An automated testing system for overhead line cables with temperature control from environment te... more An automated testing system for overhead line cables with temperature control from environment temperature to 200°C is presented. The aim of the test is to determine mechanical characteristics such as creep, thermal strain, stress/strain, fatigue, and self-damping in order to improve the design of overhead lines through the analysis of new and already-in-use cables, as well as quality control. The data are obtained through the utilization of displacement, temperature, and load sensors. The temperature and the cable tension are continuously controlled. The data acquisition, analysis, and feedback are made through an intelligent interface. The maximum load is 200 kN.
In more complex systems, such as automotive gearbox, a rigorous treatment of the data is necessar... more In more complex systems, such as automotive gearbox, a rigorous treatment of the data is necessary because there are several moving parts (gears, bearings, shafts, etc.), and in this way, there are several possible sources of errors and also noise. The basic objective of this work is the detection of damage in automotive gearbox. The detection methods used are the wavelet method, the bispectrum; advanced filtering techniques (selective filtering) of vibrational signals and mathematical morphology. Gearbox vibration tests were performed (gearboxes in good condition and with defects) of a production line of a large vehicle assembler. The vibration signals are obtained using five accelerometers in different positions of the sample. The results obtained using the kurtosis, bispectrum, wavelet and mathematical morphology showed that it is possible to identify the existence of defects in automotive gearboxes.
Geodesic domes are 3D reticulated structures used to cover large areas. As lightweight structures... more Geodesic domes are 3D reticulated structures used to cover large areas. As lightweight structures, they are sensible for dynamic effects. The structural behaviour of domes is affected by the kind of connections between their members. Semi -rigid joints produce loss of stiffness compared with rigid joints. Dynamic tests may capture the effect of semi-rigid joints. The objective of this work is to conduct both static and dynamic tests on a Geodesic Dome at the laboratory scale and compare the results with a linear elastic FE model. The research method involved designing, building and testing a prototype constructed of aluminum wit h overall dimensions of 2000 mm in diameter and 800 mm in height. A 3D finite element model was developed using beam and shell elements. Experimental and numerical results were compared in terms of displacements and frequencies. Load—displacement curves are presented for the static loading. The dynamic behaviour is evaluated by hitting an impact hammer on members and nodes to allow measurement of accelerations. An FFT technique is used to determine the frequency spectrum. The results show that the laboratory prototype presented about 20% less stiffness than predicted by the linear elastic numerical model. The difference is attributed to the transmissibility condition between nodal connectors and emphasizes the influence of semi-rigid joints. Despite being largely used to assess dome structures, standard FE models are shown to be insufficient in capturing local non-linearities.
Study of hydraulic transients in hydropower plants specifically in hydraulic turbine units, with ... more Study of hydraulic transients in hydropower plants specifically in hydraulic turbine units, with penstock, spiral case and draft tube-is necessary due to power and frequency oscillations which normally occur in generator units, mainly during load rejections. In turn, this causes large pressure and subpressure oscillations in turbine hydraulic systems and must be evaluated to avoid mechanical failures. In this context,
Orientador : Douglas Eduardo ZampieriTese (doutorado) : Universidade Estadual de Campinas, Faculd... more Orientador : Douglas Eduardo ZampieriTese (doutorado) : Universidade Estadual de Campinas, Faculdade de Engenharia MecanicaResumo: O comportamento dinâmico de um veículo de quatro rodas é analisado através de um modelo com sete graus de liberdade para duas situações de carga do veículo, carregado e descarregado, e para dois diferentes tipos de via, asfáltica e pavimentada. Varia-se a velocidade do veículo entre 5 e 30 m/ s. Para encontrar as características dos elementos suspensivos usa-se a teoria do controle estocástico linear ótimo para minimizar um índice de desempenho cujas partes integrantes são: aceleração vertical do veículo (conforto), espaço de trabalho das suspensões (limitação estrutural), deslocamentos relativos entre os centros das rodas e a via (segurança) e forças de controle. A influência destas partes no índice de desempenho é relatada através de constantes de peso. Otimiza-se primeiramente um sistema de suspensão passiva com constantes de peso favorecendo a segurança. Estuda-se a influência da velocidade nos coeficientes de rigidez e amortecimento. Em seguida otimizam-se vários sistemas de suspensão com elementos passivos em paralelo com elementos ativos com realimentação de estado e de saída. Dois tipos de constantes de peso favorecendo o conforto e a segurança são usados. Otimizam-se também as constantes de peso das forças de controle e os elementos passivos das suspensões. Verifica-se o comportamento próprio de todos os sistemas através da obtenção dos autovalores. Compara-se o desempenho de todos os sistemas quando o veículo passa por uma via com perfil aleatórioAbstract: The dynamical behaviour of a four wheeled car is analysed by the use of a seven degrees of freedom model for two load conditions of the vehicle,loaded and unloaded, and for two different