Crack Geometry Effect on Stress-Strain Fields for Crack Under Biaxial Loading

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Fumiyoshi Minami ◽  
Mitsuru Ohata ◽  
Daisuke Watanabe ◽  
Satoshi Igi ◽  
Takahiro Kubo ◽  
...  
Keyword(s):  
Brittle Fracture ◽  
Surface Crack ◽  
Biaxial Loading ◽  
Large Diameter ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Ductile Damage ◽  
Strain Fields ◽  
Stress Criterion ◽  
Crack Tip Stress

With increasing demand of high-strength and high-pressure pipelines in gas transmission industries, the fracture control design of pipelines has been a driving factor to ensure the integrity of the pipeline. This paper addresses the stress and strain fields for a crack in a wide plate component under biaxial loading, which simulates a large-diameter pipe subjected to inner pressure coupled with axial loading. Attention is focused on the initiation of brittle fracture (stress controlled type) as well as ductile fracture (strain controlled type). Three-dimensional finite element-analyses are conducted. It was found that biaxial loading has a significant effect on the stress fields of through-thickness crack; the near-crack-tip stress is elevated to a large extent by biaxial loading. By contrast, the stress field for a surface crack is not sensitive to biaxial loading, while the near-crack-tip stress at the crack corner is increased locally by biaxial loading. The Weibull stress criterion was applied to discuss the biaxial loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by biaxial loading for a through-thickness crack, whereas a surface crack has little effect of biaxial loading on the ductile damage.

Crack Geometry Effect on Stress-Strain Fields for Crack Under Biaxial Loading

2008 ◽  
Author(s):  
Fumiyoshi Minami ◽  
Mitsuru Ohata ◽  
Daisuke Watanabe ◽  
Satoshi Igi ◽  
Takahiro Kubo ◽  
...  
Keyword(s):  
Surface Crack ◽  
Biaxial Loading ◽  
Large Diameter ◽  
Three Dimensional ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Ductile Damage ◽  
Strain Fields ◽  
Stress Criterion ◽  
Crack Tip Stress

With increasing demand of high strength and high pressure pipelines in gas transmission industries, the fracture control design of pipelines has been driven primarily. This paper addresses the stress and strain fields for a crack in a wide plate component under biaxial loading, which simulates a large diameter pipe subjected to inner pressure coupled with axial loading. Three-dimensional FE-analyses are conducted. It was found that biaxial loading has a significant effect on the stress fields of through-thickness crack; the near crack-tip stress is elevated to a large extent by biaxial loading. By contrast, the stress field for a surface crack is not sensitive to biaxial loading, while the near crack-tip stress at the crack corner is increased locally by biaxial loading. The Weibull stress criterion was applied to discuss the biaxial loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by biaxial loading for a through-thickness crack, whereas a surface crack has little effect of biaxial loading on the ductile damage.

Three-Dimensional Elastic-Plastic Finite Element Analysis of Biaxially Loaded Cracked Plates

2004 ◽  
Vol 261-263 ◽  
pp. 699-704
Author(s):  
Kwang Hwa Chung ◽  
J.S. Kim ◽  
J.S. Kim ◽  
Young Jin Kim
Keyword(s):  
Finite Element ◽  
Biaxial Loading ◽  
Three Dimensional ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Limit Load ◽  
Surface Cracks ◽  
Elastic Plastic ◽  
Loaded Plate ◽  
Crack Tip Stress

