Improving the fracture toughness of dualphase austempered ductile iron

Dual Phase Austempered Ductile Irons, DPADI alloys have a microstructure with a combination of ausferrite and pro-eutectoid ferrite along with graphite and residual/retained austenite. To reach this particular microstructure ductile iron is austenized in the austenitepro- eutectoid ferrite region before being carried though an isothermal heat treatment somewhere between the bainite-start and martensite-start temperature. The special austenization procedure makes DPADI prime candidates for applications that require a high fracture toughness resistance like suspension components. The aim of this study is to identify features in the microstructure of dual-phase ADI that directly affect the fracture toughness of the investigated alloys. To do this alloys subjected to various ADI heat treatments have been impact tested and thereafter analysed by light optical microscopy, X-ray diffraction and hardness testing. From Thermo Calc Modelling and experimental investigation of the austenite to pro-eutectoid transformation zone, it was found that an austenitization temperature of 790°C resulted in a microstructure, which avoided perlite formation. In the investigation of industrial ADI heat treatment it was found that the last and first to cool regions of the sample geometry had an impact toughness of around 70 and 100 J, respectively. Furthermore a comparison of conventional ADI and DPADI heat treatments showed that the DPADI heat treatment had an impact toughness of 90 J with a scatter of ±15 J, whereas the conventional ADI heat had the same impact strength with >±20 J scatter. This reduced scatter was attributed to the encapsulation of the detrimental Mo-rich carbides by pro-eutectoid ferrite, after light optical and scanning electron microscopy. Moreover, it was observed that detrimental reductions in impact toughness resulted in areas where slag inclusion, carbides or voids were present. Consequently, it is recommended that more attention is directed to the ductile iron casting process to safeguard the success of the ADI heat treatmentIngeniería Industria

Development of binder systems based on CAB powder injection moulding (PIM) and micro powder injection moulding (μ-PIM) of zircon and invar powders