types of road, asphalt and pavement. The vehicle velocity is varied between 5 and 30m/s. To find the characteristics of the suspension elements stochastic optimallinear control theory is used through the minimization of the performance index whose constituent parts are: vehicle vertical acceleration (comfort), suspension working space (structurallimitation), road holding (safety) and the control force. The infiuence of these parts in the performance index are related through the weighting constants. The passive linear suspension system is firstly optimized with weighting constants favouring safety. The infiuence of the vehicle speed on the linear spring and damper coefficients are studied. Afterwards some systems with passive elements in parallel with active elements with state and output feedback are optimized. Two types of weighting constants favouring comfort and the safety are used. The weighting constants of the control forces and the values of the coefficients of passive suspensions are also optimized. The dynamical eigenbehaviour of the whose system is studied through the derivation of the eigenvalues. The performance of every system is compared when the vehicle is driving on a ramdom roadDoutoradoDoutor em Engenharia Mecânic
Orientador : Douglas Eduardo ZampieriDissertação (mestrado) - Universidade Estadual de Campinas, ... more Orientador : Douglas Eduardo ZampieriDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de CampinasResumo: Analisa-se o comportamento dinamico de um veiculo de quatro rodas através de um modelo com sete graus de liberdade. Primeiramente estuda-se o comportamento próprio do veículo para as duas condições de carga, descarregado e carregado, através da obtenção dos autovalores e autovetores para as duas situações. Depois estuda-se o comportamento do veículo contendo suspensão passiva convencional, trafegando por uma via reta e com perfis deterministicos das irregularidades da via modeladas por funções trigonométricas, no caso, perfis senoidais. Adota-se como critério de análise o deslocamento e a aceleração do centro de gravidade do veículo para diferentes velocidades do mesmo. Um sistema de suspensão com molas a gás é, então modelado e ajustado ao veículo. A resposta a uma excitação transiente é analisada para três tipos de suspensão: passivo, com molas a gás e semi-ativo com molas a gásAbstract: The theoretical dynamical behaviour of a four wheel car model is analysed. The physical model with seven degrees of freedom is chosen and after some simplifications the corresponding mathematical model is established. First is studied the dynamical eigenbehaviour of the model for both unloaded and loaded conditions through the obtention of the eigenvalues and eigenvestors in different situations: changing the spring stiffness coefficients and the damping coefficient of the dampers (suspensions). Subsequently it is analysed the behaviour of the vehicle with conventional passive suspension moving on a straight road. This road has a deterministic profile of irregularities. This profile is modeled with trigonometric functions, in this case, sinusoid profile. The analysis criteria adopted are: displacement and the aceleration of the gravity center for different speeds of the vehicle. A gas spring suspension system is modeled and fitted to the vehicle. Is this way, it is analysed the behaviour of the vehicle when crossing a ramp with three different suspension types: conventional passive, passive and semi-active with gas spring, in both unloaded and loaded conditionsMestradoMestre em Engenharia Mecânic
This work aims to propose an inverse methodology for the physical properties identification of sa... more This work aims to propose an inverse methodology for the physical properties identification of sandwich beams by measured flexural resonance frequencies. The physical parameters are the Young‟s modulus and the loss factor. They are estimated for each one of materials that constitute the structure of the sandwich beam which is made with the association of Hot-rolled steel, Polyurethane Rigid Foam and High Impact Polystyrene. This kind of the sandwich beam are widely used for the assembly of household refrigerators and food freezers. The solutions are obtained with parametric optimization of physical parameters of the materials that forming the sandwich beam with three methods: Genetic Algorithms (GA), Differential Evolution (DE), and Particle Swarm Optimization (PSO). Furthermore, this work intend verify the quality of the solutions obtained with parametric optimization. The parameters are estimated using measured and numeric frequency response functions (FRFs). The mathematical mode...
The Journal of the Acoustical Society of America, 2016
Absorbent materials are fibrous or porous and must have the property of being good acoustic dissi... more Absorbent materials are fibrous or porous and must have the property of being good acoustic dissipaters. The noise reduction process occurs due to transformation of a part of the sound energy into heat. The attenuation is caused by friction of the viscous air fluid inside the irregular arrangement of fibers during the sound wave propagation. This study assesses the complex wave number and the complex characteristic impedance of two natural fibers with the classical empirical equations of Delany and Bazley (1970). These properties are determined based on experimental evaluation of the flow resistivity of sisal and coconut coir fiber samples. The experimental assessment procedure was performed according to the guidelines of ASTM C522-03 (2009). Samples evaluated have approximately identical densities, different diameters, and thicknesses. The diameters were 62.0, 71.5, and 80.0 mm and thicknesses were 5, 10, 15, and 20 mm. The purpose of testing seven dimensions is to verify the effect of these differences ...
