Prediction of Failure Behavior for Nuclear Piping Using Curved Wide-Plate Test

2004 ◽  
Vol 126 (4) ◽  
pp. 419-425 ◽  
Author(s):  
Nam-Su Huh ◽  
Yun-Jae Kim ◽  
Jae-Boong Choi ◽  
Young-Jin Kim ◽  
Chang-Ryul Pyo
Keyword(s):  
Fracture Toughness ◽  
Three Dimensional ◽  
Crack Tip ◽  
Full Scale ◽  
Failure Behavior ◽  
Resistance Curve ◽  
Testing Specimen ◽  
Plate Test ◽  
Crack Tip Constraint ◽  
Three Dimensional Finite Element

One important element of the Leak-Before-Break analysis of nuclear piping is how to determine relevant fracture toughness (or the J-resistance curve) for nonlinear fracture mechanics analysis. The practice to use fracture toughness from a standard C(T) specimen is known to often give conservative estimates of toughness. To improve the accuracy of predicting piping failure, this paper proposes a new method to determine fracture toughness using a nonstandard testing specimen, curved wide-plate in tension. To show validity of the proposed curved wide-plate test, the J-resistance curve from the full-scale pipe test is compared with that from the curved wide-plate test and that from C(T) specimen. It is shown that the J-resistance curve from the curved wide-plate tension test is similar to, but that from the C(T) specimen is lower than, the J-resistance curve from the full-scale pipe test. Further validation is performed by investigating crack-tip constraint conditions via detailed three-dimensional finite element analyses, which shows that the crack-tip constraint condition in the curved wide-plate tension specimen is indeed similar to that in the full-scale pipe under bending.

Quantification of Crack-Tip Constraint Effect on Master Curve Reference Temperature Based on Two-Parameter Approach

2006 ◽  
Vol 110 ◽  
pp. 89-96 ◽  
Author(s):  
Nam Su Huh ◽  
Ludwig Stumpfrock ◽  
Xaver Schuler ◽  
Eberhard Roos
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Crack Tip ◽  
Reference Temperature ◽  
Fracture Toughness Test ◽  
Testing Specimen ◽  
Correlation Models ◽  
Dimensional Finite Element ◽  
Crack Tip Constraint ◽  
Two Parameter

The master curve has evolved into a mature technology for characterizing the fracture toughness transition of ferritic steels. However, it is well known that the master curve reference temperature (To) values estimated from small laboratory specimen may be biased low due to loss of crack-tip constraint. To quantify such variations of To resulting from differences of crack-tip constraint of testing specimen, two-parameter fracture mechanics approaches are employed in the present study. In this context, fracture toughness test and 3-dimensional finite element (FE) analysis for several standard and nonstandard test specimens are performed to quantify relationship between variations of To and constraint parameters and to find best constraint parameter representing effect of crack-tip constraint on To values evidently. Based on testing and present FE results, To and constraint parameter loci are constructed and engineering To correlation models considering crack-tip constraint are suggested

Investigation of Constraint Effects on Fracture Toughness for CC(T) Specimens

2004 ◽  
Author(s):  
Dieter Siegele ◽  
Igor Varfolomeyev ◽  
Kim Wallin ◽  
Gerhard Nagel
Keyword(s):  
Fracture Toughness ◽  
Crack Tip ◽  
Temperature Shift ◽  
Local Stress ◽  
Significant Loss ◽  
Reference Temperature ◽  
T Stress ◽  
Local Stress State ◽  
Constraint Effects ◽  
Crack Tip Constraint

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.

Three-dimensional finite element modelling of a full-scale geosynthetic-reinforced, pile-supported embankment

2015 ◽  
Vol 52 (12) ◽  
pp. 2041-2054 ◽  
Author(s):  
R. Kerry Rowe ◽  
K.-W. Liu
Keyword(s):  
Finite Element ◽  
Soft Soil ◽  
Three Dimensional ◽  
Single Layer ◽  
Full Scale ◽  
Numerical Results ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Pile Supported Embankment

The performance of four sections of a full-scale embankment constructed on soft soil is examined using a fully coupled and fully three-dimensional finite element analysis. The four sections had similar embankment loadings but different improvement options (one unimproved, one with pile-support only, one with a single layer geotextile-reinforced platform and pile-support, and one with two layers of geogrid-reinforced platform and pile-support). Like the field data, the numerical results show that the inclusion of piles decreases the settlement at the subsoil surface to 52% of that for the unimproved section, and the addition of a single layer of geotextile reinforcement (J = 800 kN/m) further reduced settlement to only 31% of that of the unimproved section. The effects of geosynthetic reinforcement and multiple layers of reinforcement on the performance of the pile-supported embankment are discussed. The relative load transfer is calculated using eight existing methods and they are compared with the field measurements and numerical results.

Effects of Temperature and Crack Tip Constraint on Cleavage Fracture Toughness in the Weld Thermal Simulated X80 Pipeline Steels

2011 ◽  
Vol 197-198 ◽  
pp. 1595-1598 ◽  
Author(s):  
Jie Xu ◽  
Yu Fan
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Crack Tip ◽  
Coarse Grained ◽  
Material Microstructure ◽  
Element Analysis ◽  
Pipeline Steels ◽  
Different Temperatures ◽  
Effects Of Temperature ◽  
Crack Tip Constraint

This paper studies the effects of temperature and crack tip constraint on cleavage fracture toughness of the weld thermal simulated X80 pipeline steels. A large number of fracture toughness (as denoted by CTOD) tests together with 3D finite element analysis are performed using single edge notched bending (SENB) and tension (SENT) specimens at different temperatures. Coarse-grained heat-affected zone (CGHAZ) is considered as the material microstructure in preparation of the weld thermal simulated fracture mechanics specimens.

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