Foram estudados os efeitos da introdução de etapas de tratamento criogênico e do alívio de tensões no ciclo térmico do aço ferramenta para trabalho a frio AISI D2. Variaram-se as temperaturas de tratamento criogênico, sendo elas principalmente: criogênica (-196°C) e subzero (-80°C). Foram variados os tempos de permanência às temperaturas criogênicas: 2, 3, 10, 24 e 30 e 36 horas. Verificou-se o efeito da adição da etapa (130°C/90 minutos) de alívio de tensões previamente ao tratamento criogênico. As amostras com diferentes ciclos térmicos foram submetidas à caracterização metalográfica, difração de raios-X e ensaios de potencial termo-elétrico. Na caracterização metalográfica as amostras foram analisadas por MEV (microscopia eletrônica de varredura) e MEV-FEG (MEV com canhão com emissão por efeito de campo). Os carbonetos secundários (micrométricos) não apresentaram variação. Os carbonetos secundários de revenido (nanométricos) apresentaram-se mais finamente dispersos na matriz nas amostras com tratamento criogênico e sem alívio de tensões. A difração de Raios-X foi realizada no Laboratório Nacional de Luz Síncroton, a luz síncroton foi essencial para detectar as variações pequenas e em escala nanométrica que ocorreram devido às inserções dos tratamentos criogênicos e de alívio de tensões. Foram verificados: i) menor fração volumétrica de austenita retida nas amostras tratadas em temperatura subzero quando comparadas às amostras tratadas em temperaturas criogênicas, indicando um comportamento cinético em C da curva de transformação; ii) diminuição da relação c/a dos parâmetros do reticulado cristalino da martensita e aumento do parâmetro a da austenita (devido à partição de carbono da martensita supersaturada em carbono para a austenita) causando estabilização da austenita com a inserção da etapa de alívio de tensões; iii) aumento no parâmetro a da austenita retida residual após revenimentos, com consequente aumento no teor de carbono da mesma, devido à partição de carbono; iv) maior fração volumétrica de carbonetos de revenido (M7C3 e M2C) nas amostras com tratamento criogênico logo após a têmpera, seguido da amostra com tratamento criogênico + alívio de tensões, seguidos da amostra somente temperada e revenida e por fim da amostra com alívio de tensões e sem tratamento criogênico. Os ensaios de potencial termo-elétrico (realizados no INSA-Lyon) foram utilizados para verificar o comportamento das amostras nas temperaturas de revenimento. Foram realizados tratamentos isotérmicos (130°C, 210°C, 350°C, 450°C e 520°C) cumulativos com tempos de 1 minuto até 130 horas. Verificou-se que: i) nos primeiros estágios do revenimento a cinética é favorecida pelo tratamento criogênico (precipitação de carbonetos \'eta\' ou \'epsilon\'); ii) o alívio de tensões atrasa os dois primeiros estágios do revenimento; iii) há maior crescimento dos carbonetos de liga nas amostras sem tratamento criogênico. O refinamento dos carbonetos secundários de revenimento foi atribuído a uma sequência de precipitações de carbonetos de revenido in situ: \'eta\' -> \'teta\' -> M7C3 e M2C. / The effects of cryogenic treatments and of stress relief treatment introduced in the thermal cycle of the cold work tool steel AISI D2 were studied. The cryogenic temperatures were varied: cryogenic (-196°C) and subzero (-80°C). It was also varied the holding times at cryogenic temperatures: 2, 3, 10, 24, 30 and 36 hours. The effect of including a stress relief heat treatment previously to the cryogenic treatment was also verified. Samples submitted to different thermal cycles were studied using metallographic characterization, X-ray diffraction and electric power measurements. The metallographic characterization used SEM (scanning electron microscopy) and SEM-FEG (SEM with field emission gun), besides OM (optical microscopy). It was not found any variation in the secondary carbides (micrometrics) precipitation. The temper secondary carbides (nanometrics) showed to be more finely dispersed in the matrix of the samples with cryogenic treatment and without stress relief. The X-ray diffractions were carried out at the Brazilian Synchrotron Light Laboratory; synchrotron