Sandwich structures are comprised of two external faces/skins(usually made of synthetic fiber/resin)and a core between them,being lightweight and with high stiffness.The employment of composite materials such as engin...Sandwich structures are comprised of two external faces/skins(usually made of synthetic fiber/resin)and a core between them,being lightweight and with high stiffness.The employment of composite materials such as engineering materials has achieved more space in various segments of the industry,due to the following properties found:low density,stiffness,resistance to abrasion,impact and corrosion developed along the technological advancement of materials.This study aimed to develop a composite structure sandwich with cork core using in the face resin unsaturated polyester and glass fiber material,in order to obtain a final material with improved mechanical and physical properties compared to a conventional composite,without core.The samples were obtained by pressing process for different volume percentage of glass fiber in order to evaluate the influence of this parameter on the behavior of the material.The different samples were mechanically analyzed using the tests by tensile,bending and hardness,revealing high efficiency,except for the bending test in which the sandwich composite showed lower values compared to the composite standard.It was also performed to test water absorption,thermal and acoustic insulation test achieving satisfactory results and proving the effectiveness of cork in the search for materials with insulating characteristics,thus enabling the use of cork as a raw material for this class of materials contributing to sustainability and helping to generate values and innovation.In addition,it functions as a great thermal and acoustic insulation.展开更多
In brake systems, where the components are exposed to mechanical and thermal loads, the numerical analysis is very helpful. The main function of the brake system is to control or reduce vehicle’s speed by transformat...In brake systems, where the components are exposed to mechanical and thermal loads, the numerical analysis is very helpful. The main function of the brake system is to control or reduce vehicle’s speed by transformation of kinetic and potential energy in thermal energy. Using finite element method and Abaqus application, the present work proposed a model to study the impact of these loads on the performance of a pneumatic S cam drum brake’s friction material. The model included the effects of the rivet process;brake torque and warming in one of the 17 t bus front brake lining. Areas where the stresses vary with considerable amplitudes during temperature increase and brake application were identified. Also, it was possible to compare results of the numerical model to vehicle’s experimental measurements and understand its proximity to real braking events. By the application of the methodology and using the numerical model, proposed in this work, it will be possible to contribute considerably for a more accurate design of the friction material, besides undertake a better selection of the sub-compounds which it is made of.展开更多
The mechanical behavior and wear of the different hardened phases with bore-induced changes in AISI 4340 and AISI D2 steels were investigated. The hardness and modulus of elasticity were measured by nanoindentation an...The mechanical behavior and wear of the different hardened phases with bore-induced changes in AISI 4340 and AISI D2 steels were investigated. The hardness and modulus of elasticity were measured by nanoindentation and the values obtained for the layers in AISI D2 steel were 18 GPa and 325 GPa in the Fe<sub>2</sub>B boride phase, and 20 GPa and 360 GPa in the FeB boride phase, respectively. The AISI 4340 steel presented mainly the Fe<sub>2</sub>B phase. It was then possible to analyze the coefficient of friction obtained in the Fe<sub>2</sub>B phase of the steel AISI 4340 presented a range of 0.04 to 0.06. The AISI D2 steel presents two different phases in the boride layer being the coefficient of friction higher for the test in the FeB phase than for Fe<sub>2</sub>B, and the values vary from 0.065 to 0.075. These parameters were obtained with micro-wear tests. No adhesion failures were observed after the sliding tests in the interface of the two different boride layers. Cracks in the FeB phase after the sliding test were much more frequent.展开更多
This study evaluates the effectiveness of a new technique that transforms doma in integrals into boundary integrals that is applicable to the boundary element method.Si mulations were conducted in which two-dimensiona...This study evaluates the effectiveness of a new technique that transforms doma in integrals into boundary integrals that is applicable to the boundary element method.Si mulations were conducted in which two-dimensional surfaces were approximated by inter polation using radial basis functions with full and compact supports.Examples involving Poisson’s equation are presented using the boundary element method and the proposed te chnique with compact radial basis functions.The advantages and the disadvantages are e xamined through simulations.The effects of internal poles,the boundary mesh refinemen t and the value for the support of the radial basis functions on performance are assessed.展开更多
