Development of a Crack Opening Displacement Assessment Procedure Considering Change of Compliance at a Crack Part in Thin Wall Pipes Made of Modified 9Cr-1Mo Steel

2018 ◽  
Author(s):  
Takashi Wakai ◽  
Hideo Machida ◽  
Manabu Arakawa ◽  
Seiji Yanagihara ◽  
Ryosuke Suzuki ◽  
...  
Keyword(s):  
Crack Opening Displacement ◽  
Work Hardening ◽  
Crack Opening ◽  
Large Diameter ◽  
Assessment Method ◽  
Leak Rate ◽  
Thin Wall ◽  
Opening Displacement ◽  
Thin Walled ◽  
Small Work

This study was carried out to establish crack opening displacement (COD) evaluation methods used in Leak-Before-Break (LBB) assessment of thin-walled large-diameter pipes of the Sodium cooled Fast Reactors (SFRs). For the pipes of SFR, the continuous leak monitoring will be adopted as an alternative to a volumetric test of the weld joints under conditions that satisfy LBB. The sodium pipes are made of ASME Gr.91 (modified 9Cr-1Mo steel). Thickness of the pipes is small, because the internal pressure is very small. Modified 9Cr-1Mo steel has a relatively large yield stress and small work hardening coefficient comparing to the austenitic stainless steels which are currently used in the conventional plants. In order to assess the LBB behavior of the sodium pipes made of modified 9Cr-1Mo steel, the coolant leak rate from a through wall crack must be estimated properly. Since the leak rate is strongly related to the crack opening displacement (COD), an appropriate COD assessment method must be established to perform LBB assessment. However, COD assessment method applicable for SFR pipes — having thin wall thickness and made of small work hardening material — has not been proposed yet. Thus, a COD assessment method applicable to thin walled large diameter pipe made of modified 9Cr-1Mo steel was proposed in this study. In this method, COD was calculated by classifying the components of COD; elastic, local plastic and fully plastic. In addition, the verification of this method was performed by comparing with the results of a series of four-point bending tests using modified 9Cr-1Mo steel pipe having a circumferential through wall notch. As a result, in some cases, COD were overestimated especially for large cracks. Although the elastic component of COD, δEE, is still over-estimated for large cracks, leak evaluation from small cracks is much more important in LBB assessment. Therefore, this study recommends that only the elastic component of COD, δEE, should be adopted in LBB assessment of SFR pipes.

Development of LBB Assessment Method for Japan Sodium Cooled Fast Reactor (JSFR) Pipes (4): Verification of Crack Opening Displacement Assessment Method for Thin Wall Pipes Made of Mod.9Cr-1Mo Steel

2011 ◽  
Author(s):  
Takashi Wakai ◽  
Hideo Machida ◽  
Shinji Yoshida ◽  
Fumiko Kawashima ◽  
Koichi Kikuchi ◽  
...  
Keyword(s):  
Crack Opening Displacement ◽  
Fast Reactor ◽  
Work Hardening ◽  
Crack Opening ◽  
Assessment Method ◽  
Experimental Results ◽  
Leak Rate ◽  
Thin Wall ◽  
Opening Displacement ◽  
Small Work

For sodium pipes of Japan Sodium cooled Fast Reactor (JSFR), the continuous leak monitoring will be adopted as an alternative to a volumetric test of the weld joints under conditions that satisfy Leak-Before-Break (LBB). The sodium pipes are made of ASME Gr.91 (modified 9Cr-1Mo) steel. Thickness of the pipes is small, because the internal pressure is very low. Modified 9Cr-1Mo steel has a relatively large yield stress and small work hardening coefficient comparing to the austenitic stainless steels which are currently used in the conventional plants. In order to discuss about the LBB of the sodium pipes made of modified 9Cr-1Mo steel, the coolant leak rate from a through wall crack must be estimated properly. Since the leak rate is strongly related to the crack opening displacement (COD), an appropriate COD assessment method must be established to perform LBB assessment. However, COD assessment method applicable for JSFR sodium pipes — thin wall and small work hardening material — has not been proposed yet. Therefore, the authors have proposed a COD assessment method applicable to thin walled large diameter pipe made of modified 9Cr-1Mo steel. In this method, COD is calculated by classifying into three components of elastic, local plastic and fully plastic. This paper describes the improved COD assessment method and verifies the validity of the method based on the results of a series of four-point bending tests at elevated temperature using thin wall modified 9Cr-1Mo steel pipe containing a circumferential through wall crack. As a result, COD values calculated by the proposed method were in a good agreement with the experimental results for the uniform pipe without weld. In the case that the crack was machined at weld metal or heat affected zone (HAZ), proposed method predicted relatively larger COD than the experimental results. The causes of such discrepancies were discussed comparing with the results of finite element analyses. Based on these examinations, the rational leak rate evaluation method in LBB assessment was proposed.

