Enhancement of a dynamic porous model considering compression-release hysteresis behavior: Application to graphite

Because of their shock wave attenuation properties, porous materials and foams are increasingly used for various applications such as graphite in the aerospace industry and polyurethane (PU) foams in biomedical engineering. For these two materials, the absence of residual compaction after compression and release cycles limits the efficiency of the usual numerical dynamic porous models such as P-α and POREQST. In this paper, we suggest a simple enhancement of the latter in order to take into account the compression-release hysteresis behavior experimentally observed for the considered materials. The new model, named H-POREQST, was implemented into a Lagrangian hydrocode and tested for simulating plate impact experiments at moderate pressure onto a commercial grade of porous graphite (EDM3). It proved to be in far better agreement with experimental data than the original model which encourages us to pursue numerical tests and developments

Localized Atomic Segregation in the Spalled Area of a Zr50Cu40Al10 BMG Induced by Laser-shock Experiment

Laser-shock experiments were performed on a ternary Zr50Cu40Al10bulk metallic glass. A spalling process was studied through post-mortem analyses conducted on a recovered sample and spall. Scanning electron microscopy magnification of fracture surfaces revealed the presence of a peculiar feature known as cup-cone. Cups are found on sample fracture surface while cones are observed on spall. Two distinct regions can be observed on cups and cones: a smooth viscous-like region in the center and a flat one with large vein-pattern in the periphery. Energy dispersive spectroscopy measurements conducted on these features emphasized atomic distribution discrepancies both on the sample and spall. We propose a mechanism for the initiation and the growth of these features but also a process for atomic segregation during spallation. Cup and cones would originate from cracks arising from shear bands formation (softened paths). These shear bands result from a quadrupolar-shaped atomic disorder engendered around an initiation site by shock wave propagation. This disorder turns into a shear band when tensile front reaches spallation plane. During the separation process, temperature gain induced by shock waves and shear bands generation decreases material viscosity leading to higher atomic mobility. Once in a liquid-like form, atomic clusters migrate and segregate due to inertial effects originating from particle velocity variation (interaction of release waves). As a result, a high rate of copper is found in sample cups and high zirconium concentration is found on spall cones

Albiglutide and cardiovascular outcomes in patients with type 2 diabetes and cardiovascular disease (Harmony Outcomes): a double-blind, randomised placebo-controlled trial

Background: Glucagon-like peptide 1 receptor agonists differ in chemical structure, duration of action, and in their effects on clinical outcomes. The cardiovascular effects of once-weekly albiglutide in type 2 diabetes are unknown. We aimed to determine the safety and efficacy of albiglutide in preventing cardiovascular death, myocardial infarction, or stroke. Methods: We did a double-blind, randomised, placebo-controlled trial in 610 sites across 28 countries. We randomly assigned patients aged 40 years and older with type 2 diabetes and cardiovascular disease (at a 1:1 ratio) to groups that either received a subcutaneous injection of albiglutide (30–50 mg, based on glycaemic response and tolerability) or of a matched volume of placebo once a week, in addition to their standard care. Investigators used an interactive voice or web response system to obtain treatment assignment, and patients and all study investigators were masked to their treatment allocation. We hypothesised that albiglutide would be non-inferior to placebo for the primary outcome of the first occurrence of cardiovascular death, myocardial infarction, or stroke, which was assessed in the intention-to-treat population. If non-inferiority was confirmed by an upper limit of the 95% CI for a hazard ratio of less than 1·30, closed testing for superiority was prespecified. This study is registered with ClinicalTrials.gov, number NCT02465515. Findings: Patients were screened between July 1, 2015, and Nov 24, 2016. 10 793 patients were screened and 9463 participants were enrolled and randomly assigned to groups: 4731 patients were assigned to receive albiglutide and 4732 patients to receive placebo. On Nov 8, 2017, it was determined that 611 primary endpoints and a median follow-up of at least 1·5 years had accrued, and participants returned for a final visit and discontinuation from study treatment; the last patient visit was on March 12, 2018. These 9463 patients, the intention-to-treat population, were evaluated for a median duration of 1·6 years and were assessed for the primary outcome. The primary composite outcome occurred in 338 (7%) of 4731 patients at an incidence rate of 4·6 events per 100 person-years in the albiglutide group and in 428 (9%) of 4732 patients at an incidence rate of 5·9 events per 100 person-years in the placebo group (hazard ratio 0·78, 95% CI 0·68–0·90), which indicated that albiglutide was superior to placebo (p<0·0001 for non-inferiority; p=0·0006 for superiority). The incidence of acute pancreatitis (ten patients in the albiglutide group and seven patients in the placebo group), pancreatic cancer (six patients in the albiglutide group and five patients in the placebo group), medullary thyroid carcinoma (zero patients in both groups), and other serious adverse events did not differ between the two groups. There were three (<1%) deaths in the placebo group that were assessed by investigators, who were masked to study drug assignment, to be treatment-related and two (<1%) deaths in the albiglutide group. Interpretation: In patients with type 2 diabetes and cardiovascular disease, albiglutide was superior to placebo with respect to major adverse cardiovascular events. Evidence-based glucagon-like peptide 1 receptor agonists should therefore be considered as part of a comprehensive strategy to reduce the risk of cardiovascular events in patients with type 2 diabetes. Funding: GlaxoSmithKline

