ML18267A088
| ML18267A088 | |
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| Issue date: | 09/24/2018 |
| From: | Tregoning R L NRC/RES/DE |
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© 2015 Electric Power Research Institute, Inc. All rights reserved.Steve Gosselin, PE, FellowLPI, Inc.Gary Stevens, PEEPRILife & Gradient Factorsfor ASME Class 1 Piping Component AnalysesWorking Group Design MethodologyAugust 2018 2© 2015 Electric Power Research Institute, Inc. All rights reserved.SummaryIntroductionFatigue Life Test DataLife and Gradient FactorsStage I LifeStage II LifeLife and Gradient Factor RegressionsExample Problem Status 3© 2015 Electric Power Research Institute, Inc. All rights reserved.IntroductionThis work examined two aspects of ASME Code fatigue life (Usage) fatigue calculation procedures -e.g. NB-3222.4, NB-3650, or XIII 3222.4(e)(5)allowable fatigue life is based on fatigue testing small diameter test specimens that are subsequently applied to all piping regardless of the actual thickness, andall component cyclic stresses are treated as uniform through-thickness membrane stresses and do not consider the presence of actual through-thickness stress gradients.
4© 2015 Electric Power Research Institute, Inc. All rights reserved.FATIGUE LIFE TEST DATA 5© 2015 Electric Power Research Institute, Inc. All rights reserved.Test Specimen 25% Load Drop Crack SizeFor constant displacement test: 25% load drop (F25%) occurs when crack area equals 25% of original test specimen area.
6© 2015 Electric Power Research Institute, Inc. All rights reserved.Fatigue Strain-Life TestingASTM Standard E 606-04 Smooth push-pull specimens tested under fully reversed through-thickness uniform (membrane) displacement controlled loadingDetermination of number of cycles to failure may vary. Current data based on force (load) drop of 25% or 50%. NUREG/CR-6909 Rev. 1 Argonne National Laboratory and Japanese dataMixture of 25% and 50% load drop data (all data normalized to 25% load drop criteria)Air test temperatures between 25°C and 290°CGauge diameters 0.2 in. (5-mm) to 0.375 in. (9.5-mm)Observation: 25% load drop criteria was associated with an average 3-mm deep crack (Chopra and Shack 2001) 7© 2015 Electric Power Research Institute, Inc. All rights reserved.LIFE & GRADIENT FACTORS 8© 2015 Electric Power Research Institute, Inc. All rights reserved.Life and Gradient FactorsGFaccounts for the increase in room temperature air Stage II life associated with through thickness stress gradientsLFaccounts for increased Stage II life associated a with piping thicknesses greater than the 0.304 inch median gauge thickness associated with the NUREG/CR-6909 Rev. 1 room temperature air test data.Stage I and Stage II life calculations for carbon steel (CS), low alloy steel (LAS) and stainless steel (SS) materials were based on material properties at room temperature (25°C).
9© 2015 Electric Power Research Institute, Inc. All rights reserved.Life Factor, LFA life factor LF corrects fatigue usage estimates for increased Stage II life associated with component thicknesses greater than the 0.304 inch median gaugethickness associated with the NUREG/CR-6909 solid pin test specimens.
10© 2015 Electric Power Research Institute, Inc. All rights reserved.GradientFactor, GFGF accounts for the increase in Stage II life associated with through thickness stress gradients 11© 2015 Electric Power Research Institute, Inc. All rights reserved.STAGE I LIFE 12© 2015 Electric Power Research Institute, Inc. All rights reserved.Stage I and Stage II LifeTwo stages of fatigue crack growth 13© 2015 Electric Power Research Institute, Inc. All rights reserved.Stage I Life (i)Assumption:Stage I initiation and growth occurs under uniform membrane loading regardless of the absence or presence of linear and non-linear through-wall stress gradients.
14© 2015 Electric Power Research Institute, Inc. All rights reserved.Test Specimen 25% load drop crack depths25% load-drop crack depth of 0.118 in. (3-mm) is associated with a 0.304 in. (7.72 mm) specimen gauge diameter that represents the median NUREG/CR-6909 test specimen size 15© 2015 Electric Power Research Institute, Inc. All rights reserved.CS, LAS, SS Stage I Life for 1.150% Strain 16© 2015 Electric Power Research Institute, Inc. All rights reserved.LAS Stage 1 Life: 1.150% Strain Range (ii) 17© 2015 Electric Power Research Institute, Inc. All rights reserved.Pin Crack Depth vs Life Fraction Comparison (Damiani and Smith) 18© 2015 Electric Power Research Institute, Inc. All rights reserved.STAGE II LIFE FOR A CYLINDER 19© 2015 Electric Power Research Institute, Inc. All rights reserved.StageII Life (i)Crack growth of a mechanically small crack (0.008 in.) to a crack depth associated with a 25% load dropStage II deterministic crack growth calculations were performed using the NRC PRAISE computer codePRAISE was modified to include a best estimate (50/50) of the C/LAS crack relationship in ASME Section XI Non-Mandatory Appendix C The alternating stress intensity was corrected for elastic-plastic material response in the HIGH strain LOW cycle region.
