Fletcher Aluminium is a New Zealand company that manufactures aluminium extrusions for the building market. Their extrusion process involves using a hydraulic ram to force heated raw supplied material, in the form of large diameter cylindrical logs, through a die land that is the desired product shape. The final quality of the extruded product is influenced by the extrusion temperature, ram pressure and extrusion speed. The speed of extrusion at Fletcher Aluminium is limited by the extrusion ram pressure because the extrusion machine is operating at the pressure limit of the compressor. Currently the company requires an increase in the extrusion speed, while maintaining quality requirements where these improvements are desired without upgrading the compressor. The press pressure is required to overcome friction and the flow stress of the billet, which is dependent on the precipitates and solutes conditions and their strengthening effects in the billet. However, the preheating temperature and extrusion speeds need to be sufficiently low enough to avoid hot tearing. This research starts to increase the ram speed by decreasing the Mg2Si content for precipitation strengthening. Heat treatment may be used to dissolve Mg2Si content by billet preheat to a temperature at or exceeds solvus temperature (TSolvus). However, a higher (than TSolvus) billet temperature may have two conflicting effects. First, a higher temperature in general reduces the flow stress thus lowering the required pressure. On the other hand, at temperature higher than Tsolvus, Mg2Si should completely dissolve, resulting in solid solution strengthening thus increasing the flow stress. The objective of the study is to quantify the strengthening contributions from solute atoms (Mg / Si) and precipitates (Mg2Si) on the as-received and heat treated test samples using room temperature mechanical testing and phase diagram analysis. The selected heat treatment conditions fully enclose the preheating temperature and time range currently used in Fletcher Aluminium production. Simulations of the extrusion were conducted by hot compression testing (Gleeble test), to measure the combination of strengthening effects during deformation at elevated temperatures. The room temperature tests have shown that hardness, yield strength (YS) and ultimate tensile strength (UTS) are minimised at approximately 405°C. The minimum point is shown to be caused by the combination of strengthening and softening due to solid solution and precipitation strengthening. The higher values of hardness, YS and UTS at lower and higher preheating temperatures are mainly due to precipitation and solution strengthening respectively. The findings show that, the solution of Mg2Si gradually increases as the temperature increases at temperatures exceeding 405°C. Hardness, YS and UTS were compared in order to determine the correlation between each mechanical property. A correlation exists, but it is not simple to translate between each mechanical property. The relationship between hardness and stress observed for 8% permanent strain was also investigated; there was no improvement in correlation. The elevated temperature tests show that initial flow stress and peak flow stress reduces linearly with temperature increases, which means higher testing temperature results lower precipitation and solid solution strengthening effects. Additionally, the constants of the Gleeble – Holomon equation were numerically calculated and are similar to published values. The Gleeble – Holomon equation was combined with Felthams equation in order to provide a relationship between extrusion velocity and extrusion temperature.

Fletcher Aluminium is a New Zealand company that manufactures aluminium extrusions for the building market. Their extrusion process involves using a hydraulic ram to force heated raw supplied material, in the form of large diameter cylindrical logs, through a die land that is the desired product shape. The final quality of the extruded product is influenced by the extrusion temperature, ram pressure and extrusion speed. The speed of extrusion at Fletcher Aluminium is limited by the extrusion ram pressure because the extrusion machine is operating at the pressure limit of the compressor. Currently the company requires an increase in the extrusion speed, while maintaining quality requirements where these improvements are desired without upgrading the compressor. The press pressure is required to overcome friction and the flow stress of the billet, which is dependent on the precipitates and solutes conditions and their strengthening effects in the billet. However, the preheating temperature and extrusion speeds need to be sufficiently low enough to avoid hot tearing. This research starts to increase the ram speed by decreasing