Decohesion
Using the Decohesion subnode, you can add decohesion properties to a contact pair. This functionality requires that an Adhesion subnode is present and active in the same parent Contact node.
The selection of the Decohesion node is the same as that of its parent Contact node. There can only be one Decohesion node under a specific Contact node.
The Decohesion subnode is only available with some COMSOL products (see https://www.comsol.com/products/specifications/).
Coordinate System Selection
The adhesive stresses are defined as boundary tractions with respect to the selected coordinate system. The selection is limited to boundary systems. Make sure that the tangents of the selected boundary system are well defined on all destination boundaries.
Decohesion
Select a Cohesive zone modelDisplacement-based damage or Energy-based damage to choose the type of variable that controls the damage process.
Select a Traction separation lawLinear, Exponential, Polynomial, or Multilinear. The definition of these differ between the two cohesive zone models, and the last option is available only for Displacement-based damage.
For the displacement-based damage models, enter:
Tensile strength, σt. This is the peak stress in pure tension.
Shear strength, σs. This is the peak stress in pure shear.
Tensile energy release rate, Gct. This is the energy released during the whole decohesion process in a state of pure tension.
Shear energy release rate, Gcs. This is the energy released during the whole decohesion process in a state of pure shear.
For the Multilinear separation law, also enter the Shape factor, λ.
When the traction separation law is Linear, Exponential, or Polynomial, select the Mixed mode criterion to be either Power law or Benzeggagh-Kenane. In either case, enter the Mode mixity exponent α. The mixed mode criterion determines how normal and shear components are combined into a single scalar failure criterion. For the Multilinear separation law, the mixed mode criterion is always linear (equivalent to a power law with  α= 1.)
For the energy-based damage models, enter:
Tensile damage threshold, G0t. This is the elastic energy at the onset of damage in pure tension.
Shear damage threshold, G0s. This is the elastic energy at the onset of damage in pure shear.
Tensile energy release rate, Gct. This is the energy released during the whole decohesion process in a state of pure tension.
Shear energy release rate, Gcs. This is the energy released during the whole decohesion process in a state of pure shear.
Mode mixity exponent, damage initiation, α0. The value determines how normal and shear components are combined into a single scalar criterion for damage initiation.
Mode mixity exponent, αc. The value determines how normal and shear components are combined into a single scalar failure criterion.
Smoothening parameter, N. This parameter adjusts the shape of the of the traction separation law. It is available for the Exponential and Polynomial options. By default, 1; a smaller value gives a smoother behavior.
In the Regularization list, it is possible to add a viscous delay to the damage growth for time dependent studies. Do this by selecting Delayed damage and enter a value for the Characteristic time, τ.
Advanced
To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box.
Maximum damage determines the residual stiffness of the adhesive layer after decohesion. By default, dmax = 1, which means that no residual stiffness remains. Enter a value smaller than 1 to introduce some residual stiffness.
Select Compute damage dissipation energy to compute and store to the energy dissipated by damage.
Including Adhesion and Decohesion, and The Decohesion Node in the Structural Mechanics Modeling chapter.
Decohesion in the Structural Mechanics Theory chapter.
Location in User Interface
Context Menus
Ribbon
Physics tab with Contact selected in the Model Builder tree: