Damage
Use the Damage subnode to model damage and cracking in brittle materials according to various criteria. It is available with the Linear Elastic Material in the Solid Mechanics and Layered Shell interfaces, and with the Layered Linear Elastic Material in the Shell interface.
Shell Properties

 
This section is only present when Damage is used as a subnode to:
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Linear Elastic Material in the Layered Shell interface. See the documentation for the Damage node in the Layered Shell chapter.
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Layered Linear Elastic Material in the Shell interface. See the documentation for the Damage node in the Shell and Plate chapter.
Damage
Select the type of Damage model — Scalar damage, Mazars damage for concrete, or Phase field damage. Then follow the instructions below.
Scalar Damage
Select the type of Equivalent strain — Rankine, stress; Rankine, strain; Smooth Rankine, stress; Smooth Rankine, strain; Norm of elastic strain tensor; or User defined. See Strain-based Damage Models for details.
The Activate damage in compression check box is available for the Rankine, stress; Rankine, strain; Smooth Rankine, stress; Smooth Rankine, strain; or User defined equivalent strain definitions, and it is not selected by default. When selected, the damage evolution law is applied on the total undamaged stress tensor.
Select the type of Damage evolution — Linear strain softening, Exponential strain softening, Polynomial strain softening, Multilinear strain softening, or User defined. See Damage Evolution for details.
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For Linear strain softening, Polynomial strain softening, Multilinear strain softening or Exponential strain softening enter the Tensile strength σts, the default is to take the value From material. Change to User defined to enter other value or expression.
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For User defined, enter an expression for the Damage evolution function d(κ).
For Linear strain softening or Exponential strain softening select the type of Strain softening input and enter the Fracture energy per area Gf, the Fracture energy per volume gf, or the Strain softening parameter εf accordingly. The available options depend on the spatial regularization method selected.
For Multilinear strain softening, also enter the Shape factor λ. Its default value is 0.5.
Select the type of Spatial regularization method — None, Crack band, or Implicit gradient. See Spatial Regularization for details.
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For the Crack band method select the type of Crack band calculation — Element volume/area, or Element size. Note that when the Crack band method is selected, only the Fracture energy per area is available as Strain softening input.
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For the Implicit gradient method enter the Internal length scale lint. If the Fracture energy per area was selected as Strain softening input, enter also the Characteristic size of the damage dissipation zone hdmg. The Implicit gradient method is available in the Solid Mechanics and Layered Shell interfaces.
Select the type of Viscous regularization method — None or Delayed Damage.
For the Delayed damage method, enter the Characteristic time τ. The Delayed damage method is intended for time dependent studies, and adds no contributions for other study types. See Viscous Regularization for details.
Mazars Damage for Concrete
Select the type of Equivalent strain — Mazars, Modified Mazars, or User defined. See Mazars Damage for Concrete for details.
Enter the Shear exponent β, the default is set to 1.06.
Select the Tensile damage evolution — Linear strain softening, Exponential strain softening, Mazars damage evolution function, or User defined.
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For Linear strain softening or Exponential strain softening enter the Tensile strength σts, the default is to take the value From material. Also select the type of Tensile strain softening and enter the Fracture energy per area Gft, the Fracture energy per volume gft, or the Strain softening parameter εft accordingly.
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For Mazars damage evolution function, enter the Tensile strain threshold ε0t, and the Tensile damage evolution parameters At and Bt.
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For User defined, enter an expression for the Tensile damage evolution function dt(κ).
Select the Compressive damage evolution — Mazars damage evolution function or User defined.
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For Mazars damage evolution function, enter the Compressive strain threshold ε0c, and the Compressive damage evolution parameters Ac and Bc.
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For User defined, enter an expression for the Compressive damage evolution function dc(κ).
Select the type of Spatial regularization method — None, Crack band, or Implicit gradient. See Spatial Regularization for details.
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For the Crack band method select the type of Crack band calculation — Element volume/area, or Element size. Note that when the Crack band method is selected, only the Fracture energy per area is available as Strain softening input.
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For the Implicit gradient method enter the Internal length scale lint. If the Fracture energy per area was selected as Strain softening input, enter also the Characteristic size of the damage dissipation zone hdmg. The Implicit gradient method is available in the Solid Mechanics and Layered Shell interfaces.
Select the type of Viscous regularization method — None or Delayed Damage.
For the Delayed damage method, enter the Characteristic time τ. The Delayed damage method is intended for time dependent studies, and adds no contributions for other study types. See Viscous Regularization for details.
Phase Field Damage
The Phase field damage model is available with the Linear Elastic Material in the Solid Mechanics interface. See Phase Field Damage Models for details.
Select the type of Crack driving force — Strain energy density or Principal stress criterion. See Crack Driving Force for details.
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For Strain energy density, enter a value for the Critical energy release rate Gc, and the Strain energy threshold Gc0.
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For Principal stress criterion, enter a value for the Critical fracture stress σc, and the Post-peak slope parameter ξ.
Enter a value for the Internal length scale lint.
Select the Damage evolution function to use — Power law; Cubic, Borden; or User defined. See Damage Evolution for Phase Field Damage for details.
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For Power law, enter a value for the Exponent m. The default is to use a quadratic function so that m=2.
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For Cubic, Borden, enter a value for the Model parameter s. This option is available when Crack driving force is set to Strain energy density.
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For User defined, enter an expression for the Damage evolution function d(φ).
Select an option for Exclude compressive energy — Volumetric only; Spectral decomposition, stress; Spectral decomposition, strain; or No. See Strain Energy Split for details.
The Viscous regularization check box is not selected by default. When selected, a viscous term is added to the evolution of the crack phase field in time dependent studies. When selected, enter a value for the Characteristic time τ. See Viscous Regularization for details.
Advanced
Enter the Maximum damage. The default value is 0.99999.
Discretization
This section is available with the Phase field damage model. Select the Lagrange order of the Crack phase field φ — Same as displacement field, Linear, Quadratic, Cubic, Quartic, or Quintic.
The Damage subnode is only available with some COMSOL products (see https://www.comsol.com/products/specifications/).
When a Mixed Formulation is selected in the parent Linear Elastic Material, the damage model can give spurious results. The Implicit gradient regularization method is more stable in this respect, and it is recommended when using the mixed formulation.
See also
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Modeling Damage in the Structural Mechanics Modeling chapter.
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Damage Models in the Structural Mechanics Theory chapter.
Location in User Interface
Context Menus
Solid Mechanics>Linear Elastic Material>Damage
Shell>Layered Linear Elastic Material>Damage
Layered Shell>Linear Elastic Material>Damage
Ribbon
Physics tab with Linear Elastic Material or Layered Linear Elastic Material, node selected in the model tree:
Attributes>Damage