Microscopic examination of crack growth in a pressure vessel steel

Isacsson, Måns; Narström, Torbjörn

doi:10.1016/s0921-5093(97)00485-1

Cited by 10 publications

(4 citation statements)

References 8 publications

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“…In the case of Fe! C precipitates, heat treatment controls their embrittlening effect and therefore affects both ductile and brittle fracture [31,32].…”

Section: Methodsmentioning

confidence: 99%

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Ductile to brittle transition of an A508 steel characterized by Charpy impact test

Tanguy

Besson

Piques

et al. 2005

Engineering Fracture Mechanics

165

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This study is devoted to the ductile-brittle transition behavior of a French A508 Cl3 (16MND5) steel. Due to its importance for the safety assessment of PWR vessels, a full characterization of this steel with Charpy V-notch test in this range of temperature was undertaken. The aim of this study is to provide a wide experimental database and microstructural observations to supply, calibrate and validate models used in a local approach methodology. Mechanical and fracture properties of the steel have been investigated over a wide range of temperatures and strain rates. Effects of impact velocity on ductile-brittle transition curve, on ductile tearing and on notch temperature rise are presented and discussed. A detailed study of ductile crack initiation and growth in Charpy specimens is also carried out. From fractographic investigations of the microvoids nucleation around carbide second phase particles, a plastic strain threshold for nucleation is determined for this material. A508 Cl3 steels undergo a transition in fracture toughness properties with temperature, due to a change in fracture mode from microvoids colaescence to cleavage fracture. A systematic investigation on the nature and the position of cleavage triggering sites and on any change in the ductile to brittle transition (DBT) range has been carried out. This leads to the conclusion that Manganese sulfide inclusions do not play an increasing role with increasing test temperature as recently mentionned in other studies on A508 Cl3 steel with a higher sulfur content. In a companion paper [1], the numerical simulation of the Charpy test in the ductile-brittle transition range using fully coupled local approach to fracture is presented.

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“…In the case of Fe! C precipitates, heat treatment controls their embrittlening effect and therefore affects both ductile and brittle fracture [31,32].…”

Section: Methodsmentioning

confidence: 99%

“…Nucleation around second phase population is well known to play an important role in the ductile damage mechanisms, as much at the beginning of the deformation history, as during the coalescence phase (localized necking) [31]. The role of Fe!…”

Section: Nucleation Around Second Phase Populationmentioning

confidence: 99%

Ductile to brittle transition of an A508 steel characterized by Charpy impact test

Tanguy

Besson

Piques

et al. 2005

Engineering Fracture Mechanics

165

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“…Os trabalhos mencionados anteriormente em adição a outros [40,41] permitiram estabelecer 3 estágios principais do processo de fratura dúctil Evidências experimentais do processo de rasgamento dúctil em aços ferríticos para vasos de pressão com a presença de trincas foram apresentadas por Isacsson e Narstroöm [43]. Neste trabalho foram executados ensaios de fratura dúctil pelos quais os autores obtiveram evidências concretas do processo de nucleação de cavidades.…”

Section: (A) (B)unclassified

Desenvolvimento de procedimentos para avaliação de curvas J-R em espécimes à fratura SE(T) utilizando o método de flexibilidade.