Development of Leak-Before-Break Assessment Method for Japan Sodium Cooled Fast Reactor Pipe—Part 1 Crack Opening Displacement Assessment of Thin Wall Pipes Made of Modified 9Cr-1Mo Steel

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Takashi Wakai ◽  
Hideo Machida ◽  
Manabu Arakawa ◽  
Shinji Yoshida ◽  
Yasuhiro Enuma
Keyword(s):  
Crack Opening Displacement ◽  
Fast Reactor ◽  
Work Hardening ◽  
Crack Opening ◽  
Assessment Method ◽  
Leak Rate ◽  
Thin Wall ◽  
Opening Displacement ◽  
Leak Before Break ◽  
Small Work

This was carried out to establish crack opening displacement (COD) evaluation methods used in leak-before-break (LBB) assessment of sodium pipes of the Japan sodium cooled fast reactor (JSFR). For sodium pipes of JSFR, the continuous leak monitoring will be adopted as an alternative to a volumetric test of the weld joints under conditions that satisfy LBB. The sodium pipes are made of ASME Gr.91 (modified 9Cr-1Mo steel). Thickness of the pipes is small, because the internal pressure is very low. Modified 9Cr-1Mo steel has a relatively large yield stress and small work hardening coefficient comparing to the austenitic stainless steels which are currently used in the conventional plants. In order to assess the LBB behavior of the sodium pipes made of modified 9Cr-1Mo steel, the coolant leak rate from a through-wall crack must be estimated properly. Since the leak rate is strongly related to the COD, an appropriate COD assessment method must be established to perform LBB assessment. However, COD assessment method applicable for JSFR sodium pipes—thin wall and small work hardening material—has not been proposed yet. Thus, a COD assessment method applicable to thin walled large diameter pipe made of modified 9Cr-1Mo steel was proposed in this study. In this method, COD was calculated by classifying the components of COD; elastic, local plastic, and fully plastic. In addition, the verification of this method was performed by comparing with the results of a series of four-point bending tests at elevated temperature using thin wall modified 9Cr-1Mo steel pipe containing a circumferential through-wall crack. As a result, COD values calculated by the proposed method were in a good agreement with the experimental results for the uniform pipe without a weld. In the case that the crack was machined in the weld metal or heat affected zone (HAZ), the proposed method predicted relatively larger COD than the experimental results. The causes of such discrepancies were discussed by comparing with the results of finite element analyses. Based on these examinations, the rational leak rate evaluation method in LBB assessment was proposed.

Development of LBB Assessment Method for Japanese Sodium Cooled Fast Reactor (JSFR) Pipes: 2—Crack Opening Displacement Assessment of Thin Wall Pipes Made of Modified 9Cr-1Mo Steel

2010 ◽  
Author(s):  
Takashi Wakai ◽  
Hideo Machida ◽  
Manabu Arakawa ◽  
Yasuhiro Enuma ◽  
Tai Asayama
Keyword(s):  
Crack Opening Displacement ◽  
Fast Reactor ◽  
Work Hardening ◽  
Evaluation Method ◽  
Crack Opening ◽  
Piping System ◽  
Thin Wall ◽  
Opening Displacement ◽  
Element Analysis ◽  
Hardening Material

This paper presents crack opening displacement (COD) evaluation methods used in leak before break (LBB) assessment of sodium piping system in the Japanese sodium cooled fast reactor (JSFR). Thin wall and low work hardening material are features of piping of JSFR. Detectability of coolant sodium is very high, the target leak detection performance of leak detector of JSFR is 100g/hr. Internal pressure of JSFR piping is very low, and large through wall crack is allowable to satisfy LBB condition. The existing COD evaluation method cannot be applied to the piping of JSFR which has above-mentioned features. Finite element analysis (FEA) were performed to evaluate COD for thin wall and low work hardening material piping with a circumferential through wall crack. These analytical results were arranged into engineering evaluation formulae. Proposed method gives high accuracy COD estimation, and is applicable to LBB assessment of JSFR piping.

Estimation of Elastic Crack Opening Displacement for Thin Elbows With Circumferential Through-Wall Cracks

2015 ◽  
Author(s):  
Min-Kyu Kim ◽  
Han-Bum Surh ◽  
Min-Gu Won ◽  
Nam-Su Huh ◽  
Moon-Ki Kim ◽  
...  
Keyword(s):  
Crack Opening Displacement ◽  
Nuclear Power ◽  
Crack Opening ◽  
Three Dimensional ◽  
Opening Displacement ◽  
Dimensional Finite Element ◽  
Elastic Crack ◽  
Thin Walled ◽  
Three Dimensional Finite Element ◽  
Leak Before Break

Leak-before-break (LBB) is an important concept that could confirm design and integrity evaluation of nuclear power plant piping. For the LBB analysis, the detective leakage rate should be calculated for a through-wall cracked pipes. For this calculation, the crack opening displacement (COD) calculation is essential. Recently, sodium faster reactor (SFR) which has thin-walled pipes with Rm/t ranged 30–40 was introduced and then the investigation of these thin walled pipes and elbows has received great attention in the LBB evaluation. In this context, the three-dimensional finite element (FE) analyses for thin elbows with circumferential crack under in-plane bending are carried out to investigate the elastic COD values. Finally, the solution for elastic COD which can cover sufficiently thin elbow is successfully addressed.

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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