Showing 2 results for SHOKOUH FAR A.
Sedghi A., Shokouh Far A., Eslami Farsani R.,
Volume 2, Issue 3 (Apr 2005)
Abstract
Carbon fibers are fabricated from different materials such as special polyacrylonitrile (PAN) fibers, cellulose fibers and pitch. But PAN fibers are recognized as the most widely used precursor for the present-day manufacture of carbon fibers. The process of fabrication carbon fibers from special PAN fibers is composed of two steps including oxidative stabilization at low temperature and carbonization at high temperatures in an inert atmosphere. Today carbon fibers are still expensive because of the high price of their raw material (special PAN fibers).This study focuses on making carbon fibers from commercial PAN fibers (low price PAN fibers used in textile industry). The results shows that in case of conducting complete stabilization process, it is possible to produce desirable carbon fibers from commercial PAN fibers. With some changes in conventional procedure of stabilization in terms of temperature and time of operation, the desirable conditions of complete stabilization are achieved.
Abbasi S.m., Shokouh Far A., Ehsani N.,
Volume 3, Issue 3 (Jul 2006)
Abstract
In this study the hot deformation behaviour of a precipitation hardened (PH) stainless steel at high strain rates has been predicted through hot compression testing. Stress-strain curves were obtained for a range of strain rates from 10-3 to 10+1 S-1 and temperatures from 850 to 1150°C. Results obtained by microstructure and stress-strain curves show that at low temperatures and high strain rates, where the Zener-Holman parameter (Z) is high, work hardening and dynamic recovery occure. By increasing temperature and decreasing strain rate, the Z parameter is decreased, so that dynamic recrystallization is the dominant softening mechanism. The results were fitted using a Log Z versus Log (sinh (a sp) diagram allowing an assessment of the behavior of the stresses measured at strain rates closer to those related to the industrial hot rolling schedules. It is clearly shown that the data collected from low strain rate testing can be fairly reasonably extrapolated to higher orders of magnitude of strain rate.
