Some experimental observations of crack-tip mechanics with displacement data

Estudio de la mecánica en el vértice de la grieta mediante datos de desplazamiento.In the past two decades, crack-tip mechanics has been increasingly studied with full-field techniques. Within these techniques, Digital Image Correlation (DIC) has been most widely used due to its many advantages, to extract important crack-tip information, including Stress Intensity Factor (SIF), Crack Opening Displacement, J-integral, T-stress, closure level, plastic zone size, etc. However, little information is given in the literature about the experimental setup that provides best estimations for the different parameters. The current work aims at understanding how the experimental conditions used in DIC influence the crack-tip information extracted experimentally. The influence of parameters such as magnification factor, size of the images, position of the images with respect the crack-tip and size of the subset used in the correlation is studied. The influence is studied in terms of SIF and T-stress by using Williams’ model. The concept of determination of the K-dominance zone from experimental data has also explored. In this regard, cyclic loading on a fatigue crack in a compact tension (CT) specimen, made of aluminium 2024-T351 alloy, has been applied and the surface deformation ahead of the crack tip has been examined. The comparison between theoretical and experimental values of KI showed that the effect of subset size on the measured KI is negligible compared to the effect of size of the image.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Reuse of use cases diagrams: an approach based on ontologies and semantic web technologies

Software reuse is defined as the use of any artifact, or part thereof, created before, on a new Project. This practice has significant benefits in reducing costs and increasing quality and productivity in software development. Numerous approaches have been proposed aimed mostly at the source code reuse, but this type of reuse has its limitations because development platforms and technologies are constantly changing. Then, it is necessary to apply reuse over software artifacts created at higher levels of software life cycle such as requirements specification. This paper presents a tool for the reuse of use case diagrams by storing their information in OWL ontology and the use of Semantic Web technologies.Software reuse is defined as the use of any artifact, or part thereof, created before, on a new Project. This practice has significant benefits in reducing costs and increasing quality and productivity in software development. Numerous approaches have been proposed aimed mostly at the source code reuse, but this type of reuse has its limitations because development platforms and technologies are constantly changing. Then, it is necessary to apply reuse over software artifacts created at higher levels of software life cycle such as requirements specification. This paper presents a tool for the reuse of use case diagrams by storing their information in OWL ontology and the use of Semantic Web technologies

Experimental and analytical study of cracks under biaxial fatigue

Most mechanical components experience multi-axial cyclic loading conditions during service. Experimental analysis of fatigue cracks under such conditions is not easy and most works tend to focus more on the simpler but less realistic case of uni-axial loading. Consequently, there are many uncertainties related to the load sequence effect that are now well known and are not normally incorporated into the growth models. The current work presents a new methodology for evaluating overload effect in biaxial fatigue cracks. The methodology includes evaluation of mixed-mode (KI and KII) stress intensity factor and the Crack Opening Displacement for samples with and without overload cycle under biaxial loading. The methodology is tested under a range of crack lengths. All crack-tip information is obtained with a hybrid methodology that combines experimental full-field digital image correlation data and Williams' elastic model describing the crack-tip field.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Study of the stress intensity factors in the bulk of the material with synchrotron diffraction

Artículo de Proceedings de Congreso Internacional Fatigue2017In this work we present the results of a hybrid experimental and analytical approach for estimating the stress intensity factor. It uses the elastic strains within the bulk obtained by synchrotron X-ray diffraction data. The stress intensity factor is calculated using a multi-point overdeterministic method where the number of experimental data points is higher than the number of unknowns describing the elastic field surrounding the crack-tip. The tool is tested on X-ray strain measurements collected on a bainitic steel. In contrast to surface techniques the approach provides insights into the crack tip mechanics deep within the sample.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. The authors are grateful to the ESRF for ID15 beamtime awarded under MA-1483. Financial support of Universidad de Malaga through Plan Propio, Junta de Andalucía through Proyectos de Excelencia grant reference TEP-3244, Campus de Excelencia Internacional del Mar (CEIMAR) and Ministerio de Economia y Competitividad through grant reference MAT2016-76951-C2-2-P is also acknowledged. PJW acknowledges an ERC advanced grant

Comportamiento cíclico de una acero St-52-3N: Influencia de los módulos de elasticidad en las estimaciones de vida a fatiga

