Avaliação numérico-experimental do comportamento mecânico de aços API X80 e investigação das variáveis mecânicas e microestruturais envolvidas no crack arrest

Abstract

Despite employing modern high toughness structural steels (API grade) in pipelines, it remains the need of predicting ductile fracture phenomena that can trigger cracks in velocities up to 500 m/s and result in significant damage to society. In this sense, and from an engineering point of view, some models for pipelines failure prediction proposed in the past no longer represent the phenomenology occurring in the current materials, contributing for the loss of similitude between the specimens (Charpy V-Notch) and real structures. Thus, the researches of Moço (2017) and Pereira (2017) have provided good practices in impact specimens and pipes simulations, for the comprehension of the crack propagation phenomena in high toughness materials, by means of load-displacement response and also an energetics perspective. Nevertheless, a deeper study is necessary, in addition to experimental tests for numerical validation and identification of mechanical and microstructural variables that directly influence in crack arrest. In this scenario, this research was conceived, including the whole experimental characterization by means of tensile and instrumented Charpy mechanical tests of API X80 steel plates, in addition to preliminaries DWTT tests, all of them followed by numerical reproduction employing GTN damage model to understand the phenomena. Moreover, despite the structuring nature of this research, the results of the experimental analyses have already briefly oriented the investigation regarding to the variables that play a role in these materials' crack arrest, as the occurrence of delaminations in the cases where the arrest didn't take place. Therefore, this work has stablished a solid base for the continuity of the energetics investigations involving the crack propagation phenomenon in high toughness steels (from the proposals made by Moço (2017) and Pereira (2017)), as the identification of the mechanical and microstructural variables that play a role in crack arrest.

Metodologias para correção de tunelamento e plasticidade na flexibilidade elástica de geometrias SE(B) e SE(T) - abordagem numérica e experimental

“…No entanto, existe uma dependência do tamanho de malha de elementos finitos na região do processo de fratura bem como tornar os parâmetros independentes de geometria é uma tarefa de extrema dificuldade (NONN;KALWA, 2013;SCHEIDER et al, 2014;SARZOSA et al, 2016). Mais detalhes sobre esta metodologia podem ser encontrados na literatura citada bem como nas dissertações de mestrado de outros membros do grupo de pesquisa onde este trabalho se insere (MOÇO, 2017;SILVA, 2019).…”