27. SOLID_MECHANICS_BC Namelist
27.1. Overview
The SOLID_MECHANICS_BC namelist is used to define boundary conditions for the solid mechanics model at external and internal boundaries. Each instance of the namelist defines a particular condition to impose over a subset \(\Gamma\) of the domain boundary. The boundary subset \(\Gamma\) is specified using mesh face sets. The namelist variable face_set_ids takes a list of face set IDs, and the boundary condition is imposed on all faces belonging to those face sets. Note that ExodusII mesh sides sets are imported into Truchas as face sets with the same IDs. Displacement x/y/z boundary conditions may alternatively be applied to node sets with the namelist variable node_set_ids.
External boundaries
The following types of external boundary conditions can be defined. The outward unit normal to the boundary \(\Gamma\) is denoted \(\hat{n}\). Note the solid mechanics package defaults to a traction-free surface with no displacement constraints at external boundaries.
Traction An applied traction condition \((\sigma \cdot \hat{n}) \cdot \hat{m}=\tau_b\) for a given vector \(\hat{m}\) on \(\Gamma\) is defined by setting type to traction-n, traction-x, traction-y, or traction-z. The boundary value \(\tau_b\) is specified using either traction for a constant value, or traction_func for a function.
Displacement A dirichlet displacement condition \(u=u_b\) on \(\Gamma\) is defined by setting type to displacement-n, displacement-x, displacement-y, or displacement-z. The boundary value \(\tau_b\) is specified using either displacement for a constant value, or displacement_func for a function.
Internal interfaces
Internal interfaces are merely coincident pairs of conforming external mesh boundaries. These are modifications to the mesh created by Truchas and are defined using the Interface_Side_Sets parameter from the MESH namelist. Only the face set IDs referenced there can be used in the definition of the following interface conditions. The following types of internal interface conditions can be defined.
Gap Contact. A gap contact condition models no-penetration sliding contact along internal surfaces \(\Gamma\). It is defined by setting type to gap-contact.
27.2. SOLID_MECHANICS_BC Namelist Features
27.3. Components
name
face_set_ids
node_set_ids
type
Option |
Description |
|---|---|
displacement-n |
Normal displacement is prescribed on the boundary. Use displacement or displacement_func to specify its value. |
displacement-x |
X-direction displacement is prescribed on the boundary. Use displacement or displacement_func to specify its value. |
displacement-y |
Y-direction displacement is prescribed on the boundary. Use displacement or displacement_func to specify its value. |
displacement-z |
Z-direction displacement is prescribed on the boundary. Use displacement or displacement_func to specify its value. |
traction-n |
Normal traction is applied on the boundary. Use traction or traction_func to specify its value. |
traction-x |
X-direction traction is applied on the boundary. Use traction or traction_func to specify its value. |
traction-y |
Y-direction traction is applied on the boundary. Use traction or traction_func to specify its value. |
traction-z |
Z-direction traction is applied on the boundary. Use traction or traction_func to specify its value. |
gap-contact |
An internal interface sliding contact condition. |