Molecular dynamics simulation of the elliptical vibration assisted machining (EVAM) of pure iron

It is well known that diamond wears out rapidly (within several metres of cutting length) when machining low carbon ferrous alloys and pure iron. The past few years have seen a growing interest in the field of elliptical vibration-assisted machining (EVAM) due to it being successful in the micromachining of difficult-to-cut materials including steel. During EVAM, a cutting tool is prescribed an oscillatory motion perpendicular to the direction of cutting, thereby causing the tool to be relieved intermittently from chemical and physical contact with the workpiece. This phenomenon serves as a guideline to develop the simulation test bed for studying EVAM in this work to compare it with conventional cutting. The pilot implementation of the EVAM came as a quasi-3-dimensional (Q3D) elliptical cutting model of body-centred cubic (BCC) iron with a diamond cutting tool using molecular dynamics (MD) simulation. The developed MD model supplemented by the advanced visualization techniques was used to probe the material removal behaviour, the development of the peak stress in the workpiece and the way the cutting force evolves during the cutting process. One of the key observations was that the cutting chips of BCC iron during conventional cutting underwent crystal twinning and became polycrystalline, while EVAM resulted in cutting chips becoming highly disordered, leading to better viscous flow compared to conventional cutting

Investigation into the environmental assisted crack initiation mechanism of CMSX-4 in simulated aero engine environments at 450 - 550°C.

The aviation industry has continued to increase the efficiency of gas turbine engines, which are now designed to operate on a wide variety of flight routes. In general, the efficiency drive has led to components spending longer times at temperatures, where accelerated corrosion can occur. This has led to a complex degradation mechanism being identified in the lower shank region under the platform of single-crystal turbine blades. This research aims to understand the mechanism of crack initiation due to the synergistic effect of stress and high temperature corrosion environments on CMSX-4 in the lower operating temperature range, 450°C - 550°C, of an aero gas turbine blade. The first part of the investigation consisted in comparing the effect of different salt deposits in a 50 ppm SO₂ - air environment at 550°C. A 50 ppm SO₂ – air concentration was considered because the air going through the lower shank is fed directly from the compressor, and not from the combustor (which is the main source of sulphur). Characterisation of the resulting scales were carried out using scanning electron microscopy, energy dispersive spectroscopy and X- ray diffraction. Results from thermodynamic modelling are also presented. The first part of the investigation showed that CMSX-4 sample under an applied stress and no applied salt did not experience accelerated corrosion attack or crack formation when exposed to 50 ppm SO₂ - air in a 400-hour period. The same observation was made for a CMSX-4 sample under an applied stress and salted with CaSO₄. Sea salt caused accelerated corrosion attack with cracks up to 1.3 mm through the substrate formed after 400 hours of exposure. Further tests using NaCl salt in 50 ppm SO₂ – air showed that cracks can initiate after just 10 minutes of exposure at 550°C. Crack growth rates are significantly reduced after two hours of exposure within a 50-hour salt cycle. Cracks with NaCl in 50 ppm SO₂ – air have also been observed at temperatures as low as 450°C. When NaCl salt was applied to CMSX-4 and exposed to air only for 50 hours, the corrosion attack was reduced considerably, and the initiation of cracks is either suppressed or significantly delayed beyond a 50-hour period. Although this PhD has only focused on a 50-hour period, longer exposure times should be carried out to determine if air exposures delay crack initiation time, or if crack initiation is completely supressed. This thesis has therefore shown that the interaction of stress, NaCl and a sulphur- containing environment are critical to cause early crack initiation in single crystal nickel-based superalloys in the temperature range 450 - 550°C. The effect of having small concentrations of moisture in the gaseous environment or as inclusions retained in the salt are still to be investigated. A working hypothesis is that that the interaction of alkali chlorides with a sulphur-containing atmosphere is the trigger to a self-sustaining cycle where metal chloride formation, vaporisation and oxidation leads to high amounts of H₂ formed at the scale/alloy interface. Potentially, the H₂ formed at the alloy/scale interface may dissociate into atomic hydrogen, and lead to hydrogen embrittlement. For further verification of this hypothesis, a set of tests have been suggested.Engineering and Physical Sciences (EPSRC)PhD in Manufacturin

Understanding nanoscale material behaviour for improved precision machining of shape memory alloys; testbed study on elliptical vibration assisted cutting of CuZr SMA.