Powder injection moulding (PIM), in its different versions, is a manufacturing method that in the last decades has been consolidated as an effective and competitive alternative to fabricate small size and complex geometry parts in large batches. Its future expansion to new applications and sectors requires an exhaustive research in new materials and the improvement of the manufacturing process itself. A better understanding between the variables materialprocessing- properties is still needed to improve the quality and repeatability. In the last decades, a growing environmental awareness has been observed not only by the costumers but by the own industry. Within the PIM process, there are many possibilities to reduce the energy consumption and the emission of hazardous products. One of those alternatives would consist on using binder systems formulations that do not involve organic solvents, toxic vapours during processing or that allow reducing the fabrication temperatures. The binder systems based on natural derivatives, such as the thermoplastic polysaccharides, offer an interesting alternative to the conventional use of petroleum derivatives that has been scarcely investigated. Their use would suppose a cero balance of CO₂emissions during the thermal debinding. This PhD Thesis studied the use of binders based on cellulose acetate butyrate (CAB) and poly(ethylene glycol) (PEG) in different type of materials, including a ceramic, the zirconium silicate, and a metallic alloy, the Invar 36. These materials share their low dimensional stability with temperature with low coefficients of thermal expansion. The scope of this work is the study and comprehension of the behaviour of the mentioned binder systems when they are employed in different PIM processes and under different conditions and powder-types. With regard to this matter, different formulations were designed with several types of PEG and CAB. These formulations were compared with commercial ones. The intrinsic characteristics of each CAB were linked with the behaviour of the different feedstock also containing PEG and powder particles. The mixtures homogeneity, the optimum and critical solid loading and its flowability were assessed by torque and capillary rheology. Other complementary techniques such as electronic and light microscopy or the measurement of the mixtures densities by pycnometry were carried out to contrast rheology results. The compatibility between the feedstocks’ components and their thermal behaviour were analysed by calorimetry and thermogravimetry techniques. These methods were employed by the first time to determine the optimal solid loading. The optimal compositions were injected by using low or high pressures or by a micro injection moulding process. The debinding and sintering stages were optimised using several atmospheres. Finally, the physical and mechanical properties of the final consolidated parts were measured. It could be concluded that the studied binder systems based on PEG and CAB presented suitable characteristics for PIM, providing improvements with respect to conventional binder systems and by a more environmental friendly processing. However, that doctoral work was just a first approach to the use of these types of binder systems in PIM. Along this work several issues were detected and some topics regarding the processing should be further investigated to obtain the best of these binder systems. ---------------------------------------------El moldeo por inyección de polvos (PIM), en sus diferentes variantes, es una técnica de fabricación que en las últimas décadas se ha consolidado como una alternativa eficaz y competitiva para la fabricación de piezas de geometría compleja, reducido tamaño y grandes series de producción. Para su futura expansión en nuevos campos de aplicación hace falta una investigación exhaustiva de su aplicabilidad en nuevos materiales y en la mejora del propio proceso productivo. Aún se requiere un mejor entendimiento entre las variables materialprocesamiento- propiedades para mejorar la calidad y reproducibilidad de las piezas fabricadas por PIM. En las últimas décadas se viene apreciando una mayor concienciación medio ambiental tanto por los consumidores como por la propia industria. Dentro de los procesos PIM existen alternativas para reducir el consumo energético y la emisión de productos perniciosos para el medio ambiente. Una de estas alternativas consistiría en utilizar formulaciones del sistema ligante que no conlleven el uso de disolventes orgánicos, la emisión de vapores tóxicos durante el procesamiento o que permitirán reducir las temperaturas de fabricación. Los sistemas ligantes basados en derivados naturales como los polisacáridos termoplásticos ofrecen una alternativa interesante al uso convencional de derivados del petróleo que prácticamente no está estudiada. Su uso supondría una emisión neta cero de CO₂durante el proceso de eliminación térmica. Esta Tesis Doctoral estudia la utilización de sistemas ligantes basados en acetato butirato de celulosa (CAB) y poli(etilenglicol) (PEG) en diferentes tipos de materiales, entre los que se incluye un cerámico, el silicato de zirconio y una aleación metálica, el Invar 36. Estos materiales tienen en común su estabilidad dimensional frente a cambios de temperatura con bajos coeficientes de expansión térmica. El objetivo buscado es el estudio y comprensión del comportamiento de los sistemas ligantes anteriormente mencionados cuando se emplean en diferentes procesos PIM bajo diferentes condiciones y tipos de polvo. Para ello se diseñaron diferentes formulaciones con diferentes tipos de CAB y PEG y se compararon con formulaciones comerciales. Se relacionó las características intrínsecas de cada CAB con el comportamiento de las mezclas con PEG cargadas con diferentes tipos de polvo. La homogeneidad de las mezclas, las cargas óptima y crítica así como su capacidad de fluir se analizaron mediante un estudio reológico exhaustivo combinando reología de “torque” con