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Abstract: In this paper, errors related to digital image correlation (DIC) technique applied to measurements of displacements are estimated. This work is based on the generation of synthetic images representative of real speckle patterns. With these images, various parameters are treated in order to determine their impact on the measurement error. These parameters are related to the type of deformation imposed on the speckle, the speckle itself (encoding of the image and image saturation) or the software (subset size). [Copyright &y& Elsevier]

Abstract: On Airbus aircraft, spherical plain bearings are used on many components; in particular to link engine to pylon or pylon to wing. Design of bearings is based on contact pressure distribution on spherical surfaces. To determine this distribution, a 3D analysis of the mechanical behaviour of aeronautical plain bearing is presented in this paper. A numerical model has been built and validated from a comparison with 3D experimental measurements of kinematic components. For that, digital volume correlation (DVC) coupled with optical scanning tomography (OST) is employed to study the mechanical response of a plain bearing model made in epoxy resin. Experimental results have been compared with the ones obtained from the simulated model. This comparison enables us to study the influence of various boundary conditions to build the FE model. Some factors have been highlighted like the fitting behaviour which can radically change contact pressure distribution. This work shows the contribution of a representative mechanical environment to study precisely mechanical response of aeronautical plain bearings. [Copyright &y& Elsevier]

Abstract: One of the current problems connected with multi-layer composite structures concerns the analysis of the distribution of the stresses around peculiarities (free edge and loaded edge) and at the interfaces of each layer. This work presents a new shear stress function in the form of the exponential function, to predict the mechanical behaviour of multi-layered laminated composite structures. As a case study, the mechanical behaviour of a laminated composite beam (90°/0°/0°/90°) is examined. The results are compared with the model “Sinus” and 2D finite element method studied. Results show that this new model is more precise than older ones as compared to the results obtained by the finite element analysis [Abaqus]. To introduce continuity on the interfaces of each layer, the kinematics defined by Ossadzow is used with the new exponential model. The equilibrium equations and natural boundary conditions are derived by the principle of virtual power. [Copyright &y& Elsevier]

This work presents a new multi-layer laminated composite structure model to predict the mechanical behaviour of multi-layered laminated composite structures. As a case study, the mechanical behaviour of laminated composite beam (90°/0°/0°/90°) is examined from both a static and dynamic point of view. The results are compared with the model “Sinus” and finite element method studied by Abou Harb. Results show that this new model is more precise than older ones as compared to the results by the finite element method (Abaqus). To introduce continuity on the interfaces of each layer, the kinematics defined by Ossadzow was used. The equilibrium equations and natural boundary conditions are derived by the principle of virtual power. To validate the new proposed model, different cases in bending, buckling and free vibration have been considered. [Copyright &y& Elsevier]

ABSTRACT To study the behaviour of a carbon-fibre reinforced-plastic laminate under a biaxial stress state, a new type of cruciform specimen has been developed. This specimen is loaded biaxially under static and cyclic fatigue conditions. The experiments are monitored simultaneously using digital image correlation with two high-speed cameras and infrared thermography. A comparison between the measurements and a finite element model is used to validate the design of the sample. [ABSTRACT FROM AUTHOR]

The complex mechanical behaviour of composite materials, due to internal heterogeneity and multi-layered composition impose deeper studies. This paper presents an experimental investigation technique to perform volume kinematic measurements in composite materials. The association of X-ray micro-computed tomography acquisitions and Digital Volume Correlation (DVC) technique allows the measurement of displacements and deformations in the whole volume of composite specimen. To elaborate the latter, composite fibres and epoxy resin are associated with metallic particles to create contrast during X-ray acquisition. A specific in situ loading device is presented for three-point bending tests, which enables the visualization of transverse shear effects in composite structures. [ABSTRACT FROM AUTHOR]

Background:The need to unfold the underlying mechanisms of lung cancer aggressiveness, the deadliest cancer in the world, is of prime importance. Because Fas-associated death domain protein (FADD) is the key adaptor molecule transmitting the apoptotic signal delivered by death receptors, we studied the presence and correlation of intra- and extracellular FADD protein with development and aggressiveness of non-small cell lung cancer (NSCLC).Methods:Fifty NSCLC patients were enrolled in this prospective study. Intracellular FADD was detected in patients' tissue by immunohistochemistry. Tumours and distant non-tumoural lung biopsies were cultured through trans-well membrane in order to analyse extracellular FADD. Correlation between different clinical/histological parameters with level/localisation of FADD protein has been investigated.Results:Fas-associated death domain protein could be specifically downregulated in tumoural cells and FADD loss correlated with the presence of extracellular FADD. Indeed, human NSCLC released FADD protein, and tumoural samples released significantly more FADD than non-tumoural (NT) tissue (P=0.000003). The release of FADD by both tumoural and NT tissue increased significantly with the cancer stage, and was correlated with both early and late steps of the metastasis process.Conclusion:The release of FADD by human NSCLC could be a new marker of poor prognosis as it correlates positively with both tumour progression and aggressiveness. [ABSTRACT FROM AUTHOR]

