Sergio Luiz Moni Ribeiro Filho

Metodologia para o cálculo dos módulos de elasticidade longitudinal e transversal em vigas de madeira de dimensões estruturais

This paper proposed a test method to obtain the shear (G) and longitudinal (E) modulus of elasticity in timber beams with structural dimensions, based on the static three-points bending tests and the Euler Bernoulli and Timoshenko beams theories. The woods tested were the Corymbia citriodora and Pinus elliottii. The results revealed that the longitudinal modulus of elasticity of Pinus elliottii is 18.70 greater than the shear modulus, and 21.16 greater than the shear modulus of Corymbia citriodora, being consistent this results when compared to the proposed by the Brazilian standard ABNT NBR 7190:1997 (Design of Wood Structures), being the longitudinal modulus of elasticity twenty times greater than the shear modulus.

Analysis of the Forces in Micromilling of Hardened AISI H13 Steel with Different Grain Sizes Using the Taguchi Methodology

The micromachining process has been applied to the free form and micromolds markets. This has occurred due to the growth in demand for microcomponents. However, micromachining of hardened steels is a challenge due to the reduction in tool life and the increase of the surface roughness when compared with the macromachining process. This paper focused on the analysis of micromilling forces on hardened AISI H13 steel with different grain sizes. Experimental tests were carried out on workpieces with different austenitic grain sizes and a hardness of 46 HRC. Micro-end-mill cutters with a diameter of 0.5 mm and (TiAl)N coatings were applied in the milling of workpieces of 11 × 11 mm. The input parameters were two radial depths of cut, two cutting speeds, and two feed rates. The influence of the input parameters on the response cutting force was analyzed using the Taguchi method. Finally, considering the large grain size, the cutting forces in the x-, y-, and z-axes direction were small.

Processing of Threads on a Magnesium Alloy Using a Special Process

Tapping is a complex process largely applied on metal cutting industry. The tapping process can be carried out using cutting or forming tools. This work presents a study of the form tapping process using a tool without cutting edge and helix angle and with external diameter much smaller than the final thread. The experimental tests were carried out with three forming speeds and three helical feed rates to produce M12 threads into the AM60 Magnesium alloy. The results showed that these specfic forming taps provided internal threads with good thread shapes and finishing forms that were as good as the traditional forming tap, which uses tools with the same final thread hole diameter. In addition, the increase of helical feed rate decreases the torque and thrust force, but the differences were greater in torque than in thrust force. The greatest decrease of torque occurred for the lowest forming speed, and the lowest decrease of torque occurred for the highest forming speed. Moreover, the thrust force and torque recorded in the experimental tests were lesser than in traditional form tapping for the same thread area, at least for the magnesiun alloy used.

Influence of Different Cooling Systems on Surface Roughness in the Turning of the Ti-6Al-4V Alloy Used as Biomaterial

Titanium and its alloy are materials with great application in the aeronautic and biomedical area. These applications have grown in the last decade due to high resistance to corrosion and biocompatibility of the Titanium alloys. However, Titanium and its alloys are classified as hard-to-machining materials that increase the production costs due to the highest tool wear. Thus, the finishing of components made of Titanium alloys can be impaired due to the complex shearing mechanism. This work shows a study of the influence of cooling systems and the input parameters on the turning of the Ti-6Al-4V alloy. Two depths of cut, two feed rates, new and worn tools, and three cooling systems were used as input parameters. The response was the surface roughness measured according to the Ra parameter. According to the results, it can be supported that the variation of all input parameters has influence on response. However, the most important input parameter on surface roughness was the feed rate. Thus, it can be concluded that the correct choice of the cutting parameters is relevant to produce high-quality components.

Geometric effects of sustainable auxetic structures integrating the particle swarm optimization and finite element method

The development of new materials based on industrial wastes has been the focus of much research for a sustainable world. The growing demand for tyres has been every year exacerbating environmental problems due to indiscriminate disposal in the nature, making a potentially harmful waste to public health. The incorporation of rubber particles from scrap tyres into polymeric composites has achieved high toughness and moderate mechanical properties. This work investigates the geometric effects (thickness, width and internal cell angle) of auxetic structures made of recycled rubber composites based on experimental and numerical data. The response surface models integrated with the swarm intelligence and finite element analysis were proposed in order to obtain a range of solutions that provides useful information to the user during the selection of geometric parameters for reentrant cells. The results revealed the cell thickness ranges from 39-40 mm and 5.98-6 mm, and the cell angle range from -0.01 to -0.06o maximize the ultimate strength. The same parameters were able to optimize the modulus of elasticity of rubber auxetic structures, excepting for the angle factor which must be set between -30o and 27.7o. The optimal Poissons ratio was found when the cell angle ranged from -30o to -28.5o, cell width ranged from 5-5.6 mm and 2 mm in thickness.

