Quantifying the creep crack-tip constraint effects using a load-independent constraint parameter Q*

Within the framework of the European research project VOCALIST, centre cracked tension, CC(T), specimens made of an RPV steel were tested and analysed to quantify the influence of local stress state on fracture toughness. The CC(T) specimens demonstrate a significant loss of crack tip constraint resulting in a considerable increase in fracture toughness as compared to standard fracture mechanics specimens. So, the master curve reference temperature, To, determined on the basis of CC(T) tests performed in this study is about 43°C lower than To obtained on standard C(T) specimens. Finite element analyses of the tests revealed that the above experimental finding is in a good agreement with the empirical correlations between the reference temperature shift and the crack tip constraint as characterised by the T-stress or Q parameter (Wallin, 2001; Wallin, 2004). The results of this work are consistent with a number of other tests performed within the VOCALIST project and contribute to the validation of engineering methods for the crack assessment in components taking account of constraint.

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Deterministic and Probabilistic Fracture Mechanics Analysis of Pipeline Weld Flaws Accounting for Crack Tip Constraint Effects

23rd International Conference on Offshore Mechanics and Arctic Engineering, Volume 2 ◽

10.1115/omae2004-51320 ◽

2004 ◽

Author(s):

Jens P. Tronskar ◽

Zhang Li

Keyword(s):

Fracture Mechanics ◽

Crack Tip ◽

Line Pipe ◽

Pipeline Construction ◽

Probabilistic Fracture Mechanics ◽

Weld Defects ◽

Specific Loading ◽

Wide Range ◽

Constraint Effects ◽

Crack Tip Constraint

The acceptability of weld defects during line pipe manufacture and pipeline construction is governed by international codes and standards such as the DNV OS-F101 or API1104. These are universal standards applicable for a wide range of pipeline usage conditions, which include typical workmanship criteria for flaw acceptance. It is, however, possible to establish more precise and often less conservative acceptance criteria using a Fitness-For-Service (FFS) approach through the application of procedures such as those of BS 7910. These are based on applying deterministic or probabilistic fracture mechanics principles on specific loading, materials and toughness properties and service conditions of a pipeline. This paper describes the conventional assessment methodology and more advanced approaches to account for crack tip constraint, dynamic loading due to VIV associated with free-spans. The paper highlights two cases as examples where the approaches have been applied for assessing the criticality of weld defects detected during pipeline construction and their impact on the reliability during service.

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Three-dimensional numerical analysis of out-of-plane creep crack-tip constraint in compact tension specimens

International Journal of Pressure Vessels and Piping ◽

10.1016/j.ijpvp.2012.06.007 ◽

2012 ◽

Vol 96-97 ◽

pp. 78-89 ◽

Cited By ~ 50

Author(s):

P.J. Sun ◽

G.Z. Wang ◽

F.Z. Xuan ◽

S.T. Tu ◽

Z.D. Wang

Keyword(s):

Numerical Analysis ◽

Three Dimensional ◽

Crack Tip ◽

Compact Tension ◽

Creep Crack ◽

Out Of Plane ◽

Crack Tip Constraint

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Theoretical approach of characterizing the crack-tip constraint effects associated with material’s fracture toughness

Archive of Applied Mechanics ◽

10.1007/s00419-018-1392-8 ◽

2018 ◽

Vol 88 (9) ◽

pp. 1637-1656 ◽

Cited By ~ 8

Author(s):

Junnan Lv ◽

Li Yu ◽

Wei Du ◽

Qun Li

Keyword(s):

Fracture Toughness ◽

Theoretical Approach ◽

Crack Tip ◽

Constraint Effects ◽

Crack Tip Constraint

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Evaluation of Crack Tip Constraint Effects on the Assessment of Pipes Subjected to Combined Loading Conditions

2008 7th International Pipeline Conference, Volume 3 ◽

10.1115/ipc2008-64277 ◽

2008 ◽

Author(s):

Sebastian Cravero ◽

Richard E. Bravo ◽

Hugo A. Ernst

Keyword(s):

Q Methodology ◽

Biaxial Loading ◽

Crack Tip ◽

Combined Loading ◽

Combined Loads ◽

Loading Effects ◽

Resistance Curves ◽

Material Fracture ◽

Constraint Effects ◽

Crack Tip Constraint

Under certain conditions, pipelines may be submitted to biaxial loading situations. In these cases, questions arise about how biaxial loading influence the driving force (i.e.: CTOD, J-integral) of possible presented cracks and how affects the material fracture toughness. For further understanding of biaxial loading effects on fracture mechanics behavior of cracked pipelines, this work presents a numerical analysis of crack-tip constraint of circumferentially surface cracked pipes and SENT specimens using full 3D nonlinear computations. The objective is to examine combined loading effects on the correlation of fracture behavior for the analyzed cracked configurations. The constraint study using the J-Q methodology and the h parameter gives information about the fracture specimen that best represents the crack-tip conditions on circumferentially flawed pipes under combined loads. Additionally, simulations of ductile tearing in a surface cracked plate under biaxial loading using the computational cell methodology demonstrate the negligible effect of biaxial loadings on resistance curves.

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