The field of ultra-precision machining has gained significant importance in the manufacture of components for the electronic, optical and medical industry. Two crucial factors that play a key role in the machinability of materials are the machining parameters and the material’s physical properties. Certain materials such as hardened steel or nickel-based superalloys are difficult-to-machine but innovations in the field of precision machining have developed a technique known as elliptical vibration assisted machining, which enables to improve the machinability of these materials. CuZr high-temperature shape memory alloy is categorized as a difficult-to-cut material and although EVAM has been applied to a wide range of metals it hasn’t yet been studied in CuZr HTSMA. In this context, the purpose of this thesis is twofold: On the one hand, to characterise the mechanical properties of CuZr SMA using Molecular Dynamics and, on the other hand, to explore the nanoscale mechanism of material removal of CuZr shape memory alloy (SMA) during elliptical vibration assisted machining (EVAM). The conclusions of this thesis can be summarized as follows. To characterise the mechanical properties of Cu₅₀Zr₅₀, Cu₂Zr and Cu₅Zr, a tensile and shear test were carried out using MD. Tensile test was done with crystal orientation and direction of tensile pulling as . The results showed that Cu₅₀Zr₅₀ and Cu₂Zr exhibited a phase transformation (pseudoelasticity) during loading. However, Cu₅Zr showed dislocation nucleation as the main plastic deformation mechanism followed by fracture. Shear tests were done in the same phases with crystal orientation and direction of shear pulling as . Interestingly, the shear test results showed no phase transformation for Cu₅₀Zr₅₀ and Cu₂Zr but the Cu₅Zr composition did show phase transformation during loading. It is important to highlight that all three phases of CuZr binary alloy that we have tested showed a different plastic response during the tensile test and the shear test. As far as machining is concerned, we observed indications that EVAM shows improved machinability compared with conventional machining. Although cutting forces were lower in EVAM, the stresses on the workpiece were slightly higher and both techniques showed the same mechanism of plasticity during machining. Neither dislocation nucleation or martensitic transformation was exhibited in either of the two machining techniques and instead, amorphisation was observed as the main plastic deformation mechanism in both cases. Interestingly, amorphisation has been previously observed by Saitoh and Kubota (2010) during loading NiTi SMA [1]; however, it didn’t show up in every crystal orientation confirming that NiTi shows significant changes in response to loading in different lattice directions. One of the main outcomes from this thesis is that CuZr SMA exhibits different modes of plastic deformation; namely amorphisation, dislocation nucleation and martensitic transformation during loading. The governing mechanism that arises during loading highly depends in the lattice direction in which the load is being applied. These findings can potentially enable reliable predictions and provide guidelines of the microstructural design of CuZr SMA systemsPhD in Manufacturin

Estrategia didáctica desde el enfoque ciencia, tecnología y sociedad para la enseñanza de los efectos del mercurio sobre la salud y el ambiente

