Strain-based J-estimation scheme for fracture assessment of misaligned clad pipelines with an interface crack

2018 ◽  
Vol 61 ◽  
pp. 238-255 ◽  
Author(s):  
Hai-Sheng Zhao ◽  
Seng-Tjhen Lie ◽  
Yao Zhang
Keyword(s):  
Interface Crack ◽  
Estimation Scheme ◽  
Fracture Assessment ◽  
J Estimation

Dissimilar Metal Weld Pipe Fracture Testing: Analysis of Results and Their Implications

2012 ◽  
Author(s):  
D. Rudland ◽  
R. Lukes ◽  
P. Scott ◽  
R. Olson ◽  
A. Cox ◽  
...  
Keyword(s):  
Experimental Data ◽  
Carrying Capacity ◽  
Nuclear Industry ◽  
Load Carrying Capacity ◽  
Base Metals ◽  
Dissimilar Metal ◽  
Load Carrying ◽  
Estimation Scheme ◽  
The Stability ◽  
J Estimation

Typically in flaw evaluation procedures, idealized crack shapes are assumed for both subcritical and critical crack analyses. Past NRC-sponsored research have developed estimation schemes for predicting the load-carrying capacity of idealized cracks in nuclear grade piping and similar metal welds at the operating conditions of nuclear power reactors. However, recent analyses have shown that growth of primary water stress corrosion cracks (PWSCC) in dissimilar metal (DM) welds is not ideal; in fact, very unusual complex crack shapes may form, i.e., a very long surface crack that has a finite length through-wall crack in the same plane. Even though some experimental data on base metals exists to demonstrate that complex shaped cracks in high toughness materials fail under limit load conditions, other experiments demonstrate that the tearing resistance is significantly reduced. At this point, no experimental data exists for complex cracks in DM welds. In addition, it is unclear whether the idealized estimation schemes developed can be used to predict the load-carrying capacity of these complex-shaped cracks, even though they have been used in past analyses by the nuclear industry. Finally, it is unclear what material strength data should be used to assess the stability of a crack in a DM weld. The NRC Office of Nuclear Regulatory Research, with their contractor Battelle Memorial Institute, has concluded an experimental program to confirm the stability behavior of complex shaped circumferential cracks in DM welds. A combination of full-scale pipe experiments and a variety of laboratory experiments were conducted. A description of the pipe test experimental results is given in a companion paper. This paper describes the ongoing analyses of those results, and the prediction of the load-carrying capacity of the circumferential cracked pipe using a variety of J-estimation scheme procedures. Discussions include the effects of constraint, appropriate base metal material properties, effects of crack location relative to the dissimilar base metals, and the limitations of the currently available J-estimation scheme procedures. This paper concludes with plans for further development of J-estimation scheme procedures for circumferential complex cracks in DM welds.

J-R Curves From Circumferentially Through-Wall-Cracked Pipe Tests Subjected to Combined Bending and Tension—Part II: Experimental and Analytical Validation

1998 ◽  
Vol 120 (4) ◽  
pp. 412-417 ◽  
Author(s):  
N. Miura ◽  
G. M. Wilkowski
Keyword(s):  
Internal Pressure ◽  
Three Dimensional ◽  
Combined Loading ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Estimation Scheme ◽  
Materials Used ◽  
Three Dimensional Finite Element ◽  
Η Factor ◽  
J Estimation

In Part I (Miura and Wilkowski, 1998) of this paper, the theory of the two η-factor solutions for circumferentially through-wall-cracked pipes subjected to combined bending and tension due to internal pressure was presented. These solutions seemed to give reasonable predictions by comparing with the existing simplified J-estimation scheme. It was also ascertained that the J would be underestimated if the effect of the internal pressure was not properly considered. Consequently, this paper presents the application of these solutions to full-scale pipe tests. The tests were performed at 288°C (550°F) under combined bending and internal pressure. The materials used for the tests were both carbon steel and stainless steel. The effect of combined loading on the J-R curves was determined and compared to C(T) specimen J-R curves. The solutions were then verified by using three-dimensional finite element analysis.

