Abstract: The objective of this study was to obtain the damping factor (ξ )as well as the elastic... more Abstract: The objective of this study was to obtain the damping factor (ξ )as well as the elasticity modulus (E) of two kinds of synthetic graphite (HLM and ATJ), using the modal analysis technique. Prismatic beams of square section (~ 11 x 11 mm) and length over thickness ratio (L/t) of about 22.7 were tested in the free free condition. The first four modes of vibration were taken into account in the analysis. In addition, numerical simulations were also carried out in this investigation. The agreement between the theoretical and the experimental results was quite good. The average values of E and ξ for the HLM graphite were 20% and 90% higher , respectively, than those presented by the ATJ graphite.
Abstract. Smart or adaptative structures are those capable to perform some special functions whe... more Abstract. Smart or adaptative structures are those capable to perform some special functions when stimulated externally. In the context of this type of structure, hybrid adaptative composite beams, reinforced with active Ni-Ti filaments, were simulated in the present work. Such beams may be adopted for vibration control, exploring the possibility of changing their bending stiffness by means of controlling the temperature of the shape memory alloy filaments. The main objective of this paper is to present, for a free-free boundary condition, the vibration modes and their frequencies obtained analytically and numerically for prismatic beams, which incorporate nineteen layers of epoxy reinforced with chopped E-glass mat (17 plies), and two symmetric active plies (A) embedded with up to four Ni-Ti wires each (2+A+13+A+2). One particular aspect of this investigation is to verify how the natural frequency of the beams changes, when an electric current passes through the Ni-Ti wire...
Em nivel mundial, tubulacoes de aco desempenham papeis fundamentais nos diversos setores industri... more Em nivel mundial, tubulacoes de aco desempenham papeis fundamentais nos diversos setores industriais. Contudo, qualquer tipo de duto esta sujeito a desgastes em sua superficie devido a corrosao. Neste sentido, tecnicas que viabilizem o reparo rapido e confiavel de dutos sao de fundamental importância para aumentar sua vida util, prevenir acidentes, minimizar danos ambientais e permitir a manutencao da eficiencia dos mesmos apos serem reparados. Reparos com materiais compositos estao tendo grande destaque no mercado internacional devido a sua alta eficiencia, baixo peso e custo acessivel. Com o objetivo de obter informacoes de interesse tecnologico para setores industriais que necessitem executar manutencao preventiva em tubulacoes e realizar reparos emergenciais em caso de necessidade, obter-se-a solucoes otimizadas de constituicao e dimensionamento do reparo hibrido em material composito, utilizado em tubos industriais de ampla aplicacao no mercado atual.
This investigation is concerned with the mechanical behavior of Shape Memory Alloy Hybrid Composi... more This investigation is concerned with the mechanical behavior of Shape Memory Alloy Hybrid Composite Beams (SMAHC), that consist of a circular bar of NiTi alloy incorporated in a 500 mm long cylindrical pipe of polypropylene (PP), with external diameter 50 mm and nominal wall thickness 7 mm, wound with a nylon/epoxy layer. The Ni-Ti alloy was characterized using: scanning electron microscopy (SEM); X-ray diffraction (XRD) and Differential thermal analysis (DSC). The nominal chemical composition of the alloy is 50.05 %Ni / 49.95%Ti, and the softer martensite is the predominant phase at room temperature. The approximate martensite (M) to Austenitic (A) phase transformation temperatures were Mstart = 32°C, Mfinal = 46°C, Astart = 38 °C and Afinal = 60°C. For temperature TAfinal it is fully converted in the Austenitic phase; and its elasticity modulus increases by a factor up to three times. This significant change in stiffness of Ni-Ti, without changing its mass, has motivated the appli...