CropPol: a dynamic, open and global database on crop pollination

This is the final version. Available from Wiley via the DOI in this record The original dataset (v1.1.0) of the CropPol database can be accessed from the ECOLOGY repository. Main upgrades of these datasets will be versioned and deposited in Zenodo (DOI: 10.5281/zenodo.5546600)Data availability. V.C. Computer programs and data-processing algorithms: The algorithms used in deriving, processing, or transforming data can be accessed in the DataS1.zip file and the Zenodo repository (DOI: 10.5281/zenodo.5546600). V.D. Archiving: The data is archived for long-term storage and access in Zenodo (DOI: 10.5281/zenodo.5546600)Seventy five percent of the world's food crops benefit from insect pollination. Hence, there has been increased interest in how global change drivers impact this critical ecosystem service. Because standardized data on crop pollination are rarely available, we are limited in our capacity to understand the variation in pollination benefits to crop yield, as well as to anticipate changes in this service, develop predictions, and inform management actions. Here, we present CropPol, a dynamic, open and global database on crop pollination. It contains measurements recorded from 202 crop studies, covering 3,394 field observations, 2,552 yield measurements (i.e. berry weight, number of fruits and kg per hectare, among others), and 47,752 insect records from 48 commercial crops distributed around the globe. CropPol comprises 32 of the 87 leading global crops and commodities that are pollinator dependent. Malus domestica is the most represented crop (32 studies), followed by Brassica napus (22 studies), Vaccinium corymbosum (13 studies), and Citrullus lanatus (12 studies). The most abundant pollinator guilds recorded are honey bees (34.22% counts), bumblebees (19.19%), flies other than Syrphidae and Bombyliidae (13.18%), other wild bees (13.13%), beetles (10.97%), Syrphidae (4.87%), and Bombyliidae (0.05%). Locations comprise 34 countries distributed among Europe (76 studies), Northern America (60), Latin America and the Caribbean (29), Asia (20), Oceania (10), and Africa (7). Sampling spans three decades and is concentrated on 2001-05 (21 studies), 2006-10 (40), 2011-15 (88), and 2016-20 (50). This is the most comprehensive open global data set on measurements of crop flower visitors, crop pollinators and pollination to date, and we encourage researchers to add more datasets to this database in the future. This data set is released for non-commercial use only. Credits should be given to this paper (i.e., proper citation), and the products generated with this database should be shared under the same license terms (CC BY-NC-SA). This article is protected by copyright. All rights reserved.OBServ Projec

Study of the dynamic behaviour of bulk metallic glasses under shock loading

Pour prémunir les structures spatiales d'impacts hyper-véloces, le secteur aérospatial est continuellement à la recherche de matériaux toujours plus performants. Dans cette optique, les verres métalliques massifs se présentent comme de potentiels éléments de blindages spatiaux. De récentes études ont mis en exergue une meilleure résistance à la pénétration de ces matériaux comparativement aux blindages actuels. Les impacts par lanceurs permettent d'étudier et caractériser le comportement sous chocs des matériaux. Cependant, les vitesses des projectiles se retrouvent actuellement limitées à 10 km/s, correspondant aux niveaux d'impacts hyper-véloces les plus modérés. Pour s'affranchir de cette limitation, il est possible de se tourner vers les lasers de puissance. Ces dispositifs permettent de générer des ondes de choc dont les niveaux de pression et de vitesse de déformation sont supérieurs aux lanceurs. Les travaux menés ont permis d'étudier et de caractériser le comportement et l'endommagement de plusieurs verres métalliques ternaires ZrCuAl sous choc laser. Plusieurs campagnes expérimentales ont été réalisées sur les installations du Laboratoire pour l'Utilisation des Lasers Intenses (LULI2000 et ELFIE). Une partie de l'équation d'état des nuances étudiées a été obtenue à la fois par choc laser et compression isentropique. Les processus d'endommagement, l'influence des vitesses de déformation et de composition sur la rupture ont été étudiés. Pour des régimes de vitesse de déformation supérieurs de trois ordres de grandeur à ceux disponibles dans la littérature, il a été mis en évidence que les verres métalliques étudiés présentaient une limite à la rupture cinq à dix fois supérieure.Space industry is always searching for efficient materials to protect space structures from high-velocity impacts. In this context, bulk metallic glasses appear as suitable elements of space debris shielding assemblies. Recent studies revealed a higher tolerance to impact of metallic glasses compared to materials currently used in shield assemblies. Gas-gun and powder launchers are usually used to study and characterize the dynamic and shock behaviour of materials. However, projectiles velocities are currently limited to 10 km/s, corresponding to the lowest high-velocity impacts levels. To overcome this limitation, one may consider shock waves induced by high-power laser facilities, whose pressure and strain rate levels can exceed those induced by canons. Hence, this work enabled to study and to characterize the dynamic and damage behaviours of several compositions of ternary ZrCuAl bulk metallic glasses subjected to shock waves induced by laser irradiation. Several experimental campaigns have been conducted on various laser facilities of the Laboratoire pour l'Utilisation des Lasers Intenses (LULI2000 and ELFIE). A part of the equation of state of the studied compositions was established using both shock waves and quasi-isentropic compressions. Damage processes and the composition and strain rate effects on fracture were also studied. For strain rate levels higher of three or more orders of magnitude than those available in the literature, it was shown that studied bulk metallic glasses displayed a five to ten times higher dynamic tensile limit

