A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates

This study presents a constitutive model for steels exhibiting SIMT, based on previous seminal works, and the corresponding methodology to estimate their parameters. The model includes temperature effects in the phase transformation kinetics, and in the softening of each solid phase through the use of a homogenization technique. The model was validated with experimental results of dynamic tensile tests on AISI 304 sheet steel specimens, and their predictions correlate well with the experimental evidence in terms of macroscopic stress–strain curves and martensite volume fraction formed at high strain rates. The work shows the value of considering temperature effects in the modeling of metastable austenitic steels submitted to impact conditions. Regarding most of the works reported in the literature on SIMT, modeling of the martensitic transformation at high strain rates is the distinctive feature of the present paper.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG10-UC3M/DPI-5596)) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2008-06408) for the financial support received which allowed conducting part of this work. The authors express their thanks to Mr. Philippe and Mr. Tobisch from the company Zwick for the facilities provided to perform the tensile tests at high strain rates

A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates

This study presents a constitutive model for steels exhibiting SIMT, based on previous seminal works, and the corresponding methodology to estimate their parameters. The model includes temperature effects in the phase transformation kinetics, and in the softening of each solid phase through the use of a homogenization technique. The model was validated with experimental results of dynamic tensile tests on AISI 304 sheet steel specimens, and their predictions correlate well with the experimental evidence in terms of macroscopic stress–strain curves and martensite volume fraction formed at high strain rates. The work shows the value of considering temperature effects in the modeling of metastable austenitic steels submitted to impact conditions. Regarding most of the works reported in the literature on SIMT, modeling of the martensitic transformation at high strain rates is the distinctive feature of the present paper.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG10-UC3M/DPI-5596)) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2008-06408) for the financial support received which allowed conducting part of this work. The authors express their thanks to Mr. Philippe and Mr. Tobisch from the company Zwick for the facilities provided to perform the tensile tests at high strain rates

Experimental survey on the behaviour of AISI 304 steel sheets subjected to perforation

This paper presents and analyzes the behaviour of AISI 304 steel sheets subjected to perforation under a wide range of impact velocities. The relevance of this steel resides in the potential transformation of austenite into martensite during mechanical loading. This process leads to an increase in strength and ductility of the material. It makes the AISI 304 attractive for many engineering applications, especially for building structural elements responsible for absorbing energy under fast loading. However, this transformation takes place only under determined loading conditions strongly dependent on initial temperature and deformation rate. In order to study the material behaviour under impact loading, perforation tests have been performed at room temperature using both, a drop weight tower and a pneumatic gas gun within the range of impact velocities 2.5 m/s≤V0≤85 m/s. The results are compared with those reported in [18] and [21] for ES steel and TRIP 1000 steel. The comparison highlights the good performance of the AISI 304 under high loading rates. Martensitic transformation taking place in this steel during perforation is identified responsible for such behaviour

Mechanical charecterization and analytical modeling of the thermo-viscoplastic behaviour AISI 304 steel under wide ranges of strain rates at room temperature

In this investigation, the thermo-viscoplastic behaviour of the steel AISI 304 has been examined. The experimental characterization of the material has been conducted in tension under wide ranges of strain rates.An analytical description of the macroscopic behaviour of this metal is reported. For such goal, the extended Rusinek-Klepaczko model to viscous drag effects is applied.It allows for proper description of the material behaviour within the whole range of loading conditions considered.In addition, the analytical formulation proposed gathers limited number of material constants and simple calibration procedure

Chemical inhibition of NAT10 corrects defects of laminopathic cells.

Down-regulation and mutations of the nuclear-architecture proteins lamin A and C cause misshapen nuclei and altered chromatin organization associated with cancer and laminopathies, including the premature-aging disease Hutchinson-Gilford progeria syndrome (HGPS). Here, we identified the small molecule "Remodelin" that improved nuclear architecture, chromatin organization, and fitness of both human lamin A/C-depleted cells and HGPS-derived patient cells and decreased markers of DNA damage in these cells. Using a combination of chemical, cellular, and genetic approaches, we identified the acetyl-transferase protein NAT10 as the target of Remodelin that mediated nuclear shape rescue in laminopathic cells via microtubule reorganization. These findings provide insights into how NAT10 affects nuclear architecture and suggest alternative strategies for treating laminopathies and aging.We thank Imagif and Institut de Chimie des Substances Naturelles, centre de recherche CNRS de Gif-sur-Yvette, France, for proteomic analysis. Research in the Jackson laboratory is funded by Cancer Research UK program grant 11 C6/A11224, the European Research Council, and the European Community Seventh Framework Programme grant agreement no. HEALTH-F2-2010-259893 (DDR). Core funding is provided by CRUK (C6946/A14492) and the Wellcome Trust (WT092096). S.P.J. receives his salary from the University of Cambridge, UK, supplemented by CRUK. D.L is funded by an EMBO Long-term fellowship ALTF 834-2011 and by a Project Grant from the Medical Research Council, UK MR/L019116/1, S.B. was funded by an EMBO Long-Term fellowship ALTF 93-2010 and Cancer Research UK. R.R. is supported by the Centre National de la Recherche Scientifique. M.D. is supported by the European Research Council grant DDREAM.