An automated testing system for overhead line cables with temperature control from environment te... more An automated testing system for overhead line cables with temperature control from environment temperature to 200°C is presented. The aim of the test is to determine mechanical characteristics such as creep, thermal strain, stress/strain, fatigue, and self-damping in order to improve the design of overhead lines through the analysis of new and already-in-use cables, as well as quality control. The data are obtained through the utilization of displacement, temperature, and load sensors. The temperature and the cable tension are continuously controlled. The data acquisition, analysis, and feedback are made through an intelligent interface. The maximum load is 200 kN.
In more complex systems, such as automotive gearbox, a rigorous treatment of the data is necessar... more In more complex systems, such as automotive gearbox, a rigorous treatment of the data is necessary because there are several moving parts (gears, bearings, shafts, etc.), and in this way, there are several possible sources of errors and also noise. The basic objective of this work is the detection of damage in automotive gearbox. The detection methods used are the wavelet method, the bispectrum; advanced filtering techniques (selective filtering) of vibrational signals and mathematical morphology. Gearbox vibration tests were performed (gearboxes in good condition and with defects) of a production line of a large vehicle assembler. The vibration signals are obtained using five accelerometers in different positions of the sample. The results obtained using the kurtosis, bispectrum, wavelet and mathematical morphology showed that it is possible to identify the existence of defects in automotive gearboxes.
Geodesic domes are 3D reticulated structures used to cover large areas. As lightweight structures... more Geodesic domes are 3D reticulated structures used to cover large areas. As lightweight structures, they are sensible for dynamic effects. The structural behaviour of domes is affected by the kind of connections between their members. Semi -rigid joints produce loss of stiffness compared with rigid joints. Dynamic tests may capture the effect of semi-rigid joints. The objective of this work is to conduct both static and dynamic tests on a Geodesic Dome at the laboratory scale and compare the results with a linear elastic FE model. The research method involved designing, building and testing a prototype constructed of aluminum wit h overall dimensions of 2000 mm in diameter and 800 mm in height. A 3D finite element model was developed using beam and shell elements. Experimental and numerical results were compared in terms of displacements and frequencies. Load—displacement curves are presented for the static loading. The dynamic behaviour is evaluated by hitting an impact hammer on members and nodes to allow measurement of accelerations. An FFT technique is used to determine the frequency spectrum. The results show that the laboratory prototype presented about 20% less stiffness than predicted by the linear elastic numerical model. The difference is attributed to the transmissibility condition between nodal connectors and emphasizes the influence of semi-rigid joints. Despite being largely used to assess dome structures, standard FE models are shown to be insufficient in capturing local non-linearities.
Study of hydraulic transients in hydropower plants specifically in hydraulic turbine units, with ... more Study of hydraulic transients in hydropower plants specifically in hydraulic turbine units, with penstock, spiral case and draft tube-is necessary due to power and frequency oscillations which normally occur in generator units, mainly during load rejections. In turn, this causes large pressure and subpressure oscillations in turbine hydraulic systems and must be evaluated to avoid mechanical failures. In this context,
Orientador : Douglas Eduardo ZampieriTese (doutorado) : Universidade Estadual de Campinas, Faculd... more Orientador : Douglas Eduardo ZampieriTese (doutorado) : Universidade Estadual de Campinas, Faculdade de Engenharia MecanicaResumo: O comportamento dinâmico de um veículo de quatro rodas é analisado através de um modelo com sete graus de liberdade para duas situações de carga do veículo, carregado e descarregado, e para dois diferentes tipos de via, asfáltica e pavimentada. Varia-se a velocidade do veículo entre 5 e 30 m/ s. Para encontrar as características dos elementos suspensivos usa-se a teoria do controle estocástico linear ótimo para minimizar um índice de desempenho cujas partes integrantes são: aceleração vertical do veículo (conforto), espaço de trabalho das suspensões (limitação estrutural), deslocamentos relativos entre os centros das rodas e a via (segurança) e forças de controle. A influência destas partes no índice de desempenho é relatada através de constantes de peso. Otimiza-se primeiramente um sistema de suspensão passiva com constantes de peso favorecendo a segurança. Estuda-se a influência da velocidade nos coeficientes de rigidez e amortecimento. Em seguida otimizam-se vários sistemas de suspensão com elementos passivos em paralelo com elementos ativos com realimentação de estado e de saída. Dois tipos de constantes de peso favorecendo o conforto e a segurança são usados. Otimizam-se também as constantes de peso das forças de controle e os elementos passivos das suspensões. Verifica-se o comportamento próprio de todos os sistemas através da obtenção dos autovalores. Compara-se o desempenho de todos os sistemas quando o veículo passa por uma via com perfil aleatórioAbstract: The dynamical behaviour of a four wheeled car is analysed by the use of a seven degrees of freedom model for two load conditions of the vehicle,loaded and unloaded, and for two different types of road, asphalt and