Cravero¹

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RESUMOEste trabalho apresenta o desenvolvimento de procedimentos para a medição de curvas de resistência J-R em espécimes SE(T) usando os métodos de flexibilidade elástica e método η. Uma descrição da metodologia sobre a qual J e o crescimento de trinca são medidos estabelece o contexto para determinar dados de resistência ao rasgamento dúctil com o emprego de curvas carga vs. deslocamento obtidas experimentalmente. A extensiva matriz de análises em estado plano de deformações de espécimes SE(T) complementada, em algumas geometrias selecionadas, com análises 3D permite a determinação numérica da flexibilidade adimensional, μ, e fatores η J e γ para uma grande faixa de proporções geométricas e propriedades de material características de aços estruturais e para dutos. Ensaios laboratoriais de um aço API 5L X60 à temperatura ambiente usando espécimes SE(T) carregados por pinos com entalhes laterais (side-grooves) fornecem os dados de carga e deslocamento necessários para validar o procedimento para determinar curvas de resistência do material. Os resultados apresentados nesta tese fornecem uma base de soluções para o futuro estabelecimento de norma padronizada para a medição experimental de curvas J-R em corpos de prova SE(T) mecanicamente similares a dutos com defeitos bidimensionais. ABSTRACTThis work provides an estimation procedure to determine J-resistance curves for pinloaded and clamped SE(T) fracture specimens using the unloading compliance technique and the η-method. A summary of the methodology upon which J and crack extension are derived sets the necessary framework to determine crack resistance data from the measured load vs. displacement curves. The extensive plane-strain analyses and key 3D results enable numerical estimates of the nondimensional compliance, μ , and parameters η and γ for a wide range of specimen geometries and material properties characteristic of structural and pipeline steels. Laboratory testings of an API 5L X60 steel at room temperature using pin-loaded SE(T) specimens with side-grooves provide the load-displacement data needed to validate the estimation procedure for measuring the crack growth resistance curve for the material. The results presented in the this thesis produce a representative set of solutions which lend further support to develop standard test procedures for constraint-designed SE(T) specimens applicable in measurements of crack growth resistance for pipelines. Avaliação da Aspectos Fenomenológicos do Rasgamento MEDIÇÃO DE CURVAS DE RESISTÊNCIA EM ESPÉCIMES SE(T)48 Método η e Método de Flexibilidade no Descarregamento 49. . . . . Correção por Rotação em Corpos-de-Prova SE(T)53 . . . . . . . . . . . . . Medição Experimental de integral MATRIZ DE ANÁLISE E PROCEDIMENTOS NUMÉRICOS FLEXIBILIDADE PARA ESPÉCIMES SE(T)96 FATORES η J , γ E RAIOS PLÁSTICOS PARA ESPÉCIMES SE(T) CARREGADOS POR PINOS Cálculo do Fator de Rotação Plástica para Espécimes SE(T)107. FATORES η J E γ PARA ESPÉCIMES SE(T) FIXADOS POR GARRAS COMPARAÇÃO DE RESULTADOS CALIBRAÇÃO DOS MODEL...

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“…Um estudo experimental para o aço ASTM A508B (aço tipicamente utilizado em vasos de pressão) feito por Isacsson e Narstrom [63] revelou as etapas de dano do material desde o arredondamento da ponta da trinca até o crescimento e propagação estável da trinca. A partir das observações metalográficas feitas em diferentes cortes transversais no plano da trinca, os autores observaram que a propagação dúctil da trinca ocorreu em uma forma alternada em uma camada coplanar à frente da trinca.…”

Section: Modelagem Micromecânica Da Fratura Dúctilunclassified

Avaliação de integridade estrutural em dutos e tubulações de alta pressão utilizando metodologias baseadas em deformação plástica.

Uribe¹,

Andres²

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Oil and gas pipelines traverse distances of the order of hundreds and even thousands of kilometers. Along those distances the pipelines may be subject to several accidental loads such as large-scale soil movement, slope slides and seabed movements. The plastic strain resulting from these events can seriously affect the structural integrity of pipelines, compromising its mechanical integrity and fluid containment in an eventual pipeline failure. For this reason, it is important to guarantee the structural integrity of those components in order to avoid their plastic instability or ductile fracture. This work explores the capability of computational cell methodology coupled with the Stress Modified Critical Strain (SMCS) damage criterion to simulate the behavior of ductile fracture in tensile specimens subjected to tension load and pipe specimens subjected to large longitudinal strains. Thus, this work focuses on the development of an engineering procedure to assess the structural integrity of pipelines, in order to predict the critical load (tensile failure load) at onset of ductile fracture in pipelines used to transport oil and gas subjected to large plastic strains. A series of tensile test conducted by Toyoda et al. [1] on tensile specimens with different notch radius, for a structural steel, provides the stress-strain response used to calibrate the SMCS damage criterion. Full scale cyclic bend test also performed by Toyoda et al. [1] on a pipe specimen with 165 mm outer diameter and 11 mm wall thickness evaluates the proposed procedure for predicting ductile fracture behavior in damaged pipelines. This exploratory study predicts the tensile failure load associated with the onset of ductile fracture in the highly damaged area by plastic strains inside buckling zone in good agreement with the experimental measurements.

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Microscopic examination of crack growth in a pressure vessel steel

Cited by 10 publications

References 8 publications

Ductile to brittle transition of an A508 steel characterized by Charpy impact test

Ductile to brittle transition of an A508 steel characterized by Charpy impact test

Desenvolvimento de procedimentos para avaliação de curvas J-R em espécimes à fratura SE(T) utilizando o método de flexibilidade.

Avaliação de integridade estrutural em dutos e tubulações de alta pressão utilizando metodologias baseadas em deformação plástica.

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