Based on detailed two-dimensional (2-D) and three-dimensional (3-D) finite element (FE)analyses, this paper attempts to quantify in-plane and out-of-plane constraint effects on elastic-plastic J and cracked tip stresses for biaxially loaded plate with a through-thickness crack and semi-elliptical surface crack. It is found that the reference stress based approach for uniaxial loading can be applied to estimate J under biaxial loading, provided that the limit load specific to biaxial loading is used, implying that quantification of the biaxiality effect on the limit load is important. Investigation on the effect of biaxiality on the limit load suggests that for relatively thin plates with small cracks, in particular with semi-elliptical surface cracks, the effect of biaxiality on the limit load can be neglected, and thus elastic-plastic J for a biaxially loaded plate could be estimated, assuming that such plate is subject to uniaxial load. Regarding the effect of biaxiality on crack tip stress triaxiality, it is found that such effect is more pronounced for a thicker plate. For plates with semi-elliptical surface cracks, the crack aspect ratio is found to be more important than the relative crack depth, and the effect of biaxiality on crack tip stress triaxiality is found to be more pronounced near the surface points along the crack front.

Crack-Tip Fields of Short Cracks in Bending As Characterized by Two Parameter Criterion

1993 ◽  
Author(s):  
J. F. Zarzour ◽  
Y. Dah-Wei ◽  
M. J. Kleinosky
Keyword(s):  
Fracture Toughness ◽  
Large Scale ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Significant Loss ◽  
Integral Approach ◽  
Rigorous Framework ◽  
Crack Tip Constraint ◽  
Two Parameter ◽  
Crack Tip Stress

Abstract Single edge notched bars (SENB), in the bending mode, with a/W ratios ranging from 0.05 to 0.5 were examined for fracture toughness in terms of the J-integral approach. The results indicate that for a/W ratios less than 0.3, there is a significant loss of J-dominance. This loss is attributed to the effect of plastic deformation on the cracked face. For a/W ratios greater than 0.3, J-dominance is maintained into the large scale yielding regime. According to the recently developed two-parameter criterion (J,Q), compressive Q-stress was interpreted as an indication of low crack-tip stress triaxiality for shallow cracks, while positive Q-stress was associated with high crack-tip stress triaxiality for deep cracks. For the material properties and specimen geometries considered herein, a fracture toughness locus was constructed in terms of the (J,Q) parameters for each of the a/W ratios. The overall fracture data are in agreement with those predicted by other approaches and provide a rigorous framework for interpreting the effect of loss of crack-tip constraint in elastic-plastic fracture analyses.

scholarly journals 3D thickness effects around notch and crack tip stress/strain fields

2015 ◽  
Vol 9 (33) ◽  
pp. 89-96 ◽  
Author(s):  
R.C.O. Góes ◽  
J.T.P. Castro ◽  
M.A. Meggiolaro
Keyword(s):  
Crack Tip ◽  
Stress Strain ◽  
Strain Fields ◽  
Crack Tip Stress

An atomistic study of brittle fracture: Toward explicit failure criteria from atomistic modeling

1995 ◽  
Vol 10 (11) ◽  
pp. 2897-2907 ◽  
Author(s):  
Peter Gumbsch
Keyword(s):  
Brittle Fracture ◽  
Mixed Mode ◽  
Failure Modes ◽  
Crack Tip ◽  
Energy Criterion ◽  
Failure Criteria ◽  
Mechanical Analysis ◽  
Coupling Scheme ◽  
Mixed Mode Loading ◽  
Stress Criterion

Atomistic techniques are used to study brittle fracture under opening mode and mixed mode loading conditions. The influence of the discreteness of the lattice and of the lattice-trapping effect on crack propagation is studied using an embedded atom potential for nickel to describe the crack tip. The recently developed FEAt (Finite Element-Atomistic) coupling scheme provides the atomistic core region with realistic boundary conditions. Several crystallographically distinct crack-tip configurations are studied and commonly reveal that brittle cracks under general mixed mode loading situations follow an energy criterion (G-criterion) rather than an opening-stress criterion (Kl-criterion). However, if there are two competing failure modes, they seem to unload each other, which leads to an increase in lattice trapping. Blunted crack tips are studied in the last part of the paper and are compared to the atomically sharp cracks. Depending on the shape of the blunted crack tip, the observed failure modes differ significantly and can drastically disagree with what one would anticipate from a continuum mechanical analysis.

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