72.1), and 75% had stage IIIB disease. Six patients underwent complete R0 resection including 2 pathologic complete responses after a planned intermediate evaluation. Thirty-three patients completed CHRT. The objective response rate was 65% (95% CI 50.2-79.8). Grade 3-4 hematologic and digestive toxicities were observed mainly during the induction phase. Grade 3 esophagitis (5%) was experienced during CHRT. With a median follow-up of 38.7 months, the median progression-free survival was 28.3 months (95% CI 11.0-35.0) and the median survival rate was 31.4 months. Cisplatin-docetaxel induction followed by concurrent 3-D conformal radiotherapy and weekly chemotherapy is a feasible protocol associated with a promising response rate and acceptable toxicity. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

A prototype X-ray pixel area detector (XPAD3.1) has been used for X-ray diffraction experiments with synchrotron radiation. The characteristics of this detector are very attractive in terms of fast readout time, high dynamic range and high signal-to-noise ratio. The prototype XPAD3.1 enabled various diffraction experiments to be performed at different energies, sample-to-detector distances and detector angles with respect to the direct beam, yet it was necessary to perform corrections on the diffraction images according to the type of experiment. This paper is focused on calibration and correction procedures to obtain high-quality scientific results specifically developed in the context of three different experiments, namely mechanical characterization of nanostructured multilayers, elastic-plastic deformation of duplex steel and growth of carbon nanotubes. [ABSTRACT FROM AUTHOR]

The article presents research which analyzed the fiber-textured thin films X-ray strain through the application of grain-interaction models. The researchers examined the anistropic elastic response of the films with the use of X-ray diffractometry and micro-tensile method. They found that the combined method can help scientists easily identify a simple linear relationship between geometrical variables and measured strains.

Abstract: The deformation behaviour of 150nm thick W/Cu nanocomposite deposited on polyimide substrates has been analysed under equi-biaxial tensile testing coupled to X-ray diffraction technique. The experiments were carried out using a biaxial device that has been developed for the DiffAbs beamline of SOLEIL synchrotron source. Finite element analysis has been performed to study the strain distribution into the cruciform shape substrate and define the homogeneous deformed volume. X-ray measured elastic strains in tungsten sub-layers could be carried out for both principal directions. The strain field was determined to be almost equi-biaxial as expected and compared to finite element calculations. [ABSTRACT FROM AUTHOR]

We have developed on the DIFFABS-SOLEIL beamline a biaxial tensile machine working in the synchrotron environment for in situ diffraction characterization of thin polycrystalline films mechanical response. The machine has been designed to test compliant substrates coated by the studied films under controlled, applied strain field. Technological challenges comprise the sample design including fixation of the substrate ends, the related generation of a uniform strain field in the studied (central) volume, and the operations from the beamline pilot. Preliminary tests on 150 nm thick W films deposited onto polyimide cruciform substrates are presented. The obtained results for applied strains using x-ray diffraction and digital image correlation methods clearly show the full potentialities of this new setup. [ABSTRACT FROM AUTHOR]

Abstract: Elastic properties of non-textured and {111}-fiber-textured gold thin films were investigated experimentally by several complementary techniques, namely in situ tensile testing under X-ray diffraction (XRD), nanoindentation and Brillouin light scattering (BLS). Specimens were probed along different directions to reveal the strong effects of elastic anisotropy at the (local) grain and (global) film scales. XRD allows the investigation of both local and global anisotropies, while BLS and nanoindentation are limited to global analyses. A micromechanical model, based on the self-consistent scheme, and accounting for the actual microstructure of the films, is applied to interpret experimental data. Although different types of elastic constants can be determined with the used experimental techniques (static/dynamic, local/global), a good agreement is obtained, showing that comparison of these techniques is feasible when carried out carefully. In particular, the use of a micromechanical model to estimate the effects of the local elastic anisotropy at the film scale is unavoidable. The presented results show that XRD, BLS and nanoindentation should capture anisotropic texture effects on elastic constants measurements for materials with a Zener anisotropy index larger than 2. Conversely, the actual texture of a given specimen should be taken into account for a proper analysis of elastic constants measurements using those three experimental techniques. [Copyright &y& Elsevier]

