2. 2 Spring-back evaluation
Spring-back is one of the most common problems
in sheet metal forming processes. It causes improper
fit which creates serious problems during assembly
of the parts. Based on the material strength. a
considerable elastic recovery during unloading can be observed.
In the present study, the spring-back evaluation
of DP600 sheets with a thickness of 2. 5 mm was investigated
in the V-shaped die which has an angle of
60° at several temperatures (RT, 200, and 300 C)
at 25 mm/min. All spring-back measurements were
taken at room temperature after the cooling. Springback
vs temperature was plotted, as shown in Fig. 8.
It can be seen that the spring-back of the material
was decreased with increasing the temperature except
for the rolling direction at 200 'C. The springback
in the rolling direction was increased with the
temperature up to 200C and after this temperature,
the spring-back was decreased from 15.5° to 11. 92°.