Shock Absorber

Used to simulate damping and stiffness behavior in assemblies

Shock absorbers are defined by their stiffness and damping properties, which are applied between two points on the model.

  1. In the Project Tree, open the Analysis workbench.
  2. In the Analysis Workbench, select Constraints > Shock absorber.
  3. For Type, select either the Shock absorber or Grounded shock absorber radio buttons.
  4. If Type is set to Shock absorber, do the following.
    1. Select End1, and then select the spot.
    2. Repeat for End2.
  5. If Type is set to Grounded shock absorber, do the following.
    1. Select End1, and then select a spot.
    2. Switch to Ground and then enter the coordinates of the ground point.
  6. Input the stiffness and damping values for the shock absorber.
    Stiffness represents the spring constant of the shock absorber (for example, N/mm, lbf/in). Damping represents the critical damping coefficient of the shock absorber (for example, N*s/mm, lbf*s/in).
  7. Click Apply.
    The constraint will appear in the boundary conditions under a valid subcase. If selected, you will see vectors representing the connection in the modeling window.
Supported Analyses

The shock absorber boundary condition can be used in the following analysis types:

Structural Analysis
In static structural analysis, the shock absorber is treated as a linear spring, applying a force proportional to the relative displacement between the two attachment points (F=kx). The damping component (c) is not considered in a static analysis, as it is only relevant for dynamic effects.
Modal Analysis
In modal analysis, shock absorbers are used to model the stiffness and damping of the system, influencing the natural frequencies and mode shapes. The stiffness (k) and damping (c) values are included in the eigenvalue problem to accurately predict the dynamic behavior of the assembly. Damping is only supported for complex eigen value analysis. Running modes automatically run complex modes.
Multi-Loadcase Analysis
Shock absorbers are supported in multi-loadcase analyses. A common shock absorber with stiffness (damping is not considered for structural static analysis) is applied for multiple loadcases.

Important Considerations

  • Proper Unit Consistency: Ensure that the units for stiffness and damping are consistent with the units of your model. Incorrect units can lead to error results.
  • Model Simplification: The shock absorber boundary condition is a powerful tool for simplifying complex assemblies. Instead of modeling the internal components of a physical shock absorber, you can represent its behavior with two simple values (k and c), significantly reducing model complexity and computation time.