the Mg2Si content for precipitation strengthening. Heat treatment may be used to dissolve Mg2Si content by billet preheat to a temperature at or exceeds solvus temperature (TSolvus). However, a higher (than TSolvus) billet temperature may have two conflicting effects. First, a higher temperature in general reduces the flow stress thus lowering the required pressure. On the other hand, at temperature higher than Tsolvus, Mg2Si should completely dissolve, resulting in solid solution strengthening thus increasing the flow stress. The objective of the study is to quantify the strengthening contributions from solute atoms (Mg / Si) and precipitates (Mg2Si) on the as-received and heat treated test samples using room temperature mechanical testing and phase diagram analysis. The selected heat treatment conditions fully enclose the preheating temperature and time range currently used in Fletcher Aluminium production. Simulations of the extrusion were conducted by hot compression testing (Gleeble test), to measure the combination of strengthening effects during deformation at elevated temperatures. The room temperature tests have shown that hardness, yield strength (YS) and ultimate tensile strength (UTS) are minimised at approximately 405°C. The minimum point is shown to be caused by the combination of strengthening and softening due to solid solution and precipitation strengthening. The higher values of hardness, YS and UTS at lower and higher preheating temperatures are mainly due to precipitation and solution strengthening respectively. The findings show that, the solution of Mg2Si gradually increases as the temperature increases at temperatures exceeding 405°C. Hardness, YS and UTS were compared in order to determine the correlation between each mechanical property. A correlation exists, but it is not simple to translate between each mechanical property. The relationship between hardness and stress observed for 8% permanent strain was also investigated; there was no improvement in correlation. The elevated temperature tests show that initial flow stress and peak flow stress reduces linearly with temperature increases, which means higher testing temperature results lower precipitation and solid solution strengthening effects. Additionally, the constants of the Gleeble – Holomon equation were numerically calculated and are similar to published values. The Gleeble – Holomon equation was combined with Felthams equation in order to provide a relationship between extrusion velocity and extrusion temperature.

O objetivo deste trabalho foi investigar a otimização da fotocura de uma resina composta odontológica por meio da fotoativacão conjugada. A fotoativação foi realizada com LED e ultrassom e LED em resina pré-aquecida. Foi utilizado LED com comprimento de onda centrado em 470 nm com densidade de potência de 600 mW/cm2 para os testes com ultrassom e pré-aquecimento associados. A aplicação de ondas mecânicas (ultrassom) ocorreu com frequência de 30 kHz (modo contínuo) e 1 MHz (modo contínuo e pulsado), e o pré-aquecimento foi feito com as temperaturas de 37oC, 50oC e 60oC. Foi avaliada também a influência da irradiância de luz na contração de polimerização por meio da técnica de variação de contraste Speckle. A resina composta utilizada foi a Filtek Z250TM (3M ESPE) na cor A2. Foram realizados os testes de microdureza Vickers e grau de conversão para a aplicação de ultrassom conjugado com LED. Para a resina pré-aquecida fotoativada com LED foram realizados realizado os testes de microdureza Vickers, grau de conversão, fluorescência, estabilidade de cor, contração e adaptação marginal. Os resultados mostraram-se promissores para a otimização da fotocura. / The aim of this study was to investigate the optimization of photo-cure of dental composite resin by combined curing methods. The curing was performed associating ultrasound and LED and LED with pre-heating composite resin. The irradiation performed was centered at 470 nm with power density of 600 mW/cm2 for the ultrasound and pre-heating association. The application of mechanical waves (ultrasound) was performed using 30 kHz (continuous mode) and 1 MHz (continuous and pulsed), and pre-heating with temperatures of 37oC, 50oC and 60oC. The influence on polymerization shrinkage was also evaluated through the variation of speckle contrast. The composite resin used was FiltekTM Z250 (3M ESPE) shade A2. Vickers microhardness and degree of conversion for the application of ultrasound in conjunction with LED were investigated. For the pre-heating composite resin and LED photo-activation, the Vickers microhardness, degree of conversion, fluorescence, color stability, shrinkage and marginal adaptation were performed. The results showed to be promising for the optimization of photo-cure of dental resins.

