title: Microstructure and Mechanical Properties of Ti-6Al-4V Produced by Selective Laser Sintering of Pre-alloyed Powders

authors: Abd Aziz, Izhar

subjects: Titanium

abstract: The purpose of this research is to investigate the microstructure and mechanical properties of Ti6Al4V pre-alloyed powders producing by direct metal laser sintering technique. Through this research, the direct fabrication of Ti6Al4V metal parts by selective laser sintering machine has been carried out using EOS GmbH M270 equipment. Employing intricate thermo-mechanical interaction between the laser beam and the metallic powders, the machine consolidates predefined cross sections and binds the particles together to form solid parts which correspond to CAD data.The geometrical feasibility of the parts, including process accuracy were statistically analysed by simple benchmark studies. The intricate correlation between powder materials and process parameters were thoroughly investigated via fractography, metallography and standard physical testing.It was found that, SLS technologies are capable of directly producing near to full density metal parts with good mechanical properties.Ti6Al4V produced by laser sintering has very fine α+  microstructure. This fine and stable microstructure demonstrated a high yield stress and UTS with low elongation at break.  The fracture surface has a dimple features typical of a ductile structure. Dimensional analyses were performed on the customised benchmark showing process accuracy below 50 m. Designated heat treatments modified the microstructure which influences the mechanical behaviour of the parts.

text: Microstructure and Mechanical Properties of Ti-6Al-4V Produced by Selective Laser Sintering of Pre-alloyed Powders The purpose of this research is to investigate the microstructure and mechanical properties of Ti6Al4V pre-alloyed powders producing by direct metal laser sintering technique. Through this research, the direct fabrication of Ti6Al4V metal parts by selective laser sintering machine has been carried out using EOS GmbH M270 equipment. Employing intricate thermo-mechanical interaction between the laser beam and the metallic powders, the machine consolidates predefined cross sections and binds the particles together to form solid parts which correspond to CAD data.The geometrical feasibility of the parts, including process accuracy were statistically analysed by simple benchmark studies. The intricate correlation between powder materials and process parameters were thoroughly investigated via fractography, metallography and standard physical testing.It was found that, SLS technologies are capable of directly producing near to full density metal parts with good mechanical properties.Ti6Al4V produced by laser sintering has very fine α+  microstructure. This fine and stable microstructure demonstrated a high yield stress and UTS with low elongation at break.  The fracture surface has a dimple features typical of a ductile structure. Dimensional analyses were performed on the customised benchmark showing process accuracy below 50 m. Designated heat treatments modified the microstructure which influences the mechanical behaviour of the parts.

year: 2010

title: Headteachers’ readings of and responses to disadvantaged contexts: evidence from English primary schools

authors: Lupton, Ruth

subjects: schools

abstract: Existing research demonstrates the impact of context on school organisation and management, curriculum and pedagogy and on student peer relations. New developments in English education policy will devolve more responsibility for dealing with these issues to headteachers. Headteachers' readings of their contexts and the responses that they make are thus of increasing interest. This paper draws on interviews with eight headteachers of less advantaged English primary schools to explore how they understand and articulate the contexts in which their schools operate and how this knowledge is translated into strategies for organising curriculum, pedagogy and other school processes. These headteachers observed context through the lens of the behaviour of parents and children in relation to school, contrasting it with an assumed middle-class normality. More critical perspectives on families' social and economic position or on the contribution of school practice to educational exclusion were largely absent. School responses were many and varied but, given the constraints of budgets, market and performative pressures, were unlikely to substantially transform the educational experiences and outcomes of disadvantaged students. We point to the continuing need for more contextualised funding mechanisms and policies to improve schools in disadvantaged areas and also, in the light of devolution to schools, to the need to develop mechanisms of support to headteachers to help them to develop critical understandings of context and to reflect on school process and practices in the light of these understandings.

text: Headteachers’ readings of and responses to disadvantaged contexts: evidence from English primary schools Existing research demonstrates the impact of context on school organisation and management, curriculum and pedagogy and on student peer relations. New developments in English education policy will devolve more responsibility for dealing with these issues to headteachers. Headteachers' readings of their contexts and the responses that they make are thus of increasing interest. This paper draws on interviews with eight headteachers of less advantaged English primary schools to explore how they understand and articulate the contexts in which their schools operate and how this knowledge is translated into strategies for organising curriculum, pedagogy and other school processes. These headteachers observed context through the lens of the behaviour of parents and children in relation to school, contrasting it with an assumed middle-class normality. More critical perspectives on families' social and economic position or on the contribution of school practice to educational exclusion were largely absent. School responses were many and varied but, given the constraints of budgets, market and performative pressures, were unlikely to substantially transform the educational experiences and outcomes of disadvantaged students. We point to the continuing need for more contextualised funding mechanisms and policies to improve schools in disadvantaged areas and also, in the light of devolution to schools, to the need to develop mechanisms of support to headteachers to help them to develop critical understandings of context and to reflect on school process and practices in the light of these understandings.

year: 2013

title: DrownBaseTM – Identifying at risk factors: Strategies and issues around Māori practices and activities towards water safety

authors: Karapu, Rolinda

subjects: Maori

abstract: Aotearoa has some of the most extensive and beautiful waterways in the world. The seas, rivers, beaches, and lakes provide endless opportunities for Māori to enjoy water activities, such as gathering kai, swimming, hoe waka, diving and fishing (Haimona & Takurua, 2003). For Māori, water is one of the greatest taonga (treasures) of this land – both physically and spiritually. Māori have always been acknowledged as possessing expertise in swimming and aquatic activities pre-European times (Haimona & Takurua, 2003). Early writers such as Best (1976) wrote extensively about Māori games and pastimes while in, on or near the water. These early descriptions illustrate the practice that Māori children were taught to swim at a very early age. The gathering of seafood and the consistent use of waterways as a mode of transport were also customary activities for Māori. The traditional beliefs and practices of Māori, demonstrate a great awareness and understanding of water, its dangers and its life-giving properties.

text: DrownBaseTM – Identifying at risk factors: Strategies and issues around Māori practices and activities towards water safety Aotearoa has some of the most extensive and beautiful waterways in the world. The seas, rivers, beaches, and lakes provide endless opportunities for Māori to enjoy water activities, such as gathering kai, swimming, hoe waka, diving and fishing (Haimona & Takurua, 2003). For Māori, water is one of the greatest taonga (treasures) of this land – both physically and spiritually. Māori have always been acknowledged as possessing expertise in swimming and aquatic activities pre-European times (Haimona & Takurua, 2003). Early writers such as Best (1976) wrote extensively about Māori games and pastimes while in, on or near the water. These early descriptions illustrate the practice that Māori children were taught to swim at a very early age. The gathering of seafood and the consistent use of waterways as a mode of transport were also customary activities for Māori. The traditional beliefs and practices of Māori, demonstrate a great awareness and understanding of water, its dangers and its life-giving properties.

year: 2008