1,559 research outputs found
Influence of projectile shape on dynamic behavior of steel sheet subjected to impact and perforation
Get PDFAuthors thank Ministry of Science and Higher Education of Poland for financial support under Grants: R00 0097 12. Authors thank also M. Tavian technician in electronics from ENIM for his contribution on the development of the residual velocity measurement sensors.The paper describes a work focused on the process of perforation of steel sheet.Experimental,analytical and numerical investigations have been carried out to analyze in details the perforation process.Based on these approaches,the ballistic properties of the material and the failure modes depending on the projectile nose shape(conical,blunt or hemispherical) have been studied.Different failure modes have been observed,including petaling, plug ejection and circumference necking.The special study about the number of petals has been done for different nose angles using conical shape projectiles.The complete energy balance is also reported and the absorbed energy by the steel sheet has been obtained by measuring initial and residual projectile velocities.A wide range of impact velocities from 35to180m/s has been covered during the tests.All the projectiles are 13mm in diameter and the plates are1mm thick.Moreover,the mass ratio(projectile mass/steel sheet mass) and the ratio between the span of the steel sheet and the diameter of the projectile are constant, equal to 0.38 and 3.85, respectively
Alexis Wright interview
No full textCoincidentally tonight, as governments continue to grapple with the on-going social crisis in Aboriginal communities, Indigenous author Alexis Wright has just been announced as the winner of the Miles Franklin Award, Australia's most prestigious literary prize, for her second novel Carpentaria. An Indigenous member of the Waanyi nation of Queensland's far north, and long-time activist on Aboriginal affairs, Alexis Wright's sweeping, poetic book explores the rich mythology, chequered history and present day drama of her Gulf country homeland, and was praised by judges as the standout in a highly competitive field, which included dual Booker Prize winner, Peter Carey
A brief conversation with Alexis Wright
No full textAn interview with the author Alexis Wright is presented. When asked about her interest in books, she explains that she is reading a series of natural history books. She also comments on her interest in travel and the process of writing another novel. The challenges of the writing process are also explored
Episode 35: Alexis Castellanos, Author of “Isla to Island”, and Her Panel Presentation during the Operación Pedro Pan Two-Day Event
No full textIn Part 1 of “Operación Pedro Pan: The Voices and Stories of Cuba’s Child Exodus—A Knights HistoryCast Mini-Series,” the Department of History’s Sebastian Garcia talked with Alexis Castellanos, an author, illustrator, graphic novelist, and a panelist at the esteemed, conspicuous, and powerful “Operación Pedro Pan: Honoring the Cultural, Historical Legacy of Cuba’s Child Exodus” Two-Day Program that Florida Humanities, UCF’s Department of English and Department of Modern Languages and Literatures sponsored (see https://cah.ucf.edu/pedro-pan/ for more details on sponsors and the program in general).
Sebastian structured this specific episode on Alexis Castellanos’ Isla to Island, a wordless graphic novel grounded by her personal family history and the history of Operación Pedro Pan (Operation Peter Pan). By analyzing such a historic event through the medium of fiction, Sebastian argued that this is one of the most unique Knights HistoryCast episodes of all time. Naturally, their conversation expanded to what she talked about during her panel presentation in Panel One, Day 1 of the event that featured “internationally renowned scholars that discussed the political, historical, and cultural legacy of Operación Pedro Pan (1960-1962).” (https://cah.ucf.edu/pedro-pan/)
To purchase Isla to Island (strongly recommend), check out: https://islatoisland.com/.