The present document aims to design a didactic strategy from the Science, Technology and Society (CTS) perspective through the simulated case study model, applied to the properties and effects that mercury has on health and the environment. The strategy was developed at the Colegio Nueva Esperanza IED with tenth grade students aged between fourteen (14) and sixteen (16) years; Initially, a Likert-type questionnaire was carried out on the beliefs and conceptions that the students had about mercury, resulting in ignorance of the uses, applications and impact. The analysis of these results, in relation to the institutional study plan, gave the guideline for the design and application of the didactic strategy framed in the simulated case study model, which was organized in three sessions. In the first one, a contextualization of mercury was carried out, in the second, a fictitious story was presented in which the problem of the uses of mercury was addressed, and finally, the development of a role play about the social actors that they are part of the environmental situation produced by the use of mercury; In this way, the simulated case strategy was implemented. The classroom strategy seeks to strengthen the articulation of the contents developed in the transversal curriculum of the science area, the daily life and interests of the students, and the environmental and health problems that arise at a social level with the uses of mercury in artisanal gold mining processes. This allows students to identify the physical and chemical properties of mercury, but above all it seeks to promote through their learning an environmental awareness that integrates concepts in science.El presente trabajo tiene como objetivo diseñar una estrategia didáctica desde la perspectiva Ciencia, Tecnología y Sociedad (CTS) a través del modelo de estudio de casos simulados, aplicado a las propiedades y efectos que tiene el mercurio en la salud y el medio ambiente. La estrategia se desarrolló en el Colegio Nueva Esperanza IED con estudiantes de grado décimo en edades entre los catorce (14) y dieciséis (16) años; inicialmente se realizó un cuestionario tipo Likert de las creencias y concepciones que tenían los estudiantes sobre el mercurio, arrojando como resultado desconocimiento en los usos, aplicaciones e impacto. El análisis de estos resultados, en relación con el plan de estudios institucional dieron la directriz para el diseño y aplicación de la estrategia didáctica enmarcada en el modelo de estudio de casos simulados, la cual se organizó en tres sesiones. En la primera de ellas se realizó una contextualización sobre el mercurio, en la segunda se presentó una noticia ficticia en la que se abordó la problemática de los usos del mercurio y por último, el desarrollo de un juego de roles acerca de los actores sociales que hacen parte de la situación ambiental que produce el uso del mercurio; de esta manera se implementó la estrategia de caso simulado. La estrategia de aula busca fortalecer la articulación de los contenidos desarrollados en el plan de estudios transversal del área de ciencias, la cotidianidad e intereses de los estudiantes, y las problemáticas ambientales y de salubridad que se presentan a nivel social con los usos del mercurio en los procesos de minería aurífera artesanal. Esto permite que los estudiantes identifiquen las propiedades físicas y químicas del mercurio, pero sobre todo busca favorecer a través de su aprendizaje una consciencia ambiental que integre conceptos en ciencias.Línea de Trabajo: Ciencia, Tecnología y Sociedad (Ambiente).Maestrí

SEVEN, Santander Fashion Industry, una estrategia transmedia para el posicionamiento y comercialización de productos de moda

SEVEN Santander’s Fashion Industry is a transmedia strategy for the positioning and marketing of fashion products created by companies, artists and designers in the department of Santander, Colombia. The study uses a qualitative descriptive design, and is based on a probabilistic sample of the participating brands, commercial brand photographers and make-up artists. The event consists of a seven-day encounter between photographers, make-up artists, designers, academics and fashion marketing professionals, together with a cross-sectoral e-commerce space providing access to products. The study was carried out virtually in July 2020, and focuses on the viewers and users who accessed the contents and assumed the role of prosumers to comment on the different proposals and contribute to future editions of the event.SEVEN, Santander Fashion Industry, es una estrategia transmedia para el posicionamiento y comercialización de los productos de moda realizados en los diferentes municipios que integran el departamento de Santander, Colombia. El proyecto se define dentro de un diseño descriptivo, con un enfoque cualitativo y una población por medio de un muestro probalístico que permitió seleccionar las marcas participantes, así como los fotógrafos expertos en marcas comerciales y maquilladoras. La estrategia se concibe por la articulación de siete días en los cuales se conocen el mismo número de fotógrafos, maquilladores, mercados de moda, espacios académicos, diseñadores y de manera transversal se complementa con un e-commerce para acceder a los productos. Esta investigación se desarrolló de manera virtual en el mes de julio de 2020 alcanzando a espectadores y usuarios que tomaron los contenidos y asumieron el rol de prosumidores para comentar sobre las diferentes propuestas y aportar en la consolidación de la siguiente versión

Realidades expandidas: Guía metodológica para proyectos transmedia de no ficción

El presente proyecto de investigación planteó el diseño de una guía metodológica para realizar audiovisuales transmedia y multipantalla de no ficción, un documento que oriente sobre el proceso de creación, navegación e interacción de proyectos en ecosistemas mediáticos. This research project proposes the design of a methodological guide for making transmedia and multiscreen non-fiction audiovisuals, a document that provides guidance on the process of creating, navigating and interacting with projects in media ecosystems. Este projeto de pesquisa propõe o desenho de um guia metodológico para fazer audiovisuais transmídia e multitela de não-ficção, um documento que fornece orientações sobre o processo de criação, navegação e interação com projetos em ecossistemas de mídia.&nbsp

Classification of skin phenotypes caused by diabetes mellitus using complex scattering parameters in the millimeter-wave frequency range

