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COB30 ANÁLISE FRACTOGRÁFICA E PROPRIEDADES MECÂNICAS DE TRAÇÃO DE UM AÇO IF AO TITÂNIO FRACTOGRAPHY AND MECHANICAL PROPERTIES BY TENSION TESTING OF Ti-ADDED IF-STEEL
Jeferson Firmino das Chagas, Alfeu Saraiva Ramos & Tomaz Manabu Hashimoto
Departamento de Materiais e Tecnologia, Faculdade de Engenharia - UNESP - Guaratinguetá CEP 12500-000 Guaratinguetá, Brasil - E-mail: Chagasjf@feg.unesp.br
In recent years, there has been significant interest in properties and development of interstitial-free (IF) steels. These steels, because of their improved formability and deep drawing capability offer a number of advantages for stamped components in automotive applications. IF steels generally exhibit more consistent mechanical properties compared to conventional aluminium killed deep drawing quality steels. The carbon contents of IF steels are well below those of steels which form pearlite after hot rolling and annealing. The objective of this work is to analyse by comparison the influence of mechanical properties on the mechanism of fracture of Ti-IF steel. It was observed that the most significant fracture mechanism was the coalescence of microvoid, and the shape of the "dimples"confirmed the high elongation values of this material.
Keywords: IF Steel, ductile fracture, microvoid coalescence, mechanical behavior, ductility/ Aço IF, fratura dúctil, coalescência de microvazios, comportamento mecânico, ductilidade.
COB33 INFLUENCE OF THE NUMBER OF SPECIMENS IN THE REFERENCE TEMPERATURE DETERMINATION - INITIAL APPROACH / INFLUÊNCIA DO NÚMERO DE CORPOS DE PROVA NA DETERMINAÇÃO DA TEMPERATURA DE REFERÊNCIA - ABORDAGEM INICIAL
Carlos Alexandre de. J. Miranda1 & John D. Landes2
1IPEN-CNEN/SP, SP, Brazil, e-mail: cmiranda@ipen.net.br;
2University of Tennessee at Knoxville, USA; e-mail: John-Landes@utk.edu
The ASTM E08.08 subcommittee is preparing a new standard, currently in the draft version #13, to determine the reference temperature To for ferritic steels in the transition region. The minimun number of valid experimental results in the data set, to be analyzed by this proposed standard, for a given temperature T, is six. In this work this assumption (six results) is verified by comparison among the results obtained, in terms of T-To, with different number of toughness values (subsets) taken from a given large set that fits perfectly the Weibull three-parameter probability distribution. The conclusion is an indication of the way to be followed to determine the minimum number of experiments/results necessary to obtain at least 90%, 95% or 98% of the possible T-To values near the target one (that of the whole set from which the subsets are taken)
Keywords: Fracture Mechanics, Transition, Reference Temperature, Reliability
Mecânica da Fratura, Transição, Temperatura de Referência, Confiabilidade
COB121 FABRICAÇÃO E CARACTERIZAÇÃO DE FERRAMENTAS DE CORTE DE Si3N4 / MANUFACTURING AND CHARACTERIZATION OF TOOLS OF THE Si3N4
Olivério Moreira de Macedo Silva, Cosme Roberto Moreira da Silva & Sandro Aparecido Baldacim
Divisão de Materiais-Instituto de Aeronáutica e Espaço-Centro Técnico Aeroespacial-Amr/Iae/Cta
Cep 12228/904 - São José dos Campos - SP - Brasil
Silicon nitride based ceramic cutting tools were developed in Brazil. Ceria and aluminium nitride were used as sintering aids. The samples evaluations were performed using especific mass determination, X ray diffraction, microhardness testing, fracture thoughness by indentation method and microstructural examination via scanning electron microscopy. After samples evaluation, some pressureless sintering silicon nitride based ceramic cutting tools were made. A piece of cast iron was machined using these cutting tools. For the purpose of comparison, a commercial hard metal cutting tools was also used to perform the same machining.
