Civil Engineering Reference
In-Depth Information
present at some locations and was dependent on the amount of strain, the tem-
perature, and time at the elevated temperature.
• The EAF applied in an incremental manner is in agreement with the square
wave electrical tests where the single pulse did not alter the grain size. As a
result, the observed mechanical variation in the yield point is suggested to be
from heat/electroplastic contributions on the dislocation density of the material.
Overall, this study showed that EAF with various electrical conditions can alter
the final microstructure, but it was more related to the local strain present as a
result of the Joule heating causing thermal distributions within the sample. Thus,
it is concluded that the observed bulk forming relations seen with EAF (reduced
flow stress/increased elongation) are more connected with the interaction of dislo-
cations which were not visible at the present scale examined. Although this section
only considered one initial grain size, it is expected that starting initial grain size
will influence the heat generated (Joule heating contribution) and thus the flow
stress reduction by thermal softening. A reduced grain size will create a greater
quantity of interactions between electrons and grain boundaries (
i.e.,
greater elec-
trical resistance), thus creating regions of greater atomic vibration or more heat
generation.
References
1. Hall EO (1951) The deformation and ageing of mild steel: III discussion of results. Proc Phys
Soc B 64:747-753
2. Hansen N (2004) Hall-Petch relation and boundary strengthening. Scripta Mater 51:801-806
3. Meyers MA, Ashworth E (1982) A model for the effect of grain size on the yield stress of
metals. Phil Mag 46(5):737-759
4. Struers Application Notes, Metallographic preparation of stainless steel.
http://www.strue
English.pdf
. Accessed 1 May
5. Salandro WA (2012) Thermo-mechanical modeling of the electrically-assisted manufacturing
(EAM) technique during open die forging. PhD dissertation, Clemson University
6. Siopis MS, Kinsey BL (2009) Experimental investigation of grain and specimen size effects
during electrical-assisted forming. In: ASME international manufacturing science & engi-
neering conference, MSEC2009-84137, p 6
7. Kalpakjian S (1997) Manufacturing processes for engineering materials, 3rd edn. Addison
Wesley Longman Inc, Menlo Park
8. NIST-SEMATECH (2012) Levene and Bartlett tests. Engineering Statistics Handbook
9. Jones JJ (2012) Flow behavior modeling and process control of electrically-assisted forming
(EAF) for sheet metals in Uniaxial Tension. PhD dissertation, Clemson University
10. Al-Samman T, Gottstein G (2008) Dynamic recrystallization during high temperature defor-
mation of magnesium. Mater Sci Eng 490:411-420
11. Ion SE, Humphreys FJ, White SH (1982) Dynamic recrystallization and the development
of microstructure during the high temperature deformation of magnesium. Acta Metall
30:1909-1919