The torsional vibration of power transmission shaft is a phenomenon whose analytical modeling can be represented by a differential equation of motion proposed by technical literature. The solutions of these equations ...The torsional vibration of power transmission shaft is a phenomenon whose analytical modeling can be represented by a differential equation of motion proposed by technical literature. The solutions of these equations need coefficients and parameters that, usually, must be experimentally estimated. This work uses a resistive electric SG （strain gage） to dynamically determine strains produced in the shaft due to harmonic oscillatory motion under multiaxial loading. This movement is simulated on a prototype specially developed for this purpose. It comprises a pulley attached to the end of a stepped cantilevered shaft, which is clamped at the opposite end. In this configuration, a cam generates a torque to the system, springs regulate the stiffness and the damping coefficient of the assembly, as well as they can be suitably adjusted to produce an underdamped condition. The main advantage, highlighted in this study, refers to a major simplification. Although the system under study shows multiple degrees of freedom （torsion and bending）, the shape and the positioning of linking SGs with the resistor bridge （Wheatstone Bridge）, allow ＂to evaluate the loading effects independently, as if only one degree of freedom of the system exists at a time domain. Strains graphs for two forms of cyclic torsional oscillation, analytical and experimental, were successfully generated.展开更多
The replacement of fossil raw materials by renewable alternatives is imperative.Renewable,biodegradable,and compostable polymers are options to be developed and adopted.Embedded in this concept,the present study...The replacement of fossil raw materials by renewable alternatives is imperative.Renewable,biodegradable,and compostable polymers are options to be developed and adopted.Embedded in this concept,the present study evaluates whether biopolymers are sustainable alternatives to replace traditional polymers used in packaging,such as polyethylene.To that end,a systematic literature review(SLR)was carried out on biopolymers applied to packaging,with an analysis of its impacts.Three sustainability criteria were adopted:a)Criteria for Developing Sustainable Packaging;b)Goals of Sustainable Development;and c)Circular Economy Criteria.The Methodology Section presents the state of the art of potential polymers for packaging and their characteristics related to the evaluation criteria adopted based on the SLR.Through data collection,it was observed that advanced obtaining techniques enable polymers economically and that,environmentally speaking,there is a positive consensus about some types of those materials.However,technological maturity and productive scale capacity are necessary to reduce costs in a competitive scenario with conventional polymers.展开更多
In face of scarcity in the supply of non-traditional Brazilian woods properly treated for use in high quality musical instruments,pieces of Amazonian wood species muiracatiara(Astronium lecointei)and maçaranduba(...In face of scarcity in the supply of non-traditional Brazilian woods properly treated for use in high quality musical instruments,pieces of Amazonian wood species muiracatiara(Astronium lecointei)and maçaranduba(Manilkara huberi)purchased in the common internal Brazilian timber market were examined.These species were pre-selected for use in fingerboards of acoustic and electric guitars due to similar properties with ebony(Diospyros crassiflora).Variabilities of elastic modulus parallel to grain and density were investigated inside wooden pieces.In addition,referred parameters were used in calculation of speed of sound.Statistical tests were performed in order to compare both species and revealed inequality for variances of dynamic elastic modulus(E_(d))and speed of sound,but equality for density.Equality of means was also examined via unequal variance t-test.Despite color differences,lower variability of M.huberi led to the indication of this species as likely capable to substitute satisfactorily ebony in fingerboards manufacturing.展开更多
