Activation
Use the Activation subnode to activate or deactivate parts of a domain according to an Activation expression that you define. The Activation subnode uses a scale factor that reduces the elastic stiffness and density of the material, to emulate that material is not present. When the Activation expression is satisfied, the material is activated in a state of zero stress.
When the material is not active, the following is done to emulate that the material is not present:
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The elasticity matrix is multiplied by the Activation scale factor.
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The density is multiplied by the square of the Activation scale factor.
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If viscoelasticity is present, shear and bulk moduli, as well as relaxation times, are scaled using the Activation scale factor.
When the material is activated, the following is done to ensure that the activation is stress free:
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At the instant of activation, that is when the Activation expression is first satisfied, the elastic strains corresponding to the previous time or parameter step are removed from the total strains.
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Initial stresses are always removed, regardless of the Activation expression.
External stresses are never removed, regardless of the Activation expression.
The Activation subnode can be used in combination with Linear Elastic Material, and in the Wire interface with Elastic Wire.
Activation
Enter the Activation expression. This is the expression that will determine whether material is active or inactive.
Enter the Activation scale factor. The default value is 10−5.
The Activation subnode is only available with some COMSOL products (see https://www.comsol.com/products/specifications/)
See also Activating and Deactivating Material in the Structural Mechanics Modeling chapter.
Location in User Interface
Context Menus
Solid Mechanics>Linear Elastic Material>Activation
Layered Shell>Linear Elastic Material>Activation
Membrane>Linear Elastic Material>Activation
Truss>Linear Elastic Material>Activation
Wire> Elastic Wire>Activation
Ribbon
Physics tab with Linear Elastic Material or Elastic Wire node selected in the model tree:
Attributes>Activation