The aim of this work is to present some experiment`s results concerning with the machinability an... more The aim of this work is to present some experiment`s results concerning with the machinability and the determination of the superficial hardness of green carbon fiber reinforced phenolic workpieces, and three different kinds of carbon fiber reinforced carbon (CRFC) samples. Firstly, this work shows a characterization of the CFRC composite related with its composition, fabrication process, mechanical properties and main applications. Secondly, two kinds of hardness were measured: (1) Rockwell, L and (2) Micro Vickers. More than 200 indentations were carried out. In the main, the results of the Rockwell L tests showed better repeatability than those based on the Micro Vickers tests. After the hardness test, a comparative analysis of the CRFC composite machinability is done about the green carbon fiber reinforced phenolic composites. Experimental of turning were carried out to study the performance of different tool materials. Experimental results showed that only diamond tools are suitable for use in finish turning. In rough turning, the cemented carbide tools showed to be the best solution. This work ends with suggestions of machining parameters for CRFC composites, allowing some basic cutting conditions to be established for the turning operations.
RESUMO No presente trabalho, adotou-se a análise estatística de Weibull para avaliação da resistê... more RESUMO No presente trabalho, adotou-se a análise estatística de Weibull para avaliação da resistência mecânica à flexão, e sua repetibilidade, de mármores sintéticos, tanto puros quanto reforçados com fibra vidro-E. O objetivo foi observar o comportamento do módulo de Weibull e da resistência mecânica, à medida que se introduz fibra de vidro picotada na composição do mármore sintético. Para isso foram avaliados quatro diferentes teores, em massa, de fibra de vidro, para estabelecer uma curva padrão do comportamento mecânico, à medida em que se alterou a fração de fibra do compósito. A metodologia de Weibull viabiliza esta análise, uma vez que, além dos corpos de prova possuírem grande semelhança dimensional de espessura com os produtos fabricados em mármore sintético, ela quantifica a ocorrência de imperfeições devido ao processo de fabricação. Os resultados demonstraram que a inserção de fibra de vidro, em uma massa de 3 Kg de mármore sintético, em proporções de 12,5 a 100 gramas p...
In comparison with steel, concrete, and polymeric pipes, glass-reinforced plastic (GRP) pressure ... more In comparison with steel, concrete, and polymeric pipes, glass-reinforced plastic (GRP) pressure pipes use more expensive raw materials. Thus, despite of their attractive structural performance, mainly in terms of mechanical strength combined with low weight, the higher cost can be a limitation in many applications. In this scenario, an alternative to reduce the final price of GRP pipes is the addition of quartz sand filler. In this experimental and numerical study, filament-wound E-glass/polyester pipes with nominal inside diameter of 300 mm and wall thickness of 5.7 mm were produced with the incorporation of quartz sand as filler and tested to failure under internal pressure. The mechanical behavior of the composite pipes was evaluated experimentally, throughout short-time hydraulic failure pressure tests, as well as using finite element analysis (FEA). In the FEA simulations, the shell wall was modeled as an axisymmetric layered orthotropic material. A good agreement, varying from 96% to 98%, was obtained between the average hydraulic failure pressure measured and FEA predicted failure pressures, using Tsai—Hill and Hoffman failure criteria, respectively.
This work presents the numerical simulation of thin perfect, machined and repaired PVC pipes subj... more This work presents the numerical simulation of thin perfect, machined and repaired PVC pipes subjected to internally hydrostatic pressure, with ratio between the diameter (D) and the thickness (t), above or equal 20, D/t > 20. The numerical simulations were carried out with a finite element program, called Compshell, using PVC tubes, from elastic behavior to the failure. The boundary conditions were: clamped in one end and simple supported in the other, with freedom along the axial direction. The longitudinal and radial displacements, the bending moments and normal stresses resultants for pipes were evaluated. The maximum pressure was estimated using the Tsai-Hill failure criterion. The best result for repaired pipes was obtained with a laminate of epoxy matrix (E) filled with cotton cloth (C), since this composite and PVC Young's modulus are close to each other. The ideal composite repairing is the one that restores the structural stiffness of the affected region, in the way...
ABSTRACT Six hemispherical and four torispherical composite plastic domes reinforced with either ... more ABSTRACT Six hemispherical and four torispherical composite plastic domes reinforced with either carbon or E-glass woven fabrics or a combination of both have been tested under external pressure. The domes were prepared using male or female moulds and employed the hand lay-up/vacuum bag method for their manufacture. The domes were observed to fail either by buckling or as a result of material failure. Both modes of failure were usually located at the meridian having the minimum average thickness. These domes were then repaired using a recommended technique and retested. It has been shown that the integrity of the repaired zones was guaranteed and further damage to the domes during retesting moved to new locations usually corresponding to the areas of the new minimum average thickness meridian. Two computer programs based on finite difference and finite element methods were employed to predict the critical buckling or material failure loads. The theoretical predictions were shown to correlate very well with the experimental results.
