Towards a Semantic Search Engine for Scientific Articles

Because of the data deluge in scientific publication, finding relevant information is getting harder and harder for researchers and readers. Building an enhanced scientific search engine by taking semantic relations into account poses a great challenge. As a starting point, semantic relations between keywords from scientific articles could be extracted in order to classify articles. This might help later in the process of browsing and searching for content in a meaningful scientific way. Indeed, by connecting keywords, the context of the article can be extracted. This paper aims to provide ideas to build such a smart search engine and describes the initial contributions towards achieving such an ambitious goal

Utilisation de l'imagerie IR pour l'étude de la fatigue des aciers : Premières observations d'effets de surface

International audienceDe nouvelles méthodes de caractérisation de la tenue à la fatigue des matériaux métalliques par mesure thermique sont développées depuis plusieurs années. Elles donnent accès en quelques dizaines de minutes à une estimation de la limite d'endurance et de la dispersion des résultats de fatigue d'un matériau, là où plusieurs jours sont nécessaires traditionnellement. Un des axes de développement de ces méthodes consiste à caractériser à l'aide de ces techniques les effets de surface sur les propriétés à la fatigue. Pour capter l'information due à l'hétérogénéité locale provoquée par le traitement de surface, il est nécessaire de passer d'une vision moyenne à des mesures de champ. Deux points clefs peuvent être considérés pour ce passage. Le premier concerne la mesure et est traité dans cet article. Le second concerne l'identification du champ de sources locales à partir du champ de température mesurée et n'est pas traité ici. Un protocole expérimental de mesure du champ de température d'une tôle mince avec une précision suffisante (incertitude de l'ordre du milliKelvin) est présenté pour discerner des hétérogénéités de propriété à la fatigue (p. ex. surface vs. cœur). L'article expose les différentes sources d'artefacts rencontrés et les techniques utilisées pour les supprimer

Dissipation measurements in steel sheets under cyclic loading by use of infrared microthermography

WOSInternational audienceHeterogeneous dissipation in steel sheets due to cyclic loading is difficult to measure, especially in the transverse direction because of the high conductivity and low thickness of the sheets. The goal of this article is thus to develop an experimental protocol allowing for the dissipation field determination from infra-red thermography. The protocol is based on a specific differential measurement and an asynchronous acquisition. It reduces measurement artefacts due to coating, rigid body motion, convection, and optical deleterious effects. It is eventually applied to different specimens

Probabilistic multiscale models and measurements of self-heating under multiaxial high cycle fatigue

WOSInternational audienceDifferent approaches have been proposed to link high cycle fatigue properties to thermal measurements under cyclic loadings, usually referred to as “self-heating tests.” This paper focuses on two models whose parameters are tuned by resorting to self-heating tests and then used to predict high cycle fatigue properties. The first model is based upon a yield surface approach to account for stress multiaxiality at a microscopic scale, whereas the second one relies on a probabilistic modelling of microplasticity at the scale of slip-planes. Both model identifications are cost effective, relying mainly on quickly-obtained temperature data in self-heating tests. They both describe the influence of the stress heterogeneity, the volume effect and the hydrostatic stress on fatigue limits. The thermal effects and mean fatigue limit predictions are in good agreement with experimental results for in and out-of phase tension-torsion loadings. In the case of fatigue under non-proportional loading paths, the mean fatigue limit prediction error of the critical shear stress approach is three times less than with the yield surface approach

Rapid multiaxial high cycle fatigue limit predictions using self-heating-based probabilistic multiscale models

Thermal measurements under multiaxial cyclic loadings are used herein to predict multiaxial fatigue properties. Two models describing random microplasticity activation via a Poisson Point Process. The thermal response is interpreted as the “mean” behaviour of the microplastic activity, whereas the fatigue limit relies on the weakest link assumption. The first model is based upon a yield surface approach to account for stress multiaxiality at a microscopic scale. The second one relies on a probabilistic modelling of microplasticity at the scale of slip-planes. Both models are identified on thermal results and a uniaxial mean fatigue limit, and then validated using fatigue limits as well as thermal responses in the case of tension-torsion loadings on tubular specimens made of medium carbon steel. They predict well hydrostatic stress, volume and proportional multiaxial effects. The model with microplasticity described at the scale of slip-planes also offers a good prediction of nonproportional mean fatigue limits (~ 5% error) whereas the other model is less predictive (~ 17% error)

Dialogue essais-modèle pour l'interprétation des liens entre mesure d'auto-échauffement sous chargement cyclique et fatigue polycyclique

WOSInternational audienceUne démarche de développement d'un modèle probabiliste à deux échelles pour la fatigue HCF des aciers est proposée. Elle est basée sur l'utilisation de mesure d'autoéchauffement sous chargements cycliques et est validée sur la base de la prévision des courbes de Wöhler d'un acier dual-phase pour différents rapport de charge

Prévision de l'échauffement et de la microplasticité des aciers sous sollicitations cycliques

L'élévation de température dans les aciers sous chargement cyclique est une manifestation de l'existence de mécanismes irréversibles qui sont aussi à l'origine de l'amorçage des microfissures. Ainsi, afin d'optimiser la microstructure des aciers pour le comportement en fatigue, un modèle polycristallin est proposé pour mieux comprendre les interactions entre les mécanismes dissipatifs et la microstructure. Le cadre de la plasticité cristalline est utilisé pour décrire ces mécanismes dissipatifs qui sont soit dus à des oscillations de segments de dislocations, soit dus au glissement plastique. Le modèle ainsi développé est validé au travers d'une comparaison avec des résultats expérimentaux

Prediction of self-heating measurements under proportional and non-proportional multiaxial cyclic loadings

WOSInternational audienceSelf-heating measurements under cyclic loadings allow for fast estimations of fatigue properties. These tests are performed under tension–torsion loadings on a medium-carbon steel and a model accounting for heterogeneities is proposed to analyse heat transfer results. Both proportional and non-proportional loading paths are predicted

Analysis of Residual Stress Relaxation Under Mechanical Cyclic Loading of Shot-Peened TRIP780 Steel

Shot-peening is a popular mechanical surface treatment used in automotive and aeronautical industries to enhance life duration of mechanical parts by introducing compressive residual stresses. TRIP 780 fatigue type specimens are shot-peened and loaded under cyclic bending. The martensite phase transformation and the evolution of residual stresses in the different phases are determined by XRD at different number of cycles. A FEM model is also proposed to better understand the evolution of residual stresses in the first cycles

Analysis of residual stress relaxation under mechanical cyclic loading of shot-peened trip780 steel until fatigue lifetime

TRIP aided steels are used in the automotive industry due to their high strength, ductility and toughness properties. Typical parts made of TRIP steels (as engine sub-frame for instance) are submitted to cyclic loading during their lifetime. Those parts could be also shot-peened to minimise the risk of fatigue failure. Studies have investigated the fatigue life of non-treated TRIP aided steels [1-3], the shot peening of TRIP steels [4-9] but very few [10] have investigated the mechanical residual stress stability after shot peening on TRIP steels and the impact on fatigue life. TRIP steels exhibit a multiphased microstructure of ferrite, bainite, residual austenite and martensite created after thermomechanical loading/straining. Shot peening on TRIP steel generates austenite to martensite phase transformation and a gradient of microstructure and residual stresses from the surface as characterized by Guiheux [9]. The aim of this study is to analyse the evolution of residual stresses (RS) generated by shot-peening during cycling and the effects of shot peening on fatigue life of a cold rolled TRIP780 steel. The stability of RS was assessed using X-ray diffraction techniques. Macroscopic finite element simulation of fatigue life