Finite Element Method in Machining Processes: A Review

An ecological production and low cost is the target of several industries. Increasingly, the product development is critical stage to obtain a great quality and fair price. This stage will define shapes and parameters that will able to reduce wastes and improve the product. However, the expense of prototypes also should be reduced, because, in general, the prototypes are more expensive that final product. The use of finite element method (FEM) can avoid much tests that reduce number of prototypes, and consequently the project cost. In the machining processes simulation, several cutting conditions can be reproduced to define the best tool and parameters in function of analyzed forces, stress, damages and others. This paper debates the use of FEM in the machining processes, shows some researches and indicates the main attributes to develop simulation studies for conventional machining and micromachining.

Metodologia alternativa para o cálculo do módulo de elasticidade em vigas de madeira de dimensões estruturais

This study aims to present an alternative calculation methodology based on the Least Squares Method for determining the modulus of elasticity in bending wooden beams of structural dimensions. The equations developed require knowledge of three or five points measured in displacements along the piece, allowing greater reliability on the response variable, using the statistical bending test at three points and non-destructively, resulting from imposition of measures from small displacements L/300 and L/200, the largest being stipulated by the Brazilian norm NBR 7190:1997. The woods tested were Angico, Cumaru, Garapa and Jatoba. Besides obtaining the modulus of elasticity through the alternative methodology proposed, these were also obtained employing the Brazilian norm NBR 7190:1997, adapted to the condition of non-destructive testing (small displacements) and for pieces of structural dimensions. The results of the modulus of elasticity of the four species of wood according to both calculation approaches used proved to be equivalent, implying the good approximation provided by the methodology of calculation adapted from the Brazilian norm.

Módulo de elasticidade em vigas de madeira de dimensões estruturais pelo método dos mínimos quadrados

Este trabalho propoe uma metodologia alternativa de calculo fundamentada no Metodo dos Minimos Quadrados para a obtencao do modulo de elasticidade na flexao de vigas de madeira com dimensoes estruturais. As equacoes desenvolvidas requerem o conhecimento de um ou cinco pontos de deslocamentos medidos ao longo do comprimento das pecas. Esse metodo permite maior precisao sobre a variavel resposta e tem como base o ensaio de flexao estatica a tres pontos. A metodologia proposta foi empregada em concordância com as recomendacoes da norma Brasileira NBR 7190:1997, adaptada para pecas de dimensoes estruturais. Os ensaios mecânicos foram realizados em sete pecas de madeira Corymbia citriodora com 540cm de comprimento, 15cm de altura e 5cm de largura. Em testes preliminares determinou-se o valor da forca responsavel por provocar um deslocamento vertical no meio do vao de L/200, sendo L a distância entre os apoios das vigas. A forca obtida foi dividida em sete incrementos iguais (39,60N), fornecendo sete valores de deslocamento distintos. Os resultados de ambas as metodologias mostraram-se convergentes a medida que os deslocamentos se aproximaram da razao L/200, validando o uso desta relacao. Os resultados do intervalo de confianca entre medias indicaram equivalencia estatistica entre os modulos de elasticidade por ambas as formas de calculo e para os sete incrementos de deslocamentos. Em razao da possivel presenca de defeitos e da heterogeneidade da madeira, os resultados obtidos nao devem ser extrapolados para outras madeiras de mesma ou de especies diferentes, justificando o uso da presente metodologia de calculo em cada pesquisa desenvolvida.

A NOVEL RECYCLING ROUTE FOR POLYETHYLENE BOTTLE CAPS AS CIRCULAR HONEYCOMB CORE

The disposal of plastic wastes in the environment has been an urgent issue due to pollution of the soil and the sea. The incorporation of polymeric residues into innovative and sustainable structural composites can be considered a promising recycling route. This work investigates the use of disposed polyethylene (PE) caps from drinking water bottles as a sustainable honeycomb core with circular cell geometry. A full factorial design was conducted to identify the effect of bottle caps orientation (single and alternated directions), polymeric adhesive (epoxy and polymer), and aluminium roughness (smooth and rough surface) on the mechanical properties of sandwich panels. The use of epoxy polymer contributes significantly to enhance panel strength and stiffness. Smooth aluminium skins lead to increased panel strength, suggesting a limited effect of roughness increase to enhance aluminium and skin bonding. Finally, single directed caps in the core achieve better mechanical performance than alternated caps. The results evidence the feasibility of alternative uses for bottle caps into structural and sustainable applications.

Pinus caribaea var. hondurensis Wood Impregnated with Methyl Methacrylate

AbstractThis paper investigates the normal hardness, the compressive strength, and the modulus (parallel to the grain) of Pinus caribaea var. hondurensis wood in pristine condition and impregnated ...