light was essential to detect small and nano sized variations occurring due to the addition of the cryogenics and stress relief treatments. It was verified: i) lower austenite volumetric fraction in the samples with subzero treatment if compared to the cryogenic treated samples, an indication of a C curve kinetic behavior of the transformation; ii) the stress relief treatment produced an decrease in the c/a relationship of the martensite lattice parameters and an increase in the austenite a parameter (explained by carbon atoms partition from the supersatured martensite to the retained austenite); iii) after double tempering occurred an increase in the a parameter of the remaining austenite lattice, indicating an increase in the carbon content of the residual retained austenite, due to carbon partition; iv) higher volumetric fraction of temper carbides (M7C3 and M2C) if the samples were cryogenic treated just after quench (to room temperature), followed by the sample with cryogenic treatment + stress relief, after the sample just quenched and tempered and finally by the samples with stress relief without cryogenic treatment. Thermo-electric power measurements (carried out at INSA-Lyon) characterized the samples behavior after tempering at different temperatures. Cumulative isothermal treatments (130°C, 210°C, 350°C, 450°C e 520°C) with increasing times (from 1 minute to 130 hours) were used. It was verified that: i) the kinetic is favoured by the cryogenic treatment in the first temper stage (\'eta\' or \'epsilon\' carbide precipitation); ii) the stress relief delayed the first and second temper stage; iii) the samples without cryogenic treatment showed to have a bigger growing for the alloys carbides in the last stage of temper. The refinement of the temper secondary carbides was attributed to an in situ carbide precipitation during tempering: \'eta\' -> \'teta\' -> M7C3 e M2C.

Submitted by AMÉRICO BIANCALANA NETO null (abiancalana@confab.com.br) on 2016-09-21T15:55:15Z No. of bitstreams: 1 DISSERTAÇÃO_Américo Biancalana Neto.pdf: 6507235 bytes, checksum: 42c17d17ef5a510dd34876071a8ff043 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-09-26T19:52:21Z (GMT) No. of bitstreams: 1 biancalananeto_a_me_guara.pdf: 6507235 bytes, checksum: 42c17d17ef5a510dd34876071a8ff043 (MD5) / Made available in DSpace on 2016-09-26T19:52:21Z (GMT). No. of bitstreams: 1 biancalananeto_a_me_guara.pdf: 6507235 bytes, checksum: 42c17d17ef5a510dd34876071a8ff043 (MD5) Previous issue date: 2016-07-22 / Os processos tradicionais de produção de tubos API 5CT N80Q envolvem processos de bobinamento e desbobinamento, conformação por dobramento, soldagem, etapas de usinagem e expansão dos diâmetros interno e externo, tratamentos térmicos de têmpera e revenimento e endireitamento. Essas etapas são responsáveis por introduzir tensões residuais no material constituinte do tubo. Estas tensões residuais podem alcançar valores próximos aos do limite de escoamento do material base do tubo, podendo produzir distorções geométricas, falhas prematuras, baixa resistência à corrosão, e diminuição na sua capacidade de absorção de cargas em trabalho. O método mais utilizado para alívio de tensões é o tratamento térmico. Porém, a aplicação de vibrações mecânicas, (Vibratory Stress Rielif) para reduzir e redistribuir as tensões residuais em estruturas conformadas a frio e em estruturas soldadas, tem sido utilizada com sucesso em várias partes do mundo, principalmente nos Estados Unidos, China e Canada. Para verificar a viabilidade deste processo, como um método alternativo para o alivio de tensões, selecionamos um tubo API 5CT 80NQ, com diâmetro de 178 mm com 8,05 mm de espessura e 3000 mm de comprimento. Os ensaios de vibração foram executados na frequência de ressonância do tubo, através de um indutor de vibração montado no seu comprimento médio, dentro de um intervalo de tempo correspondente ao seu peso. Comparando os valores de tensões residuais existentes no tubo antes e após o tratamento de vibração conseguimos uma redução média de 16% no valor das mesmas. Para a caracterização mecânica do tubo, antes e depois do processo vibratório, foram realizados