Dada la dependencia de los módulos de elasticidad en los métodos de estimación de vida a fatiga, se analiza el comportamiento cíclico y la variación de estos con el grado de deformación. En este estudio se llevan a cabo una serie de experimentos de fatiga uniaxial en control de deformación, con R=-1, a bajo número de ciclos y a temperatura ambiente, para caracterizar el comportamiento cíclico del acero al carbono St-52-3N. Se realizaron ensayos de fatiga uniaxial tanto de tracción como de torsión. Se compara los valores de los módulos de elasticidad monotónico y cíclico, además de los valores cíclicos correspondientes a los segmentos de descarga y carga (E1 ,E2) (acordes con ISO/DIS 121106). Se pone de manifiesto la variabilidad cometida al calcular el incremento de deformación plástica según el Método Estándar de ensayo que utilicemos (BS/ISO, ASTM, AECMA) y que determinará en cada caso la estimación del módulo de elasticidad cíclicoUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Evaluación de la zona plástica en fatiga para un acero bainitico mediante difracción de rayos x

En este artículo se presenta una nueva metodología para medir la zona plástica de una grieta en fatiga. Se han adquirido datos de difracción de rayos X sincrotrón para una probeta Compact Tension de acero bainítico, en el plano medio a través del espesor. Estos datos han sido traducidos a campos 2D de deformación en torno al vértice. Se ha generado un campo de deformación angular artificial para, en consonancia con los anteriores, obtener el campo de deformación equivalente de Von Mises. La aplicación de la ley de comportamiento elástico ha permitido hallar campos de tensión equivalente entorno al vértice de grieta. Así, se permite estimar la zona plástica y sus dimensiones. Finalmente se estudia la precisión de la metodología a través de una comparación con los modelos de zona plástica de Irwin y de Dugdale.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech Los autores agradecen la financiación aportada para la realización de este trabajo al Ministerio de Economía y Competitividad (referencia MAT2016-76951-C2-2-P) y al Fondo Social Europeo a través de la Iniciativa de Empleo Juvenil (referencia UMAJI84)

Orientación laboral y vida floreciente en doce países iberoamericanos

Introducción/Objetivo: La orientación laboral incluye las creencias del individuo sobre el papel del trabajo en su vida como un todo y lo que está buscando en su carrera. La orientación laboral examina cómo el trabajo se conecta con la vida de las personas y es un constructo apropiado para evaluar el efecto del trabajo en el florecimiento humano. Se propone explorar la orientación laboral en 12 países iberoamericanos; e investigar si la orientación laboral afecta el florecimiento humano. Método: Tres mil adultos participaron en este estudio. Se utilizó el Work-Life Questionnaire para evaluar el tipo de relación que los empleados informan tener con su trabajo, de acuerdo con las distinciones entre trabajo, carrera y vocación. Se utilizó la Escala de Florecimiento Multidimensional para medir tres aspectos del florecimiento: bienestar social, psicológico y emocional. Resultados: La mayoría de los participantes informaron un alto nivel de orientación laboral como vocación. En la mayoría de los países, aquellos que trabajan por vocación informaron niveles más altos de bienestar social y psicológico que aquellos que trabajan solo por una motivación económica. Conclusiones: Esta investigación es la primera en comparar la relación entre la orientación al trabajo y el florecimiento humano en Iberoamérica. Los hallazgos nos ayudan a comprender que la orientación al trabajo no es un aspecto secundario de la vida de una persona, sino que tiene implicaciones fundamentales en los trabajadores.Introduction/Objetive: Work orientation includes the individual’s beliefs regarding the role of work in his/her life as a whole and what they are searching for in their careers. There are three types of orientation to work: job, career, and vocation. Work orientation has the distinction of examining how work connects with people’s lives and is, therefore, an appropriate construct for evaluating the impact of work on human flourishing. The aims of this study are first to explore work orientation in twelve Ibero-American countries; and second, to investigate whether work orientation affects flourishing in the lives of adults in twelve Ibero-American countries. Method: A total of 3000 adults participated in this study. The University of Pennsylvania Work-Life Questionnaire was used to evaluate the type of relationship that employees reported having with their work, according to the distinctions between job, career, and calling. A 12-item version of the Multidimensional Flourishing Scale was used to measure three aspects of flourishing: social, psychological, and emotional well-being. Results: Most participants reported a high level of calling in their work orientation. In most countries, those with a calling orientation reported higher levels of social and psychological well-being than those with a job orientation. The results indicate a clear relationship between a calling orientation and social and psychological well-being. Conclusion: This research is the first to compare the relationship between work-orientation and flourishing in Ibero-America. The findings help us understand that work-orientation is not a secondary aspect of a person’s life but has fundamental implications in the lives of workers.Fil: Mesurado, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral; ArgentinaFil: Idrovo Carlier, Sandra. Universidad de la Sabana; ColombiaFil: Rodríguez, Omar. Universidad Austral; ArgentinaFil: Debeljuh, Patricia. Universidad Austral; ArgentinaFil: Crespo, Ricardo Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral; Argentin

Influencia del tamaño mínimo de elemento en el análisis tridimensional por elementos finitos del cierre de grieta inducido por plasticidad

