الفهرس 
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Abstract
A Study of Workability in The Upsetting of Steels
In the present study, an experimental investigation was performed for the partially-constrained and fullyrained upsetting processes of five kinds of steels; AISI 1018,1045,1078,4140 and 4340 A; to study the workability limits of Steels.
Seven die sets were designed and manufactured to study the effect of die geometry on the deformation behaviour. Specimens were prepared to the required dimensions, and
upset between the specified dies until deformation is comppleted. Photo-aided visioplastisity technique was utilized
to study the grid distorsion on specimen surfaces at every step of deformation. Negative film pieces were used to measure grid dimensions, eleminating the errors resulting
from moving specimens from the machine and returning it, or these errors resulting from using photo-papers which shrink
by time. Standard block-gauges were used as scales, giving magnification factors which differ for each position. Grid measurements were used to get strain paths. Least mean squares method was utilized to approximate the experimentallyyobtained strain paths into curves which have definite equattions. Best-fit curves were merged with the workability diagram of AISI 1045 steel, to conclude the phenomenon of dependency of workability limits on the pre-gained volume strain ratio (PVSR) of the specimens at the beginning of deformation. The rate of change of circumferential strain
to axial strain at fracture , (dE:e IdE: z) f was related to a stress formability index, S, which depends on the value of hydrostatic stress and effective stress components.
It was concluded that the partially constrained and fully-constrained upsetting processes could be used to evalluate the workability limits by adding a specified range to the workability diagram, besides other processes like free upsetting, and upsetting of tapered and flanged specimens. Relative workability of different steel types was checked. AISI 1045 and 1078 gave fractures, while 1018,4140, and
4340 A did not. (up to 712 KN) Deformation ratio and strain path curves were changed by changing die and specimen geometries.
A new factor was introduced, the pre-gained volume strain ratio (PVSR), which was defined as the difference between the actual specimen volume and die design volume, divided by the die design volume. It was concluded that the new factor could be related to the rate of change of circumferential strain to axial strain at fracture,
(d E:~d E:~ f ’ and hence could be related to the stress forrmabili ty index, S •
The new factor is very important because it can alter the strain path configuration of certain material
in certain process, and so a huge number of preforms could be checked.