Comparative study of phenomenological coupled damage models - Application to industrial forming processes

International audienceXue's damage model [Xue, 2007] accounts for the third invariant of deviatoric stress tensor, allowing a better balance between respective effects of shear and elongation on damage. It has been implemented in Forge® Finite Element (FE) software to investigate ductile damage occurring during industrial forming processes. Material and damage parameters identification has been carried out for both Xue and Lemaître models. Application to wire drawing followed by flat rolling shows that in such shearinducing processes, both models predict damage at different locations, due to their different emphasis on shear with respect to elongational strain damage

Damage Prediction Using Several Types of Macro-scale Damage Models in Different Cold Wire Production Lines

International audienceThe purpose of the present paper is to show how and to what extent the introduction of refined, shear sensitive models improves on previous ones, based on triaxiality only, for the phenomenological description of ductile damage in bulk cold metal forming processes. Wire-drawing and wire rolling are taken as examples. A set of mechanical tests has been conducted: round bar tension, notched bar tension, plane strain tension, and torsion for pure shear deformation. Both constitutive and damage model parameters have been carefully identified, with back-computation of the laboratory tests for validation. Application of the models to the cold forming processes, described here, shows the superiority of the shear-enhanced models for locating maximum damage in flat wire rolling, where a significant amount of shear is present (“blacksmith's cross” deformation pattern). On the contrary, it proves unnecessary for low-shear processes such as wire-drawing. The cavity-growth Gurson-Tvergaard-Needleman model seems to be the best basis for damage prediction in patented high carbon steel, a very ductile material

Static two-body potential at fifth post-Newtonian order

We determine the gravitational interaction between two compact bodies up to the sixth power in Newton's constant GN, in the static limit. This result is achieved within the effective field theory approach to General Relativity, and exploits a manifest factorization property of static diagrams which allows to derive static post Newtonian (PN) contributions of (2n+1)-order in terms of lower order ones. We recompute in this fashion the 1PN and 3PN static potential, and present the novel 5PN contribution.Comment: 7 pages, 3 figures. In v2: references added, published on PR

Optimization of a range of 2D and 3D bulk forming processes by a meta-model assisted evolution strategy

International audienceAfter decades of developing efficient software, FORGE, for bulk metal forming simulation, its coupling with an optimization algorithm is considered in order to solve the actual engineering problem, the design problem, using the meta-model assisted evolution strategy proposed by Emmerich et al. The first application regards the shape optimization of a cylindrical preform to produce a crankshaft by closed die forging. It aims at minimizing the volume of the material while satisfying the filling of the dies. In the second application, the open die forging of an axisymmetric thick plate is considered. The objective is to optimize the initial geometry in order to minimize the material weight while overlapping a prescribed geometry at the end of forging. The third example regards a four-stepped wire drawing sequence. In order to prevent the formation of cracks, it is desired to minimize a damage criterion while keeping the targeted diameter of the final wire. The geometries of the four dies are optimized: reduction ratio, die angle and die length. The necessary calculations are run in parallel, by using both the parallel version of the software and by evaluating several designs at the same time

Impact of mechanical anisotropy on flat-rolled wires geometry

International audienceA precise final geometry of flat-rolled wires is required in view of their industrial applications. However, comparison between experimental and computed cross-sections shows a gap of 10%. This difference might originate in the anisotropy introduced by wire drawing. Coefficients of an anisotropic constitutive model (Hill 48) have been identified from transverse compression tests. Then Lam3®, a finite element software, has been used to simulate rolling passes. The anisotropic law previously established significantly improves the estimation of the final width: yet the underestimation of the experimental width is 5% instead of 10%. Possible ways for further improvement are discussed

Generación de empresas de base tecnológica spin-off basadas en el desarrollo de investigación científica aplicada patentable de la Facultad de Farmacia y Bioquímica de la Universidad Nacional Mayor de San Marcos