os seguintes ensaios conforme a norma API 5CT 2001: impacto Charpy “V”, ensaios de tração e dureza Rockwell C, tanto no metal base do tubo, como na região da solda. Foi realizada, também, a sua caracterização micro estrutural através, microscopia ótica, antes e depois dos ensaios de vibração. Para avaliação das tensões residuais, antes e após os ensaios de vibração, foi utilizado o método de secção longitudinal de um anel (splitting ring test) conforme a norma ASTM EN 1928-13. / The traditional production processes API 5CT N80Q pipes involve coiling and uncoiling processes the plate, conformation by bending, welding, machining steps and expansion of its internal and external diameters, heat treatment of quenching and tempering and straightening. These steps are responsible for introducing residual stresses in the material of the tube. These residual stresses can reach values close to the yield strength of the pipe`s base material and may produce geometric distortions, premature failure, low corrosion resistance and reduction its capacity of absorption loads in the work. The most widely used method for relieving stress is the heat treatment. The application of mechanical vibrations, Vibratory stress relief ( VSR), to reduce and redistribute the residual stresses in cold shaped structures and welded structures, has been used with success in various parts of the world, especially the United States, China and Canada. Thus, the mechanical vibration, Vibratory stress relief (VSR), can prove to be an interesting process to relieve stress in the tubes. To verify the feasibility of this process, as an alternative method for the relief of stresses, we selected an API 5CT 80NQ tube with a diameter of 178 mm, with 8.05 mm thickness and 3000 mm in length. Vibration tests were performed in pipe resonance frequency, via a vibration-inducing mounted at its mid-length, within a time corresponding to their weight. Comparing the values of residual stress existing in the tube before and after the vibration treatment achieved a mean reduction of 16 % in the amount thereof. For the mechanical characterization of the pipe, before and after the vibration process, the following tests were conducted according to API standard 5CT 2001: Charpy 'V', tensile tests and hardness Rockwell C, both in the metal base tube, and in the weld region. It was also carried out their microstructural characterization through optical microscopy before and after the vibration tests. To evaluate the residual stress before and after the vibration tests, we used the ring splitting test according to ASTM E1928-13.

目前計畫是創立一間律動瑜珈教室，交導學生熱瑜珈，交導如何放鬆身心、避免受傷，並由此獲益。 / The product of Movement Yoga Studio is Bikram yoga. Bikram Yoga is a demanding series of 26 postures and two breathing exercises, suitable for all ages and levels of ability. Each posture stretches, strengthens and prepares specific muscles, ligaments and joints for the next posture. The Bikram method also stimulates the organs, glands and nerves, moving fresh oxygenated blood to 100% of the body, restoring all systems to a healthy working order. Bikram scientifically designed this 90-minute program to deliver total health through the balancing and strengthening of every system in the body in order to prevent illness, injury, promote weight loss and limit the effects of aging. The series of postures combine skills of concentration, patience, determination and self-control which increase mental clarity and reduce stress. Bikram Yoga is practiced in a heated room at 40 °C with a humidity of 40% to warm your muscles, allow a deeper workout and cleanse the body by flushing toxins. Deep relaxation is taught in each class after completion of the postures. The intention of the instructors at Movement Yoga Studio is to assist students in the development of physical, mental, and spiritual well-being - a truly priceless health advantage. Movement Yoga Studio features well-trained, professional instructors, progressive teaching methods, a non-competitive and encouraging atmosphere, and a beautiful light-filled facility. Movement Yoga Studio also has a shop that will sell workshop clothing and yoga training aides.

