Loading...
Publication
Análise do fator de intensidade de tensões em carregamentos multiaxiais
| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 2.77 MB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
De forma a evitar falhas estruturais, a integridade dos componentes é avaliada através de uma área de grande importância na engenharia: a Mecânica da Fratura. No fundo, trata de investigar a resistência á fratura dos materiais, tendo em conta, quando é necessário, o estudo da fadiga. Um dos parâmetros que torna possível caracterizar a resistência á fratura do material em estudo é o Fator de Intensidade de Tensão (𝐾). Uma das formas de avaliar a resistência á fratura de componente pelo Fator de Intensidade de Tensão é através de métodos computacionais, em softwares. No presente trabalho o principal objetivo passa por simular o comportamento mecânico de dois tipos de provetes, um provete CTS (Compact Tension Shear) e um provete Flexão em 3 Pontos (3 Point Bending), fabricados em distintas ligas de alumínio e um aço inoxidável, através de ensaios de tenacidade á fratura e de um ensaio á fadiga, no software ANSYS®, recorrendo á ferramenta dos elementos finitos para obtenção de resultados fiáveis e com erros baixos. Tendo as propriedades de cada material, foram modelados os provetes, de acordo com as normas ASTM E399-09, e retirados os valores de KI, KII, KIII e Keq. Desta forma, foram realizados 4 ensaios com valores distintos de cargas aplicadas, em Modo I + II, podendo-se fazer comparações de resultados e quais as condições de carregamento afetam mais os distintos materiais. Após resultados obtidos, foi feita uma comparação entre os resultados numéricos e os analíticos, avaliando-se qual o melhor critério para o cálculo de Keq. Por último, simulou-se o Keq em Modo I + III e calculou-se analiticamente também o valor máximo do momento torsor que o aço inoxidável aguenta antes que haja propagação instável da fenda, e posteriormente procedeu-se á dissecação da fórmula do critério de Richard para cálculo do Keq, fazendo uma explicação sobre como cada constante é inserida e utilizada.
Abstract To avoid structural failure, the integrity of components is assessed by an area of great importance in engineering: Fracture mechanics. Essentially, this involves examining the fracture strength of materials, taking fatigue into account where appropriate. One of the parameters that makes it possible to characterize the fracture strength of the material under investigation is the stress intensity factor (𝐾). One way to evaluate the fracture strength of a component based on the stress intensity factor is to apply calculation methods in a software. In this work, the main objective is to simulate the mechanical behavior of two types of specimens, a CTS (Compact Tension Specimen) specimen and a 3-point Bending specimen made of different aluminum alloys and a metallic steel, through fracture toughness tests and a fatigue test in ANSYS® software, using the finite element tool to obtain reliable results with low errors. Once the properties of each material were known, the specimens were modeled according to ASTM E399-09 standards and the values of KI, KII, KIII and Keq were determined. In this way, 4 tests were performed with different load values in mode I and II to compare the results and determine which materials were most affected by the different loading conditions. The numerical and analytical results were then compared to determine the best classification for the calculation of Keq. Finally, Keq was simulated in mode I + III and the maximum value of torque that the stainless steel can withstand before unstable crack propagation occurs was also calculated analytically, and then the Richard's Criteria formula for Keq was decomposed, explaining how each constant is inserted and used and where its values come from.
Abstract To avoid structural failure, the integrity of components is assessed by an area of great importance in engineering: Fracture mechanics. Essentially, this involves examining the fracture strength of materials, taking fatigue into account where appropriate. One of the parameters that makes it possible to characterize the fracture strength of the material under investigation is the stress intensity factor (𝐾). One way to evaluate the fracture strength of a component based on the stress intensity factor is to apply calculation methods in a software. In this work, the main objective is to simulate the mechanical behavior of two types of specimens, a CTS (Compact Tension Specimen) specimen and a 3-point Bending specimen made of different aluminum alloys and a metallic steel, through fracture toughness tests and a fatigue test in ANSYS® software, using the finite element tool to obtain reliable results with low errors. Once the properties of each material were known, the specimens were modeled according to ASTM E399-09 standards and the values of KI, KII, KIII and Keq were determined. In this way, 4 tests were performed with different load values in mode I and II to compare the results and determine which materials were most affected by the different loading conditions. The numerical and analytical results were then compared to determine the best classification for the calculation of Keq. Finally, Keq was simulated in mode I + III and the maximum value of torque that the stainless steel can withstand before unstable crack propagation occurs was also calculated analytically, and then the Richard's Criteria formula for Keq was decomposed, explaining how each constant is inserted and used and where its values come from.
Description
Dissertação para obtenção do grau de Mestre em Engenharia Mecânica, na Área de Especialização de Manutenção e Produção
Keywords
Fator de intensidade de tensão Ansys Lei de Paris Propagação de fenda por fadiga Stress intensity factor Paris law Fatigue crack propagation
Citation
DIOGO, Eduardo Nuno Campos Dias – Análise do fator de intensidade de tensões em carregamentos multiaxiais. Lisboa: Instituto Superior de Engenharia de Lisboa. 2024. Dissertação de Mestrado.