Finite element simulation of semi-finishing turning of Electron Beam Melted Ti6Al4V under dry and cryogenic cooling

open6noIn the last few years, important step forwards have been made on Finite Element Simulation of machining operations. Wrought Ti6Al4V alloy has been deeply investigated both numerically and experimentally due to its wide application in the industry. Recently, Additive Manufacturing technologies as the Electron Beam Melting and the Direct Melting Laser Sintering are more and more employed in the production of biomedical and aeronautical components made of Ti6Al4V alloy. Fine acicular microstructures are generated by the application of additive manufacturing technologies, affecting the mechanical properties and the machinability. By the consequence, this peculiarity has to be considered in modelling the material behaviour. In this work, a numerical analysis of cylindrical external turning on Electron Beam Melted (EBM) Ti6Al4V alloy is presented. A Johnson-Cook constitutive equation was implemented as a flow stress model and adapted with respect to the wrought Ti6Al4V alloy. The model was calibrated and validated through the cutting forces and temperatures measurements acquired under dry and cryogenic lubricating conditions.openBordin, A; Imbrogno, S.; Rotella, G.; Bruschi, S.; Ghiotti, A.; Umbrello, D.Bordin, Alberto; Imbrogno, S.; Rotella, G.; Bruschi, Stefania; Ghiotti, Andrea; Umbrello, D

Finite element modeling of microstructural changes in hard machining of SAE 8620

Surface and subsurface microstructural characterization after machining operations is a topic of great interest for both academic and industrial research activities. This paper presents a newly developed finite element (FE) model able to describe microstructural evolution and dynamic recrystallization (DRX) during orthogonal hard machining of SAE 8620 steel. In particular, it predicts grain size and hardness variation by implementing a user subroutine involving a hardness-based flow stress and empirical models. The model is validated by comparing its output with the experimental results available in literature at varying the cutting speed, inser0000-0001-6268-6720t geometry and flank wear. The results show a good ability of the customized model to predict the thermo-mechanical and microstructural phenomena taking place during the selected processes

Modelización de datos de supervivencia en nidos: estudio comparativo de varios métodos desarrollados recientemente que pueden implementarse en MARK y SAS

Estimating nest success and evaluating factors potentially related to the survival rates of nests are key aspects of many studies of avian populations. A strong interest in nest success has led to a rich literature detailing a variety of estimation methods for this vital rate. In recent years, modeling approaches have undergone especially rapid development. Despite these advances, most researchers still employ Mayfield’s ad–hoc method (Mayfield, 1961) or, in some cases, the maximum–likelihood estimator of Johnson (1979) and Bart & Robson (1982). Such methods permit analyses of stratified data but do not allow for more complex and realistic models of nest survival rate that include covariates that vary by individual, nest age, time, etc. and that may be continuous or categorical. Methods that allow researchers to rigorously assess the importance of a variety of biological factors that might affect nest survival rates can now be readily implemented in Program MARK and in SAS’s Proc GENMOD and Proc NLMIXED. Accordingly, use of Mayfield’s estimator without first evaluating the need for more complex models of nest survival rate cannot be justified. With the goal of increasing the use of more flexible methods, we first describe the likelihood used for these models and then consider the question of what the effective sample size is for computation of AICc. Next, we consider the advantages and disadvantages of these different programs in terms of ease of data input and model construction; utility/flexibility of generated estimates and predictions; ease of model selection; and ability to estimate variance components. An example data set is then analyzed using both MARK and SAS to demonstrate implementation of the methods with various models that contain nest–, group– (or block–), and time–specific covariates. Finally, we discuss improvements that would, if they became available, promote a better general understanding of nest survival rates.La estimación del éxito de nidificación y la evaluación de los factores potencialmente relacionados con las tasas de supervivencia de los mismos son aspectos clave de numerosos estudios sobre poblaciones de aves. El gran interés por el éxito de nidificación se ha traducido en una rica literatura que detalla varios métodos de estimación de esta tasa vital. En los últimos años, los enfoques de modelización han experimentado un rápido desarrollo. No obstante, pese a estos avances, la mayoría de los investigadores siguen empleando el método ad–hoc de Mayfield (Mayfield, 1961) o, en algunos casos, el estimador de probabilidad máxima de Johnson (1979) y Bart & Robson (1982). Tales métodos permiten el análisis de datos estratificados, pero, en cambio, no permiten modelos más complejos y realistas de la tasa de supervivencia en nidos cuando se incluyen covariantes que cambian según el individuo, la edad del nido, el tiempo, etc., y que pueden ser continuas o categóricas. Actualmente, con la ayuda de Program MARK, así como de Proc GENMOD y Proc NLMIXED de SAS, es posible implementar métodos que permiten a los investigadores evaluar rigurosamente la importancia de varios factores biológicos susceptibles de incidir en las tasas de supervivencia en nidos. Por consiguiente, no está justificada la utilización del estimador de Mayfield sin antes evaluar la necesidad de emplear modelos más complejos para determinar la tasa de supervivencia en nidos. Con objeto de incrementar el empleo de métodos más flexibles, primero describimos la probabilidad empleada para estos modelos, para posteriormente tomar en consideración cuál es el tamaño de muestra eficaz para el cálculo de AICc. Seguidamente, tomamos en consideración las ventajas y desventajas de estos programas por lo que respecta a la facilidad de introducción de datos y de construcción de modelos, la utilidad/flexibilidad de las estimaciones y predicciones generadas, la facilidad de la selección de modelos y la capacidad para estimar los componentes de la varianza. A continuación, analizamos un conjunto de datos de ejemplo utilizando los programas MARK y SAS con objeto de demostrar la implementación de los métodos con varios modelos que contienen nido–, grupo– (o bloque–), y covariantes específicas al tiempo. Por último, comentamos varias mejoras que, si estuvieran disponibles, fomentarían una mejor comprensión general de las tasas de supervivencia en nidos