20© 2015 Electric Power Research Institute, Inc. All rights reserved.Stage II Life (ii)PRAISE was modified to include a best estimate version of the C, LAS and SS crack growth relationships in room temperature air The elastic alternating stress intensity, KI, is subsequently adjusted for elastic-plastic material response in the high-strain low---tip.Elastic J-integral range, Jelastic, was obtained from linear elastic finite element analyses, and the elastic-plastic J-integral range, Jelastic-plastic, was computed by performing elastic-plastic finite element analyses 21© 2015 Electric Power Research Institute, Inc. All rights reserved.C/LAS Stage II Life 22© 2015 Electric Power Research Institute, Inc. All rights reserved.SS Stage II Life 23© 2015 Electric Power Research Institute, Inc. All rights reserved.LIFE & GRADIENT FACTOR REGRESSIONS 24© 2015 Electric Power Research Institute, Inc. All rights reserved.Life & Gradient Factor DataCarbon/Low Alloy Steel and Stainless SteelRoom temperature air environmentCyclic Loads: % Strain Range () = 0.48, 0.8, 1.15, 1.5, 2, 2.5Nominal Pipe Sizes: NPS 2, 2.5, 3, 4, 5, 6, 8, 10, 12, 14, 16,18, 20, 22, and 24Pipe Schedules:80 and 160Pipe Thickness Range: 0.154 in. to 2.344 in.Data3780 Life Factors3780 Gradient Factors 25© 2015 Electric Power Research Institute, Inc. All rights reserved.C/LAS Life & Gradient Factor Data* (ii)* Carbon steel data shown 26© 2015 Electric Power Research Institute, Inc. All rights reserved.SS Life & Gradient Factor Data* (ii)* Stainless steel data shown 27© 2015 Electric Power Research Institute, Inc. All rights reserved.C/LAS Life Factor Regression ModelsCarbon SteelLow Alloy Steel 28© 2015 Electric Power Research Institute, Inc. All rights reserved.SS Life Factor Regression ModelsStainless Steel 29© 2015 Electric Power Research Institute, Inc. All rights reserved.C/LAS Gradient Factor Regression ModelsCarbon SteelLow Alloy Steel 30© 2015 Electric Power Research Institute, Inc. All rights reserved.SS Gradient Factor Regression ModelsStainless Steel 31© 2015 Electric Power Research Institute, Inc. All rights reserved.EXAMPLE NPS 10 Schedule 80 Reducing Elbow 32© 2015 Electric Power Research Institute, Inc. All rights reserved.BWR 4 LPCS 10 x 12 Reducing Elbow60 year design fatigue usage calculation at a Schedule 80 (LPCS) systemOriginal calculation performed according to stress analysis procedures specified in ASME III NB-3600The highest fatigue usage was located at Node 330 where -60 year fatigue usage estimates are corrected the component thickness and the presence of through-wall stress gradients.
33© 2015 Electric Power Research Institute, Inc. All rights reserved.Node 330 60-yr Air and Water Fatigue Usages 34© 2015 Electric Power Research Institute, Inc. All rights reserved.Node 330 Membrane-to-Gradient Ratios 35© 2015 Electric Power Research Institute, Inc. All rights reserved.Node 330 Stage I Life 36© 2015 Electric Power Research Institute, Inc. All rights reserved.Node 330 LF and GF Calculation 37© 2015 Electric Power Research Institute, Inc. All rights reserved.Node 330: C/LAS/SS Life FactorCarbon SteelLow Alloy SteelStainless Steel 38© 2015 Electric Power Research Institute, Inc. All rights reserved.Node 330: C/LAS/SS Gradient FactorCarbon SteelLow Alloy SteelStainless Steel 39© 2015 Electric Power Research Institute, Inc. All rights reserved.CS/LAS/SS LF & GF Comparisons 40© 2015 Electric Power Research Institute, Inc. All rights reserved.
41© 2015 Electric Power Research Institute, Inc. All rights reserved.DISCUSSION 42© 2015 Electric Power Research Institute, Inc. All rights reserved.