Étude du comportement dynamique sous choc des verres métalliques massifs

Space industry is always searching for efficient materials to protect space structures from high-velocity impacts. In this context, bulk metallic glasses appear as suitable elements of space debris shielding assemblies. Recent studies revealed a higher tolerance to impact of metallic glasses compared to materials currently used in shield assemblies. Gas-gun and powder launchers are usually used to study and characterize the dynamic and shock behaviour of materials. However, projectiles velocities are currently limited to 10 km/s, corresponding to the lowest high-velocity impacts levels. To overcome this limitation, one may consider shock waves induced by high-power laser facilities, whose pressure and strain rate levels can exceed those induced by canons. Hence, this work enabled to study and to characterize the dynamic and damage behaviours of several compositions of ternary ZrCuAl bulk metallic glasses subjected to shock waves induced by laser irradiation. Several experimental campaigns have been conducted on various laser facilities of the Laboratoire pour l'Utilisation des Lasers Intenses (LULI2000 and ELFIE). A part of the equation of state of the studied compositions was established using both shock waves and quasi-isentropic compressions. Damage processes and the composition and strain rate effects on fracture were also studied. For strain rate levels higher of three or more orders of magnitude than those available in the literature, it was shown that studied bulk metallic glasses displayed a five to ten times higher dynamic tensile limit.Pour prémunir les structures spatiales d'impacts hyper-véloces, le secteur aérospatial est continuellement à la recherche de matériaux toujours plus performants. Dans cette optique, les verres métalliques massifs se présentent comme de potentiels éléments de blindages spatiaux. De récentes études ont mis en exergue une meilleure résistance à la pénétration de ces matériaux comparativement aux blindages actuels. Les impacts par lanceurs permettent d'étudier et caractériser le comportement sous chocs des matériaux. Cependant, les vitesses des projectiles se retrouvent actuellement limitées à 10 km/s, correspondant aux niveaux d'impacts hyper-véloces les plus modérés. Pour s'affranchir de cette limitation, il est possible de se tourner vers les lasers de puissance. Ces dispositifs permettent de générer des ondes de choc dont les niveaux de pression et de vitesse de déformation sont supérieurs aux lanceurs. Les travaux menés ont permis d'étudier et de caractériser le comportement et l'endommagement de plusieurs verres métalliques ternaires ZrCuAl sous choc laser. Plusieurs campagnes expérimentales ont été réalisées sur les installations du Laboratoire pour l'Utilisation des Lasers Intenses (LULI2000 et ELFIE). Une partie de l'équation d'état des nuances étudiées a été obtenue à la fois par choc laser et compression isentropique. Les processus d'endommagement, l'influence des vitesses de déformation et de composition sur la rupture ont été étudiés. Pour des régimes de vitesse de déformation supérieurs de trois ordres de grandeur à ceux disponibles dans la littérature, il a été mis en évidence que les verres métalliques étudiés présentaient une limite à la rupture cinq à dix fois supérieure

Sujet de thèse en cours : Étude du comportement dynamique sous choc des verres métalliques massifs [Soutenance 22.11.2018]

supervisors Jean-Christophe Sangleboeuf (department of mechanics and glass) and Laurent Berthesous la direction de Jean-Christophe Sangleboeuf dans le département de Mécanique et Verres et de Laurent Berth

Zr-based bulk metallic glasses equation of state under laser shock compression and spall strength

International audienc

Zr-based bulk metallic glasses equation of state under laser shock compression and spall strength

International audienc

Zr-based bulk metallic glasses equation of state under laser shock compression and spall strength

International audienc