#### ACTIVATE_ELEMENTS

###### Mesh commands
*ACTIVATE_ELEMENTS
"Optional title"
coid, entype, enid, $t_{birth}$, $t_{death}$, $\xi$
##### Parameter definition
VariableDescription
coid Command ID
entype Entity type
options: ES, G, GS, P, PS
enid Entity ID
$t_{birth}$ Time or FUNCTION defining element activation
$t_{death}$ Time or FUNCTION defining element deactivation
$\xi$ Optional strength of not yet activated elements
default: 0
##### Description

This command lets the user activate or deactivate elements at a pre-defined time or on a certain signal. If a FUNCTION is used an element is activated or deactivated on function values > 0.

The optional constant $0 \le \xi \le 1$ is used to scale the internal forces of unactivated elements. $\xi$ is typically used in situations where nodes of unactivated elements are part of a MERGE interface and where the nodes need to be active from time 0 to avoid the formation of gaps. A typical application is weld seams where the weld elements need to follow the deformation of the base material. Else they will not be activated at the correct location.

##### Example
###### Multiple activations/deactivations with function

An element is activated/deactivated each time the element in motion is in close proximity to it with function ID 1000 and 2000.

*PARAMETER
%tend = 0.05, "Termination time"
%L = 0.1, "Element side length"
%S = 0.2, "Distance between boxes"
%n = 4, "Number of boxes"
*TIME
[%tend], , , [%tend/10000]
*OUTPUT
[%tend/100]
*UNIT_SYSTEM
SI
~repeat [%n]
*COMPONENT_BOX
[r1], [r1], 1, 1, 1
[(r1-1)*(%L+%S)], 0, 0, [r1*%L+(r1-1)*%S], [%L], [%L]
*OUTPUT_SENSOR
[r1], [r1], [(r1-1)*(%L+%S)+(%L/2)], [%L/2], [%L/2]
*PART
[r1], 1
~end_repeat
*MAT_ELASTIC
1, 7800, 210e9, 0.3
*INITIAL_VELOCITY
P, 2, 100
*CHANGE_P-ORDER
ALL, 0, 3
*BC_MOTION
ALL, 0, YZ
*SET_PART
134
1, 3, 4
*BC_MOTION
PS, 134, X
*CONTACT
1
ALL, 0, ALL, 0
#
# --- ACTIVATE ELEMENTS ---
#
*ACTIVATE_ELEMENTS
1, P, 3, fcn(1000), fcn(2000)
*FUNCTION
1000
abs(xs(3)-xs(2))-%L
*FUNCTION
2000
-(abs(xs(2)-xs(3))-%L)
*END
###### Deactivation with coordinates

ACTIVATE_ELEMENTS is used to remove elements at the end of the bar as they go outside the range defined in function ID 222.

*UNIT_SYSTEM
SI
*TIME
0.001
*COMPONENT_BOX
1, 1, 30, 4, 4
-0.15, -0.01, -0.01, 0.15, 0.01, 0.01
*MAT_METAL
1, 7800.0, 210.0e9, 0.3
1
*FUNCTION
1
1.0e9 + 1.0e9*epsp^0.4
*PART
1, 1
*INITIAL_VELOCITY
P, 1, fcn(123)
*FUNCTION
123
4.0e3*x
#
# --- DEACTIVATING ELEMENTS ---
#
*ACTIVATE_ELEMENTS
"remove elements at the ends"
1, P, 1, 0, fcn(222)
*FUNCTION
222
H(abs(x) - 0.18)
*END
###### Deactivation with damage

ACTIVATE_ELEMENTS is used to remove elements based on damage. Element set ID 123 is evaluated in function ID 333. The elements in the element set are deactivated as the damage value exceeds 0.6.

*UNIT_SYSTEM
SI
*PARAMETER
%tend = 0.0001, "Termination time"
*TIME
[%tend], , , [%tend/1000]
*COMPONENT_BOX
1, 1, 30, 2, 2
-0.15, -0.01, -0.01, 0.15, 0.01, 0.01
*MAT_METAL
1, 7800.0, 210.0e9, 0.3, 1
1
*PROP_DAMAGE_CL
1, 1
500.0e6
*FUNCTION
1
1.0e9 + 1.0e9*epsp^0.4
*PART
1, 1
*INITIAL_VELOCITY
P, 1, fcn(123)
*FUNCTION
123
3.0e3*x
#
# --- DEACTIVATING ELEMENTS ---
#
*ACTIVATE_ELEMENTS
"remove elements based on damage"
1, ES, 123, 0, fcn(333)
*SET_ELEMENT
123
15, 16, 45, 46, 75, 76, 105, 106
*FUNCTION
333
H(dmg_es(123)-0.6)
*END