ML18270A092
| ML18270A092 | |
| Person / Time | |
|---|---|
| Issue date: | 09/24/2018 |
| From: | Giovanni Facco NRC/RES/DE/CIB |
| To: | |
| Michael Benson | |
| Shared Package | |
| ML18270A088 | List: |
| References | |
| Download: ML18270A092 (13) | |
Text
EXPLORING CAPABILITIES OF XFEMFOR USE IN FLAW EVALUATIONS 1Public Meeting9/24/2018Giovanni FaccoRES/DE/CIB ObjectivesIntroduce Plan to Investigate Use of xFEMMethods to Investigate PWSCC Growth
-Motivation, Plan, Preliminary Results
-FeedbackDiscuss International Efforts/Collaboration 2
Motivation
- RES has identified that future PWSCC flaw evaluations may involve 3D Finite Element Models of crack growth with complex stresses in asymmetrical components.
- In order to be able to properly evaluate this kind of model RES plans to continue building upon its computational expertise in this potentially regulatory significant area.
- Developing these capabilities and sharing what we learn we hope to improve and modernize how these issues are evaluated in the future 3
Current FEA Application
-Model WRS in complex geometries by simulating weld parameters 1.Perform thermal analysis 2.Impose thermal history in mechanical analysis to generate WRS profile
-Multiple weld histories can be explored without the need for new model or re
-meshing-These Results can then be used to calculate crack growth ratesNo RepairLarge ID RepairOD RepairRoot RepairNo RepairLarge ID RepairOD RepairRoot RepairThermal ModelMechanical Model 4
Traditional FEA vs xFEMTraditional FEA
- Results in very accurate SIF and stress states
- Requires re
-meshing for any change crack size or geometry
- Analysis usually limited to idealized crack shapes and planar crack growth due to complexity of modelsxFEM*Mesh-independent analysis of discontinuities and singularities
- Can quickly calculate SIF of multiple cracks and crack lengths without major modifications to model
- Can model realistic 3D crack growth without re
-meshingTraditional FEA Crack Growth 5
Current Crack Growth Rate Methods
- Crack growth calculations based on ASME Methodology
-2D approximations
-Uses idealized crack shape and growth model (semi
-elliptical
)-Assumes planar crack growth, perpendicular to pipe wall
-WRS profile for crack growth is path dependent and user defined 6 Research Project PlanPWSCC Crack Growth Development
-Reproduce PWSCC Growth Behaviors-Investigate Cracking Property Response
-Investigate Simulation Parameter ResponseModel Material Behavior
-Develop material property relationships using experimental component geometry (e.g. C(T) Specimen) to benchmark model response.
Industry Relevant Models-Compared xFEMresults to similar industry relevant models evaluated using traditional methods.
7 Methodology
- ABAQUS can simulate fatigue crack growth using a Paris Law type relationship=*ASME Code analysis determines PWSCC crack growth behavior using a similar power law relationship=*G and K are interrelated by a linear relationship in LEFM=where E'=E for plane stress and =()for plane strain 8 Initial ResultsComparison of NondimensionalStress Intensity FactorsContourABAQUSBenchmarkRES Model% Difference% Error (Handbook Value of 2.826) 22.85372.87120.610981.599 32.96432.98150.579675.504 43.00272.99560.236796.001 52.96962.97260.102185.189Fatigue Crack Growth(Video)Stress Intensity Factor Calculations2D Single Edge Notch=9 Status*Successfully used ABAQUS simplified fatigue crack growth method, to grow a crack in a static stress field (externally applied or internal) in a 2D model*Developed preliminary parameter relationships between ABAQUS fatigue model and PWSCC model *Cracking parameter response (G & K) for 2D models shows good agreement with handbook values 10 International Benchmarking Efforts
- In cooperation with Committee on the Safety of Nuclear Installations (CSNI) the NRC is taking part in a technical round robin project exploring X
-FEM Capabilities.
-Multinational group (Public and Private, 12 Countries)
-Focus is on an preliminary comparison of the X-FEM capabilities of the different codes used in the nuclear industry-Goal is to share Methodology and Results in order to evaluate capabilities and develop best practices.
11 International Benchmarking Efforts
- Three benchmark problems
-Surface Crack in Plate
-Embedded Crack in Plate Subjected to Shear Load
-Underclad Crack in Core Shell of an RPV*Evaluate stationary cracks
- Thermal and mechanical loading*Static and transient conditions 12 Summary*Developing xFEMTechniques
-Investigate Use of xFEMfor PWSCC Growth-International Collaboration Efforts*Feedback 13