Microstructural and Mechanical Properties of Al2O3 and Al2O3/TiB2 Ceramics Consolidated by Plasma Pressure Compaction

Alumina oxide ceramics were produced by plasma pressure compaction (P2C) sintering process. Two types of pure α-alumina (Al2O3) and a mixture of alumina and titanium diboride (TiB2) powders were used as starting materials. Microstructure and mechanical properties, namely hardness, elastic modulus, and fracture toughness, were analyzed and correlated to the type of the sintered powders and the adopted manufacturing route. The microstructural development and the chemical composition variation induced by the sintering process were assessed by using scanning electron microscopy and x-ray diffraction. Nano-indentation and Chevron notch beam techniques were adopted to estimate the mechanical properties of the sintered ceramics. The conducted analyses show the capability of P2C technique to produce sound alumina ceramics. Pure alumina bulks exhibit a good level of compaction and mechanical properties close to those achievable with conventional sintering processes, such as hot isostatic pressing or spark plasma sintering. No significant alterations in the chemical composition of the ceramics were observed. The addition of the titanium diboride in the alumina powders caused a moderate increase in the grain size lowering the hardness and Young’s modulus of the sintered alumina and, at the same time, increased its fracture toughness to the occurrence of toughening mechanisms, like crack bridging and crack deflection

Two-Lenses Model to Unfold Sustainability Innovations: A Tool Proposal from Sustainable Business Model and Performance Constructs

This research combines corporate sustainability performance and sustainable business model concepts to improve the corporate sustainability of organizations. The main objective of this article is to propose and apply a tool to identify sustainable innovation opportunities through a structured brainstorming process while providing a systemic business perspective and a strong multi-stakeholder orientation. The present qualitative research was carried out in two phases. The first phase consisted of a critical analysis of literature that enabled the proposition of the Two-Lenses Model (2LM) for sustainability innovation. The corporate sustainability performance lens encompasses strategic drivers, business processes, capabilities, stakeholders’ satisfaction and contributions. The sustainable business models lens considers value proposition, value creation and delivery system and value capture and sharing. The second phase consists of applying the 2LM in two industrial cases. The results show that the proposed model has the potential to trigger the identification of opportunities through two mechanisms: misalignments between performance dimensions and gaps in stakeholder satisfaction. Further research opportunities lie on deepening into these findings and investigating the implementation process for the identified innovation opportunities.</jats:p

Cardiovascular health in migrants: current status and issues for prevention. A collaborative multidisciplinary task force report.

OBJECTIVES: To review information on cardiovascular health and migration, to stress the attention of researchers that much needs to be done in the collection of sound data in Italy and to allow policy makers identifying this issue as an important public health concern. BACKGROUND: In Italy, the rate of immigrants in the total number of residents increased from 2.5% in 1990 to 7.4% in 2010, and currently exceeds 10% in regions such as Lombardia, Emilia Romagna and Toscana. METHODS: A consensus statement was developed by approaching relevant Italian national scientific societies involved in cardiovascular prevention. Task force members were identified by the president and/or the boards of each relevant scientific society or working group, as appropriate. To obtain a widespread consensus, drafts were merged and distributed to the scientific societies for local evaluation and revision by as many experts as possible. The ensuing final draft was finally approved by scientific societies. RESULTS: In several western European countries, the prevalence of hypertension, diabetes, chronic kidney disease, obesity and metabolic syndrome was found to be higher among immigrants than in the native population. Although migrants are often initially healthier than non-migrant populations in their host countries, genetic factors, and changing environments with lifestyle changes, social exclusion and insufficient medical control may expose them to health challenges. Cultural reasons may also hamper both the dissemination of prevention strategies and migrant communication with healthcare providers. However, great diversity exists across and within different groups of migrants, making generalizations very difficult and many countries do not collect registry or survey data for migrant's health. CONCLUSIONS: In the present economic context, the European Union is placing great attention to improve data collection for migrant health and to support the implementation of specific prevention policies aimed at limiting the future burden of cardiovascular and renal disease, and the consequent load for health systems. Wider initiatives on the topic are awaited in Italy