reología capilar. Otras técnicas como la inspección por microscopía electrónica o microscopía óptica o la medición de la densidad de las mezclas mediante picnometría se utilizaron para contrastar los resultados de reología. La compatibilidad entre los componentes y el comportamiento térmico de las mezclas se analizó mediante técnicas de calorimetría y termogravimetría. Estas técnicas se emplearon por primera vez para determinar la carga óptima de polvo. Las formulaciones óptimas se inyectaron a baja o a alta presión o mediante un proceso de micro inyección. La eliminación del ligante así como la sinterización fueron optimizadas empleando diferentes atmósferas. Finalmente se midieron diversas propiedades físicas y mecánicas de las piezas finales. En general, se puede concluir que los sistemas ligantes estudiados basados en PEG y CAB presentan características que les hacen idóneos para el PIM, aportando mejoras con respecto a sistemas ligantes convencionales y mediante un procesamiento más ecológico. Sin embargo, este trabajo doctoral supone sólo una primera aproximación al empleo de este tipo de sistemas ligantes en PIM. Durante este trabajo se detectaron algunos puntos de mejora y aspectos que podrían ser objeto de futuras investigaciones para obtener lo mejor de estos sistemas ligantes para su empleo en la tecnología PIM. -------------------------------------------------------------------Le moulage par injection de poudres (MIP) et toutes ses variantes sont un procédé de fabrication qui s’est positionné comme une alternative efficiente et compétitive pour l’élaboration en grande série de petites pièces possédant une géométrie complexe. Pour continuer son émergence et voir apparaitre de nouveaux champs d’application, une investigation exhaustive du développement de nouveaux matériaux plus fonctionnels, ainsi que l’amélioration du procédé sont encore nécessaire. Une meilleure compréhension des phénomènes mécaniques et thermo physiques entre les paramètres des différentes étapes du procédé, les nuances des matériaux employées et de leurs interactions, ainsi que les propriétés désirées, est indispensable. De plus, les développements technologiques doivent conduire à l’augmentation de la qualité et de la reproductibilité des pièces élaborées par ce procédé. Aux cours de la dernière décennie, l’intérêt pour l’environnement est devenu un enjeu international accru aussi bien pour les consommateurs et les industriels. Le procédé MIP a des potentialités avérées et potentielles pour réduire la consommation énergétique et l’émission de produits pernicieux pour l’environnement lors de son utilisation industrielle. Quelques alternatives peuvent être l’emploie de liants qui n’utilise pas dissolvants organiques, qui n’émettent plus de vapeurs toxiques pendant le processus d’élimination thermique au niveau de la phase de déliantage. De plus, la réduction des températures du processus ou de nouvelles investigations pour réduire de manières drastiques les temps de cycle lors des étapes de densification ou déliantage sont des voies à investiguées dans le futur. Les liants basés en matériaux biosourcés comme les polysaccharides thermoplastiques offrent une alternative intéressante à l’utilisation conventionnelle de produits dérivés du pétrole. Cette alternative n’a pratiquement pas été étudiée. L’utilisation de ces éco-matériaux comme liants représenterait zéro émission de CO₂pendant le déliantage thermique a été développé au cours de cette thèse de doctorat. Les contributions de cette thèse de doctorat sont focalisées sur les développements de formulations à base de polymères biosourcés et déliantable à l’eau basés sur l’emploi d’acétate butyrate de cellulose (CAB) et de polyéthylène glycol (PEG). Ces nouvelles formulations ont été appliquées sur différentes nuances de poudres métalliques (invar) et céramiques (zircones). Ces matériaux possèdent une bonne stabilité dimensionnelle sous une large gamme de température imposée et possèdent de très bas coefficients d’expansion thermique. L’objective est l’étude et la compréhension du comportement des liants à base de CAB et PEG quand ils sont utilisés dans les variantes du procédé MIP (étapes de moulage avec ou sans pression, conditions particulières liées à la micro-injection, …) réalisées avec différentes nuances de poudres et différentes granulométries. Les caractéristiques intrinsèques de chaque CAB, leurs interactions avec le PEG et les poudres, l’influence de la nuance de poudre employée, ainsi que la granulométrie et la morphologie des poudres employées ont été étudiées et analysées en fonction du comportement final de la formulation développé et des taux de charges obtenues. L’homogénéité des mélanges développés, leurs taux de charge critique et maximal, ainsi que leurs comportements mécaniques, thermiques et rhéologiques ont été analysés et investigués par différentes études mécaniques, thermo et physico-chimiques. De nouvelles analyses chimiques et physiques ont été introduites par accroitre les connaissances sur les formulations développées. Les formulations optimales ont été validées pour différentes applications et avec l’emploi de différentes variantes du procédé MIP conduisant à l’élaboration de composants et de micro-composants PIM obtenus sans défauts et possédant d’excellentes propriétés fonctionnelles. L’étape de déliantage ainsi que l’étape de densification ont été optimisées en termes de cinétique et d’atmosphère aboutissant aux propriétés physiques et mécaniques escomptées pour l’ensemble des nuances de poudres considérées dans cette étude. En conclusion, les formulations développés des liants basées sur l’emploie de CAB et PEG son exploitable au niveau de la recherche et au niveau industriel dans le procédé MIP. Elles apportent des améliorations par rapport aux liants conventionnels grâce à un procédé plus écologique. Cette première contribution représente une avancée significative dans l’émergence d’un procédé MIP plus écologique mais d’autres travaux futurs sont encore possibles