Toughness Behavior of Through-Wall Cracks in Dissimilar Metal Welds

2013 ◽  
Author(s):  
D. Rudland ◽  
R. Lukes ◽  
D.-J. Shim ◽  
S. Kalyanam
Keyword(s):  
Fracture Toughness ◽  
Carrying Capacity ◽  
Compact Tension ◽  
Load Carrying Capacity ◽  
Base Metals ◽  
Dissimilar Metal ◽  
Steel Base ◽  
Load Carrying ◽  
Estimation Scheme ◽  
J Estimation

Over the years, J-estimation scheme procedures have been develop to predict the load-carrying capacity of through-wall cracks in nuclear grade piping materials. These procedures employ analytical or numerical procedures coupled with the fracture toughness of the material to predict the pipe response. For cracks in welds, the behavior has been shown to be related to the toughness of the weld and strength of the typically lower-strength base metal. However, with the advent of primary water stress corrosion cracking (PWSCC), flaws in dissimilar metal (DM) welds have occurred. These welds consist of a nickel-based weld joining stainless steel and carbon steel base metals. Prior research has demonstrated that crack-driving force for through-wall circumferential cracks in DM welds is highly influenced by both the stainless steel and carbon steel base metals, and is related to the axial position of the flaw within the weld. This effect brings into question the accuracy of typical J-estimation scheme procedures for calculation of load carrying capacity for circumferential through-wall flaws in DM welds. In addition, it is unknown if the apparent toughness of the cracked pipe is also affected by the position of the crack in the weld. Work is currently underway, sponsored by the NRC Office of Nuclear Regulatory Research, to investigate the behavior of through-wall and complex cracks in DM welds. In a prior paper, a series of full-scale pipe bend and laboratory-sized fracture experiments were documented. Initial analyses of those test results suggest that typical J-estimation scheme procedures could be used to predict the response if the weld toughness from a compact tension specimen and the appropriate material strength was used. In this paper, the fracture toughness from the DM weld is estimated from the pipe experiments using an η-factor solution and numerical techniques and these results are compared to the compact tension results. The results from this paper add insight into the effect of crack size and location within the DM weld on the apparent pipe toughness for through-wall cracks in DM welds.

Development of a J-Estimation Scheme for Surface Cracks in Piping Welds

2008 ◽  
Author(s):  
Patrick Le Delliou ◽  
Ste´phane Marie ◽  
Yann Kayser ◽  
Bruno Barthelet
Keyword(s):  
Mechanical Loading ◽  
Analytical Methods ◽  
Equivalent Stress ◽  
Base Material ◽  
Strain Curve ◽  
Surface Cracks ◽  
Pressurized Water ◽  
Cooperative Program ◽  
Estimation Scheme ◽  
J Estimation

The RSE-M Code provides rules and requirements for in-service inspection of French Pressurized Water Reactor power plants. The Code gives non mandatory guidance for analytical evaluation of flaws. Flaw assessment procedures rely on fracture mechanics analyses based on simplified methods (i.e. analytical). Analytical methods were developed under a cooperative program between EDF, CEA and AREVA NP to calculate the J integral in various cracked piping components (straight pipe, tapered transition, elbow and pipe-to-elbow junction). These methods are available for mechanical loading (in-plane bending moment, pressure, torsion moment), thermal loading as well as for combined loading. Moreover, they can be used either for materials with Ramberg-Osgood stress-strain curves or for real materials (stainless steels and carbon manganese steels, including those with yield plateaus). However, for the analysis of cracks in welds, they use the tensile properties of the weakest material between the base material and the weld material. This induces some conservatism on the estimated J values. A cooperative program was launched in 2004 to develop a J estimation scheme which takes into account the strength mismatch effects. The scheme relies on the definition of an ‘equivalent’ stress-plastic strain curve, as proposed in the R6 rule (section III.8: allowance for strength mismatch effects). This curve is then used with the analytical methods for homogeneous cracked components. In a first step, the method is developed for circumferential surface cracks in straight buttwelded pipes submitted to mechanical loading. It takes into account the geometry of the weld joint (V-shaped), as well as the location of the crack within the weld. This paper presents the current state of development of this J estimation-scheme.

