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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Conformabilidade plástica dos metais pela mecânica da fratura não-linear. / Plastic formability of metals thru nonlinear fracture mechanics.

Gomes, Edson 13 December 1990 (has links)
Este trabalho visa modelar e estabelecer procedimentos experimentais para permitir a construção de mapas de conformabilidade plástica dos metais fundamentados na mecânica da fratura não-linear elasto-plástica. Um critério de conformabilidade plástica foi desenvolvido pela utilização de uma integral invariante generalizada baseada no teorema de Noether das integrais invariantes. Discute-se também as limitações da teoria da plasticidade que impossibilitam a obtenção de critérios de conformabilidade por seu intermédio. É um importante objetivo proporcionar o surgimento de uma metodologia de ensaio contendo alto rigor técnico mas sendo de baixo custo e de fácil implementação em simples instalações industriais. O procedimento foi aplicado no estudo do caso do forjamento a frio em matriz aberta, simulado por ensaio de compressão em prensa hidráulica. / The present study is aimed to the development of a low cost, to be implemented with ease, and technicality satisfactory industrial type testing for metal forming workability analysis. It is concerned with the development of an experimental procedures to permit the building up the metal forming workability maps, based on the nonlinear elastic-plastic fracture mechanics. A generalized nonlinear fracture mechanics invariant integral was applied to the case problem of the cold forging in flat open die of a ductile metallic material. At end a fracture criterion was developed in order to be possible the construction of the fracture deformation maps of the case study.
2

Modelování lomového procesu v kvazikřehkých materiálech / Modeling of fracture process in quasi-brittle materials

Klon, Jiří January 2016 (has links)
This work is focused on the evaluation of the selected fracture parameters of quasi-brittle material, especially concrete, and an assessment of their dependence on the size and shape of the fracture process zone developing at the tip of the macroscopic crack during fracture. For this purpose, experimentally obtained loading diagrams published in the scientific literature have been utilized. These diagrams have been processed into a form enabling creation and calibration of numerical models of these tests in the ATENA FEM program. The results obtained from simulations of the three-point bending tests on beams of four sizes, with three notches lengths, using the created numerical models were used for determination of fracture parameters of concrete. Results of the work consist of the determined values of the specific energy dissipated for creation of new surfaces of the effective crack and an estimation of the specific energy dissipated in the volume of the fracture process zone, which exhibits specific parameters for each beam size and notch length.

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