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{{#Wiki_filter: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
{{#Wiki_filter:EXPLORING CAPABILITIES OF XFEM FOR USE IN FLAW EVALUATIONS Public Meeting 9/24/2018 Giovanni Facco RES/DE/CIB 1
-Motivation, Plan, Preliminary Results
 
-FeedbackDiscuss International Efforts/Collaboration 2
Objectives Introduce Plan to Investigate Use of xFEM Methods to Investigate PWSCC Growth
  - Motivation, Plan, Preliminary Results
  - Feedback Discuss International Efforts/Collaboration 2
 
Motivation
Motivation
*RES has identified that future PWSCC flaw evaluations may involve 3D Finite Element Models of crack growth with complex stresses in asymmetrical components.
* 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.
* 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
* 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
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  
  - Model WRS in complex geometries by simulating weld parameters
-Multiple weld histories can be explored without the need for new model or re
: 1. Perform thermal analysis
-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
: 2. Impose thermal history in mechanical analysis to generate WRS profile
Traditional FEA vs xFEMTraditional FEA
  - Multiple weld histories can be explored without the need for new model or re-meshing
*Results in very accurate SIF and stress states
  - These Results can then be used to calculate crack growth rates No Repair          OD Repair                  No Repair              OD Repair Root Repair      Large ID Repair            Root Repair          Large ID Repair 4      Thermal Model                                    Mechanical Model
*Requires re
 
-meshing for any change crack size or geometry
Traditional FEA vs xFEM Traditional FEA                                 xFEM
*Analysis usually limited to idealized crack shapes and planar crack growth due to complexity of modelsxFEM*Mesh-independent analysis of discontinuities and singularities
* Results in very accurate SIF and
*Can quickly calculate SIF of multiple cracks and crack lengths without major modifications to model
* Mesh-independent analysis of stress states                                   discontinuities and singularities
*Can model realistic 3D crack growth without re
* Requires re-meshing for any
-meshingTraditional FEA Crack Growth 5
* Can quickly calculate SIF of multiple change crack size or geometry                    cracks and crack lengths without major
* Analysis usually limited to                        modifications to model idealized crack shapes and planar
* Can model realistic 3D crack growth crack growth due to complexity of                without re-meshing models Traditional FEA Crack Growth 5
 
Current Crack Growth Rate Methods
Current Crack Growth Rate Methods
*Crack growth calculations based on ASME Methodology
* Crack growth calculations based on ASME Methodology
-2D approximations
  - 2D approximations
-Uses idealized crack shape and growth model (semi
  - Uses idealized crack shape and growth model (semi-elliptical)
-elliptical
  - Assumes planar crack growth, perpendicular to pipe wall
)-Assumes planar crack growth, perpendicular to pipe wall
  - WRS profile for crack growth is path dependent and user defined 6
-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
Research Project Plan PWSCC Crack Growth Development
-Investigate Simulation Parameter ResponseModel Material Behavior
  - Reproduce PWSCC Growth Behaviors
-Develop material property relationships using experimental component geometry (e.g. C(T) Specimen) to benchmark model response.
  - Investigate Cracking Property Response
Industry Relevant Models-Compared xFEMresults to similar industry relevant models evaluated using traditional methods.
  - Investigate Simulation Parameter Response Model Material Behavior
7 Methodology
  - Develop material property relationships using experimental component geometry (e.g. C(T)
*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
Specimen) to benchmark model response.
*In cooperation with Committee on the Safety of Nuclear Installations (CSNI) the NRC is taking part in a technical round robin project exploring X
Industry Relevant Models
-FEM Capabilities.
  - Compared xFEM results to similar industry relevant models evaluated using traditional methods.
-Multinational group (Public and Private, 12 Countries)
7
-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
Methodology
*Three benchmark problems
* ABAQUS can simulate fatigue crack growth using a Paris Law type relationship
-Surface Crack in Plate
 
-Embedded Crack in Plate Subjected to Shear Load
                                          =
-Underclad Crack in Core Shell of an RPV*Evaluate stationary cracks  
* ASME Code analysis determines PWSCC crack growth behavior using a similar power law relationship
*Thermal and mechanical loading*Static and transient conditions 12 Summary*Developing xFEMTechniques
 
-Investigate Use of xFEMfor PWSCC Growth-International Collaboration Efforts*Feedback 13}}
                                            =
* G and K are interrelated by a linear relationship in LEFM 2
                                            =  
 
where E'=E for plane stress and =                   for plane strain (12 )
8
 
Initial Results Stress Intensity Factor Calculations                    Fatigue Crack Growth 2D Single Edge Notch                                  (Video)
 
                                  =
 
Comparison of Nondimensional Stress Intensity Factors Contour  ABAQUS        RES        %     % Error (Handbook Benchmark    Model    Difference  Value of 2.826) 2      2.8537    2.8712    0.61098          1.599 3      2.9643    2.9815    0.57967          5.504 4      3.0027    2.9956    0.23679          6.001 5      2.9696    2.9726    0.10218          5.189 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 xFEM Techniques
    - Investigate Use of xFEM for PWSCC Growth
    - International Collaboration Efforts
* Feedback 13}}

Revision as of 14:03, 20 October 2019

09/24/2018 Exploring Capabilities of Xfem for Use in Flaw Evaluations
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)
v • d • e


Text

EXPLORING CAPABILITIES OF XFEM FOR USE IN FLAW EVALUATIONS Public Meeting 9/24/2018 Giovanni Facco RES/DE/CIB 1

Objectives Introduce Plan to Investigate Use of xFEM Methods to Investigate PWSCC Growth

- Motivation, Plan, Preliminary Results

- Feedback Discuss 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 rates No Repair OD Repair No Repair OD Repair Root Repair Large ID Repair Root Repair Large ID Repair 4 Thermal Model Mechanical Model

Traditional FEA vs xFEM Traditional FEA xFEM

  • Results in very accurate SIF and
  • Mesh-independent analysis of stress states discontinuities and singularities
  • Requires re-meshing for any
  • Can quickly calculate SIF of multiple change crack size or geometry cracks and crack lengths without major
  • Analysis usually limited to modifications to model idealized crack shapes and planar
  • Can model realistic 3D crack growth crack growth due to complexity of without re-meshing models Traditional 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 Plan PWSCC Crack Growth Development

- Reproduce PWSCC Growth Behaviors

- Investigate Cracking Property Response

- Investigate Simulation Parameter Response Model Material Behavior

- Develop material property relationships using experimental component geometry (e.g. C(T)

Specimen) to benchmark model response.

Industry Relevant Models

- Compared xFEM results 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 2

=

where E'=E for plane stress and = for plane strain (12 )

8

Initial Results Stress Intensity Factor Calculations Fatigue Crack Growth 2D Single Edge Notch (Video)

=

Comparison of Nondimensional Stress Intensity Factors Contour ABAQUS RES  %  % Error (Handbook Benchmark Model Difference Value of 2.826) 2 2.8537 2.8712 0.61098 1.599 3 2.9643 2.9815 0.57967 5.504 4 3.0027 2.9956 0.23679 6.001 5 2.9696 2.9726 0.10218 5.189 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

Summary

  • Developing xFEM Techniques

- Investigate Use of xFEM for PWSCC Growth

- International Collaboration Efforts

  • Feedback 13
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