Optical full-field measurement methods such as Digital Image Correlation (DIC) are increasingly used in the field of experimental mechanics, but they still suffer from a lack of information about their metrological performances. To assess the performance of DIC techniques and give some practical rules for users, a collaborative work has been carried out by the Workgroup “Metrology” of the French CNRS research network 2519 “MCIMS (Mesures de Champs et Identification en Mécanique des Solides / Full-field measurement and identification in solid mechanics, )”. A methodology is proposed to assess the metrological performances of the image processing algorithms that constitute their main component, the knowledge of which being required for a global assessment of the whole measurement system. The study is based on displacement error assessment from synthetic speckle images. Series of synthetic reference and deformed images with random patterns have been generated, assuming a sinusoidal displacement field with various frequencies and amplitudes. Displacements are evaluated by several DIC packages based on various formulations and used in the French community. Evaluated displacements are compared with the exact imposed values and errors are statistically analyzed. Results show general trends rather independent of the implementations but strongly correlated with the assumptions of the underlying algorithms. Various error regimes are identified, for which the dependence of the uncertainty with the parameters of the algorithms, such as subset size, gray level interpolation or shape functions, is discussed. [ABSTRACT FROM AUTHOR]

Abstract: In order to predict the flight parameters and to improve the life time of long duration super-pressure balloon, a research program on modelization and experimental simulation of the balloon envelope mechanical behavior is carried out. The balloon is a 10m diameter type made with multilayer polymeric films and tapes. A facility was developed to measure, via a stereo-correlation system, the 3D displacement and the in plane solicitation strain of a 1.5m diameter balloon envelope part in realistic flight conditions, i.e. pressure, temperature and loading at the sample boundaries. A time dependant non-linear Maxwell model of the polymeric material behavior was identified from uniaxial creep and relaxation tests and implemented in a Finite Elements code, simulating the sample tested in the facility. The Poisson ratio of the transparent and supple balloon film has been measured with an image correlation system. Experimental results are obtained both at room and in cold conditions (−60°C) for various values of differential pressure. Vertical displacement and in plane 2D strain of apex part deduced from the numerical modeling are compared to experimental results. [Copyright &y& Elsevier]

This study was undertaken to evaluate the possibility to obtain a molecular signature of rheumatoid arthritis (RA) comparatively osteoarthritis (OA), and to lay the bases to develop new diagnostic tools and identify new targets. Microarray technology was used for such an analysis. The gene expression profiles of synovial tissues from patients with confirmed RA, and patients with OA were established and compared. A set of 63 genes was selected, based, more specifically, on their overexpression or underexpression in RA samples compared to OA. Results for six of these genes have been verified by quantitative PCR using both samples identical to those used in the microarray experiments and entirely separate samples. Expression profile of the 48 known genes allowed the correct classification of additional RA and OA patients. Furthermore, the distinct expression of three of the selected genes was also studied by quantitative RT-PCR in cultured synovial cells. Detailed analysis of the expression profile of the selected genes provided evidence for dysregulated biological pathways, pointed out to chromosomal location and revealed novel genes potentially involved in RA. It is proposed that such an approach allows valuable diagnosis/prognostics tools in RA to be established and potential targets for combating the disease to be identified.Genes and Immunity (2004) 5, 597-608. doi:10.1038/sj.gene.6364132 Published online 21 October 2004 [ABSTRACT FROM AUTHOR]

Long duration super-pressure balloons constitute a great challenge in scientific ballooning. For any type of balloons (spherical, pumpkin, …), it is necessary to have a good knowledge of the mechanical behavior of envelopes regarding the level and the lifetime of the flight. For this reason CNES, ONERA and ENIT are carrying out a research program of modelization and experimentation in order to predict the envelope shape of a balloon in different conditions of temperature and differential pressure. This study was conducted in two parts. During the first one, we defined, with parameters obtained from unidirectional tests, the mechanical laws (elasticity, plasticity and viscosity properties of polymers) of materials involved in the envelope. These laws are introduced in a finite element code, which predicts the stress and strain status of a complex envelope structure. During the second one, we developed an experimental set-up to measure the 3D strain on a balloon subsystem, which includes envelope, assemblies and apex parts, in real flight conditions. This facility, called NIRVANA, is a 1 m3 vacuum chamber with cooled screens equipped with a stereoscopic CCD measurement system. A 1.5 m diameter sample can be tested under differential pressure, regulated temperature (from +20 to -120 °C) and a load (up to 6 tonnes) applied on tendons. This paper presents the first results obtained from the modelizations and measurements done on an envelope sample submitted to axisymmetrical stress due to the differential pressure. This sample consists of a 50 μm multilayer polymer film with an assembly, used in 10 m diameter STRATEOLE super-pressure balloons. The modelization gives results in good accordance with the experiments and will enable us to follow this work with cold conditions, time dependence (creeping) and more complex structures. [Copyright &y& Elsevier]

A correction is presented to the article "Assessment of Digital Image Correlation Measurement Errors: Methodology and Results [Experimental Mechanics 49(3)]" which was published in previous issue of the periodical.