Neste trabalho, são apresentadas simulações numéricas de tubos de PVC de parede fina submetidos à... more Neste trabalho, são apresentadas simulações numéricas de tubos de PVC de parede fina submetidos à pressão hidrostática interna, íntegros, desbastados e reparados, com uma razão entre o diâmetro (D) e a espessura (t) superior ou igual a 20, i.e. D/t > 20. Foram realizadas simulações numéricas com o programa de elementos finitos, chamado Compshell, utilizando tubos de PVC, desde o regime elástico até a ruptura, com a condição de contorno engastado numa extremidade e com liberdade de deslocamento axial na outra. São analisados os resultados dos deslocamentos longitudinal e radial, resultantes de momentos fletores e de tensões normais para tubos. As pressões máximas foram estimadas com o critério de falha de Tsai-Hill. O melhor resultado para tubos reparados foi obtido com o laminado de matriz epóxi (E) e carga de enchimento de algodão (A) com módulos de Young do compósito, E E/A = 3,5 GPa, e do tubo de PVC, E PVC = 3,0 GPa. O reparo compósito ideal é aquele que restitui a rigidez es...
O objetivo deste trabalho foi avaliar a distribuição de tensões na resina em contato com os filet... more O objetivo deste trabalho foi avaliar a distribuição de tensões na resina em contato com os filetes de roscas de mini-implantes cilíndricos e cônicos, submetidos à carga lateral e torção de inserção. Um modelo fotoelástico foi confeccionado com gelatina transparente, para simular o osso alveolar. O modelo foi observado com um polariscópio plano e fotografado antes e após a ativação dos mini-implantes com força lateral e de inserção. A aplicação de cargas laterais provocou momentos fletores nos mini-implantes, aparecimento de franjas isocromáticas ao longo dos filetes do corpo dos mini-implantes e no ápice. Quando foi aplicado o torque de inserção, verificou-se a concentração de tensões próxima ao ápice. Concluiu-se que: (1) o mini-implante cilíndrico apresentou maior concentração de tensões no ápice, e (2) o mini-implante cônico apresentou maior concentração de tensões nos filetes de rosca apicais.
Journal of the Brazilian Society of Mechanical Sciences, 2000
... 12228-904.São José dos Campos.SP.Brazi pardini@iae.cta.br Flamínio Levy Neto Universidade de ... more ... 12228-904.São José dos Campos.SP.Brazi pardini@iae.cta.br Flamínio Levy Neto Universidade de Brasília. ... In the first part, a modelling of mechanical properties was carried out for two bi-directional composites using a model based on the Bernoulli-Euler theory for symmetric ...
O objetivo principal desde trabalho é apresentar os valores de deformações normais circunferencia... more O objetivo principal desde trabalho é apresentar os valores de deformações normais circunferenciais obtidos através de simulações numéricas de tubos metálicos (Aço AISI 1020, comprimento L = 400 mm, diâmetro externo D = 100 mm e espessura t = 2 mm) nas três condições a seguir: (i) inicialmente íntegros; (ii) desbastados em 50% na espessura, ao longo de 25% de sua região central, para simular um defeito; e (iii) reparados com o compósito Carbono / Epóxi (tecido balanceado de fibras, AS4 - Hexcel), submetidos a diferentes pressões internas, na faixa de 2 a 10 MPa, utilizando para isso o software não linear de elementos finitos COMPSHELL. E, adicionalmente, verificar se os reparos compósitos aplicados restauram a rigidez original do tubo, anterior ao desbaste. Observou-se que existe uma espessura mínima necessária para que o reparo de Carbono/Epóxi recupere totalmente a rigidez local perdida com o desbaste, sendo utilizadas como referências para avaliar a eficácia do reparo o deslocame...