Keywords: Sintering, tools, silicon nitride, ceria, aluminun nitride / Sinterização, ferramentas, nitreto de silício, céria, nitreto de alumínio
COB151 Determination of the Viscoplastic Characteristics of a PolYester Resin Mixture
Luiz Claudio Oliveira3, Henner Alberto Gomide1 & Raquel Santini Leandro Rade2
1Mechanical Engineering Dept, 2Physical Sciences Dept, 3PhD Student, Mech Eng Dept, UFU - Federal University of Uberlândia -
Uberlândia, MG - CEP 38400-089, E-mails: lclaudio@ufu.br, hagomide@ufu.br, domingos@ufu.br
It is aimed the identification of typical basic behaviors of a mixture of two types of polyester resins for a broader characterization of mechanical and optical properties to be used in photoplastic studies. The first step shown in this paper refers to the identification of viscoplastic behavior at different temperatures through a tension test with multiple relaxations, using specimens with different proportions of the types of resin. Proportional parts in weight of a flexible resin (Resapol 10.069) and a rigid one (10.116) are mixed and cured with hardeners, and out of this material specimens are machined. A temperature control chamber to be used with a polariscope has been specially designed and constructed to be adapted to the universal testing machine used. This chamber is of very low cost, works at a temperature range 0~80ºC, with accurate means of temperature control. These experimental studies intend to incorporate the obtained results into a theoretical-computational model in development. The model aims the broad description of the mechanical and optical properties and behavior of the resin mixtures, which will allow the design of experimental-numerical simulations of specimens/parts with complex geometry and/or loading, through the use of prototypes made with the model material developed.
Keywords: Mechanical Properties, Resins, Viscoplasticity, Temperature Control, Relaxation /
Propriedades Mecânicas, Resinas, Viscoplasticidade, Controle de Temperatura, Relaxação
COB364 PROPRIEDADES MECÂNICAS DE UM AÇO MICROLIGADO EM ALGUMAS CONDIÇÕES MICROESTRUTURAIS / MECHANICAL PROPERTIES OF A MICROALLOYED STEEL IN SOME MICROSTRUCTURAL CONDITIONS
Tácito Brandão Pinto, Enrico José Giordani, Peterson Ferrandini, Valdir Alves Guimarães & Itamar Ferreira
Departamento de Engenharia de Materiais, Faculdade de Engenharia Mecânica - UNICAMP - C.P. 6122 - CEP 13.083-970 Campinas, Brasil - E-mail: itamar@fem.unicamp.br
The purpose of this work is to analyze the mechanical properties of a titanium and niobium microalloyed low carbon steel, an API 5L X65, in some microstructural conditions: as received and from the thermal treatment (quenching and austempering from the intercritical annealing at two temperatures: 1043 and 1083 K). Tension, crack tip opening displacement and Vickers hardness tests have been conducted in order to analyze the strength, ductility, fracture toughness, and hardness. The as received condition, with a ferrite and perlite microstructure, presented tensile strength of 617 MPa, elongation of 25.4%, reduction in area of 74.3% and fracture toughness of d m=0.35mm. The quenching in oil from the intercritical zone showed a microstructure composed basically of ferrite and martensite, and presented, for the 1083 K, good levels of tensile strength (637 MPa), elongation (29.7%), reduction in area (70.6%), and fracture toughness (d m=0.45mm); this condition is optimized when comparing to the as received condition, and for the 1043 K, high tensile strength levels (690 MPa), but low values of reduction in area (61.2%) and fracture toughness (d m=0.27mm). The austempering in 643 K, from the intercritical zone (1043 K), showed a microstructure composed of ferrite and bainite and presented good levels of tensile strength (598 MPa), elongation (28.5 %), and fracture toughness (d m=0.44mm), and very high levels of reduction in area (81.7 %), indicating a better relationship among the mechanical properties when comparing to the quenching condition from the same intercritical temperature (1043 K), and also an optimization in relation to the as received condition, in spite of the decrease in the tensile strength.
Keywords: Mechanical properties, Microalloyed steel, Intercritical annealing. Propriedades mecânicas, Aço microligado, Tratamento térmico intercrítico.
COB690ANÁLISE TÉRMICA DA INFLUÊNCIA DOS SKIDS NO AQUECIMENTO DE PLACAS EM FORNOS DE REAQUECIMENTO DE SOLEIRA MÓVEL/THERMAL ANALYSIS OF SKIDS INFLUENCE UPON SLABS REHEATING PROCESS IN WALKING BEAM FURNACES
Bruno Santos Pimentel & Márcio Ziviani
Departamento de Engenharia Mecânica, Escola de Engenharia - UFMG - Belo Horizonte - Av. Antônio Carlos, 6627 - CEP 31.270-010 Belo Horizonte, Brasil - E-mail: ziviani@vesper.demec.ufmg.br
The following paper presents a mathematical model to simulate the reheating process of slabs in a walking beam furnace. The detrimental influence of the skids upon the temperature profile homogeneity (skidmarks) is avaliated relative to the main characteristics of this specific furnace. Also, a simple solution to the skidmark problem is proposed: a staggered arrengement of the beams of the soaking zone, allowing the cold areas to not be shielded from radiation. The results of this improvement show a large reduction of the skidmarks, providing better product quality and significant energy saving.
Keywords: Skidmarks, Reheating Furnaces, Metalurgical Quality, Energy Saving, Fornos de Reaquecimento, Qualidade Metalúrgica, Economia de Energia
COB1082 PROPRIEDADES MECÂNICAS DE UMA LIGA Al-Li / MECHANICAL PROPERTIES OF AN Al-Li ALLOY
Luis Augusto Hernandez Terrones, Christianne dos Santos Ferreira & Sérgio Neves Monteiro
Laboratório de Materiais Avançados, Centro de Ciência e Tecnologia - UENF
CEP 28015-620 Campos dos Goytacazes-RJ, Brasil - Fax: (0247) 23-0160
In this work the mechanical properties of a 2090 Al-Li alloy were determined for different thermo mechanical treatments. These treatments correspond to the alloys in the conditions of solution treated and aged at different times, with and without previous deformation. The results of tension tests have shown an increase in the strength of the material (yield and ultimate stresses) with the aging time. The best results were obtained for samples which were pre-deformed before aging. The ductility was greater for the solution treated material and decreases for the aged alloy. An improvement in the ductility occurs for the pre-deformed samples before aging.
The changes observed in the tensile properties are related to the different precipitates formed during the aging treatment as well as to the increase in dislocation density due to the pre-deformation before aging.
Keywords: Mechanical Properties, Aluminum Alloy, Precipitation, Tension Test, Dislocations
COB1401 INFLUENCE OF THE NUMBER OF SPECIMENS IN THE REFERENCE TEMPERATURE dETERMINATION: THe Monte-Carlo APPROACH / INFLUÊNCIA DO NÚMERO DE CORPOS DE PROVA NA DETERMINAÇÃO DA TEMPERATURA DE REFERÊNCIA: MÉTODO MONTE-CARLO
Carlos Alexandre de. J. Miranda1 & John D. Landes2
1IPEN-CNEN/SP, SP, Brazil, e-mail: cmiranda@net.ipen.br
2University of Tennessee at Knoxville, TN, USA; e-mail: John-Landes@utk.edu
This work verifies the assumption of six results to determine the master curve for ferritic steels, as stated by the draft #13 of the ASTM E08.08 subcommittee, using the Reference Temperature approach. The Monte-Carlo Method was used to select the analyzed subsets representing the experimental results taken from an infinite ‘universe’ that fits perfectly the so-called Weibull Three-Parameter probability distribution. This verification becomes important due to the large results scatter in the transition and no defined reliability level in that assumption. A direct approach to address this problem defining an ‘universe’ represented by a finite set of results was presented in the part I of this work. It showed the necessity of a new approach to consider the infinity possible results given by an experiment. The reliability of the master curve obtained with a given subset of experimental results is indicated as well the minimum number of experimental results necessary to have a confidence level of 90%, 95% or 98% in the obtained Reference Temperature value and the respective Master Curve.
Keywords: Fracture Mechanics, Transition, Reference Temperature, Reliability
Mecânica da Fratura, Transição, Temperatura de Referência, Confiabilidade
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