Runtime Switching between Flexible and Rigid

A flexible body's representation can be switched between rigid and flexible during an analysis. This is useful when only a subset of an event requires flexibility in a given component. Simulation time can be reduced by treating some components flexibly for only those portions of the analysis where the result accuracy actually requires it. To use this capability one must, either in Adams View or in the .adm file, declare a flexible body to be a "dual-representation" body and specify its initial representation as rigid or flexible (modal). For details on the procedure, see the Flexible Body Modify dialog box help or the FLEX_BODY statement description within the Adams Solver documentation. Then, in an .acf one can use the extended FLEX_BODY command to switch the representation at a specific time or after a SENSOR has been triggered and returned control back to the .acf. The command syntax follows:

One can switch from rigid to flexible or from flexible to rigid. One can also perform multiple switches in the same simulation script or .acf. Whenever the representation is set to rigid, the flexible body behaves as though the inertia modeling selection is set to rigid (also known as disabling INVAR6). Since Adams 2012 flexible bodies set to have a rigid representation via the inertia modeling options perform much more closely to true rigid bodies (parts) in terms of simulation speed. This makes it much easier to compare the accuracy/performance balance of your model versus swapping true rigid parts with flexible bodies.

When post-processing a dual-representation flexible body one will of course notice that outputs specific to the flexible representation (stress/strain recovery, flexible mode states and so on.) lack any data for the duration(s) in which the representation was set to rigid. Also, one will see a significant speed up in animation for those time intervals when a flexible body is rigid since the animation code does not need to compute changes in deformations or stress/strain.