Continuum and micromechanics treatment of constraint in fracture

H, Dodds, Jr, R; Shih, C. F.; Anderson, TL

doi:10.2172/10175312

Cited by 52 publications

(67 citation statements)

References 11 publications

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“…We believe a key feature in the success of the present methodology, and of the Dodds-Anderson toughness scaling model as well, lies in the overall similarity of the crack-tip stress fields across the various geometries considered in this and previous studies [11,60]. The crack-tip stresses in through-crack and surface-crack specimens subjected to uniaxial tension or uniaxial bending all appear remarkably similar except for the amplitude.…”

Section: Discussion and Concluding Remarkssupporting

confidence: 52%

“…The model enables robust predictions of constraint effects on cleavage fracture toughness provided the crack-tip stress fields of the various specimens differ only in the level oftriaxiality [60], i.e., contours of principal stress change only in "size" and not in "shape" under increased specimen loading. In contrast, consider two specimens which have the same material volume To overcome these limitations, the present work proposes a modified toughness scaling model to assess the combined effects of constraint variations and ductile tearing on cleavage fracture toughness data.…”

Section: A Modified Toughness Scaling Modelmentioning

confidence: 99%

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A transferability model for brittle fracture including constraint and ductile tearing effects: a probabilistic approach

1996

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Annual: 10-1-95 to 9-30-96 14.This study describes a computational framework to quantify the influence of constraint loss and ductile tearing on the cleavage fracture process, as reflected by the pronounced effects on macroscopic toughness (J c , Dc). Our approach adopts the Weibull stress, Ow, as a suitable near-tip parameter to describe the coupling of remote loading with a micromechanics model incorporating the statistics of microcracks (weakest link philosophy). Unstable crack propagation (cleavage) occurs at a critical value of Ow which may be attained prior to, or following, some amount of stable, ductile crack extension. A central feature of our framework focuses on the realistic numerical modeling of ductile crack growth using the computational cell methodology to define the evolution of near-tip stress fields during crack extension. Under increased remote loading (J), development of the Weibull stress reflects the potentially strong variations of near-tip stress fields due to the interacting effects of constraint loss and ductile crack extension. Computational results are discussed for well-contained plasticity, where the near-tip fields for a stationary and a growing crack are generated with a modified boundary layer (MBL) formulation (in the form of different levels of applied T-stress). These analyses demonstrate clearly the dependence of Ow on crack-tip stress triaxiality and crack growth. The paper concludes with an application of the micromechanics model to predict the measured geometry and ductile tearing effects on the cleavage fracture toughness, J c , of an HSLA steel. Here, we employ the concept of the Dodds-Anderson scaling model, but.replace their original local criterion based on the equivalence of near-tip stressed volumes by attainment of a critical value of the Weibull stress. For this application, the proposed approach successfully predicts the combined effects of loss of constraint and crack growth on measured Jc-values. ABSTRACTThis study describes a computational framework to quantify the influence of constraint loss and ductile tearing on the cleavage fracture process, as reflected by the pronounced effects on macroscopic toughness (J e , oe). Our approach adopts the Weibull stress, a w , as a suitable near-tip parameter to describe the coupling of remote loading with a micromechanics model incorporating the statistics of microcracks (weakest link philosophy). Unstable crack propagation (cleavage) occurs at a critical value of a w which may be attained prior to, or following, some amount of stable, ductile crack extension.A central feature of our framework focuses on the realistic numerical modeling of ductile crack growth using the computational cell methodology to define the evolution of near-tip stress fields during crack extension. Under increased remote loading (J), development of the Weibull stress reflects the potentially strong variations of near-tip stress fields due to the interacting effects of constraint loss and ductile crack extension.Computational results are dis...

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Section: Discussion and Concluding Remarkssupporting

confidence: 52%

Section: A Modified Toughness Scaling Modelmentioning

confidence: 99%

A transferability model for brittle fracture including constraint and ductile tearing effects: a probabilistic approach

1996

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“…The *-V* model [27], which represents the attainment of equivalent stressed volume V* for a given critical stress *, is another approach mainly used as a "toughness-scaling" model to predict the toughness variation from one specimen size to another. In its simple form, the statistical effects are not taken into account.…”

Section: Local Approach: *-V* Modelmentioning

confidence: 99%

3D finite element and experimental study of the size requirements for measuring toughness on tempered martensitic steels

Mueller¹,

Spätig²

2009

Journal of Nuclear Materials

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The fracture properties of the tempered martensitic steel Eurofer97, which is among the main candidates for fusion power plant structural applications, were studied with two sizes of pre-cracked compact specimens (0.35T C(T) and 0.87T C(T)). The fracture toughness behavior was characterized within the temperature range -80 to -40 ºC. The ductile-to-brittle transition reference temperature, as defined in the ASTM standard E1921, was around T 0 ≈ -75 ºC. At -60 °C, it was found that two sets of toughness data obtained with 0.35T and 0.87T C(T) specimens are not consistent with the size adjustments recommended in the ASTM standard. It was then shown that the underlying reason of this inconsistency is an inappropriate specimen size limit of the ASTM standard for this type of steel. From published fracture toughness data on the tempered martensitic steel F82H steel, similar results were also highlighted. 3D finite elements simulations of the compact specimens were performed to compare the stresses and deformations at the onset of fracture. A local approach model based on the attainment of a critical stress and a critical volume was used to study the constraint loss phenomenon. Within the framework of this model, the strong toughness increase by reducing the specimen size could be satisfactorily explained.2

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“…They designated the amplitude of this approximate difference field by the letter Q, Two operational definitions of the Q-family of fields are presented in Ref. 17. The first definition is given in terms of the opening-mode stress, on, where SSY refers to the small-scale-yielding reference solution.…”

Section: Finite Element Models and Local Crack-tip Fieldsmentioning

confidence: 99%

Fracture assessment of HSST Plate 14 shallow-flaw cruciform bend specimens tested under biaxial loading conditions

Bass¹,

McAfee²,

Williams³

et al. 1998

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Continuum and micromechanics treatment of constraint in fracture

Cited by 52 publications

References 11 publications

A transferability model for brittle fracture including constraint and ductile tearing effects: a probabilistic approach

A transferability model for brittle fracture including constraint and ductile tearing effects: a probabilistic approach

3D finite element and experimental study of the size requirements for measuring toughness on tempered martensitic steels

Fracture assessment of HSST Plate 14 shallow-flaw cruciform bend specimens tested under biaxial loading conditions

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