Abstract: The objective of this study was to obtain the damping factor (ξ )as well as the elastic... more Abstract: The objective of this study was to obtain the damping factor (ξ )as well as the elasticity modulus (E) of two kinds of synthetic graphite (HLM and ATJ), using the modal analysis technique. Prismatic beams of square section (~ 11 x 11 mm) and length over thickness ratio (L/t) of about 22.7 were tested in the free free condition. The first four modes of vibration were taken into account in the analysis. In addition, numerical simulations were also carried out in this investigation. The agreement between the theoretical and the experimental results was quite good. The average values of E and ξ for the HLM graphite were 20% and 90% higher , respectively, than those presented by the ATJ graphite.
Abstract. Smart or adaptative structures are those capable to perform some special functions whe... more Abstract. Smart or adaptative structures are those capable to perform some special functions when stimulated externally. In the context of this type of structure, hybrid adaptative composite beams, reinforced with active Ni-Ti filaments, were simulated in the present work. Such beams may be adopted for vibration control, exploring the possibility of changing their bending stiffness by means of controlling the temperature of the shape memory alloy filaments. The main objective of this paper is to present, for a free-free boundary condition, the vibration modes and their frequencies obtained analytically and numerically for prismatic beams, which incorporate nineteen layers of epoxy reinforced with chopped E-glass mat (17 plies), and two symmetric active plies (A) embedded with up to four Ni-Ti wires each (2+A+13+A+2). One particular aspect of this investigation is to verify how the natural frequency of the beams changes, when an electric current passes through the Ni-Ti wire...
Em nivel mundial, tubulacoes de aco desempenham papeis fundamentais nos diversos setores industri... more Em nivel mundial, tubulacoes de aco desempenham papeis fundamentais nos diversos setores industriais. Contudo, qualquer tipo de duto esta sujeito a desgastes em sua superficie devido a corrosao. Neste sentido, tecnicas que viabilizem o reparo rapido e confiavel de dutos sao de fundamental importância para aumentar sua vida util, prevenir acidentes, minimizar danos ambientais e permitir a manutencao da eficiencia dos mesmos apos serem reparados. Reparos com materiais compositos estao tendo grande destaque no mercado internacional devido a sua alta eficiencia, baixo peso e custo acessivel. Com o objetivo de obter informacoes de interesse tecnologico para setores industriais que necessitem executar manutencao preventiva em tubulacoes e realizar reparos emergenciais em caso de necessidade, obter-se-a solucoes otimizadas de constituicao e dimensionamento do reparo hibrido em material composito, utilizado em tubos industriais de ampla aplicacao no mercado atual.
This investigation is concerned with the mechanical behavior of Shape Memory Alloy Hybrid Composi... more This investigation is concerned with the mechanical behavior of Shape Memory Alloy Hybrid Composite Beams (SMAHC), that consist of a circular bar of NiTi alloy incorporated in a 500 mm long cylindrical pipe of polypropylene (PP), with external diameter 50 mm and nominal wall thickness 7 mm, wound with a nylon/epoxy layer. The Ni-Ti alloy was characterized using: scanning electron microscopy (SEM); X-ray diffraction (XRD) and Differential thermal analysis (DSC). The nominal chemical composition of the alloy is 50.05 %Ni / 49.95%Ti, and the softer martensite is the predominant phase at room temperature. The approximate martensite (M) to Austenitic (A) phase transformation temperatures were Mstart = 32°C, Mfinal = 46°C, Astart = 38 °C and Afinal = 60°C. For temperature TAfinal it is fully converted in the Austenitic phase; and its elasticity modulus increases by a factor up to three times. This significant change in stiffness of Ni-Ti, without changing its mass, has motivated the appli...
