Process page enables the setup of basic process parameter for
superplastic forming such as pressure curve, percent to terminate, tool
contact, desired strain rate, termination time, etc. The user can modify
process parameters according to practical situation. The Process page for
superplastic forming is illustrated in Figure 8.7.1.
The user can select one or two phase analysis. If one phase analysis is
selected, the sheet is directly formed into the final part shape by applied
pressure. If two phase analysis are selected, preforming is performed in the
first phase to partially or fully make the sheet to conform to preformed die.
In the second phase, reverse pressure is applied to confirm the sheet to die
geometry to obtain the final part shape. Pressure and reverse pressure are
usually used for superplastic forming process to obtain even part thickness.
PHASE I
Define parameters such as pressure curve, percent to terminate and
contact tool.
PRESSURE CURVE
Click on <none> button to define pressure curve using the Load
Curve dialog box described in previous section.
CONTACT TOOL
Select tools contacting with the sheet.
PERCENT TO TERMINATE
Enter the contact node percent between sheet and selected contact tool.
The user can use contact node percent to control the termination time of this
phase. If the sheet contacts with 80% nodes of the contact tool, this forming
phase is terminated.
Figure 8.7.1 Process page
PERCENT TO AUTOJUMP
Key in the contact node percent in this field if autojump option is
selected in the Advanced dialog box. The current phase is automatically
terminated if the contact nodes reach the input percent.
PHASE II
If the part is formed in two phases, the definition of parameters for
Phase II is added to the interface. The definition of parameter for Phase II is
similar to Phase I. Refer to the above description.
COMMON
DESIRED STRAIN RATE (ERATE)
Set desired strain rate. Strain
rate is the derivative of equivalent plastic strain with respect to time.
ADVANCED
Set advanced forming parameters. Refer to LS-DYNA Keyword User’s Manual
for description about advanced setting.
Figure 8.7.2 Advance setting for superplastic forming