Determina el potencial para la creación de empresas de base tecnológica (Spin-off), originada de la actividad investigadora patentable en la Facultad de Farmacia y Bioquímica de la Universidad Nacional Mayor de San Marcos, como una forma de retribuir económicamente el tiempo de investigación e inversión y como un medio de transferencia tecnológica, lo que motiva a buscar resultados de investigación para formar empresas con productos exclusivos. Se inicia el estudio realizando un análisis del nivel de cultura emprendedora a partir de la investigación científica, recopilada en un cuestionario aplicado a docentes y alumnos, utilizando escala Likert, registrando: el grado de conocimiento de la base legal de la universidad; el grado de importancia para las actividades dirigidas a la detección fomento de la cultura emprendedora; importancia de la búsqueda, detección, valorización y seguimiento de ideas de negocio; y finalmente la percepción que tienen del entorno para la creación de empresa. Según los resultados obtenidos hay falta de apoyo operativo, legal y administrativo, esta carencia puede deberse a una parvedad en el incentivo de cultura emprendedora en la comunidad universitaria. Posteriormente se evaluó la patentabilidad de la investigación realizada durante el periodo 2008-2010, presentando aquellas investigaciones que cumplen con todas las características para ser protegidas por una patente. Luego se demuestra la viabilidad de la creación de empresa, con la evaluación del atractivo tecnológico – posición competitiva de la idea de negocio, se planteó el desarrollo de un Spin-off universitaria (SOU) con miras a identificar competencias y estrategias que fomente su creación, buscando el soporte se revisó la base legal de la universidad. Finalmente, a la luz de los resultados encontrados, se propone una serie de recomendaciones que sirvan para la mejora en la orientación de la investigación realizada para la creación empresas, sin embargo, es una primera aproximación a este tema, se requiere más investigación en cada uno de estos frentes para que puedan realizarse en la práctica.Tesi

Estudio comparativo del material granular proveniente de la cantera Sojo - Sullana para sub bases de pavimentos flexibles con adición del polímero PET reciclado

En nuestra localidad de Piura, los problemas que saltan a la vista son el rápido deterioro de la infraestructura vial, esto se debe principalmente a la dificultad de obtener materiales granulares de calidad adecuada; debido a eso el ingeniero debe emplear materiales granulares de baja calidad con respecto a las especificaciones técnicas que el ministerio de transportes exige. En este caso el ingeniero debe intentar mejorar las propiedades del material ya sea por medios químicos o mecánicos. Así, En nuestra investigación se utilizó el PET (Tereftalato de Polietileno) reciclado como material aditivo, para modificar el comportamiento de una sub base granular. A partir de ensayos como Proctor modificado y CBR (california bearing ratio), se comparó el comportamiento del material natural de la cantera Sojo de la ciudad de Sullana con la alternativa del proyecto, el cual fue combinado con diferentes porcentajes (3%, 2%, 1%, 0.5%) de PET reciclado. Los resultados de la investigación nos ayudaron a determinar que con la adición de cierto porcentaje de PET (0.5%, 1% y 2%) aumenta el CBR, disminuye su peso y los costos de realizar una mejora de sub bases disminuye. Con esta investigación tenemos una propuesta eco amigable ya que tendríamos un CBR mejorado a menor costo reduciendo hasta un 7% y a su vez, cuidaríamos el medio ambiente, ya que las botellas plásticas que son las que más se desechan podrían ser reutilizables siempre y cuando sean PET.In our locality of Piura, the problems that are in sight are the improvement of the road infrastructure, this is mainly due to the difficulty of obtaining granular materials of adequate quality; Because of this, the engineer must use low quality granular materials with respect to the technical specifications that the transport ministry requires. In this case, the engineer must try to improve the properties of the material and the chemical or mechanical means. Thus, in our research it refers to recycled PET (Polyethylene Terephthalate) as an additive material, to modify the behavior of a granular subbase. From tests such as modified Proctor and CBR (relationship of bearings from California), the behavior of the natural material of the Sojo quarry of the city of Sullana was compared with the alternative of the project, which was combined with different percentages (3%, 2%, 1%, 0.5%) of recycled PET. The results of the research helped us to determine what was obtained as well as the PET, the CBR, the weight and the costs of an improvement of the bases. With this research we have an ecofriendly proposal that we would have a CBR we improve a lower cost and once again, we take care of the environment, and that the plastic bottles are easier to use.Tesi

Diversity regained: Precautionary approaches to COVID-19 as a phenomenon of the total environment

As COVID-19 emerged as a phenomenon of the total environment, and despite the intertwined and complex relationships that make humanity an organic part of the Bio- and Geospheres, the majority of our responses to it have been corrective in character, with few or no consideration for unintended consequences which bring about further vulnerability to unanticipated global events. Tackling COVID-19 entails a systemic and precautionary approach to human-nature relations, which we frame as regaining diversity in the Geo-, Bio-, and Anthropospheres. Its implementation requires nothing short of an overhaul in the way we interact with and build knowledge from natural and social environments. Hence, we discuss the urgency of shifting from current to precautionary approaches to COVID-19 and look, through the lens of diversity, at the anticipated benefits in four systems crucially affecting and affected by the pandemic: health, land, knowledge and innovation. Our reflections offer a glimpse of the sort of changes needed, from pursuing planetary health and creating more harmonious forms of land use to providing a multi-level platform for other ways of knowing/understanding and turning innovation into a source of global public goods. These exemplary initiatives introduce and solidify systemic thinking in policymaking and move priorities from reaction-based strategies to precautionary framework

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030