Abstracts Book - IMRC 2018

• SE1-O002
EXPLOITATION OF MATERIALS SOFTENING IN PULSATION-
IMPOSED HOT SHEET METAL FORMING IN COMBINATION WITH
RAPID COOLING TO IMPROVE THE FORMABILITY
Peter Birnbaum 1 , Verena Kraeusel 1 , Dirk Landgrebe 1
1 Technische Universität Chemnitz, Professorship for Forming and Joining, Germany.
Servo lead screw presses become progressively important for the sheet metal
forming industry due to the high flexibility in motion profiles. This allows for
various combinations of acceleration, motion, and temporary stops of the
forming tool. The newly developed press technology of cushion-ram pulsation
(CRP) utilizes these advantages, for instance to reduce wrinkling and optimize
lubrication. In combination with hot sheet metal forming, the pulsation at
forming causes material phenomena which can be exploited to increase the
formability.
The developed process is investigated with the help of FE simulation, using the
software Simufact Forming V13. The simulated model provides theoretical
values for strain states, strain rates, holding periods, forming temperatures and
cooling rates. The experiments are conducted on the basis of these parameters
with the help of the forming simulator BAEHR DIL 805 A/D. The forming
properties at defined temperatures and cooling rates as well as static softening
at forming stops are analysed. An optimized process route is developed on the
basis of experimental results of forming and softening at characteristic
temperatures. Subsequently, deep drawing experiments of cups confirm the
developed process technology.
The combination of CRP and rapid cooling of austenitized steel leads to
improved forming properties as a result of materials softening. The performed
investigations focus on the material behaviour at stepwise forming and rapid
cooling of manganese-boron steel 22MnB5. Targeting the materials
phenomena, there are two general mechanisms that need to be taken into
account. At first, dynamic softening occurs during hot sheet metal forming which
depends mainly on the forming rate and the temperature. The second
mechanism for enhanced formability is static softening. This occurs at holding
periods of stepwise forming if sufficient time is provided for static recovery and
recrystallization. The degree of static softening mainly depends on holding time,
temperature and the degree of forming. Preheated forming tools lead to