Using the Adhesion subnode, you can add adhesion properties to a contact pair. This functionality requires that the contact is modeled using the penalty method, and that no offset is used in the penalty stiffness function.
The selection of the Adhesion node is the same as that of its parent
Contact node. There can only be one
Adhesion node under a specific
Contact node.
The Adhesion subnode is only available with some COMSOL products (see
https://www.comsol.com/products/specifications/).
Select an Activation criterion to describe the onset of the adhesion between the source and destination boundaries.
When the criterion is Pressure, enter the minimum contact pressure
p0, at which adhesion is initiated.
When the criterion is Gap, enter the distance between the source and destination boundaries
δ0, at which adhesion is initiated. A negative value indicates that there must be a certain overclosure before adhesion is activated.
When the criterion is User Defined, enter a Boolean expression such that when it evaluates to true, adhesion is activated.
When the criterion is Always active, the source and destination boundaries are always in adhesive contact, unless broken by decohesion.
Select how to specify the Adhesive stiffness of the adhesive layer —
From contact penalty factor,
User defined, or
Use material data. The default is to use
From contact penalty factor, in which case the normal stiffness is the same as the
Contact pressure penalty factor specified in the settings of the parent
Contact node.
To define the tangential stiffness, select Shear stiffness defined using to be either
Normal to shear ratio or
Adhesive Poisson’s ratio. For
Normal to shear ratio, enter the ratio between the shear stiffness and the normal stiffness
nτ. For
Adhesive Poisson’s ratio, enter Poisson’s ratio for the adhesive layer,
ν, explicitly.
When Adhesive stiffness is set to
User defined, enter each component of the stiffness vector
k individually.
When Adhesive stiffness is set to
Use material data, the stiffness vector
k is computed from material data and layer thickness. From the
Specify list, select a pair of elastic properties —
Young’s modulus and Poisson’s ratio,
Young’s modulus and shear modulus, or
Bulk modulus and shear modulus. Each of these pairs define the elastic properties and it is possible to convert from one set of properties to another according to
Table 4-10. For the chosen properties, select from the applicable list to use the value
From material or enter a
User defined value or expression. In order to use
From material, you must have assigned a material to the selected boundaries.
Enter a Thickness,
ds, to specify the physical thickness of the adhesive layer.
In this section you can control how adhesive and friction forces interact. In the When adhesion activated menu, specify how friction forces are treated once the
Activation criterion for adhesion is true.
Add friction forces is the default option, which means that friction forces and adhesive force are additive. This option has the advantage that there will be a smooth transition from an adhesive bond to a pure friction state when for example a bond is broken by decohesion. Select
Ignore friction forces to disregard any friction forces once adhesion is activated. There will be no residual strength due to friction even if the adhesive bond is broken.
Physics tab with Contact selected in the Model Builder tree:
