Made available in DSpace on 2014-12-17T14:58:03Z (GMT). No. of bitstreams: 1 ErikaCCL_DISSERT_1-65.pdf: 4712655 bytes, checksum: a7d827be13ca2b8a6228ba742c487da6 (MD5) Previous issue date: 2010-12-21 / We developed an assay methodology that considered the temperature variation and the scanning electron microscopy as a method to quantify and characterize respectively the consumption evolution in three 46 LA machines, with internal combustion and two-stroke engines, 7.64 cm3 cylinder capacity, 23.0 millimeters diameter and 18.4 millimeters course, RPM service from 2.000 to 16.000 rpm, 1.2 HP power, and 272 grams weight. The investigated engines components were: (1) head of the engine (Al-Si alloy), (2) piston (Al-Si alloy) and (3) piston pin (AISI 52100 steel). The assays were carried out on a desktop; engines 1 and 2 were assayed with no load, whereas in two assays of engine 3 we added a fan with wind speed that varied from 8.10 m/s to 11.92 m/s, in order to identify and compare the engine dynamic behavior as related to the engines assayed with no load. The temperatures of the engine s surface and surroundings were measured by two type K thermopairs connected to the assay device and registered in a microcomputer with data recording and parameters control and monitoring software, throughout the assays. The consumed surface of the components was analyzed by scanning electron microscopy (SEM) and microanalysis-EDS. The study was complemented with shape deformation and mass measurement assays. The temperature variation was associated with the oxides morphology and the consumption mechanisms were discussed based on the relation between the thermal mechanical effects and the responses of the materials characterization / Foi desenvolvida uma metodologia de ensaio que considerou a varia??o da temperatura e a microscopia eletr?nica de varredura um m?todo de quantificar e qualificar respectivamente a evolu??o do desgaste em tr?s m?quinas 46 LA de motor de combust?o interna de dois cursos, com uma capacidade de cilindro de 7,64 cm3, de 23,0 mil?metros de di?metro e de curso de 18.4 mil?metros, RPM de servi?o de 2.000 a 16.000 rpm, pot?ncia de 1,2 HP, peso de 272 gramas. Os componentes do motor investigados foram: (1) cabe?a do motor (liga Al-Si), (2) pist?o (liga Al-Si) e (3) pino do pist?o (A?o AISI 52100). Os ensaios foram realizados em uma bancada, os motores 1 e 2 foram ensaiados sem carga, e o motor 3 foi adicionado a dois ensaios um ventilador com velocidade do vento que variava entre 8,10 m/s a 11,92 m/s, com a finalidade de identificar e comparar o comportamento din?mico do motor com os motores ensaiados sem carregamento. As temperaturas pr?xima ao contato e ambiente foram medidas atrav?s de dois termopares tipo K conectados ao dispositivo de ensaio e registradas por um microcomputador com software de aquisi??o de dados, controle e monitoramento dos par?metros durante os ensaios. A superf?cie desgastada dos componentes foi analisada por microscopia eletr?nica de varredura (MEV) e microan?lise-EDS. O estudo foi complementado por ensaios de desvio de forma e medi??o de massa. A varia??o de temperatura associou-se ? morfologia dos ?xidos e os mecanismos de desgastes evidenciados foram discutidos correlacionando-se a solicita??o termomec?nica ?s respostas da caracteriza??o dos materiais

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-08-16T22:41:17Z No. of bitstreams: 1 JoaoPauloDeBarrosCavalcante_DISSERT.pdf: 25549974 bytes, checksum: 7d7077941a19b96d7263afec72ec7622 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-08-23T23:20:29Z (GMT) No. of bitstreams: 1 JoaoPauloDeBarrosCavalcante_DISSERT.pdf: 25549974 bytes, checksum: 7d7077941a19b96d7263afec72ec7622 (MD5) / Made available in DSpace on 2016-08-23T23:20:29Z (GMT). No. of bitstreams: 1 JoaoPauloDeBarrosCavalcante_DISSERT.pdf: 25549974 bytes, checksum: 7d7077941a19b96d7263afec72ec7622 (MD5) Previous issue date: 2016-03-11 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O presente trabalho consiste na an?lise num?rica via M?todo dos Elementos Finitos (MEF) de treli?as submetidas a carregamentos t?rmicos, mec?nicos e suas respectivas intera??es. A metodologia proposta baseia-se no teorema da m?nima energia potencial, escrita em rela??o as posi??es nodais ao inv?s dos deslocamentos para lidar com problemas termomec?nicos, levando-se em considera??o os efeitos das