L’inhibition chimique de NAT10 corrige les défauts des cellules laminopathiques

La lamina nucléaire maintient l’architecture du noyau Chez les eucaryotes, la membrane interne du noyau est bordée d’un maillage de protéines fibrillaires appelé lamina nucléaire, composé des protéines dénommées lamines, incluant les lamines A et C [1]. La lamina nucléaire est un élément crucial du maintien de l’architecture et de la forme du noyau, ainsi que de l’organisation globale de la chromatine, car elle sert de plateforme d’ancrage pour l’hétérochromatine et pour les régions télomériques [2, 3]. La lamina fait aussi le lien entre le noyau et le cytosquelette car elle interagit avec des protéines transmembranaires telles que SUN1 (Sad1 and UNC84 domain containing 1) ou les protéines nesprines [4]. Ces propriétés de la lamina expliquent son rôle essentiel dans l’organisation structurelle de la cellule. De ce fait, les mutations des gènes codant pour les lamines sont associées à un large éventail de maladies, regroupées sous le nom de laminopathies [5], dont fait partie le syndrome de vieillissement prématuré Hutchinson-Gilford progeria syndrome (HGPS)

La lecture, les formes et la vie : Entretien avec Marielle Macé

Dans son dernier livre, Façons de lire, manières d’être, Marielle Macé replace l’expérience de lecture à l’intérieur d’une vaste « stylistique de l’existence » ; elle établit un lien entre cet élargissement de la question du style aux formes de la vie, et ce que nous pouvons attendre des livres : la lecture lui apparaît comme l’une de ces conduites par lesquelles, quotidiennement, nous donnons un aspect, une figure, des formes, des rythmes, quelque chose comme « un style » à notre existence. Son ouvrage part d’une réinterprétation des rapports entre la littérature et la vie ; il pose que c’est dans la vie elle-même que les œuvres se tiennent, déposent leurs traces et exercent leur force. Il n’y a pas d’un côté la littérature, et de l’autre la vie ; il y a au contraire, dans la vie elle-même, des formes, des images, des styles d’être qui circulent entre les sujets et les œuvres, qui les exposent, les animent, les affectent, les transforment (ou les laissent indifférents). En sorte que les formes littéraires se proposent dans la lecture comme de véritables phrasés de la vie, engageant des conduites, des rythmes, des puissances de façonnement, des valeurs pratiques. Dans l’expérience ordinaire et extraordinaire de la lecture, chacun peut alors se réapproprier son rapport à soi, à son langage, à ses possibles, à ses modes d’être, et la littérature apparaît comme le lieu où se médite ce qu’il entre de formes dans la vie

Numerical simulation of the effect of adiabatic temperature increase in martensitic transformation of austenitic steels

This work presents a constitutive model for metastable austenitic steels exhibiting Strain Induced Martensitic Transformation (SIMT). Based on the description of the kinetics of phase transformation proposed by Olson and Cohen [3], and later generalized to 3D by Stringfellow et al. [7] and Papatriantafillou et al. [4], this model includes the effect of temperature increase on the kinetics of SIMT and on the thermal softening of the phases. This allows capturing relevant phenomena exhibited by metastable austenitic steels when subjected to plastic deformation at high strain rates. A systematic procedure for the identification of the constitutive parameters has been proposed. The predictions of the constitutive description are compared with experiments for the austenitic steel AISI 304 provided by Rodríguez-Martínez et al. [6]. Good correlation between experiments and modelling are achieved in terms of macroscopic strain-stress curves and volume fraction of martensite formed during straining

Numerical Simulation of the effect adiabatic temperature increase in martensitic transformation of austenitic steels

The predictions of the constitutive model agree with experimental results in terms of macroscopy stress-strain curves and volume fraction of martensite formed during loadin

Experimental survey on the behaviour of AISI 304 steel sheets subjected to perforation

This paper presents and analyzes the behaviour of AISI 304 steel sheets subjected to perforation under a wide range of impact velocities. The relevance of this steel resides in the potential transformation of austenite into martensite during mechanical loading. This process leads to an increase in strength and ductility of the material. It makes the AISI 304 attractive for many engineering applications, especially for building structural elements responsible for absorbing energy under fast loading. However, this transformation takes place only under determined loading conditions strongly dependent on initial temperature and deformation rate. In order to study the material behaviour under impact loading, perforation tests have been performed at room temperature using both, a drop weight tower and a pneumatic gas gun within the range of impact velocities 2.5 m/s≤V0≤85 m/s. The results are compared with those reported in [18] and [21] for ES steel and TRIP 1000 steel. The comparison highlights the good performance of the AISI 304 under high loading rates. Martensitic transformation taking place in this steel during perforation is identified responsible for such behaviour