The aim of this work is to present some experiment`s results concerning with the machinability an... more The aim of this work is to present some experiment`s results concerning with the machinability and the determination of the superficial hardness of green carbon fiber reinforced phenolic workpieces, and three different kinds of carbon fiber reinforced carbon (CRFC) samples. Firstly, this work shows a characterization of the CFRC composite related with its composition, fabrication process, mechanical properties and main applications. Secondly, two kinds of hardness were measured: (1) Rockwell, L and (2) Micro Vickers. More than 200 indentations were carried out. In the main, the results of the Rockwell L tests showed better repeatability than those based on the Micro Vickers tests. After the hardness test, a comparative analysis of the CRFC composite machinability is done about the green carbon fiber reinforced phenolic composites. Experimental of turning were carried out to study the performance of different tool materials. Experimental results showed that only diamond tools are suitable for use in finish turning. In rough turning, the cemented carbide tools showed to be the best solution. This work ends with suggestions of machining parameters for CRFC composites, allowing some basic cutting conditions to be established for the turning operations.
RESUMO No presente trabalho, adotou-se a análise estatística de Weibull para avaliação da resistê... more RESUMO No presente trabalho, adotou-se a análise estatística de Weibull para avaliação da resistência mecânica à flexão, e sua repetibilidade, de mármores sintéticos, tanto puros quanto reforçados com fibra vidro-E. O objetivo foi observar o comportamento do módulo de Weibull e da resistência mecânica, à medida que se introduz fibra de vidro picotada na composição do mármore sintético. Para isso foram avaliados quatro diferentes teores, em massa, de fibra de vidro, para estabelecer uma curva padrão do comportamento mecânico, à medida em que se alterou a fração de fibra do compósito. A metodologia de Weibull viabiliza esta análise, uma vez que, além dos corpos de prova possuírem grande semelhança dimensional de espessura com os produtos fabricados em mármore sintético, ela quantifica a ocorrência de imperfeições devido ao processo de fabricação. Os resultados demonstraram que a inserção de fibra de vidro, em uma massa de 3 Kg de mármore sintético, em proporções de 12,5 a 100 gramas p...
In comparison with steel, concrete, and polymeric pipes, glass-reinforced plastic (GRP) pressure ... more In comparison with steel, concrete, and polymeric pipes, glass-reinforced plastic (GRP) pressure pipes use more expensive raw materials. Thus, despite of their attractive structural performance, mainly in terms of mechanical strength combined with low weight, the higher cost can be a limitation in many applications. In this scenario, an alternative to reduce the final price of GRP pipes is the addition of quartz sand filler. In this experimental and numerical study, filament-wound E-glass/polyester pipes with nominal inside diameter of 300 mm and wall thickness of 5.7 mm were produced with the incorporation of quartz sand as filler and tested to failure under internal pressure. The mechanical behavior of the composite pipes was evaluated experimentally, throughout short-time hydraulic failure pressure tests, as well as using finite element analysis (FEA). In the FEA simulations, the shell wall was modeled as an axisymmetric layered orthotropic material. A good agreement, varying from 96% to 98%, was obtained between the average hydraulic failure pressure measured and FEA predicted failure pressures, using Tsai—Hill and Hoffman failure criteria, respectively.
This work presents the numerical simulation of thin perfect, machined and repaired PVC pipes subj... more This work presents the numerical simulation of thin perfect, machined and repaired PVC pipes subjected to internally hydrostatic pressure, with ratio between the diameter (D) and the thickness (t), above or equal 20, D/t > 20. The numerical simulations were carried out with a finite element program, called Compshell, using PVC tubes, from elastic behavior to the failure. The boundary conditions were: clamped in one end and simple supported in the other, with freedom along the axial direction. The longitudinal and radial displacements, the bending moments and normal stresses resultants for pipes were evaluated. The maximum pressure was estimated using the Tsai-Hill failure criterion. The best result for repaired pipes was obtained with a laminate of epoxy matrix (E) filled with cotton cloth (C), since this composite and PVC Young's modulus are close to each other. The ideal composite repairing is the one that restores the structural stiffness of the affected region, in the way...
ABSTRACT Six hemispherical and four torispherical composite plastic domes reinforced with either ... more ABSTRACT Six hemispherical and four torispherical composite plastic domes reinforced with either carbon or E-glass woven fabrics or a combination of both have been tested under external pressure. The domes were prepared using male or female moulds and employed the hand lay-up/vacuum bag method for their manufacture. The domes were observed to fail either by buckling or as a result of material failure. Both modes of failure were usually located at the meridian having the minimum average thickness. These domes were then repaired using a recommended technique and retested. It has been shown that the integrity of the repaired zones was guaranteed and further damage to the domes during retesting moved to new locations usually corresponding to the areas of the new minimum average thickness meridian. Two computer programs based on finite difference and finite element methods were employed to predict the critical buckling or material failure loads. The theoretical predictions were shown to correlate very well with the experimental results.