Pulse width modulation (PWM) voltage source converters (VSC) are one type of motor drives that have become popular because they enable precise control of speed and torque in medium voltage motors. However, these drives are known to have adverse effects on the insulation system particularly on conductive armour tape (CAT) and semi-conductive stress grading tape (SGT). These tapes, which are crucial components of the insulation system, control the surface electrical stresses in the stator slot and in the end portion of the form-wound coils outside the grounded stator. The material properties of CAT and SGT and the methods by which they are applied on form-wound motor coils are traditionally designed for power frequency, or a 60 Hz sinusoidal voltage. However, because of the high frequencies associated with the repetition rate and the fast rise time of the PWM pulses, elevated electrical and thermal stresses develop in these tapes, which can lead to premature insulation failure. Little research has been conducted with respect to understanding the mechanism of dielectric heating as a function of frequency and repetitive pulse characteristics. The material characterization of CAT and SGT is a vital part of an investigation of the performance of the stress relief system at high frequencies. In this study, the anisotropic dielectric properties of CAT and SGT have been measured in dc and ac and in low and high electric fields. The laboratory experiments for determining the material characteristics are discussed and the results analyzed. According to the ac space charge limited field (SCLF) theory, the maximum ac tangential component of the electric field in a nonlinear resistive SGT on medium voltage form-wound motor coils can be predicted from the field dependent electrical conductivity and the frequency. However, the SCLF theory cannot predict the total electric field (vector sum of the tangential and normal components) in the air adjacent to the surface of the tapes. Simulations of the electric field using a finite element method (FEM), is one of the best ways of finding the resultant electric field distribution in the air space adjacent to the SGT. However, prior to this study, researchers simplified the modelling of the stress relief system to avoid the convergence problems that develop due to the nonlinearity of the SGT conductivity as a function of the electric field, and also because of the geometry and dimensions of the tapes when their depths are orders of magnitude smaller than the other dimensions associated with form-wound coils. For modelling the stress grading (SG) system at power frequency and at the rated voltage, the dc isotropic conductivity of the SGT and CAT has also been extensively investigated. However, relatively little work has been done with respect to the ac electrical behaviour of these materials and dc modelling cannot reflect the effects of high-frequency stresses on the machine insulation. In this study, comprehensive transient FEM modelling has been developed in order to simulate the insulation system with nonlinear field dependent materials. The actual dimensions of the components are applied in the model, and the appropriate material parameters for the FEM simulations are extracted from the experimental test results. One crucial point that has not been considered in previous studies is the effect of the component of the electric field that is normal to the surface of the coil. In most studies, only the tangential component of the electric field is considered; however, in this study, both components and the resultant electric field are computed. The surface tangential field is calculated with reference to the gradient of the surface potential as measured with an electrostatic voltmeter. It is shown that this technique can provide a reasonable estimate for the tangential field along the SG system, but not without limitations, which are discussed in detail. Based on laboratory work and analytical analysis, this research has successfully determined the relationship between the thermal effect of the PWM voltage and the other repetitive fast pulses, such as square wave and impulse voltages. The influence of the pulse characteristics on the development of stresses has also thoroughly investigated, and the results are presented. A coupled electric and thermal model that incorporates the finite element method (FEM) is used as a means of studying thermal stresses and determining appropriate remedies. However, using transient analysis as an approach for finding the temperature profile associated with high repetitive impulses (1-10 kHz) and fast rise times (~200 ns) is both difficult and impractical. According to these considerations, an alternative method has been developed from stationary analyses based on two sinusoidal voltages of different frequencies. The frequency and amplitude of these sinusoids are measured relative to the switching frequency, signal power, and nonlinearity of the system, and the results of the simulation are then verified experimentally, thus showing the efficacy of this method. This research also concluded that a capacitive SG system with conductive foil embedded in the groundwall insulation can be a practical alternative to a conventional SGT of form-wound coils in inverter fed motors. The performance of the capacitive SG scheme is independent of frequency and can therefore provide the required mitigation of the stress caused by repetitive fast pulses. The results of the evaluation of this system with respect to qualification tests demonstrate the effectiveness of the system.