To find out more about Alexis and her professional work, check out her website at https://alexiscastellanos.com/https://stars.library.ucf.edu/knightshistorycast/1034/thumbnail.jp
THE MYSTIC ROAD : SELECTED POEMS - ALEXIS KARPOUZOS
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Alexis karpouzos (born on April 09, 1967) is a philosopher, author, spiritual master and pioneer of higher consciousness. He is author of several books on philosophy, metaphysics, spirituality, modern science. His most famous books are: ‘’Universal consciousness’’, ‘’non-duality’’, ‘’An ocean of souls’’, ‘’Beyond the heaven’’. Alexis Karpouzos is also a recording artist. He has recorded two music albums and twenty-four singles songs. He has also appeared in two documentary films, television and radio productions. He is the pioneer of the post-ontology consciousness and the wisdom of universal wholeness. The global language of poetry of Alexis Karpouzos, by following the paths of wisdom, is a vehicle for transmitting human knowledge and values, history, ancient traditions, and links with nature. It transmits the human values and worldly knowledge that are essential for opening ourselves to the Other. Poetic creation, therefore, forges very strong links between humans -it transcends beyond languages, beliefs and cultures. Each poem appears in its original form, in a vibrant celebration of life, diversity, language, and the enduring power of poetry. At a time when the Humanities are under threat, this book offers a defense of poetry within the context of growing interest in mindfulness in spirituality, in consciousness, in art, in education.</p
Experimental characterization and behavior modeling of 304 stainless steel under various strain rates and temperatures
No full textL’acier inox austénitique 304 est utilisé pour de nombreuses applications industrielles, notamment à cause de l’effet TRIP qui lui confère des propriétés particulières. Au cours de son élaboration ou lorsqu’il est utilisé en service, il peut être soumis à différentes vitesses de déformation et températures. Le travail présenté ici vise à étudier le comportement de cet acier sous différents trajets de chargement. Tout d’abord, un système de refroidissement a été ajouté aux barres de Hopkinson pour étudier le comportement de cet acier en compression avec des vitesses de déformation comprises entre 0.001 s-1 et 3000 s-1 et des températures entre -163°C et 172°C. Le modèle de Rusinek-Klepaczko, qui prend en compte le phénomène de transformation martensitique, a été utilisé en parallèle pour simuler son comportement thermo-viscoplastique. Pour les vitesses de déformation au-delà de 3000 s-1, un nouveau design d’éprouvette de cisaillement a ensuite été proposé et validé et l’effet de la vitesse de déformation entre 3000 s-1 et 39000 s-1 a été étudié. Enfin, un autre système de refroidissement a été développé pour les essais d’impact et de perforation à différentes vitesses (entre 80 et 180 m.s-1) et températures (entre -163°C et 200°C) et les lois de comportement ont été validées en comparant expériences et simulations numériques.Due to the unique Transformation Induced Plasticity (TRIP) effect, 304 austenitic stainless steel (ASS) is widely used in many engineering areas. During working and manufacturing process or in service, it may undergo deformation over a wide range of strain rates and temperatures. The current work presents a systematic deformation behavior study of 304 ASS by both experiments and numerical simulations. With an original cooling device coupled to the split Hopkinson pressure bar system, the compression behavior at strain rates between 0.001 s-1 and 3000 s-1 and temperatures between -163°C and 172°C was investigated. An extension of the Rusinek-Klepaczko (RK) model considering strain-induced martensitic transformation (SIMT) phenomenon was also used to simulate the thermo-viscoplastic behavior of this steel. To study the deformation behavior at extremely high strain rates exceeding 3000 s-1, a new single shear zone (SSS) specimen has been proposed and validated. Then, the effects of strain rate between 3000 s-1 and 39000 s-1 was analyzed. Finally, with a specially designed cooling device, the ballistic impact behavior under initial projectile velocities between 80 and 180 m.s-1 and temperatures between -163°C and 200°C was studied. By comparison between experiments and numerical simulations for perforation, the previously obtained constitutive relations were validated
EXPERIMENTAL CHARACTERISATION AND MODELLING OF THE THERMO-VISCOPLASTIC BEHAVIOUR OF STEEL AISI 304 WITHIN WIDE RANGES OF STRAIN RATE AT ROOM TEMPERATURE
No full textInternational audienceIn this investigation, thermo-viscoplastic behaviour of austenitic steel AISI 304 has been characterised in tension under wide ranges of strain rate at room temperature. This metal possesses an elevated strain hardening rate and ductility which enhance its capability for absorbing energy under mechanical 1028 A. Rusinek et al. loading. It has been observed that the rate sensitivity of the material is independent of plastic strain. Moreover, it has been noticed that beyond a certain level of loading rate the flow stress of the material sharply increases. In agreement with experimental evidences reported in the literature, this behaviour is assumed to be caused by the drag deformation mode taking place at high strain rates. Based on such considerations, the thermo-viscoplastic behaviour of the material has been macroscopically modelled by means of the extended Rusinek-Klepaczko model to viscous drag effects. Satisfactory matching has been found between the experiments and analytical predictions provided by the constitutive relation
Study of the dynamic behavior and thermoviscoplastic modeling of steel sheet subjected to ballistic impact
