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This paper presents high temperature quasi-static and dynamic tensile testing. Samples are heated by an induction system controlled with a pyrometer. A high-speed camera (500 fps) is used to determine displacement fields with a digital image correlation software. For such tests a specific marking procedure of the sample is applied. This method is used to characterize the mechanical behaviour of a C68 high-carbon steel at temperatures up to 720 °C. Stress-strain curves are given from room temperature up to 720 °C at strain rates ranging from 400 / s to 4 × 10 / s. [ABSTRACT FROM AUTHOR]

This article extends the concept of forming limit curves to very thin (0.1 mm) metallic materials. The forming limit curves for these materials are referred in this paper as microforming limit curves. To study the microformability of such materials, a microdrawing press based on the Marciniak principle, coupled with an image acquisition system, was designed and built in the laboratory. Images of the sample surface were obtained during the microdrawing process and processed using a deformation measurement system based on image correlation. The microformability of aluminium 1050A (99.5 %) and aluminium alloy (Al-3 % Mg) were characterised in tests at three different geometries and then analysed. Besides, a new technique for estimating the strain at the onset of necking was developed and tested against a proven method. This technique is more easily automated because it does not rely on subjective criteria. Thus, it is possible to have the microforming limit curve for very thin sheet by a rapid and objective experimental method. [ABSTRACT FROM AUTHOR]

This paper introduces the application of micro-deep drawing of single and multicrystals of aluminium in order to identify parameters of micro-mechanical models. The information obtained experimentally is abundant: load-displacement curves of the punch, the evolution of grain orientation, mapping deformations throughout the test. All this experimental data was used to validate the multiscale models introduced in a finite element code for loading paths ranging from biaxial tensile to simple tensile. [ABSTRACT FROM AUTHOR]

This paper presents the determination of virtual micro-forming limit diagrams from two types of numerical simulations based on the finite element method: one with modelling of the full tool for micro-deep drawing and a thin blank with geometric imperfections, based on a defined roughness; and a second called "reduced simulation" where different deformation paths were simulated with appropriate boundary conditions by introducing the same type of geometric imperfections on aluminium 1050A (99.5%). A new test for detecting the onset of necking, called the "change of slope" criterion has been defined. Several methods based on histograms to represent the distributions of major and minor strains, have been used to determine the strain at the onset of necking. The numerical micro-forming limit diagrams (MFLD) were then compared to one obtained experimentally. [ABSTRACT FROM AUTHOR]

In this paper, we characterize two deterministic implied volatility models, defined by assuming that either the per-delta or the per-strike implied volatility surface has a deterministic evolution. Practitioners have recently proposed these two models to describe two regimes of implied volatility (see Derman (1999 Risk 4 55–9)). In an arbitrage-free sticky-delta model, we show that the underlying asset price is the exponential of a process with independent increments under the unique risk neutral measure and that any square-integrable claim can be replicated up to a vanishing risk by trading portfolios of vanilla options. This latter result is similar in nature to the quasi-completeness result obtained by Bjork et al (1997 Finance Stochastics 1 141–74) for interest rate models driven by Levy processes. Finally, we show that the only arbitrage-free sticky-strike model is the standard Black-Scholes model. [ABSTRACT FROM AUTHOR]

