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Master's Dissertation
DOI
10.11606/D.3.2018.tde-27082018-075853
Document
Author
Full name
Carlos Andres Cuenca Cabrera
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2018
Supervisor
Committee
Burgos, Diego Felipe Sarzosa (President)
Bianchi, Kleber Eduardo
Tobar, Lenin Marcelo Paredes
Title in English
Ductile failure prediction using phenomenological fracture model for steels: calibration, validation and application.
Keywords in English
Damage
Ductile
FEM
Fracture
SMCS (Method)
Abstract in English
The present thesis shows the analysis, calibration, and application of the stress modified criticai strain criterion to predict ductile failure for an A285 steel. To obtain the mechanical behavior of the material, experimental tests were carried out by implementation of 5 different types of geometries: smooth round bar, notched round bar (R=1 , 2, 3 mm), and, deep and shallow cracked SE(B) specimens. Then, for the calibration process of the mechanical properties finite element models were generated, using 30 solid elements with 8 nodes (C308), matching the geometry and the properties of the tested specimens. To calibrate the elastoplastic behavior was used the experimental and numerical response obtained from the smooth and notched round bar specimens; and, for the damage calibration was used the responses obtained from both deep and shallow crack SE(B) specimens. Once the mechanical properties were calibrated, then there were obtained the SMSC criterion factors represented by the equation ..... and, the damage condition which is represented by the displacement at failure (.......) and exponential factor (....). This calibrated model was able to recover the SE(B) experimental responses that validate the use of the characterized material in a complex structure. Then, the fully characterized material was applied in two pipelines which have externai initial circumferential elliptical crack; being the first one pipe with shallow crack and the second one with deep crack. Finally, both pipes were submitted to tension loads to predict the ductile damage behavior, obtaining the necessary load to the crack start growing, and the evolution of the failure.
Title in Portuguese
Previsão de falha dúctil usando modelo fenomenológico de fratura para aços: calibração, validação e aplicação.
Keywords in Portuguese
Aço
Ductilidade
FEM
Fraturas
SMCS (Método)
Abstract in Portuguese
A presente dissertação apresenta o processo de análise, calibração e aplicação das propriedades mecânicas, incluindo o comportamento elastoplástico e de dano, para o aço A285, utilizando o critério "Stress modified criticai strain" (SMCS). Para obter o comportamento mecânico do material, testes experimentais foram realizados com a implementação de 5 tipos diferentes de geometrias: barra cilíndrica sem entalhe, barra cilíndrica com entalhe (R = 1, 2, 3 mm) e corpos de prova SE(B) com trinca inicial profunda e rasa. Para o processo de calibração das propriedades mecânicas foram gerados modelos de elementos finitos, utilizando elementos sólidos 30 com 8 nós (C3D8), que representam de forma adequada a geometria e as propriedades dos corpos de prova testados. Para calibrar o comportamento elastoplástico e iniciação do dano, utilizou-se a resposta experimental e numérica obtida para as amostras de barra cilíndrica com e sem entalhe; e, para a calibração da evolução do dano, foram utilizadas as respostas obtidas para os espécimes SEB de trincas profundas e rasa. Este modelo calibrado foi capaz de recuperar as respostas experimentais dos corpos de prova SE(B), o que valida o uso do material caracterizado em uma estrutura complexa. Uma vez calibradas as propriedades mecânicas, foram obtidos os fatores do critério SMSC representados pela equação ....... , e, a condição de dano que é representada pelo deslocamento na falha .... e o fator de amolecimento exponencial .... . Depois, o material totalmente caracterizado foi aplicado em dois dutos que possuem trinca elíptica circunferencial inicial externa; sendo o primeiro tubo com trinca superficial e o segundo com trinca profunda. Finalmente, ambos os tubos foram submetidos a cargas de tensão para prever o comportamento do dano dúctil, obtendo a carga necessária para o início do crescimento da trinca e a evolução da falha.
 
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Publishing Date
2018-09-03
 
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