Linear Elastic Material
The Linear Elastic Material node adds the equations for a linear elastic truss element, and an interface for defining the elastic material properties.
By adding the following subnodes to the Linear Elastic Material node you can incorporate many other effects:
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Thermal Expansion (for Linear Elastic Material)
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Hygroscopic Swelling
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Initial Stress and Strain
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External Stress
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Damping
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Plasticity
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Activation
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Safety
Linear Elastic Material
Define the linear elastic material properties. These settings are the same as described under Linear Elastic Material for the Beam interface.
Geometric Nonlinearity
The settings in this section control the overall kinematics, the definition of the strain decomposition, and the behavior of inelastic contributions, for the material.
Select a Formulation — From study step, Total Lagrangian, or Geometrically linear to set the kinematics of the deformation and the definition of strain. When From study step is selected, the study step controls the kinematics and the strain definition.
When From study step is selected, a total Lagrangian formulation for large strains is used when the Include geometric nonlinearity checkbox is selected in the study step. If the checkbox is not selected, the formulation is geometrically linear, with a small strain formulation.
To have full control of the formulation, select either Total Lagrangian, or Geometrically linear. When Total Lagrangian is selected, the physics will force the Include geometric nonlinearity checkbox in all study steps.
When inelastic deformations are present, such as for plasticity, the elastic strain can be obtained in different ways: using additive decomposition of strains or logarithmic stretches, or using multiplicative decomposition of deformation gradients.
Select a Strain decomposition — Automatic, Additive, Logarithmic, or Multiplicative to decide how the inelastic deformations are treated. This option is not available when the formulation is set to Geometrically linear.
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When Automatic is selected, a multiplicative or additive decomposition is used with a total Lagrangian formulation, depending on the Include geometric nonlinearity checkbox status in the study step.
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Select Additive to force an additive decomposition of strains.
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Select Logarithmic to force an additive decomposition of logarithmic stretches. This option is only visible if Formulation is set to Total Lagrangian.
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Select a Method — Analytic or Padé to decide how the logarithm of the right stretch tensor is computed.
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Select Multiplicative to force a multiplicative decomposition of deformation gradients. This option is only visible if Formulation is set to Total Lagrangian.

 
The Logarithmic strain decomposition is available for Linear Elastic materials in the Solid Mechanics and Solid Mechanics, Explicit Dynamics interfaces.
The Strain decomposition input is only visible for material models that support both additive and multiplicative decomposition of the deformation gradient.
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There are some cases when a small strain formulation could be useful for a certain domain, even though the study step is geometrically nonlinear. One such case is contact analysis, where the study step is always geometrically nonlinear, but where a geometrically linear formulation is sufficient for the material.
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When a multiplicative decomposition is used, the order of the subnodes matters. The inelastic deformations are assumed to occur in the same order as the subnodes appear in the model tree.
For more information, see
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Lagrangian Formulation, Deformation Measures, and Inelastic Strain Contributions in the Structural Mechanics Theory chapter.
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Modeling Geometric Nonlinearity in the Structural Mechanics Modeling chapter.
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Study Settings in the COMSOL Multiphysics Reference Manual.
Energy Dissipation
Select how to compute the energy dissipated by Creep, Plasticity, Viscoplasticity, or other dissipative processes.
Select how to Store dissipation — From physics interface, Individual contributions, Total, Domain ODEs (legacy), or Off.

 
The option Domain ODEs (legacy) is not available in the interfaces intended for time-explicit dynamic analysis.
Use From physics interface to treat the dissipative processes as specified in the settings of the physics interface, see for instance Energy Dissipation in the Solid Mechanics interface.
Use Individual contributions to treat each dissipative process independently. Selecting this option gives a more flexible implementation for problems where dissipation occurs at different time scales, and you want to distinguish each phenomenon separately.
Use Total to accumulate all the dissipative processes into one common variable.
Use Domain ODEs to accumulate the dissipative processes into ODE variables instead of internal state variables.
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Dissipated Energy
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Energy Variables
Quadrature Settings
Select the Reduced integration checkbox to reduce the number of integration points for the weak contribution from the material.
The default is that the Reduced integration checkbox is cleared in the Truss interface and selected in the Truss, Explicit Dynamics interface.
See also Reduced Integration and Hourglass Stabilization in the Structural Mechanics Theory chapter and Using Reduced Integration in the Structural Mechanics Modeling chapter.
Location in User Interface
Context Menus
Truss > Material Models > Linear Elastic Material
Truss, Explicit Dynamics > Material Models > Linear Elastic Material
Ribbon
Physics tab with Truss or Truss, Explicit Dynamics selected:
Edges > Material Models > Linear Elastic Material