Prediction of Dynamic Break-Opening Area Under Beyond Design Basis Seismic Loading

2015 ◽  
Author(s):  
M. Uddin ◽  
E. Kurth ◽  
F. W. Brust ◽  
G. M. Wilkowski ◽  
A. A. Betervide ◽  
...  
Keyword(s):  
Crack Length ◽  
Crack Opening Displacement ◽  
Crack Closure ◽  
Crack Opening ◽  
Time History ◽  
Seismic Loading ◽  
Opening Displacement ◽  
Ductile Tearing ◽  
Design Basis ◽  
The Moment

The thermal-hydraulics computer code, RELAP (Reactor Excursion and Leak Analysis Program) is used to analyze loss of coolant accidents (LOCAs) and system transients in PWRs and BWRs. However, RELAP requires the knowledge of break-opening area versus time history for Double-Ended Guillotine Break (DEGB) of a pipe fracture event as an input to calculate pressure drops at critical locations in the primary pipe loop. Previously authors conducted a detailed dynamic FE analyses to determine the condition for DEGB that provided moment versus rotation of the cracked-pipe and time histories for DEGB under beyond design basis seismic loading. In this paper, crack-opening area was calculated using the moment-rotation-time history obtained from dynamic FE analyses. In the LBB.ENG2 J-estimation scheme for circumferentially cracked pipe, the rotation at the cracked-pipe cross-sectional location (rotation due to the crack) is uniquely related to the total crack length and crack-opening displacement at the center of the crack. However, the relationship is only valid when the moment versus rotation from the FE analyses corresponds to the ductile tearing curve from the LBB.ENG2 ductile fracture analysis. During any unloading (and reloading) parts of the applied seismic history, the rotation can drop down from the upper-envelope for the tearing resistance of the cracked pipe in an elastic unloading manner from the seismic/cyclic unloading. During this part of the seismic time-history, the crack length remains constant but the center-crack-opening displacement decreases, i.e., there is crack closure with a constant crack length which needs to be included in predicting crack-opening area. Based on a number of past cyclic pipe fracture tests with large amounts of ductile tearing, a procedure was developed to predict the crack-opening area that included crack closure during cyclic loading of the seismic event. The resulting opening-area versus time history then becomes the input to the RELAP analysis for determination of emergency core cooling/safety processes.

Estimates of J and COD for Complex-Cracked Pipes Based on FE Analyses and ERS Method

2014 ◽  
Author(s):  
Jae-Uk Jeong ◽  
Jae-Boong Choi ◽  
Nam-Su Huh ◽  
Yun-Jae Kim
Keyword(s):  
Finite Element ◽  
Crack Opening Displacement ◽  
Crack Closure ◽  
Crack Opening ◽  
Crack Depth ◽  
J Integral ◽  
Opening Displacement ◽  
Reference Stress ◽  
Estimation Scheme ◽  
Complex Crack

A complex crack can occur at the dissimilar metal weld parts of nuclear pipes due to stress corrosion cracking. The fracture behavior of such crack is different with those of a simple through-wall crack. Thus, the engineering estimation equations for predicting the fracture mechanics parameters, i.e. crack opening displacement and J-integral, should be newly provided in order to evaluate the leak-before-break of pipe including complex cracks. In the previous research, an engineering scheme using reduced thickness analogy was suggested to calculate the crack opening displacement and J-integral for complex cracked pipes. However, this method has limitations in the sense that a through-wall crack is assumed to be developed only in the circumferential direction, and the effect of crack closure cannot be considered. Another scheme for complex cracked pipes is the enhanced reference stress method considering crack closure effect by suggesting the optimized reference load for complex crack geometry. It presented the more accurate results compared to previous engineering estimation scheme. However, an elastic component of crack opening displacement and J-integral were calculated by assuming the crack shape as the simple through-wall crack due to the absence of engineering solutions for complex-cracked pipes. In this context, finite element based evaluation of fracture parameters was performed to confirm the validation of previous estimation schemes. Moreover, the variations of crack opening displacement and J-integral according to a change of surface crack depth ratio of complex crack are systematically investigated based on detailed 3-D finite element analyses. Furthermore, enhanced reference stress method considering finite element based elastic values from the complex-cracked pipe models is assessed to overcome the limitation of previous enhanced reference stress approach.

