100 research outputs found
FIRST STEPS OF EXPERIMENTAL VALIDATION OF A NUMERICAL MODEL ABOUT MECHANICAL BEHAVIOR OF NITI ENDODONTIC INSTRUMENTS
Oral Communication presented at the ";Forum des Jeunes Chercheurs";, Brest (France) 2011
Towards a faster determination of high cycle fatigue properties taking into account the influence of a plastic pre-strain from selfheating measurements
AbstractThe high cycle fatigue (HCF) is a major element for a great design of automotive parts. A wide part of the steel sheets for the automotive industry are stamped, sometimes deeply. During this operation, the steel is plastically strained in different directions, so that a good prediction of the fatigue behaviour requires the determination of the fatigue properties of the pre-strained material. Nowadays, the evolution of HCF properties is often neglected. There are two major reasons for this lack. On the one hand, a good finite element simulation of the forming operation to predict pre-strain field is still a difficult task. On the other hand the time dedicated to traditional fatigue test campaigns (e.g. staircase method) to quantitatively identify this influence is prohibitive. To determine faster this influence, it is proposed to use self heating measurements under cyclic loadings. To illustrate this approach, different pre-strain paths are studied: shear and tension. Finally, a model taking into account the influence of pre-strain on high cycle fatigue properties is proposed and identified from self-heating measurements. The validation of the proposed approach is obtained by predicting S/N curves for pre-strain to 20% of a dual phase steel
Apport des mesures de champs de température pour l'identification de propriétés en fatigue polycyclique
L'utilisation de mesure de champs pour l'identification de paramètres matériaux est une voie prometteuse. En effet, la réalisation, certes délicate, de tests mécaniques dans des conditions non homogènes (i.e., où les contraintes, et/ou la température ne sont pas uniformes dans la ZOI) conjugués à l'utilisation de mesure de champs donne accès à une base de données souvent très riche. Cela est particulièrement le cas lorsque l'hétérogénéité est « bien maîtrisée ». On propose, ici, une stratégie d'identification de propriétés à la fatigue polycyclique à partir de mesure de champs de température
Apport des mesures de l'auto-échauffement sous sollicitations cycliques pour la détermination des propriétés en fatigue polycyclique d'un matériau très inclusionnaire
Des essais d'auto-échauffement sous chargement cyclique sur des éprouvettes en fer puddlé ont été mis en uvre afin de déterminer les propriétés en fatigue du matériau. Celui-ci étant hétérogène et fortement inclusionnaire, la notion de VER se pose. Nous montrons qu'il est possible de construire une bonne répartition des inclusions au sein du matériau à partir des mesures d'auto-échauffement sur des éprouvettes de faible volume. Le modèle de répartition est validé sur des éprouvettes plus volumineuses
Actionneur à architecture antagoniste à base d'alliages à mémoire de forme : Modèle thermomécanique simplifié pour la commande
L'effet mémoire des AMF est obtenu sous un chargement thermomécanique. Ceci peut être exploité et être à l'origine du développement d'actionneurs de nouvelle génération. Le point fort de ces actionneurs est la simplification du mécanisme mais le comportement complexe de ces matériaux rend la commande de l'actionneur plus difficile. Dans ce papier nous avons développé un modèle thermomécanique simplifié de ces matériaux pour établir un schéma de commande en prenant en compte la physique du système. Ce modèle permet la description du comportement non linéaire des AMF sous chargements thermomécaniques pour des structures simples telles que les ressorts. Nous nous intéressons aux actionneurs intégrant des ressorts à base d'AMF. Deux types d'actionneurs seront étudiés : un actionneur simple qui comporte un ressort sous une charge constante et un actionneur antagoniste comportant un ressort en AMF et un ressort élastique de rappel
Identification of the electroelastic coupling from full multi-physical fields measured at the micrometre scale
Outcome of Ph negative myeloproliferative neoplasms transforming to accelerated or leukemic phase
Myeloproliferative neoplasms (MPN) are chronic disorders that can sometimes evolve into accelerated or leukemic phases. We retrospectively identified 122 patients with such blastic phases. The overall median survival was four months: 10.2 months for patients treated with intensive treatments compared to three months for best supportive care (p = .005). Azacytidine, intensive chemotherapies, or allogeneic stem cell transplantation gave the highest median survivals with 9, 10.2, and 19.4 months, respectively. Accelerated phases (AP) had a longer median survival compared to acute leukemia (4.8 months vs. 3.1 months; p = .02). In this retrospective and observational study, we observe that the longest survivals are seen in patients eligible for intensive treatments. Azacytidine shows interesting results in patients non-fit for intensive chemotherapy. Supportive care should probably be restricted to elderly patients and those with unfavorable karyotype. An early diagnosis of AP could also result in a better survival rate
Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment
The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410
has been developed by Hamamatsu for dark matter direct detection experiments
using liquid xenon as the target material. We present the results from the
joint effort between the XENON collaboration and the Hamamatsu company to
produce a highly radio-pure photosensor (version R11410-21) for the XENON1T
dark matter experiment. After introducing the photosensor and its components,
we show the methods and results of the radioactive contamination measurements
of the individual materials employed in the photomultiplier production. We then
discuss the adopted strategies to reduce the radioactivity of the various PMT
versions. Finally, we detail the results from screening 216 tubes with
ultra-low background germanium detectors, as well as their implications for the
expected electronic and nuclear recoil background of the XENON1T experiment.Comment: 10 pages, 5 figure
Comment on "On the subtleties of searching for dark matter with liquid xenon detectors"
In a recent manuscript (arXiv:1208.5046) Peter Sorensen claims that
XENON100's upper limits on spin-independent WIMP-nucleon cross sections for
WIMP masses below 10 GeV "may be understated by one order of magnitude or
more". Having performed a similar, though more detailed analysis prior to the
submission of our new result (arXiv:1207.5988), we do not confirm these
findings. We point out the rationale for not considering the described effect
in our final analysis and list several potential problems with his study.Comment: 3 pages, no figure
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