The early stages of product development are characterized by uncertainties.Designers must deal with challenges that arise unexpectedly in an agile and responsive manner.Expert information systems based on ontological ...The early stages of product development are characterized by uncertainties.Designers must deal with challenges that arise unexpectedly in an agile and responsive manner.Expert information systems based on ontological models are a promising approach to capture knowledge and rationale of domain specialists,either for decision making or knowledge reuse.The present study presents a bibliometric analysis on the use of ontologies in product development for cost estimation.It identifies trends and research opportunities that can orient future works.From a general search in scientific databases,31 articles were found and selected based on criteria established using the Proknow-C method.Results indicate that there are several possibilities for solutions using ontological and hybrid,transdisciplinary approaches.Using intelligent systems is not only promising but is also challenging as a new and real transdisciplinary research area of interest.展开更多
文摘Sandwich structures are comprised of two external faces/skins(usually made of synthetic fiber/resin)and a core between them,being lightweight and with high stiffness.The employment of composite materials such as engineering materials has achieved more space in various segments of the industry,due to the following properties found:low density,stiffness,resistance to abrasion,impact and corrosion developed along the technological advancement of materials.This study aimed to develop a composite structure sandwich with cork core using in the face resin unsaturated polyester and glass fiber material,in order to obtain a final material with improved mechanical and physical properties compared to a conventional composite,without core.The samples were obtained by pressing process for different volume percentage of glass fiber in order to evaluate the influence of this parameter on the behavior of the material.The different samples were mechanically analyzed using the tests by tensile,bending and hardness,revealing high efficiency,except for the bending test in which the sandwich composite showed lower values compared to the composite standard.It was also performed to test water absorption,thermal and acoustic insulation test achieving satisfactory results and proving the effectiveness of cork in the search for materials with insulating characteristics,thus enabling the use of cork as a raw material for this class of materials contributing to sustainability and helping to generate values and innovation.In addition,it functions as a great thermal and acoustic insulation.
文摘In brake systems, where the components are exposed to mechanical and thermal loads, the numerical analysis is very helpful. The main function of the brake system is to control or reduce vehicle’s speed by transformation of kinetic and potential energy in thermal energy. Using finite element method and Abaqus application, the present work proposed a model to study the impact of these loads on the performance of a pneumatic S cam drum brake’s friction material. The model included the effects of the rivet process;brake torque and warming in one of the 17 t bus front brake lining. Areas where the stresses vary with considerable amplitudes during temperature increase and brake application were identified. Also, it was possible to compare results of the numerical model to vehicle’s experimental measurements and understand its proximity to real braking events. By the application of the methodology and using the numerical model, proposed in this work, it will be possible to contribute considerably for a more accurate design of the friction material, besides undertake a better selection of the sub-compounds which it is made of.
文摘The mechanical behavior and wear of the different hardened phases with bore-induced changes in AISI 4340 and AISI D2 steels were investigated. The hardness and modulus of elasticity were measured by nanoindentation and the values obtained for the layers in AISI D2 steel were 18 GPa and 325 GPa in the Fe<sub>2</sub>B boride phase, and 20 GPa and 360 GPa in the FeB boride phase, respectively. The AISI 4340 steel presented mainly the Fe<sub>2</sub>B phase. It was then possible to analyze the coefficient of friction obtained in the Fe<sub>2</sub>B phase of the steel AISI 4340 presented a range of 0.04 to 0.06. The AISI D2 steel presents two different phases in the boride layer being the coefficient of friction higher for the test in the FeB phase than for Fe<sub>2</sub>B, and the values vary from 0.065 to 0.075. These parameters were obtained with micro-wear tests. No adhesion failures were observed after the sliding tests in the interface of the two different boride layers. Cracks in the FeB phase after the sliding test were much more frequent.
文摘This study evaluates the effectiveness of a new technique that transforms doma in integrals into boundary integrals that is applicable to the boundary element method.Si mulations were conducted in which two-dimensional surfaces were approximated by inter polation using radial basis functions with full and compact supports.Examples involving Poisson’s equation are presented using the boundary element method and the proposed te chnique with compact radial basis functions.The advantages and the disadvantages are e xamined through simulations.The effects of internal poles,the boundary mesh refinemen t and the value for the support of the radial basis functions on performance are assessed.