The Swedish pulp and paper industry meets higher demand for energy efficiencyi mprovements with increasing energy prices and changes in the Swedish renewable energy certificate system. One action of energy efficiency improvement is by using secondary heat, that otherwise would have been treated as waste heat, for use in a system with lower temperature demands. The aim of this Master´s thesis is to identify possible secondary heat sources in a typical Swedish pulp and paper mill and to investigate what economic benefits the secondary heat will provide when being used for pre heating of wood chips to a kraft digester. The Master´s thesis focuses on three secondary heat sources; dry warm air, warm water and moisture saturated warm air located inside the pulp or paper mill. Two types of kraft digesters are simulated within this study, a typical Scandinavian digester and a modern twin vessel steam phase digester. Due to quality aspects and low temperature level drying is the drying technology with dry warm air rejected. Using warm water in direct contact with wood chips increases the quantity of water to the evaporation plant and thus reduced pulp or paper production and is therefore also rejected. The thesis nevertheless indicates a goodopportunity for further investigation of using moisture saturated warm air for preheating of wood chips. The humid air, from a drying machine or produced from secondary heat warm water, is used in a theoretical modified belt drier. Conservative assumptions regarding heat transfer and investment cost calculations yield a yearly net saving for a typical Swedish pulp mill at over 5 MSEK with a return on investment at 7years.

Butia odorata (butiazeiro) é uma palmeira que ocorre em regiões subtropicais da América do Sul, onde constitui formações savânicas em áreas associadas com o manejo pecuário. Após a dispersão, suas sementes apresentam dormência, que pode ser superada por tratamentos de calor úmido. Esta tese visou avaliar como esta dormência responde a variáveis térmicas e de umidade do ambiente e de que forma ela influencia o sucesso de recrutamento de suas plântulas. Para isto foram feitos três estudos: no primeiro, os efeitos de diferentes tratamentos de temperatura, secagem e armazenamento dos diásporos sobre o sucesso germinativo da espécie foram avaliados em laboratório; no segundo, foram investigados os efeitos sazonais e de micro-hábitat (área aberta e mancha florestal) sobre a emergência de plântulas a partir de diásporos semeados no campo, relacionando as respostas às variáveis ambientais, à dormência e à viabilidade das sementes; no terceiro, foram igualmente avaliados os efeitos sazonal e de micro-hábitat, porém sobre o sobre o recrutamento de plântulas, através da semeadura em duas épocas distintas do ano (antes e após o verão), de diásporos previamente tratados para superação da dormência. Os resultados destes estudos mostraram que períodos de préaquecimento úmido (40ºC) após secagem dos diásporos atuam no alívio da dormência das sementes de B. odorata. Estes fatores também foram relacionados com a liberação da dormência das sementes em condições de campo, agindo de forma cíclica sobre este processo ao longo do ano. Esta estratégia concentrou a emergência de plântulas após o verão, quando as condições térmicas e hídricas foram mais favoráveis. Esta resposta foi potencializada pela presença de manchas florestais, que prolongaram a viabilidade das sementes e aumentaram o recrutamento de plântulas. / Butia odorata (pindo palm) is a palm tree that occurs in the subtropical regions of South America, where it composes a savanna-like vegetation in areas associated with livestock. After dispersal, seeds exhibit dormancy, which can be overcome by moist heat treatments. This thesis aimed to evaluate how such dormancy responds to thermal and moisture variables of the environment and how it influences the success of seedlings recruitment. To accomplish this, three studies were conducted: in the first, the effects of different temperature, drying and storage treatments imposed to the diaspores on the germination success of the species were evaluated in the laboratory; in the second, we investigated the effects the seasonal and microhabitat (open area vs. forest patch) on seedling emergence from diaspores sown in the field, and related the responses to environmental variables, dormancy and seed viability; in the third, the seasonal and microhabitat effects were also evaluated, but now on seedling recruitment, by doing the sowing at two different times of the year (before and after the summer) of seeds which had been previously treated for overcoming dormancy. The results of these studies showed that periods of wet preheating (40 °C) after seed drying act on relieving seed dormancy of B. odorata. These factors were also related to the release of seed dormancy under field conditions, acting in a cyclical way along the year. This strategy concentrated seedling emergence after the summer, when temperature and water conditions were more favorable. This response was enhanced by the presence of forest patches, which extended seed viability and increased seedling recruitment.

Laser joining processes, such as brazing and welding, are a common application in industry, especially in the automotive industry. These processes are the key to lightweight and efficient design with regard to the automotive industry. There, laser brazing is used mainly for visible joints due to the superior paint adhesion and surface roughness of brazed joints compared to welds. As laser brazing is applied in the automotive industry without using any fluxes or shielding gas, this leads to a difficulty in maintaining and ensuring the quality of brazed joints.