Because of the increase of the computational power, during last years the use of three-dimensional finite element models to analyse the plasticity induced crack closure phenomenon has spread. However, the methodology employed is directly inherit from bi-dimensional analysis. As is well known, several numerical parameters can affect to the obtained results, being one of them, the mesh size close to the crack front. In the present work, a CT aluminium alloy specimen has been three-dimensionally modelled in order to analyse the influence of the mesh size close to the crack front. The results have been analysed in terms of the crack opening and closure values as well as taking into account the strain and stress fields around the crack front.Debido al incremento de la capacidad computacional disponible hoy en día, en los últimos años se ha extendido el uso de modelos tridimensionales para el análisis del cierre de grieta en fatiga empleando el método de los elementos finitos. Sin embargo, la metodología que se emplea es directamente heredada de los modelos bidimensionales. Es bien conocido que diferentes parámetros numéricos pueden afectar a los resultados obtenidos, siendo uno de ellos el tamaño de la malla en el entorno del frente de la grieta. En el presente trabajo, se ha modelado tridimensionalmente una probeta CT de una aleación de aluminio, con objeto de evaluar la influencia del tamaño de la malla en el entorno del frente de la grieta, analizando los resultados en función de los valores de apertura y cierre de la grieta, así como considerando los campos de tensiones y deformaciones entrono al frente de la grieta.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Determinación experimental de la carga de apertura de grieta en fatiga bajo cargas aleatorias

El concepto de carga de apertura o cierre de grieta es ampliamente utilizado en fatiga para justificar el comportamiento del crecimiento de grietas con distintas relaciones de carga y el efecto de interacción de las cargas. Hasta la fecha son numerosas las técnicas experimentales propuestas para medir la apertura de grieta y entre ellas los métodos de flexibilidad son ampliamente utilizados por su simplicidad. En este trabajo se propone una modificación del método propuesto por la ASTM y se presentan los resultados obtenidos en ensayos de crecimiento de grietas por fatiga bajo cargas aleatorias. Así mismo, los valores experimentales de cargas de apertura son comparados con los calculados analíticamente por un modelo de simulación tipo “strip-yield” implementado en el software NASGRO. En general, se ha encontrado una concordancia razonablemente buena entre los valores experimentales y los obtenidos por simulación.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Los autores agradecen la financiación aportada para la realización de este trabajo al Ministerio de Economía y Competitividad (referencia MAT2016-76951-C2-2-P)

In vitro and in vivo development of mice morulae after storage in non-frozen conditions

BACKGROUND: Interchange of genetically modified (GM) mice between laboratories using embryos provides several advantages. Not only is transport stress avoided, but also the health status of the recipient colony is not compromised. Embryos do not need to be shipped in frozen stage, which requires expensive packaging in addition to a certain degree of expertise in order to freeze and thaw them correctly. The aim of this study was to examine different storage conditions and their effect on embryo viability in order to establish the feasibility of practical, non-frozen conditions for embryo shipment. METHODS: Mouse morulae developed in vivo (collected from donors 2.5d post coitum) or in vitro (zygotes cultured until morulae stage) were stored, combining two different media (KSOMeq or KSOM-H) and temperatures (4 degrees C, 15 degrees C and 37 degrees C) throughout 24 or 48 hours. After storage in vitro viability was assessed determining percentage of development to blastocyst and total cell number. In vivo viability was determined based on the number of implantations and living fetuses after embryo transfer of stored embryos. The storage effect at the molecular level was assessed by studying a gene pool involved in early development by quantitative RT-PCR. RESULTS: In vivo-produced morulae stored for 24 hours did not show differences in development up to the blastocyst stage, regardless of the storage type. Even though a decrease in the total cell number in vivo was observed, embryo development after embryo transfer was not affected. All 24 hour storage conditions tested provided a similar number of implantations and fetuses at day 14 of pregnancy. Morulae obtained from in vitro embryo culture collected at the 1-cell stage showed a decreased ability to develop to blastocyst after 24 hours of storage at 15degrees C both in KSOMeq and KSOM-H. Concomitantly, a significant decrease of embryo implantation rates after transfer to recipients was also found. In order to further characterize the effect of non-frozen storage combining a molecular approach with the ordinary in vitro culture evaluation, embryos collected at the morula stage were submitted to the same storage conditions described throughout 48 hours. In vitro culture of those embryos showed a significant decrease in their developmental rate to blastocyst in both KSOMeq and KSOM-H at 15degrees C, which also affected the total number of cells. Gene transcription studies confirmed significant alterations in retrotransposons (Erv4 and Iap) after 48 h of storage at 15degrees C. CONCLUSIONS: Our results show that both KSOMeq and KSOM-H can be equally used, and that several temperature conditions allow good survival rates in vitro and in vivo. Some of these storage conditions can substitute freezing in order to maintain embryo viability for 24–48 hours, providing a reliable and less demanding technical alternative for embryo interchanges