文摘The torsional vibration of power transmission shaft is a phenomenon whose analytical modeling can be represented by a differential equation of motion proposed by technical literature. The solutions of these equations need coefficients and parameters that, usually, must be experimentally estimated. This work uses a resistive electric SG （strain gage） to dynamically determine strains produced in the shaft due to harmonic oscillatory motion under multiaxial loading. This movement is simulated on a prototype specially developed for this purpose. It comprises a pulley attached to the end of a stepped cantilevered shaft, which is clamped at the opposite end. In this configuration, a cam generates a torque to the system, springs regulate the stiffness and the damping coefficient of the assembly, as well as they can be suitably adjusted to produce an underdamped condition. The main advantage, highlighted in this study, refers to a major simplification. Although the system under study shows multiple degrees of freedom （torsion and bending）, the shape and the positioning of linking SGs with the resistor bridge （Wheatstone Bridge）, allow ＂to evaluate the loading effects independently, as if only one degree of freedom of the system exists at a time domain. Strains graphs for two forms of cyclic torsional oscillation, analytical and experimental, were successfully generated.
文摘The replacement of fossil raw materials by renewable alternatives is imperative.Renewable,biodegradable,and compostable polymers are options to be developed and adopted.Embedded in this concept,the present study evaluates whether biopolymers are sustainable alternatives to replace traditional polymers used in packaging,such as polyethylene.To that end,a systematic literature review(SLR)was carried out on biopolymers applied to packaging,with an analysis of its impacts.Three sustainability criteria were adopted:a)Criteria for Developing Sustainable Packaging;b)Goals of Sustainable Development;and c)Circular Economy Criteria.The Methodology Section presents the state of the art of potential polymers for packaging and their characteristics related to the evaluation criteria adopted based on the SLR.Through data collection,it was observed that advanced obtaining techniques enable polymers economically and that,environmentally speaking,there is a positive consensus about some types of those materials.However,technological maturity and productive scale capacity are necessary to reduce costs in a competitive scenario with conventional polymers.
文摘In face of scarcity in the supply of non-traditional Brazilian woods properly treated for use in high quality musical instruments,pieces of Amazonian wood species muiracatiara(Astronium lecointei)and maçaranduba(Manilkara huberi)purchased in the common internal Brazilian timber market were examined.These species were pre-selected for use in fingerboards of acoustic and electric guitars due to similar properties with ebony(Diospyros crassiflora).Variabilities of elastic modulus parallel to grain and density were investigated inside wooden pieces.In addition,referred parameters were used in calculation of speed of sound.Statistical tests were performed in order to compare both species and revealed inequality for variances of dynamic elastic modulus(E_(d))and speed of sound,but equality for density.Equality of means was also examined via unequal variance t-test.Despite color differences,lower variability of M.huberi led to the indication of this species as likely capable to substitute satisfactorily ebony in fingerboards manufacturing.
基金This work was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior[grant number Edital 05/2017]Fundação Araucária:[grant number PI 04/2017 Programa Mobility Confap Italy-MCI].
文摘The early stages of product development are characterized by uncertainties.Designers must deal with challenges that arise unexpectedly in an agile and responsive manner.Expert information systems based on ontological models are a promising approach to capture knowledge and rationale of domain specialists,either for decision making or knowledge reuse.The present study presents a bibliometric analysis on the use of ontologies in product development for cost estimation.It identifies trends and research opportunities that can orient future works.From a general search in scientific databases,31 articles were found and selected based on criteria established using the Proknow-C method.Results indicate that there are several possibilities for solutions using ontological and hybrid,transdisciplinary approaches.Using intelligent systems is not only promising but is also challenging as a new and real transdisciplinary research area of interest.