Pulse width modulation (PWM) voltage source converters (VSC) are one type of motor drives that have become popular because they enable precise control of speed and torque in medium voltage motors. However, these drives are known to have adverse effects on the insulation system particularly on conductive armour tape (CAT) and semi-conductive stress grading tape (SGT). These tapes, which are crucial components of the insulation system, control the surface electrical stresses in the stator slot and in the end portion of the form-wound coils outside the grounded stator. The material properties of CAT and SGT and the methods by which they are applied on form-wound motor coils are traditionally designed for power frequency, or a 60 Hz sinusoidal voltage. However, because of the high frequencies associated with the repetition rate and the fast rise time of the PWM pulses, elevated electrical and thermal stresses develop in these tapes, which can lead to premature insulation failure. Little research has been conducted with respect to understanding the mechanism of dielectric heating as a function of frequency and repetitive pulse characteristics. The material characterization of CAT and SGT is a vital part of an investigation of the performance of the stress relief system at high frequencies. In this study, the anisotropic dielectric properties of CAT and SGT have been measured in dc and ac and in low and high electric fields. The laboratory experiments for determining the material characteristics are discussed and the results analyzed. According to the ac space charge limited field (SCLF) theory, the maximum ac tangential component of the electric field in a nonlinear resistive SGT on medium voltage form-wound motor coils can be predicted from the field dependent electrical conductivity and the frequency. However, the SCLF theory cannot predict the total electric field (vector sum of the tangential and normal components) in the air adjacent to the surface of the tapes. Simulations of the electric field using a finite element method (FEM), is one of the best ways of finding the resultant electric field distribution in the air space adjacent to the SGT. However, prior to this study, researchers simplified the modelling of the stress relief system to avoid the convergence problems that develop due to the nonlinearity of the SGT conductivity as a function of the electric field, and also because of the geometry and dimensions of the tapes when their depths are orders of magnitude smaller than the other dimensions associated with form-wound coils. For modelling the stress grading (SG) system at power frequency and at the rated voltage, the dc isotropic conductivity of the SGT and CAT has also been extensively investigated. However, relatively little work has been done with respect to the ac electrical behaviour of these materials and dc modelling cannot reflect the effects of high-frequency stresses on the machine insulation. In this study, comprehensive transient FEM modelling has been developed in order to simulate the insulation system with nonlinear field dependent materials. The actual dimensions of the components are applied in the model, and the appropriate material parameters for the FEM simulations are extracted from the experimental test results. One crucial point that has not been considered in previous studies is the effect of the component of the electric field that is normal to the surface of the coil. In most studies, only the tangential component of the electric field is considered; however, in this study, both components and the resultant electric field are computed. The surface tangential field is calculated with reference to the gradient of the surface potential as measured with an electrostatic voltmeter. It is shown that this technique can provide a reasonable estimate for the tangential field along the SG system, but not without limitations, which are discussed in detail. Based on laboratory work and analytical analysis, this research has successfully determined the relationship between the thermal effect of the PWM voltage and the other repetitive fast pulses, such as square wave and impulse voltages. The influence of the pulse characteristics on the development of stresses has also thoroughly investigated, and the results are presented. A coupled electric and thermal model that incorporates the finite element method (FEM) is used as a means of studying thermal stresses and determining appropriate remedies. However, using transient analysis as an approach for finding the temperature profile associated with high repetitive impulses (1-10 kHz) and fast rise times (~200 ns) is both difficult and impractical. According to these considerations, an alternative method has been developed from stationary analyses based on two sinusoidal voltages of different frequencies. The frequency and amplitude of these sinusoids are measured relative to the switching frequency, signal power, and nonlinearity of the system, and the results of the simulation are then verified experimentally, thus showing the efficacy of this method. This research also concluded that a capacitive SG system with conductive foil embedded in the groundwall insulation can be a practical alternative to a conventional SGT of form-wound coils in inverter fed motors. The performance of the capacitive SG scheme is independent of frequency and can therefore provide the required mitigation of the stress caused by repetitive fast pulses. The results of the evaluation of this system with respect to qualification tests demonstrate the effectiveness of the system.

No description available.

Choral music has played an important role in the liberation of South African people, and it is still very popular today, including among Setswana-speaking choral groups. This study looks at the role of music, particularly choral music, in the expression of Setswana-speakers’ identity as well as the psychological effects on the psychosocial well-being of the choristers. A qualitative research approach, supported by in-depth interviews, was adopted in this study to better understand the singing experiences of two male choir conductors and two female choristers. For this purpose, thematic analysis technique was employed. The results indicate that singing in the choir contributes to the choristers’ physical, emotional, mental, social, and spiritual well-being as well as to their identity formation. Participants also highlighted challenges such as time constraints, poor leadership, socio-economic conditions, unforeseen circumstances, discrimination against younger members, love affairs, and gossip within the choral groups. The results indicate a positive and socially engaging contribution of choral music in the expression of identity as well as in the sense of belonging and connection of choristers. The findings are in line with the literature and indicate that participation in a choir enhances and strengthens psychosocial well-being, that is self-discipline, healthy lifestyle, self-confidence, self-esteem, motivation, physical fitness, emotional expressivity, emotional processing and stress relief, social responsibility, moral growth and development, mental alertness and focus, upliftment and inspiration, connection with God, and nurtures the community social fabric. / Psychology / M.A. (Clinical Psychology)