The pathological skin phenotype caused by hyperglycemia is an important indicator for the progress of diabetes mellitus. An early detection of diabetes assures an early intervention to regulate the carbohydrate metabolism. In this publication a non-invasive detection principle based on the measurement of complex scattering parameters in the millimeter-wave frequency range is presented. The measurement principle provides evidence of the applicability for the identification of different glycemic states in animal models. The method proposed here can be used to predict diabetes status in animal models and is interesting for application on humans in view of safeness of millimeter-wave radiation. Furthermore the complex scattering parameters give important information about the anatomic varieties between the analyzed skin samples of the different mice strains. In contrast to other methods, our approach is less sensitive to skin variations between animals

Diagnóstico y Análisis para la implementación de un sistema integrado de Gestión en la Empresa de servicios EMSERPLA E.S.P

La empresa EMSERPLA E.S.P., es una entidad creada desde el año 1997 mediante el Acuerdo No. 031, para satisfacer la demanda de servicios de Acueducto, Alcantarillado y Aseo en el municipio de La Plata-Huila  Nombre y/o razón social: Empresa de Servicios Públicos EMSERPLA E.S.P Organización jurídica: Empresa Industrial y Comercial del Estado de Derecho Privado. NIT: No. 813002781-2 Actividad principal: Prestación de los servicios de acueducto, aseo y alcantarillado.The company EMSERPLA E.S.P., is an entity created since the year 1997 through Agreement No. 031, to meet the demand for Aqueduct, Sewerage and Cleanliness services in the municipality of La Plata-Huila Name and/or company name: Public Services Company EMSERPLA E.S.P Legal organization: State Industrial and Commercial Company of Private Law. NIT: No. 813002781-2 Main activity: Provision of aqueduct services, sanitation and sewage

In-vivo, non-invasive detection of hyperglycemic states in animal models using mm-wave spectroscopy

Chronic or sustained hyperglycemia associated to diabetes mellitus leads to many medical complications, thus, it is necessary to track the evolution of patients for providing the adequate management of the disease that is required for the restoration of the carbohydrate metabolism to a normal state. In this paper, a novel monitoring approach based on mm-wave spectroscopy is comprehensively described and experimentally validated using living animal models as target. The measurement method has proved the possibility of non-invasive, in-vivo, detection of hyperglycemia associated conditions in different mouse models, making possible to clearly differentiate between several hyperglycemic states

Efectos preliminares de la Beca Vocación de Profesor

Mientras los países más exitosos en materias educacionales reclutan a sus profesores entre el mejor 30% de los alumnos egresados, Chile se concentra en el resto de la distribución. En este contexto, el Ministerio de Educación (MINEDUC) implementó, durante el año 2010, la Beca Vocación Profesor (BVP), cuyo principal objetivo es incentivar a los jóvenes que obtienen altos puntajes en la Prueba de Selección Universitaria (PSU), a seguir carreras de pedagogía, mediante el financiamiento de sus estudios. En el año 2011 se logró que la proporción de inscritos en pedagogía provenientes del mejor 30% de la distribución de resultados en la PSU de los matriculados aumentara de un 10,7% a un 18,1%, en comparación con el promedio del período 2007-2010, lo que se explica por el aumento de cerca de 1.400 alumnos con 600 o más puntos. En términos de puntajes promedio PSU, el incremento fue de 13 puntos en todas las carreras de pedagogía y de 27 puntos en las carreras elegibles a la BVP. Asimismo, creció entre 30% a 40% la probabilidad de que un alumno con 600 puntos o más en la PSU escoja pedagogía y en más de un 100% para los alumnos sobre 700, aunque este último parte de una base pequeña. Este aumento proporcional es mayor para establecimientos municipales. Se debe resaltar, sin embargo, que el efecto de esta beca en el sistema es limitado, ya que solo un 40% de los matriculados en el área de formación docente pertenecen a carreras elegibles por la BVP, ya sea porque las demás prefirieron no participar o porque no cumplían los requisitos para hacerlo. Si bien la BVP es un paso importante para avanzar en mejorar la calidad y formación de los docentes, habrá que esperar para conocer el impacto que esta política tendrá en los resultados educativos de los futuros niños y jóvenes que serán alumnos de estos nuevos docentes