n?o linearidades f?sica e geom?trica. Referente aos problemas din?micos, a solu??o da equa??o de equil?brio ? alcan?ada atrav?s da discretiza??o temporal perante diferentes algoritmos de integra??o temporal, expl?citos e impl?citos. A formula??o ? estendida para problemas de impacto entre treli?as e anteparo r?gido, onde as posi??es nodais s?o restringidas atrav?s da condi??o de penetra??o nula. Sendo assim, apresenta-se uma formula??o termodinamicamente consistente, fundamentada na primeira e segunda lei da termodin?mica e na energia livre de Helmholtz, para analisar problemas din?micos de estruturas treli?adas com comportamento termoel?stico e termopl?stico. A implementa??o dos problemas consiste no desenvolvimento de rotinas computacionais, sendo os resultados num?ricos da formula??o proposta confrontados com exemplos encontrados na literatura especializada. / This work presents the numerical analysis of nonlinear trusses summited to thermomechanical actions with Finite Element Method (FEM). The proposed formulation is so-called positional FEM and it is based on the minimum potential energy theorem written according to nodal positions, instead of displacements. The study herein presented considers the effects of geometric and material nonlinearities. Related to dynamic problems, a comparison between different time integration algorithms is performed. The formulation is extended to impact problems between trusses and rigid wall, where the nodal positions are constrained considering nullpenetration condition. In addition, it is presented a thermodynamically consistent formulation, based on the first and second law of thermodynamics and the Helmholtz free-energy for analyzing dynamic problems of truss structures with thermoelastic and thermoplastic behavior. The numerical results of the proposed formulation are compared with examples found in the literature.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-09-05T19:41:33Z No. of bitstreams: 1 RafaelaLopesDaSilva_DISSERT.pdf: 5244464 bytes, checksum: f14dfee1270966b169af76ce9e23f4c6 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-09-15T21:04:19Z (GMT) No. of bitstreams: 1 RafaelaLopesDaSilva_DISSERT.pdf: 5244464 bytes, checksum: f14dfee1270966b169af76ce9e23f4c6 (MD5) / Made available in DSpace on 2017-09-15T21:04:19Z (GMT). No. of bitstreams: 1 RafaelaLopesDaSilva_DISSERT.pdf: 5244464 bytes, checksum: f14dfee1270966b169af76ce9e23f4c6 (MD5) Previous issue date: 2017-03-24 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Este trabalho apresenta um estudo sobre a influ?ncia dos efeitos t?rmicos no comportamento din?mico de estruturas de p?rtico plano n?o lineares f?sicos e geom?tricos, nas quais esfor?os de flex?o e cisalhamento s?o predominantes. Uma formula??o fundamentada na primeira e segunda leis da termodin?mica e energia livre de Helmholtz ? apresentada neste trabalho para considerar os efeitos t?rmicos neste tipo de estrutura. Utiliza-se como ferramenta de an?lise estrutural o M?todo dos Elementos Finitos Posicional, que difere do m?todo convencional pelo simples fato de adotar como inc?gnitas as posi??es nodais, ao inv?s dos deslocamentos nodais. O problema n?o linear din?mico ? solucionado diante da combina??o do processo iterativo de Newton-Raphson com uma gama de algoritmos de integra??o temporal, expl?citos e impl?citos, sendo os resultados num?ricos confrontados com exemplos encontrados na literatura especializada. Como tamb?m, apresenta-se uma descri??o de uma t?cnica para solu??o de problemas de impacto. / This work presents a study considering the thermal effects in the dynamic behaviour of nonlinear 2D-frame structures (physical and geometric), in which the effects of bending and shear are predominant. A formulation based on the first and second laws of thermodynamic and the Helmholtz free-energy is presented in this work to consider the thermic effects on this type of structure. The Finite Element Method based on nodal positions, rather than nodal displacements, is used as structural analysis tool. The solution of the nonlinear dynamic problem is given through the combination of Newton-Raphson iterative process with several explicit and implicit time integration methods, wherein the numerical results are compared with the ones found on specialized literature. As well, it is presented a description of one technique to solution of impact problems.