modeling of cavity growth during creep at high ss
TRANSCRIPT
MODELING OF CAVITY GROWTH DURING CREEP AT HIGH TEMPERATURE
-by Loïc Renversade
Research project - February 16Tutor : Andras Borbely
2
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.
THE CONTEXT
4
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
5
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.
What are the related issues ?
Thermal power plants
Jet engines
6
7
A need for creep resistant materials
Electricity generation : improvement of efficiency.
8
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.
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
9
10
X-ray micro-tomography:
Damage assessment techniques
rotation
Tray
X-ray source
detector
data collectionstep-by-steprotation
volume reconstructi
on
THE PROJECT
12
The experiments
Constant load
Constant pressure
Heating element
Measure of extension
Creep experiments performed at MPA, Stuttgart.
13
The experiments
Volume for
tomography
Extraction of samples:
Measurements done at European Synchrotron Radiation Facility.
Z
14
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
15
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
CONCLUSION
Industrial need for creep resistant materials.
Need for research to better understand creep.
QUESTIONS ?