Civil Engineering Reference
In-Depth Information
area of the specimen was less than 1.5 %, which cannot explain the drastic drop in
temperature between the two tests. This leads to the conclusion that a significant
part of the electric energy is actually imparted by the flow of electrons to the mate-
rial and this aids the deformation, as described earlier, and the remaining energy
is converted into bulk heating [
21
]. Thus, the higher temperatures recorded at the
beginning of the test may result in rapid evaporation of the lubricant, and poten-
tially change in a less favorable lubrication regime.
9.2.9 EAF/Tribology Conclusions
The advance of EAF for larger-scale applications depends on identifying a well-
performing lubricant. Three lubricants chosen from three different groups were
tested under different current densities and their performance was evaluated. The
ring compression tribo-test was used and a friction factor was determined from the
friction calibration curves generated through finite element analysis. The following
conclusions were drawn from this study:
• The use of electricity during deformation processes has beneicial effects in
reducing flow stress, thus the energy required to reach the same level of defor-
mation as in conventional forming is lower. Also, larger strains are reached for
the same mechanical load.
• The lubricants analyzed indicated more severe tribological conditions with the
application of electricity and with the increase of current density. The higher
temperatures resulted in rapid evaporation of the lubricant and chemical decom-
position, thus the lubrication mechanism changed to a less favorable regime.
• Although the forming load, thus the interface pressure, decreased in all cases
when the electricity was applied, there is potential for even more reduction if the
lubricant withstands the effects of electricity. The higher temperatures suggest that
pressure additives are needed in order to maximize the efficiency of the process.
• The oil-based/synthetic lubricants performed better than water-based lubri-
cants. Thus, it is recommended that the development of the lubricants for EAF
should take into consideration the temperature rise, rather than just dielectric
permittivity.
References
1. Holm R (1976) Electric contacts, theory and applications. Springer, Berlin
2.Bunget C, Ngaile G (2008) Ultrasonic microforming. VDM, Saarbrucken. ISBN
978-3-639-00055-9
3. Timsit RS (2001) Connector lubricants enhance performance.
www.interconnectionworld.com
.
Accessed 06 Jun 2011
4. Bowden FP, Tabor D (1939) The area of contact between stationary and between moving sur-
faces. Proc R Soc Lond A 169(938):391-413