Butia odorata (butiazeiro) é uma palmeira que ocorre em regiões subtropicais da América do Sul, onde constitui formações savânicas em áreas associadas com o manejo pecuário. Após a dispersão, suas sementes apresentam dormência, que pode ser superada por tratamentos de calor úmido. Esta tese visou avaliar como esta dormência responde a variáveis térmicas e de umidade do ambiente e de que forma ela influencia o sucesso de recrutamento de suas plântulas. Para isto foram feitos três estudos: no primeiro, os efeitos de diferentes tratamentos de temperatura, secagem e armazenamento dos diásporos sobre o sucesso germinativo da espécie foram avaliados em laboratório; no segundo, foram investigados os efeitos sazonais e de micro-hábitat (área aberta e mancha florestal) sobre a emergência de plântulas a partir de diásporos semeados no campo, relacionando as respostas às variáveis ambientais, à dormência e à viabilidade das sementes; no terceiro, foram igualmente avaliados os efeitos sazonal e de micro-hábitat, porém sobre o sobre o recrutamento de plântulas, através da semeadura em duas épocas distintas do ano (antes e após o verão), de diásporos previamente tratados para superação da dormência. Os resultados destes estudos mostraram que períodos de préaquecimento úmido (40ºC) após secagem dos diásporos atuam no alívio da dormência das sementes de B. odorata. Estes fatores também foram relacionados com a liberação da dormência das sementes em condições de campo, agindo de forma cíclica sobre este processo ao longo do ano. Esta estratégia concentrou a emergência de plântulas após o verão, quando as condições térmicas e hídricas foram mais favoráveis. Esta resposta foi potencializada pela presença de manchas florestais, que prolongaram a viabilidade das sementes e aumentaram o recrutamento de plântulas. / Butia odorata (pindo palm) is a palm tree that occurs in the subtropical regions of South America, where it composes a savanna-like vegetation in areas associated with livestock. After dispersal, seeds exhibit dormancy, which can be overcome by moist heat treatments. This thesis aimed to evaluate how such dormancy responds to thermal and moisture variables of the environment and how it influences the success of seedlings recruitment. To accomplish this, three studies were conducted: in the first, the effects of different temperature, drying and storage treatments imposed to the diaspores on the germination success of the species were evaluated in the laboratory; in the second, we investigated the effects the seasonal and microhabitat (open area vs. forest patch) on seedling emergence from diaspores sown in the field, and related the responses to environmental variables, dormancy and seed viability; in the third, the seasonal and microhabitat effects were also evaluated, but now on seedling recruitment, by doing the sowing at two different times of the year (before and after the summer) of seeds which had been previously treated for overcoming dormancy. The results of these studies showed that periods of wet preheating (40 °C) after seed drying act on relieving seed dormancy of B. odorata. These factors were also related to the release of seed dormancy under field conditions, acting in a cyclical way along the year. This strategy concentrated seedling emergence after the summer, when temperature and water conditions were more favorable. This response was enhanced by the presence of forest patches, which extended seed viability and increased seedling recruitment.

