Microscopic investigation of cleavage initiation in modified A508B pressure vessel steel

Narström, Torbjörn; Isacsson, Måns

doi:10.1016/s0921-5093(99)00201-4

Cited by 15 publications

(5 citation statements)

References 6 publications

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“…Following Reference 43, mm is lowest at low temperatures but is assumed to increase with temperature [44] and becomes higher than pm . If y is the yield stress of the material and I (or, respectively, M-A ) is the local maximum principal stress (or, respectively, the maximum stress in the M-A particle as given by Eq.…”

Section: Results Given By the Db Modelmentioning

confidence: 99%

Mechanisms and modeling of cleavage fracture in simulated heat-affected zone microstructures of a high-strength low alloy steel

Lambert-Perlade¹,

Gourgues

Besson

et al. 2004

Metall Mater Trans A

242

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The effect of the welding cycle on the fracture toughness properties of high-strength low alloy (HSLA) steels is examined by means of thermal simulation of heat-affected zone (HAZ) microstructures. Tensile tests on notched bars and fracture toughness tests at various temperatures are performed together with fracture surface observations and cross-sectional analyses. The influence of martensite-austenite (M-A) constituents and of "crystallographic" bainite packets on cleavage fracture micromechanisms is, thus, evidenced as a function of temperature. Three weakest-link probabilistic models (the "Master-curve" (MC) approach, the Beremin model, and a "double-barrier" (DB) model) are applied to account for the ductileto-brittle transition (DBT) fracture toughness curve. Some analogy, but also differences, are found between the MC approach and the Beremin model. The DB model, having nonfitted, physically based scatter parameters, is applied to the martensite-containing HAZ microstructures and gives promising results.

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Section: Results Given By the Db Modelmentioning

confidence: 99%

Mechanisms and modeling of cleavage fracture in simulated heat-affected zone microstructures of a high-strength low alloy steel

Lambert-Perlade¹,

Gourgues

Besson

et al. 2004

Metall Mater Trans A

242

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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%

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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“…A number of authors have shown that the critical local stress necessary to cross the grain boundaries is lowest at low temperature but increases with temperature and eventually becomes larger than the stress necessary to propagate a crack nucleated from a particle (see, e.g. Narström and Isacsson, 1999). The effect of temperature on fracture toughness can thus be described by considering four temperature ranges.…”

Section: Multiple Barrier Modelmentioning

confidence: 99%

Development of the Local Approach to Fracture over the Past 25 years: Theory and Applications

Pineau

2006

Int J Fract

173

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This review paper is devoted to the local approach to fracture (LAF) for the prediction of the fracture toughness of structural steels. The LAF has been considerably developed over the past two decades, not only to provide a better understanding of the fracture behaviour of materials, in particular the failure micromechanisms, but also to deal with loading conditions which cannot easily be handled with the conventional linear elastic fracture mechanics and elastic-plastic fracture mechanics global approaches. The bases of this relatively newly developed methodology are first presented. Both ductile rupture and brittle cleavage fracture micromechanisms are considered. The ductile-to-brittle transition observed in ferritic steels is also briefly reviewed. Two types of LAF methods are presented: (i) those assuming that the material behaviour is not affected by damage (e.g. cleavage fracture), (ii) those using a coupling effect between damage and constitutive equations (e.g. ductile fracture). The micromechanisms of brittle and ductile fracture investigated in elementary volume elements are briefly presented. The emphasis is laid on cleavage fracture in ferritic steels. The role of second phase particles (carbides or inclusions) and grain boundaries is more thoroughly discussed. The distinction between nucleation and growth controlled fracture is made. Recent developments in the theory of cleavage fracture incorporating both the effect of stress state and that of plastic strain are presented. These theoretical results are applied to the crack tip situation to predict the fracture toughness. It is shown that the ductile-to-brittle transition curve can reasonably be well predicted using the LAF approach. Additional applications of the LAF approach methods are also shown, including: (i) the effect of loading rate and prestressing; (ii) the influence of residual stresses in welds; (iii) the mismatch effects in welds; (iv) the warm-prestressing effect. An attempt is also made to delineate research areas where large improvements should be made for a better understanding of the failure behaviour of structural materials.

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Microscopic investigation of cleavage initiation in modified A508B pressure vessel steel

Cited by 15 publications

References 6 publications

Mechanisms and modeling of cleavage fracture in simulated heat-affected zone microstructures of a high-strength low alloy steel

Mechanisms and modeling of cleavage fracture in simulated heat-affected zone microstructures of a high-strength low alloy steel

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

Development of the Local Approach to Fracture over the Past 25 years: Theory and Applications

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