Forgeabilité des aciers inoxydables austéno-ferritiques

tel-00672279, version 1 - 21 Feb 2012
146 Chapter IV. STRAIN PARTITIONING
IV.7 Limits of the technique
Technical and conceptual limitations of the microgrid technique were found during the present investi-
gation, but could not be addressed due to time constraints. These different limitations of the microgrid
technique are discussed in this section.
IV.7.1 A time consuming technique
Although the modified microgrid method is very well-adapted at high temperature, this technique is
time consuming, see Table IV.21. The time required to obtain a result on one insert depends signifi-
cantly on the time necessary to match the homologous points (grid intersections) between the de-
formed and the undeformed configurations. Indeed, most of the time, the initial satisfying grey level
contrast is affected by the temperature and the deformation. As a consequence the automatic match-
ing of the grid intersections cannot be used and only a manual matching which takes a lot of time (5h)
provides a result.
Procedure Aims Equipment
Heat treatments
Specimen
machining
Polishing
of insert
Electro-etching
Resin depositing
and polymerizing
To generate model microstruc-
tures
To have modified plane strain
compression specimens
To obtain a flat and good
quality surface
To reveal the austenite ferrite
microstructure
To process the microgrid
Time
needed
Success
rate
Furnace 1day 100%
Machining 4h 100%
Polishing wheels 1h 100%
DC Power Source 15min 90%
Rotating stage
Furnace
Place
SIMaP
(Grenoble)
SIMaP
(Grenoble)
SIMaP
(Grenoble)
SIMaP
(Grenoble)
45min 100% LMS (Paris)
Resin irradiating To process the microgrid SEM 15min 80% LMS (Paris)
Microgrid
engraving
High-resolution
picture
Insert-sample
assembling
Compression
test
Microgrid
extraction
High-resolution
picture
Analysis
of results
To process the microgrid DC Power Source 5min 40% LMS (Paris)
To obtain picture in the unde-
formed conditions
To embed the insert in the
work piece
To carry out the plane strain
compression with the specified
conditions
To see the microgrid after
deformation
To obtain picture in the de-
formed conditions
To measure and map the
deformation
SEM 30min 100% LMS (Paris)
TIG welding device 1h 100%
Thermo-mechanical
compression machine
Crosscut saw
Polishing wheels
2h 90%
1h 90%
University of
Sheffield
University of
Sheffield
SIMaP
(Grenoble)
SEM 30min 100% LMS (Paris)
CorrelManuV
software
TOTAL ≈ 40h
6h 90%
SIMaP
(Grenoble)
Table IV.21. Summary of the required equipment and estimation of the time needed to perform and
analyze a test with the modified microgrid technique.