Butia odorata (butiazeiro) é uma palmeira que ocorre em regiões subtropicais da América do Sul, onde constitui formações savânicas em áreas associadas com o manejo pecuário. Após a dispersão, suas sementes apresentam dormência, que pode ser superada por tratamentos de calor úmido. Esta tese visou avaliar como esta dormência responde a variáveis térmicas e de umidade do ambiente e de que forma ela influencia o sucesso de recrutamento de suas plântulas. Para isto foram feitos três estudos: no primeiro, os efeitos de diferentes tratamentos de temperatura, secagem e armazenamento dos diásporos sobre o sucesso germinativo da espécie foram avaliados em laboratório; no segundo, foram investigados os efeitos sazonais e de micro-hábitat (área aberta e mancha florestal) sobre a emergência de plântulas a partir de diásporos semeados no campo, relacionando as respostas às variáveis ambientais, à dormência e à viabilidade das sementes; no terceiro, foram igualmente avaliados os efeitos sazonal e de micro-hábitat, porém sobre o sobre o recrutamento de plântulas, através da semeadura em duas épocas distintas do ano (antes e após o verão), de diásporos previamente tratados para superação da dormência. Os resultados destes estudos mostraram que períodos de préaquecimento úmido (40ºC) após secagem dos diásporos atuam no alívio da dormência das sementes de B. odorata. Estes fatores também foram relacionados com a liberação da dormência das sementes em condições de campo, agindo de forma cíclica sobre este processo ao longo do ano. Esta estratégia concentrou a emergência de plântulas após o verão, quando as condições térmicas e hídricas foram mais favoráveis. Esta resposta foi potencializada pela presença de manchas florestais, que prolongaram a viabilidade das sementes e aumentaram o recrutamento de plântulas. / Butia odorata (pindo palm) is a palm tree that occurs in the subtropical regions of South America, where it composes a savanna-like vegetation in areas associated with livestock. After dispersal, seeds exhibit dormancy, which can be overcome by moist heat treatments. This thesis aimed to evaluate how such dormancy responds to thermal and moisture variables of the environment and how it influences the success of seedlings recruitment. To accomplish this, three studies were conducted: in the first, the effects of different temperature, drying and storage treatments imposed to the diaspores on the germination success of the species were evaluated in the laboratory; in the second, we investigated the effects the seasonal and microhabitat (open area vs. forest patch) on seedling emergence from diaspores sown in the field, and related the responses to environmental variables, dormancy and seed viability; in the third, the seasonal and microhabitat effects were also evaluated, but now on seedling recruitment, by doing the sowing at two different times of the year (before and after the summer) of seeds which had been previously treated for overcoming dormancy. The results of these studies showed that periods of wet preheating (40 °C) after seed drying act on relieving seed dormancy of B. odorata. These factors were also related to the release of seed dormancy under field conditions, acting in a cyclical way along the year. This strategy concentrated seedling emergence after the summer, when temperature and water conditions were more favorable. This response was enhanced by the presence of forest patches, which extended seed viability and increased seedling recruitment.

O objetivo deste trabalho foi investigar a otimização da fotocura de uma resina composta odontológica por meio da fotoativacão conjugada. A fotoativação foi realizada com LED e ultrassom e LED em resina pré-aquecida. Foi utilizado LED com comprimento de onda centrado em 470 nm com densidade de potência de 600 mW/cm2 para os testes com ultrassom e pré-aquecimento associados. A aplicação de ondas mecânicas (ultrassom) ocorreu com frequência de 30 kHz (modo contínuo) e 1 MHz (modo contínuo e pulsado), e o pré-aquecimento foi feito com as temperaturas de 37oC, 50oC e 60oC. Foi avaliada também a influência da irradiância de luz na contração de polimerização por meio da técnica de variação de contraste Speckle. A resina composta utilizada foi a Filtek Z250TM (3M ESPE) na cor A2. Foram realizados os testes de microdureza Vickers e grau de conversão para a aplicação de ultrassom conjugado com LED. Para a resina pré-aquecida fotoativada com LED foram realizados realizado os testes de microdureza Vickers, grau de conversão, fluorescência, estabilidade de cor, contração e adaptação marginal. Os resultados mostraram-se promissores para a otimização da fotocura. / The aim of this study was to investigate the optimization of photo-cure of dental composite resin by combined curing methods. The curing was performed associating ultrasound and LED and LED with pre-heating composite resin. The irradiation performed was centered at 470 nm with power density of 600 mW/cm2 for the ultrasound and pre-heating association. The application of mechanical waves (ultrasound) was performed using 30 kHz (continuous mode) and 1 MHz (continuous and pulsed), and pre-heating with temperatures of 37oC, 50oC and 60oC. The influence on polymerization shrinkage was also evaluated through the variation of speckle contrast. The composite resin used was FiltekTM Z250 (3M ESPE) shade A2. Vickers microhardness and degree of conversion for the application of ultrasound in conjunction with LED were investigated. For the pre-heating composite resin and LED photo-activation, the Vickers microhardness, degree of conversion, fluorescence, color stability, shrinkage and marginal adaptation were performed. The results showed to be promising for the optimization of photo-cure of dental resins.