No full textCe travail de thèse a pour but de contribuer à l'étude du comportement thermomécanique des matériaux métalliques soumis à un impact balistique. Des études expérimentales, analytiques et numériques ont été réalisées pour analyser en détail le processus de perforation. Deux matériaux ont été étudiés au cours de ce travail : un acier doux ES et un acier IF. Dans un premier temps, des essais de caractérisation mécanique (traction et compression quasi-statique et dynamique) ont été réalisés en vue de la modélisation du comportement mécanique des matériaux étudiés. Les résultats montrent que l'acier doux ES et l'acier IF sont très sensibles à la vitesse de déformation. Deux modèles constitutifs, l'un empirique (Johnson-Cook) et l'autre semi-physique (Rusinek-Klepaczko) ont été utilisés pour modéliser le comportement thermoviscoplastique des matériaux. Une identification complète des constantes définissant les deux modèles a été réalisée pour chaque matériau en vue de l'implémentation des lois dans un code éléments finis pour la simulation numérique des essais d'impact et de perforation. Le comportement à l'impact des matériaux a ensuite été étudié. Les essais d'impact et de perforation ont été réalisés à l'aide d'un canon à gaz. L'influence de la géométrie du projectile, des propriétés mécaniques du matériau le constituant, de l'épaisseur de la cible et de sa configuration (sandwich ou monolithique) sur le processus de perforation a été analysée. Les résultats montrent que le mode de rupture, la limite balistique et la capacité d'absorption d'énergie de la cible métallique sont fortement liés à la forme du projectile utilisé. Il a été montré que les cibles métalliques monolithiques résistent mieux à la perforation que les configurations sandwichs (épaisseur totale inférieure ou égale à 4 mm). En outre, il a été trouvé que la limite balistique de la cible est fortement influencée par la rigidité du projectile utilisé. Enfin un modèle EF 3D a été développé permettant de simuler le comportement mécanique des cibles métalliques soumises à l'impact et à la perforation. Les résultats issus des prévisions numériques ont été comparés aux résultats expérimentaux. Il a été observé de façon globale un bon accord entre les prévisions numériques et l'expérience notamment en termes de courbes balistiques, d'énergie absorbée, de modes de rupture et de temps de rupture pour chaque type de projectile. Les résultats numériques montrent l'importance d'une description précise du comportement des matériaux dans les conditions dynamiques basée sur des expériences de laboratoire incluant les effets d'adoucissement thermique, d'écrouissage et de sensibilité à la vitesse de déformation, dans la modélisation numérique de processus physiquesThis thesis aims to contribute to the study of the thermo-mechanical behaviour of metallic materials subjected to ballistic impact. Experimental, analytical and numerical studies were performed to analyze in details the process of perforation. Two materials have been investigated in this work : mild steel ES and IF steel. As a first step, mechanical characterization tests (tensile and compression tests under quasi-static and dynamic conditions) As have been made towards to modeling the mechanical behaviour of the materials studied. The results show that mild steel ES and IF steel are highly susceptible to the strain rate. Two constitutive equations, one empirical (Johnson-Cook) and other semi-physical (Rusinek-Klepaczko) were used to model the thermoviscoplastic behaviour of materials. A complete identification of constants defining the two models was carried out for each material in order to implements the constitutive laws into a finite element code for the numerical simulation of impact and perforation tests. The behaviour of materials under impact was then examined. The effect of the projectile shape, the mechanical properties of the projectile material, the target thickness and it is configuration (monolithic or sandwich) on the perforation process was analyzed. The results show that the failure mode, the ballistic limit and the energy absorption power of the metal target are strongly related to the shape of the projectile used. It has been shown that the monolithic targets plates are more strong to be perforate than the sandwich configurations (total thickness less than or equal to 4 mm). In addition, it was found that the ballistic limit of the target is strongly influenced by the rigidity of the projectile used. Finally, a 3D FE model was developed to simulate the mechanical behaviour of metal targets subjected to ballistic impact. The results from the numerical predictions were compared with experiments. It has been observed globally a good agreement between the numerical predictions and experiments especially in terms of ballistic curves, energy absorbed, failure modes and failure time for each kind of projectile. The numerical results show the importance of an accurate description of materials behaviour under dynamic conditions based on laboratory experiments including thermal softening effects, strain hardening and strain rate sensitivity in numerical modeling of physical processe
Material Behavior Description for a Large Range of Strain Rates from Low to High Temperatures: Application to High Strength Steel
No full textInternational audienceCurrent needs in the design and optimization of complex protective structures lead to the development of more accurate numerical modelling of impact loadings. The aim of developing such a tool is to be able to predict the protection performance of structures using fewer experiments. Considering only the numerical approach, the most important issue to have a reliable simulation is to focus on the material behavior description in terms of constitutive relations and failure model for high strain rates, large field of temperatures and complex stress states. In this context, the present study deals with the dynamic thermo-mechanical behavior of a high strength steel (HSS) close to the Mars ® 190 (Industeel France, Le Creusot, France). For the considered application, the material can undergo both quasi-static and dynamic loadings. Thus, the studied strain rate range is varying from 10 −3-10 4 s −1. Due to the fast loading time, the local temperature increase during dynamic loading induces a thermal softening. The temperature sensitivity has been studied up to 473 K under quasi-static and dynamic conditions. Low temperature measurements (lower than the room temperature) are also reported in term of σ − ε|˙ε ,T curves. Experimental results are then used to identify the parameters of several constitutive relations, such as the model developed initially by Johnson and Cook; Voyiadjis and Abed; and Rusinek and Klepaczko respectively termed Johnson-Cook (JC), Voyiadjis-Abed (VA), and Rusinek-Klepaczko (RK). Finally, comparisons between experimental results and model predictions are reported and compared
Mechanical charecterization and analytical modeling of the thermo-viscoplastic behaviour AISI 304 steel under wide ranges of strain rates at room temperature
No full textInternational audienceIn 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
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