# Activate

Command ElementSwitches on a formerly deactivated model element, and the modeling element can then be subsequently used in an analysis.

## Format

<Activate
element_type   = "string"
element_id     = "integer"
/>

## Attributes

element_type
Specifies the type of the element to be activated. See Comment 1 for valid element types.
element_id
Specifies the ID of the element to be activated.

## Example

<Activate
element_type = "JOINT"
element_id   = "301002"
/>

1. The element_type must be one of the following keywords:
Keyword
Corresponding model element(s)
"BEAM"
Force_Beam
"BUSH"
Force_Bushing
"CONTACT"
Force_Contact
"COUPLER"
Constraint_Coupler
"CVCV"
Constraint_CVCV
"CVSF"
Constraint_CVSF
"DIFF"
Control_Diff
"FIELD"
Force_Field
"FORCE"
All action forces.
"FRICTION"
Force_JointFriction
"GCON"
Constraint_General
"GEAR"
Constraint_Gear
"GFORCE"
Force_Vector_[One|Two]Body - Force and torque
"GSE"
Control_StateEqn - of type USERSUB
"JOINT"
Constraint_Joint
"JPRIM"
Constraint_Jprim
"LSE"
Control_StateEqn - of type LINEAR
"MATE"
Constraint_Mate
"MFORCE"
Force_FlexModal
"MOTION"
Motion_Joint or Motion_Marker
"NFORCE"
Force_MultiPoint
"PFORCE"
Force_Penalty
"PTCV"
Constraint_PTCV
"PTDCV"
Constraint_PTdCV
"PTDSF"
Constraint_PTdSF
"PTDSFF"
Force_PTdSF
"PTSF"
Constraint_PTSF
"SENSOR"
Sensor_Event or Sensor_Proximity
"SFORCE"
Force_Scalar_[One|Two]Body - Force or Torque
"SFSF"
Constraint_SFSF
"SPDP"
Force_SpringDamper
"TFSISO"
Control_SISO
"UCON"
Constraint_UserConstr
"VFORCE"
Force_Vector_[One|Two]Body - Force only
"VTORQUE"
Force_Vector_[One|Two]Body - Torque only
"YFORCE"
Force_StateEqn
2. Constraints such as joints (Constraint_Joint) and joint primitives (Constraint_Jprim) are frequently used to "temporarily" constrain a system such an automobile, so that static equilibrium can be more easily found. In this scenario, the system has a neutral equilibrium position - the automobile can come to equilibrium anywhere in the X-Y plan that represents the ground.
3. The Activate command may also be used to simulate the "breaking" of a rigid body. A rigid body is defined as an assembly of two rigid bodies connected together with a fixed joint. As long as the fixed joint is active, the two bodies behave together like one body. The forces in the fixed joint may be monitored, and when they reach a critical value, the fracture value, the fixed joint is replaced with a revolute joint that allows free rotation about one axis. This is accomplished most easily by (a) deactivating the fixed joint, and, (b) activating a previously deactivated revolute joint.
4. Activate in conjunction with Deactivate may be used to change the topology of the model during a simulation. For instance, the docking of a space ship on the space station may end in the "activation" of a joint that firmly connects the space ship to the space station.