Predicción de impagos en correduría de seguros

Depto. de Estadística y Ciencia de los DatosFac. de Estudios EstadísticosTRUEunpu

Facies model, cementation and sedimentary evolution of a 20th-century beach and beachrock: The Gorrondatxe wave and tidal coastal system (NE Spain)

Lithology, bedding, and sedimentary structures of the Gorrondatxe coastal and beach system show an upper shoreface around the low-water level and containing the coarsest grain sizes; a foreshore in the main intertidal zone, which is mainly composed of sands with minor gravels and a distinctive low-angle, seaward-dipping, planar-parallel lamination; and a backshore zone with a mixture of marine-derived sands (washover) and nonmarine sands and muds (aeolian, subaerial ponds) above the high-tide water level. The facies model shows a wave-dominated, mesotidal, composite beach with a fining-upwards and aggradational trend. Over the 20th century, a beachrock developed in this area as a result of heavy-industry waste dumping (steel industry) off the coast, which later became attached to the coast. There are a variety of cements and degrees of lithification in the beachrock, suggesting that the beachrock-related processes, although coetaneous, were not similar in all these zones and that different cements developed at the same time. Sand cementation can be used to recognize such facies in the stratigraphic record or in well cores, when other kinds of data are not available. The upper shoreface sandstones are hard andwell-cemented, with awhitish circumgranular aragonite cement and good intergranular porosity; the foreshore sands are medium-hard, with a brown, irregular, aragonite needle cement, which shows higher intergranular porosity; finally, the backshore sands are only lightly cemented,with a brown aragonite and rhombohedral calcite cement, with the highest intergranular porosity. SEM images show the presence of Coccus-type bacteria in all the different facies and zones; these are the best proof of metabolic activity, probably of ureolytic bacteria, in the origin of all these cements.Over the course of the 20th century,Gorrondatxe evolved from a formerly dissipative, ridge and runnel beach to an active, aggrading and prograding, reflective beach, and finally to an inactive beach prone to erosion. The change to a reflective profile and the cementation of the beachrock indicate that anthropic offshore inputs were rapidly recycled into the beachface. Another major change occurred when waste discharges ended, and the former sediments and beachrock started to be eroded to their current state.The present study has been funded by the Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), research group GIU18/16317/05; MINECO/MCI/ERDF-EU project PID2019-105670GB-I00/AEI/10.13039/501100011033 of the Spanish Government

The role of parenting styles on behavior problem profiles of adolescents

Parental behavior is one of the most influential factors on the development of adolescent externalizing and internalizing behavior problems. These behavioral problems are closely related and often co-occur. The objectives of this work were: (i) to identify adolescents profiles according to their behavior problems; (ii) to explore individual, family, and social characteristics associated with these profiles; and (iii) to analyze the potential role of parenting styles in belonging to adolescents’ profiles. A total of 449 Spanish adolescents (223 from families declared at-risk and enrolled in Child Welfare Services and 226 from families from the general population) participated in this study. The analyses revealed three profiles of adolescents based on external and internal behavior problems (adjusted, external maladjustment, and internal maladjustment). Parenting styles explained the adolescents’ belonging to different profiles, in which the indulgent style was the most favorable in general terms. The distinctive role of parenting styles on two types of maladjustment profiles was confirmed. The relationship between parenting styles and adolescent adjustment is a key component that should be included in interventions according to adolescents’ behavior problem profiles. Furthermore, the results shed light on the need that family interventions are complemented with individualized interventions with adolescents that accumulate stressful life events.Ministerio de Economía y Competitividad EDU2013-41441-

Thermal stability and degradation kinetics of feedstocks for powder injection moulding - A new way to determine optimal solid loading?

Degradation kinetics and the thermal stability of zircon powder injection moulding feedstocks (PIM) based on cellulose acetate butyrate (CAB) and polyethylene glycol (PEG) binders were investigated using simultaneous thermogravimetric analysis (STA). The initial decomposition temperature (IDT) and the integral procedure decomposition temperature (IPDT) were used to analyse the thermal stability of the binder system as a function of the solid loading content. The degradation kinetics was studied, and the degradation activation energy was assessed for varying zircon powder contents using isoconversional methods. All the methodologies revealed changes in the thermal degradation behaviours of the feedstocks for solid loadings that were previously determined to correspond to optimal solid loadings using other experimental procedures. These results may promote the proposal of thermodynamic degradation studies of feedstocks as an alternative or complementary technique to determine optimal solid loading contents in powder injection moulding (PIM). The studies in this paper also examined PIM process operation temperatures for zircon feedstocks.The authors also wish to thank GUZMÁN GLOBAL S.L. and MIMTECH ALFA for their collaboration on the ECOPIM project (ref. IPT-2011-0931-20000) that was funded by the Spanish Ministry of the Economy and Competitiveness. Furthermore, the authors would like to acknowledge the strong support from the ESTRUMAT projects (ref. S2009/MAT-1585), which were funded by the CAM-Consejería Educación Dir. Gral. Universidades e Investigación, and from the COMETAS project (ref. MAT2009/14448-C02-02), which was funded by the Spanish Ministry of the Economy and Competitiveness.Publicad

