| Summary: | 碩士 === 國立成功大學 === 機械工程研究所 === 83 === The plastic behavior of Ti-6Al-4V alloy during isothermal
forging has been studied. Using dimensionless spike height,
flow patterns of forgings, flow line and forging load as
indexes, the influence of the friction condition, the billet
geometry and the ram speed on the forming characteristics of
this titanium alloy was studied. A rigid-plastic finite element
analysis of this i- sothermal forging operation on hydrulic
forming machine is pre- sented by using two dimensional
computer code DEFORM. The spike test, having lateral flow and
axial filling, can be used to simulate the forging
characteristics of most products with rib-web design. For
titanium alloy, the flow stress in gen- eral has a high
sensitivity to strain rate, so effect of ram speed on the
dimensionless spike height was explored. Analyses on
conventional forging and hot-die foring were also conducted,
and the results showed that spike height of isother- mal
forging is slightly smaller than that of conventional forg-
ing, however, the forging load of isothermal forging is lower
than that of conventional forging. The spike height constructed
by this thesis can be used for preform design and die shape
design.
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