The Prescribed Displacement node adds an edge (3D), boundary (2D), or point (2D and 3D) condition where the displacements are prescribed in one or more directions. It is also possible set maximum and minimum limits for the displacements, so that for example a one-sided support can be modeled.
If any displacement component is set to Limited, an additional section
Limited displacement is visible. Select the
Method used to implement the weak inequality constraint —
Penalty or
Augmented Lagrangian. For both methods, enter a
Penalty factor kp.
By default, the Penalty method is suggested, which in principle enforces the maximum and minimum limits for the displacement by adding nonlinear springs with a stiffness equal to
kp when the limits are exceeded. This method is usually robust, but the accuracy is directly dependent on the chosen penalty factor.
The Augmented Lagrangian method adds extra degrees of freedom to improve the accuracy of the constraint. Here, the penalty factor is a numerical parameter, and has less impact on the accuracy of the constraint compared to when using the penalty method. The implementation of the augmented Lagrangian method puts no restrictions on the solver sequence, but for good convergence, proper scaling of the extra degrees of freedom can be important.
In 3D, 2D, or 2D axisymmetry, click the General notation to specify the displacements using a general notation that includes any linear combination of displacement components. For example, for 2D components, use the relationship
For H matrix
H select
Isotropic,
Diagonal,
Symmetric, or
Full and then enter values as needed in the field or matrix. Enter values or expressions for the
R vector
R.
) and select Advanced Physics Options in the Show More Options dialog box.
,