Powder injection moulding: processing of small parts of complex shape

This paper is a revised and expanded version of a paper entitled ‘Torque rheology of zircon feedstocks for powder injection moulding’, presented at Feedstock Development for Powder Injection Molding of Zirconium Silicate PM2011 Euro Congress – Powder Injection Moulding – Processing, Barcelona, Spain, 9–12 October, 2011.Powder Injection Moulding (PIM), Metal Injection Moulding (MIM) when is limited to metals, is a fabrication route of parts with the final shape desired. This process combines the high capability of polymer injection moulding to produce complex shapes with the advantages of a powder route to process metallic, ceramic or composites materials. The process has some limitations that comes from different technological steps involved in the production of the part (feedstock production, injection, debinding and sintering). All of these different steps can be industrially controlled, being the PIM process a real alternative to produce complex parts in a high rate production method that can compete with many other processing methods to produce materials. In this work, we will go through the different steps of this manufacturing process, making special emphasis on the solutions provided by the powder technology group of the University Carlos III of Madrid (UC3M)

An analysis of different resources and programmes supporting at-risk families in Spain

The purpose of this research was to present an overview of the existing family support resources in Spain for at-risk families. We analysed 64 family support services from 16 agencies belong to 11 regions of Spain. In a second phase, 20 positive parenting programmes were analysed in depth to ascertain the extent to which they met evidence-based programme quality criteria. Our results suggest that services for at-risk families are delivered by public, local and social agencies. Most interventions were psycho-educational and aimed at parental training. The analysis of the positive parenting programmes ’ quality showed both strengths and weaknesses. Most programmes relied on a previous needs analysis and interventions were, to some extent, outlined in a manual. Nevertheless, few programmes have been evaluated according to evidence-based programme criteria. In light of these results, we discuss several practical implications for services and family support policies aimed at at-risk families.Ministerio de Economía y Competitividad de España EDU2013-41441-

Torque rheology of zircon feedstocks for powder injection moulding

In this work, a cellulose acetate butyrate (CAB) and polyethylene glycol (PEG) blend is used as the binder system in a zirconium silicate mineral powder feedstock for powder injection moulding. These irregular zircon powders make the mixing process and the selection of an optimal solid loading level a difficult task. Torque rheology methodologies combined with other techniques are used for evaluation of the parameters affecting the mixing process and determination of the critical powder volume concentration (CPVC). Temperature variations during the mixing process are monitored and used as an indicator of the friction energy of the system and thus for the optimal solid loading selection. There have thus far been limited amounts of work conducted on torque rheology of highly loaded feedstocks that incorporate a study of the system's temperature evolution. A detailed study could be a key factor for understanding the mixing behaviour of highly loaded feedstocks.The authors would like to acknowledge the companies GUZMÁNGLOBAL S.L and ALFAMIMTech for their support and partnership in the project IPT-2011-0931-020000 granted from the Spanish Ministry of the Economy and Competitiveness and the European Funds for Regional Development (FEDER). They would also kindly thank the Applied Mechanics Department of FEMTO-ST Institute and the ENSMM (Besançon, France) where some of the experimental works were performed. The suggestions and technical support of T. Barriere and G. Michele were much appreciated

Parenting stress, coping strategies and risk assessment in mothers from at-risk families assisted by Child and Family Protection Services

En este artículo se analizan los niveles de estrés asociados al rol parental y las estrategias para hacerle frente en una muestra de 109 madres de familias con un expediente de riesgo en los Servicios Sociales Comunitarios. Los resultados indican que más de la mitad de las mujeres experimentaban niveles clínicos de estrés, y que las estrategias de afrontamiento en mayor medida utilizadas fueron las centradas en el problema. Tanto el estrés parental como el tipo de afrontamiento guardaron relación con diferentes características socio-demográficas de las usuarias y de sus familias. El nivel de riesgo de estas mujeres de acuerdo con los profesionales que las atenían se relacionó con el estrés parental que experimentaban estas usuarias.In this study parenting stress and coping strategies in a sample of 109 mothers from at-risk families were analyzed. Results obtained show over half of these women experienced clinical levels of parenting stress, and problem focused coping strategies were the most commonly used. Moreover, the main characteristics of these families and their trajectories in Child and Family Protection Services were correlated with parenting stress and coping strategies. The global valuation of family risk informed by professionals was significantly related to parenting stress