Modeling of cavity growth during creep at high ss
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Transcript of Modeling of cavity growth during creep at high ss
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MODELING OF CAVITY GROWTH DURING CREEP AT HIGH TEMPERATURE
-by Loïc Renversade
Research project - February 16Tutor : Andras Borbely
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Outline
1) Context of the project:• What is creep ?• Why do we need creep resistant
materials ?• How to assess creep damage ?
2) Presentation of the project:• The starting point.• The approach.
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THE CONTEXT
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What is creep ?
time
elo
ng
at
ion
Thermally activated : T > 0.3 Tm.
Time dependant plastic deformation.
0.2 Tm
0.5 Tm
Constant load
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What is creep ?
Failure : nucleation, growth and coalescence of cavities.
Thermally activated : T > 0.3 Tm.
Stresses lower than elastic limit.
Time dependant plastic deformation.
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What are the related issues ?
Thermal power plants
Jet engines
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A need for creep resistant materials
Electricity generation : improvement of efficiency.
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A need for creep resistant materials
Electricity generation : improvement of efficiency.
Increasing efficiency = materials in harsher environments.
Development of creep resistant materials: precise chemistry and microstructures control.
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Damage assessment techniques
Microscopy sample preparation
(polishing). complex shapes of
voids.
Ultrasonic technique qualitative measures. in-service
components.
X-ray microtomography quantitative
measures. 3D imaging.
Destructive methods Non-destructive methods
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X-ray micro-tomography:
Damage assessment techniques
rotation
Tray
X-ray source
detector
data collectionstep-by-steprotation
volume reconstructi
on
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THE PROJECT
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The experiments
Constant load
Constant pressure
Heating element
Measure of extension
Creep experiments performed at MPA, Stuttgart.
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The experiments
Volume for
tomography
Extraction of samples:
Measurements done at European Synchrotron Radiation Facility.
Z
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Reconstruction from tomography
Statistics
38 000h – 600°C
10 000h – 575°C
300 μm
Outer surface
Inner surface
Inner pressure
3D images
Z
5 μm
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Project approach
•Model of cavity growth.•Material parameters of the steels.
Literature review
•Simulation of experiments using finite-elements (experimental measures).•Simulation of cavity growth.
Modeling
•Influence of variables and parameters.•Limits of the model.
Interpretation of results
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CONCLUSION
Industrial need for creep resistant materials.
Need for research to better understand creep.
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QUESTIONS ?