Effect of Interface Damage on Fatigue Crack Growth for SiC Fiber-Reinforced Ti-15-3 Matrix Composite

2000 ◽  
Author(s):  
Yoshihisa Tanaka ◽  
Yu-Fu Liu ◽  
Chitoshi Masuda
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Length ◽  
Crack Growth ◽  
Crack Opening Displacement ◽  
Test Temperature ◽  
Wear Behavior ◽  
Crack Opening ◽  
Opening Displacement ◽  
Crack Wake

Abstract The fatigue crack growth behavior in SiC (SCS-6) fiber reinforced Ti-15-3 matrix alloy composite subjected to a constant tension-tension loading mode was studied using single edge specimen in 2 × 10−3 Pa vacuum at 293 and 823K, with a frequency of 2 Hz, and a stress ratio of R = 0.1. Direct measurement of the fatigue crack length, and the crack opening displacement along the crack wake during the test were carried out by scanning electron microscope (SEM). The increase in the test temperature was found to lead to a decrease in the fatigue crack growth rate. The degradation of bridging fibers in the crack wake was severe for T = 293K, and this behavior was dependent of the test temperature. Fine particle-like debris was found on the fracture surface in the region of crack propagation in specimens tested at T = 823K. This is thought to be caused by the interface wear behavior. The crack opening displacement along the crack wake tested at T = 823K decreased with increasing crack length, and this tendency is dependent on the applied stress range. The associated increase in the crack tip shielding is explained on the basis of the crack closure due to the matrix relaxation by fatigue creep and the interface wear behavior.

Fatigue Crack Growth Tests on Glass Fibre Reinforced Polymer Matrix Composite

2005 ◽  
Vol 473-474 ◽  
pp. 189-194
Author(s):  
Zilia Csomós ◽  
János Lukács
Keyword(s):  
Cyclic Loading ◽  
Crack Opening Displacement ◽  
Matrix Composite ◽  
Glass Fibre ◽  
Crack Opening ◽  
Loading Conditions ◽  
Opening Displacement ◽  
Interfacial Cracks ◽  
Glass Fibre Reinforced ◽  
Number Of Cycles

E-glass fibre reinforced polyester matrix composite was investigated, which was made by pullwinding process. Round three point bending (RTPB) specimens were tested under quasi-static and mode I cyclic loading conditions. Load vs. displacement (F-f), load vs. crack opening displacement (F-v) and crack opening displacement range vs. number of cycles (ΔCOD-N) curves were registered and analysed. Interfacial cracks were caused the final longitudinal fracture of the specimens under quasi-static and cyclic loading conditions.

Uncertainty Characterization of the CrCOD Circumferential Crack Opening Displacement Module for xLPR

2015 ◽  
Author(s):  
Richard Olson ◽  
Paul Scott
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
Opening Displacement ◽  
Crack Face ◽  
Pipe Surface ◽  
Circumferential Crack ◽  
The Us ◽  
Experimental Values ◽  
Metal Weld

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 crack opening displacement module, CrCOD, estimates crack opening displacement (COD) at the inside pipe surface, at the mid-wall thickness location, and at the outside pipe surface using a combined tension/crack face pressure/bending GE/EPRI-like solution. Each module has an uncertainty beyond the uncertainty of the xLPR data inputs. This paper documents the uncertainty for CrCOD. Using 36 pipe fracture experiments, including: base metal, similar metal weld, and dissimilar metal weld experiments; bend only and pressure and bend loading; static and dynamic load histories; cracks that range from short to long, the uncertainty of the CrCOD methodology is characterized. Module uncertainty is presented in terms mean fit and standard deviation between prediction and experimental values.

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