Aços ferríticos ligados ao cromo e molibdênio, como o ASTM A335 P22, são largamente utilizados nos geradores de vapor em plantas termoelétricas ao redor do mundo e podem apresentar trincas por fadiga durante sua operação. A montagem dos componentes dos geradores de vapor em campo é realizada através de técnicas manuais de soldagem e tem sido apontada como um fator crítico para a qualidade destes equipamentos quando algum parâmetro de soldagem é negligenciado durante o processo. A região soldada de um aço ligado sofre grande influência do ciclo térmico durante a soldagem, cujos elementos de liga mesmo em pequenas quantidades presentes no aço e metal da solda aumentam a temperabilidade, e que dessa forma favorece a formação de microestruturas bainíticas ou martensíticas na região soldada. Neste estudo, uma solda realizada de acordo com o procedimento qualificado, com pré-aquecimento e alivio de tensões pós-soldagem, foi comparada com uma solda realizada sem os tratamentos de pré-aquecimento e alivio de tensões, e foi comparada ainda com uma solda realizada sem os tratamentos térmicos de pré-aquecimento e alivio de tensões e com aporte de calor acima do determinado pelo procedimento. Para isto, o desempenho de cada solda foi analisado quanto ao desempenho nos ensaios de tração, dobramento lateral (requisitos de qualificação de procedimento pelo código ASME IX), e nos ensaios complementares de resistência ao impacto charpy e tenacidade à fratura de cada região principal da solda (Material base, ZTA e Metal de adição). A tenacidade à fratura de cada uma das regiões foi determinada através da técnica da mecânica da fratura elasto-plástica do Deslocamento da Abertura da ponta da trinca, \"Crack Tip Open Displacement\" (CTOD), aplicada a materiais dúcteis. O resultado deste estudo comparativo mostra que mesmo negligenciando os limites dos parâmetros do procedimento de soldagem especificado para o aço ASTM A335 P22, com espessura de 21mm e 304,8mm de diâmetro, o procedimento teria sido aprovado nos ensaios de qualificação estabelecidos pela norma (tração e dobramento lateral). Contudo, os resultados dos ensaios de Impacto charpy e CTOD realizados nas regiões da solda, mostraram que o metal de adição apresentou tenacidade bem a baixo do que foi observado para a ZTA e para o material base. Desta forma a realização do pré-aquecimento e tratamento de alívio pós-soldagem produziu microestruturas de menor dureza, mas que não refletiu em um aumento da tenacidade do metal de adição. / Ferritic alloy steels with chromium and molybdenum, as ASTM A335 P22, are widely used in steam generators in power plants around the world and may have broken fatigue during operation. The assembly of the components of the steam generators in the field is performed by manual welding techniques and has been identified as a critical factor for the quality of these devices when some parameter is ignored during the welding process. The welded region of an alloy is influenced thermal cycle during welding, alloying elements present in the steel and weld metal increases hardenability, and thus favors the formation of bainíticas or martensitic microstructures in the welded region. In this study, a weld made according to the procedure qualified, pre-heating and post-weld relief of stress was compared with a weld treatments performed without preheating and relieving stress, and was further compared with a solder heat treatments performed without preheating and stress relief heat input and determined by the above procedure. For this, the performance of each weld was analyzed for performance in tensile tests, lateral bending (qualification requirements of ASME IX by procedure code), and testing of Charpy impact resistance and toughness of each major region of the fracture weld (base material, HAZ and weld metal). The fracture toughness of each region was determined by fracture mechanics technique of elastic-plastic fracture Crack Tip Open Displacement (CTOD) applied to ductile materials. The result of this comparative study shows that even neglecting the parameters limits of the welding procedure specified for ASTM A335 P22 with thickness of 21mm and diameter of 304.8 mm, the procedure would have passed in qualification tests established by ASME IX (tensile and lateral bending). However, the results of Charpy impact and the CTOD tests performed in weld regions showed that the weld metal had a very low tenacity than was observed in the HAZ and the base material. Thus the realization of pre-heating and post-weld treatment relief produced microstructures with lower hardness but that was not reflected in an increase in the toughness of weld metal.