Neste trabalho, são apresentadas simulações numéricas de tubos de PVC de parede fina submetidos à... more Neste trabalho, são apresentadas simulações numéricas de tubos de PVC de parede fina submetidos à pressão hidrostática interna, íntegros, desbastados e reparados, com uma razão entre o diâmetro (D) e a espessura (t) superior ou igual a 20, i.e. D/t > 20. Foram realizadas simulações numéricas com o programa de elementos finitos, chamado Compshell, utilizando tubos de PVC, desde o regime elástico até a ruptura, com a condição de contorno engastado numa extremidade e com liberdade de deslocamento axial na outra. São analisados os resultados dos deslocamentos longitudinal e radial, resultantes de momentos fletores e de tensões normais para tubos. As pressões máximas foram estimadas com o critério de falha de Tsai-Hill. O melhor resultado para tubos reparados foi obtido com o laminado de matriz epóxi (E) e carga de enchimento de algodão (A) com módulos de Young do compósito, E E/A = 3,5 GPa, e do tubo de PVC, E PVC = 3,0 GPa. O reparo compósito ideal é aquele que restitui a rigidez es...
O objetivo deste trabalho foi avaliar a distribuição de tensões na resina em contato com os filet... more O objetivo deste trabalho foi avaliar a distribuição de tensões na resina em contato com os filetes de roscas de mini-implantes cilíndricos e cônicos, submetidos à carga lateral e torção de inserção. Um modelo fotoelástico foi confeccionado com gelatina transparente, para simular o osso alveolar. O modelo foi observado com um polariscópio plano e fotografado antes e após a ativação dos mini-implantes com força lateral e de inserção. A aplicação de cargas laterais provocou momentos fletores nos mini-implantes, aparecimento de franjas isocromáticas ao longo dos filetes do corpo dos mini-implantes e no ápice. Quando foi aplicado o torque de inserção, verificou-se a concentração de tensões próxima ao ápice. Concluiu-se que: (1) o mini-implante cilíndrico apresentou maior concentração de tensões no ápice, e (2) o mini-implante cônico apresentou maior concentração de tensões nos filetes de rosca apicais.
Journal of the Brazilian Society of Mechanical Sciences, 2000
... 12228-904.São José dos Campos.SP.Brazi pardini@iae.cta.br Flamínio Levy Neto Universidade de ... more ... 12228-904.São José dos Campos.SP.Brazi pardini@iae.cta.br Flamínio Levy Neto Universidade de Brasília. ... In the first part, a modelling of mechanical properties was carried out for two bi-directional composites using a model based on the Bernoulli-Euler theory for symmetric ...
O objetivo principal desde trabalho é apresentar os valores de deformações normais circunferencia... more O objetivo principal desde trabalho é apresentar os valores de deformações normais circunferenciais obtidos através de simulações numéricas de tubos metálicos (Aço AISI 1020, comprimento L = 400 mm, diâmetro externo D = 100 mm e espessura t = 2 mm) nas três condições a seguir: (i) inicialmente íntegros; (ii) desbastados em 50% na espessura, ao longo de 25% de sua região central, para simular um defeito; e (iii) reparados com o compósito Carbono / Epóxi (tecido balanceado de fibras, AS4 - Hexcel), submetidos a diferentes pressões internas, na faixa de 2 a 10 MPa, utilizando para isso o software não linear de elementos finitos COMPSHELL. E, adicionalmente, verificar se os reparos compósitos aplicados restauram a rigidez original do tubo, anterior ao desbaste. Observou-se que existe uma espessura mínima necessária para que o reparo de Carbono/Epóxi recupere totalmente a rigidez local perdida com o desbaste, sendo utilizadas como referências para avaliar a eficácia do reparo o deslocame...
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