Effect of Stress Triaxiality and Strain Rate on Ductile Fracture Initiation in Steel

Shimanuki, Hiroshi; Furuya, Hitoshi; Inoue, Tatsuo; Hagiwara, Yukito; Toyoda, Masao

doi:10.2534/jjasnaoe1968.1999.186_475

Cited by 17 publications

(3 citation statements)

References 2 publications

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“…On the basis of observations at ductile crack initiation, the mechanical parameters controlling initiation are expressed in terms of two-parameter criterion, that is equivalent plastic strain ε p and stress triaxialityσm / σ , (σ m : mean stress, σ : Von Mises equivalent stress) based on a ductile void growth mechanism [5]. It has been experimentally shown using circumferentially notched specimens that the critical strain for ductile fracture initiation decreased with increasing stress triaxiality associated with notch acuity [6][7][8][9][10][11]. A quantitative evaluation of ductile fracture initiation has been developed using the two-parameter criterion [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…It has been experimentally shown using circumferentially notched specimens that the critical strain for ductile fracture initiation decreased with increasing stress triaxiality associated with notch acuity [6][7][8][9][10][11]. A quantitative evaluation of ductile fracture initiation has been developed using the two-parameter criterion [8][9][10]. Welded joint in a steel structure exhibits not only geometrical heterogeneities, but also strength mismatch.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Strength Mismatch on Ductile Crack Initiation Behavior from Notch Root under Static Loading

An¹,

Ohata

Mochizuki

et al. 2005

KEM

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It has been well known that ductile fractures of steels are accelerated by triaxial stresses. The characteristics of ductile crack initiation in steels are evaluated quantitatively using two-parameter criterion based on equivalent plastic strain and stress triaxiality. It has been demonstrated by authors using round-bar specimens with circumferential notch in single tension that the critical strain to initiate ductile crack from specimen center depends considerably on stress triaxiality, but surface cracking of notch root is in accordance with constant strain condition. This study fundamentally clarifies the effect of strength mismatch, which can elevate plastic constraint due to heterogeneous plastic straining under static loading, on critical conditions for ductile cracking from the pre-notch root. In order to evaluate the stress/strain state in the pre-notch root of specimens, a thermal elastic-plastic finite element (FE) analysis has been carried out.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Strength Mismatch on Ductile Crack Initiation Behavior from Notch Root under Static Loading

An¹,

Ohata

Mochizuki

et al. 2005

KEM

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“…延性材料が破壊する限界ひずみは，応力三軸度の増加に伴い低下するが，このような限界特性を取得するために，切欠き付試験片の引張試験が実施される．切欠き付丸棒試験片の重要な利点は，切欠き曲率半径を極めて小さくしない限り (安他， 2001) (An et al, 2001)，材料の破壊が必ず切欠き断面の中心から起こることである．切欠き断面中心の破損は，通常，荷重-変位線図がそれまでの傾向線から外れた点，屈曲点から検出できる ) (島貫他，1999) (Shimanuki et al, 1999)．この時の切欠き断面中心の応力・ひずみ状態から，材料の限界ひずみ-応力三軸度線図(以下「限界ひずみ線図」という． )を決定できる．これまで多くの研究では(大塚他，1984) (Otsuka et al, 1984) (5) Fig. 19 Equivalent stress-equivalent plastic strain curves of base metal, HAZ and weld metal, identified by the elastoplastic analysis of tensile test results of small-size notched round-bar The stress-strain curves of HAZ and weld metal of the SGV480 weld joint showed higher values than that of base metal.…”

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原子炉格納容器鋼材の局部破損の限界条件（母材・溶接部材の切欠き付丸棒引張試験）

NAKAMURA,

ARAI,

KIKUCHI

2023

Transactions of the JSME (In Japanese)

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Tensile tests were conducted for notched round-bar specimens to acquire the limit conditions of local failure, which is ductile failure after large local deformation for three types of steel, SGV480, SPV490 and SGV410, for nuclear containment structures. The notch deformation was monitored using a profile projector. The notch's cross-section radius and the curvature radius of the notched profile were continuously measured by image analysis in the tensile test. From those measurements, the stress and strain at the notch's cross-section center were determined by Bridgman's approximate solution and the elastoplastic FEM analysis. The true stress-true strain curve for the elastoplastic FEM was identified a priori by an optimization program that searches for the good curve in the exponential form applicable to large strain regions. No cracks were observed at the notch bottom surface in all specimens until the final rupture. The failure at the notch's cross-section center was detected from the inflection point of the load-displacement curve. The limit strain diagrams were compared with those of ASME Sec. VIII-2 and its conservatism were discussed. Further, small-size notched round-bar specimens were sampled from the weld joints of SGV480 and SPV490 to determine the limit strain diagrams and true stress-true strain curves of the base metal, HAZ, and weld metal. The limit strain diagrams at each material of the weld joints were as high as or higher than the base metal, except for the weld metal of SPV490. The authors discussed the optical micrographs for fracture surfaces of specimens, the fracture morphology of weld joints, and the modified expression of a limit failure stress index regarded as the stress indication of the limit strain diagram in the high-stress triaxiality region.

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The effects of compressive and tensile prestrain on ductile fracture initiation in steels

Enami

2005

Engineering Fracture Mechanics

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Effect of Stress Triaxiality and Strain Rate on Ductile Fracture Initiation in Steel

Cited by 17 publications

References 2 publications

Effect of Strength Mismatch on Ductile Crack Initiation Behavior from Notch Root under Static Loading

Effect of Strength Mismatch on Ductile Crack Initiation Behavior from Notch Root under Static Loading

原子炉格納容器鋼材の局部破損の限界条件（母材・溶接部材の切欠き付丸棒引張試験）

The effects of compressive and tensile prestrain on ductile fracture initiation in steels

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