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