Introduction La prescription est la première étape du processus d’administration d’un médicament pouvant conduire à une erreur médicamenteuse (EM). La mise en place d’un relevé informatisé des effets indésirables liés aux soins (EI) dans notre unité de réanimation chirurgicale pédiatrique en 2011, a montré que la moitié des EI était des EM. Plus d’un tiers d’entre elles étaient dues à des erreurs de prescriptions [1] . Des consignes de prescription ont alors été établies et diffusées. L’objectif de ce travail était d’évaluer la conformité des prescriptions médicamenteuses à ces règles. Matériel et méthodes Évaluation rétrospective d’un échantillon de prescriptions tirées au sort entre septembre 2012 et février 2013. Douze points de qualité ont été établis à partir des règles de prescription médicamenteuses diffusées à chaque médecin du service. Les données étaient recueillies et analysées par deux médecins du service. Les comparaisons statistiques étaient réalisées avec un test exact de Fisher. Le critère de jugement principal était le taux global de conformité. Les critères de jugements secondaires étaient les taux de conformité pour chaque item, pour chaque classe de médicaments et une comparaison entre les internes (DESAR) et les seniors (MAR). Résultats Soixante-huit prescriptions ont été analysées. L’âge moyen des enfants était de 95,5 mois IC 95 [76,1–114,9]. Le poids moyen était de 25,5 kg IC 95 [20,2–30,8]. Le taux de conformité global était de 78 %, IC 95 [76–82], avec une différence significative entre les DESAR (84 %, IC 95 [81–87]) et les MAR (74 %, IC 95 [70–77]), p < 0,01. Les résultats sont présentés dans la Fig. 1 . Pour les traitements injectables, la posologie était précisée dans 99 % IC 95 [98–100] des cas, le nombres d’injections quotidiennes dans 77 % IC 95 [72–82] des cas et la voie d’administration dans 52 % IC 95 [46–58] des cas. Discussion Le taux de conformité globale est difficilement comparable à d’autres études du fait d’une grande variabilité des référentiels et des critères de qualités choisis. On retrouve cependant de nombreuses similitudes avec notre étude comme une identification du prescripteur faible, une lisibilité perfectible, la voie d’administration insuffisamment précisée [2] . La différence entre les DESAR et les MAR s’explique probablement par une répétition plus fréquente des règles de prescription ; les DESAR recevant les consignes à chaque semestre alors que les MAR ne les ont reçues qu’une fois. La sensibilisation régulière semble être une des voies d’amélioration à privilégier. D’autres voies sont possibles. L’informatisation actuelle des prescriptions devrait permettre une amélioration de leur qualité. D’autres méthodes pourraient être envisagées comme la création dans le service d’une zone isolée, dédiée à la prescription [3] . L’amélioration de la conformité de nos prescriptions est essentielle. Cela permettra de faciliter les contrôles en aval de l’étape de prescription, de dépister plus d’erreurs de prescription et d’améliorer la sécurité de nos patients. [ABSTRACT FROM AUTHOR]

Nowadays, numerical simulation by finite element analysis is an essential tool that allows performing virtually sheet metal forming processes, and therefore to reproduce various phenomena such as springback ( SB ) and necking that are generated by plastic deformation. However, the quality of the model used to represent the mechanical behaviour is a determining factor for the realism of numerical simulations. To perform well, the model must reproduce all the properties of the material such as the anisotropy and the strain hardening induced by plastic deformation. The main purpose of this work is to show, by means of numerical simulations, the influence of constitutive modelling on the prediction of the degree of SB in the case of a stretch bending test. Tests have been carried out on titanium sheets which have a wide range of applications for high tech industries because of specific mechanical and physical properties. At the same time, we have investigated the dependence of some process parameters such as the clamping force on SB . In order to prove the accuracy and reliability of the proposed finite element model, experimental data were used to compare with the numerical results. [ABSTRACT FROM AUTHOR]

This paper presents experimental tensile test results obtained on flat aluminum magnesium alloy samples on a hard machine. The mechanical response, kinematic fields and acoustic emissions were simultaneously obtained in an experimental setup. Propagation instabilities associated with the Portevin–Le-Châtelier effect were observed as localized intense strain increment bands. Depending on the strain rate, A, B or C types were studied on the basis of stress drops, acoustic emission and strain fields. Then the band characteristics (position, orientation, width, thickness reduction, intensity, acoustic emission, principal strain direction) were presented in various strain rate conditions. [ABSTRACT FROM AUTHOR]

The objective is to determine the finest finite element simulations of deep-drawing operations, including spring-back effect, until the occurrence of strain localisation.This paper insists on two aspects that have a major influence on the results of the simulations: precise determination of the equivalent stress–equivalent strain relationship and description of boundary conditions.The stress–strain curve has been determined using duplicate analysis of tensile test. The classic extensometric strain measurement is compared with the measurements of strain with an automatic analysis of digital images caught at various deformation stages. The measurements by image analysis allow the determination of local strains and give them a more precise determination for the high strains.As to boundary limit problems managed with explicit algorithm, success mainly depends on the control of the process that has to remain in quasi-static range.In order to analyse the accordance of the results of the simulation and then obtained by the experiment, the precise method of residual stress calculation is elaborated for the case of the original tensile test: simultaneous loading and subsequent unloading to the equilibrium state of assembly of three samples with different lengths.The comparisons of the experimental and numerical results are very satisfactory. [Copyright &y& Elsevier]