pavement. The vehicle velocity is varied between 5 and 30m/s. To find the characteristics of the suspension elements stochastic optimallinear control theory is used through the minimization of the performance index whose constituent parts are: vehicle vertical acceleration (comfort), suspension working space (structurallimitation), road holding (safety) and the control force. The infiuence of these parts in the performance index are related through the weighting constants. The passive linear suspension system is firstly optimized with weighting constants favouring safety. The infiuence of the vehicle speed on the linear spring and damper coefficients are studied. Afterwards some systems with passive elements in parallel with active elements with state and output feedback are optimized. Two types of weighting constants favouring comfort and the safety are used. The weighting constants of the control forces and the values of the coefficients of passive suspensions are also optimized. The dynamical eigenbehaviour of the whose system is studied through the derivation of the eigenvalues. The performance of every system is compared when the vehicle is driving on a ramdom roadDoutoradoDoutor em Engenharia Mecânic
Orientador : Douglas Eduardo ZampieriDissertação (mestrado) - Universidade Estadual de Campinas, ... more Orientador : Douglas Eduardo ZampieriDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de CampinasResumo: Analisa-se o comportamento dinamico de um veiculo de quatro rodas através de um modelo com sete graus de liberdade. Primeiramente estuda-se o comportamento próprio do veículo para as duas condições de carga, descarregado e carregado, através da obtenção dos autovalores e autovetores para as duas situações. Depois estuda-se o comportamento do veículo contendo suspensão passiva convencional, trafegando por uma via reta e com perfis deterministicos das irregularidades da via modeladas por funções trigonométricas, no caso, perfis senoidais. Adota-se como critério de análise o deslocamento e a aceleração do centro de gravidade do veículo para diferentes velocidades do mesmo. Um sistema de suspensão com molas a gás é, então modelado e ajustado ao veículo. A resposta a uma excitação transiente é analisada para três tipos de suspensão: passivo, com molas a gás e semi-ativo com molas a gásAbstract: The theoretical dynamical behaviour of a four wheel car model is analysed. The physical model with seven degrees of freedom is chosen and after some simplifications the corresponding mathematical model is established. First is studied the dynamical eigenbehaviour of the model for both unloaded and loaded conditions through the obtention of the eigenvalues and eigenvestors in different situations: changing the spring stiffness coefficients and the damping coefficient of the dampers (suspensions). Subsequently it is analysed the behaviour of the vehicle with conventional passive suspension moving on a straight road. This road has a deterministic profile of irregularities. This profile is modeled with trigonometric functions, in this case, sinusoid profile. The analysis criteria adopted are: displacement and the aceleration of the gravity center for different speeds of the vehicle. A gas spring suspension system is modeled and fitted to the vehicle. Is this way, it is analysed the behaviour of the vehicle when crossing a ramp with three different suspension types: conventional passive, passive and semi-active with gas spring, in both unloaded and loaded conditionsMestradoMestre em Engenharia Mecânic
This work aims to propose an inverse methodology for the physical properties identification of sa... more This work aims to propose an inverse methodology for the physical properties identification of sandwich beams by measured flexural resonance frequencies. The physical parameters are the Young‟s modulus and the loss factor. They are estimated for each one of materials that constitute the structure of the sandwich beam which is made with the association of Hot-rolled steel, Polyurethane Rigid Foam and High Impact Polystyrene. This kind of the sandwich beam are widely used for the assembly of household refrigerators and food freezers. The solutions are obtained with parametric optimization of physical parameters of the materials that forming the sandwich beam with three methods: Genetic Algorithms (GA), Differential Evolution (DE), and Particle Swarm Optimization (PSO). Furthermore, this work intend verify the quality of the solutions obtained with parametric optimization. The parameters are estimated using measured and numeric frequency response functions (FRFs). The mathematical mode...
The Journal of the Acoustical Society of America, 2016
Absorbent materials are fibrous or porous and must have the property of being good acoustic dissi... more Absorbent materials are fibrous or porous and must have the property of being good acoustic dissipaters. The noise reduction process occurs due to transformation of a part of the sound energy into heat. The attenuation is caused by friction of the viscous air fluid inside the irregular arrangement of fibers during the sound wave propagation. This study assesses the complex wave number and the complex characteristic impedance of two natural fibers with the classical empirical equations of Delany and Bazley (1970). These properties are determined based on experimental evaluation of the flow resistivity of sisal and coconut coir fiber samples. The experimental assessment procedure was performed according to the guidelines of ASTM C522-03 (2009). Samples evaluated have approximately identical densities, different diameters, and thicknesses. The diameters were 62.0, 71.5, and 80.0 mm and thicknesses were 5, 10, 15, and 20 mm. The purpose of testing seven dimensions is to verify the effect of these differences ...
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