• The largest deviation on frequency is caused by the uncertainty on Young's modulus. • Frequency deviations from machining are lower than that induced from Young's modulus. • The uncertainty in stress estimation using a laser coupled with FEM is 3.2%. • The uncertainty in stress estimation using strain gauges is 3%. • The uncertainty in stress estimation using XRD is 10%. • These uncertainties underline a good agreement in stress amplitude estimation. • The stress amplitude was found to vary linearly with the displacement amplitude. • The material response at the macroscopic scale can be considered as purely elastic. • XRD provides an experimental 1D profile of stress amplitude along the sample length. Piezo-electric ultrasonic fatigue machines are used to carry out fatigue tests more rapidly than what is possible using other technologies, at a frequency of 20 kHz. The very high cycle fatigue (VHCF) domain can be studied with these machines as 10 9 cycles are reached within 14 h when specimens are loaded at stress amplitudes below the yield stress or conventional fatigue strength. The estimation of stress in specimens fatigued at high frequency is a current challenge when adopting this technology. This paper discusses the accuracy and reliability of three methods used to estimate stress amplitudes in specimens subjected to VHCF tests at a high loading frequency. Two historically used methods using strain gauges and a laser vibrometer are discussed and compared with a third, recently developed method based on time-resolved in situ X-ray diffraction (XRD). The three methods are applied to estimate the stress amplitude in a pearlitic steel specimen. The experimental artifacts and uncertainties are evaluated quantitatively to compare the benefits and limits of the methods. The experimental results show that the three methods correctly estimate the stress amplitudes applied to fatigued specimens. [ABSTRACT FROM AUTHOR]

Vinorelbine intravenously (i.v.) demonstrated its efficacy and tolerability in advanced non-small cell lung cancer (NSCLC) patients, including elderly subjects. Since vinorelbine is now available as an oral formulation this phase II open study was designed to evaluate its activity and tolerability in advanced, elderly NSCLC patients. A total of 56 chemonaive patients were recruited from April 2001 through to March 2002. The dosage schedule, already tested in younger NSCLC patients, was 60 mg/m2once a week for three weeks (first cycle), followed by 80 mg/m2 once a week until disease progression or development of unacceptable toxicity. A limited sampling scheme was used for performing pharmacokinetic analysis on 52 of 56 patients enrolled in the study. Treatment was well tolerated with grade 3/4 neutropenia in 11/17 patients (20/30%) and febrile neutropenia in 1 (2%). Six partial responses (11%) and 25 stable disease responses were recorded, with a disease control rate of 55%. Median overall survival was 8.2 months (95% Confidence Interval (CI) [6.2–11.3]). The clinical benefit response rate was 31% on 32 evaluable patients. Pharmacokinetic profiles appeared quite similar to the historical profiles recorded following i.v. administration. Oral vinorelbine appears to be a reasonable alternative to i.v. vinorelbine, both in terms of activity and tolerability, in advanced, elderly NSCLC patients. [Copyright &y& Elsevier]

Synchrotron x-ray radiation was used for in situ strain measurements during uniaxial tests on polymer substrates coated by a metallic gold film 400 nm thick deposited without interlayer or surface treatment. X-ray diffraction allowed capturing both components elastic strains and determining how these were partitioned between the metallic film and the polymeric substrate. For strains below 0.8%, deformation is continuous through the metal-polymer interface while above, the onset of plasticity in the metallic film induces a shift between film and substrate elastic strains. [ABSTRACT FROM AUTHOR]

Synchrotron x-ray diffraction combined with in situ tensile testing is used to investigate the anisotropic elastic behavior of gold thin films exhibiting a fiber texture and columnar grains. Micromechanical modeling based on the self-consistent model and accounting for both crystallographic and morphological textures is applied. Flat-disk shaped inclusions must be used in the model to reproduce accurately experimental data, owing to the surface effects. [ABSTRACT FROM AUTHOR]