Fully-Plastic Strain-Based J Estimation Scheme for Circumferential Surface Cracks in Pipes Subjected to Reeling

2013 ◽  
Author(s):  
Luís F. S. Parise ◽  
Claudio Ruggieri ◽  
Noel P. O’Dowd
Keyword(s):  
Driving Force ◽  
Driving Forces ◽  
Fracture Behaviour ◽  
Applied Strain ◽  
J Integral ◽  
Surface Cracks ◽  
Crack Driving Force ◽  
Numerical Assessment ◽  
Estimation Scheme ◽  
J Estimation

Modern installation techniques for marine pipelines and subsea risers are often based on the reel-lay method, which introduces significant (plastic) strains on the pipe during reeling and un-reeling. The safe assessment of crack-like flaws under such conditions requires accurate estimations of the elastic-plastic crack driving forces, ideally expressed in a strain-based formulation to better account for the displacement controlled nature of the reeling method. This paper aims to facilitate such assessments by presenting a strain-based expression of the well-known EPRI estimation scheme for the J integral, which is directly based upon fully plastic descriptions of fracture behaviour under significant plasticity. Parametric finite element simulations of bending of circumferentially cracked pipes have been conducted for a set of crack geometries, pipe dimensions and material hardening properties representative of current applications. These provide the numerical assessment of the crack driving force upon which the non-dimensional factors of the EPRI methodology, which scale J with applied strain, are derived. Finally, these factors are presented in convenient graphical and tabular forms, thus allowing the direct and accurate assessment of the J integral for circumferentially cracked pipes subjected to reeling.

Uncertainty Characterization of the TWC_Fail Through-Wall Circumferential Crack Stability Module for xLPR

2015 ◽  
Author(s):  
Richard Olson ◽  
Paul Scott
Keyword(s):  
Crack Size ◽  
Circumferential Crack ◽  
The Us ◽  
Estimation Scheme ◽  
Crack Stability ◽  
Experimental Values ◽  
Scheme Analysis ◽  
Metal Weld ◽  
J Estimation

The US NRC/EPRI xLPR (eXtremely Low Probability of Rupture) probabilistic pipe fracture analysis program uses deterministic modules as the foundation for the calculation of the probability of pipe leak or rupture as a consequence of active degradation mechanisms, vibration or seismic loading. The circumferential through-wall crack stability module, TWC_Fail, evaluates through-wall circumferential crack stability based on the minimum crack size from the Net-Section Collapse or an EPFM J-estimation scheme analysis. Beyond the uncertainty of xLPR data inputs, each module has an uncertainty. This paper documents the module uncertainty for TWC_Fail. Using 32 pipe fracture experiments, including: base metal, similar metal weld, and dissimilar metal weld experiments; bend only and pressure and bend loading; pipe diameters from 2-inch nominal diameter to 42-inch diameter, cracks that range from short to long, the uncertainty of the TWC_Fail methodology is characterized. Results show that TWC_Fail predictions are sensitive to the choice of J-R curve input (J-D or J-M from C(T) specimen tests) and the fit of the stress-strain data. Module uncertainty is characterized in terms mean fit and standard deviation between predictions and experimental values.

scholarly journals Comparison of Fracture Methodologies for Flaw Stability Analysis of Storage Tanks

2004 ◽  
Author(s):  
P.-S. Lam ◽  
R. L. Sindelar
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stability Analysis ◽  
Full Range ◽  
Storage Tanks ◽  
Element Analysis ◽  
Curvature Correction ◽  
Failure Assessment ◽  
Estimation Scheme ◽  
J Estimation

Fracture mechanics methodologies for flaw stability analysis of a storage tank were compared in terms of the maximum stable through-wall flaw sizes or “instability lengths.” The comparison was made at a full range of stress levels at a specific set of mechanical properties of A285 carbon steel and with a specific tank configuration. The two general methodologies, the J-integral-tearing modulus (J-T) and the failure assessment diagram (FAD), and several specific estimation schemes were evaluated. A finite element analysis of a flawed tank was also performed for validating the J estimation scheme with a curvature correction and for constructing the finite element-based FAD. The calculated instability crack lengths show that the J-T methodology based on a center-cracked panel solution with a curvature correction, and the material-specific FAD, most closely approximate the result calculated with finite element analysis for the stresses at the highest fill levels in the storage tanks (less than 124 MPa or 18 ksi). The results from the other FAD methods show instability lengths less than the J-T results over this range.

Sign in / Sign up

Export Citation Format

Share Document