Inertia Relief—Creo Ansys Simulation
Use the Inertia Relief setting to model and analyze an unconstrained model. This option is useful for models that can be considered floating freely in space, but with loads applied. If the model has constraints defined and you select the Inertia Relief option then the defined constraints are ignored and the study considers inertia relief instead.
During a study with the Inertia Relief option selected constraints are internally set using a 3–2–1 constraint set containing three-point constraints. Any constraints defined for a study are ignored and inertia relief is considered instead.
The three-point constraints affect the displacement solution but not the stress solution.
To Define Inertia Relief for a Model
You can define inertia relief for a model by using any of the following settings:
• To use the inertia relief setting for all studies in a session, click > and then select Simulation from the Applications list in the left pane. The Set Simulation Options page opens. Click Solver Settings to open the Solver Settings dialog box. Select On from the list for the Inertia Relief setting.
• For a study, click > 
Simulation Setup to open the Solver Settings dialog box. Select On from the list for the Inertia Relief setting.
Simulation Setup to open the Solver Settings dialog box. Select On from the list for the Inertia Relief setting.Best Practises when using Inertia Relief
The following are some guidelines to follow when using Inertia Relief settings in Creo Ansys Simulation:
• In mixed models you need to ensure that contacts are properly defined in order to get correct results with inertia relief. You must define contacts manually in the following cases:
◦ Beam to beam
◦ Beam to shell
◦ Beam to solid
◦ Shell to solid
• For the software to automatically define 3–2–1 constraints for a model, there must be at least 3 non-colinear points in the model. Note that for models comprised of only spheres, the software cannot use the inertia relief setting.
• For simulation studies with inertia relief ensure that the model does not have more than one disjoint body. If multiple disjoint bodies exist in your model, then the analysis fails with an underconstrained error. To run an inertia relief analysis with multiple disjoint bodies, ensure that all the disjoint bodies are connected in such a way that there is no relative motion between the bodies. If the connections are such that relative motion exists between any two bodies in the model, then the inertia relief analysis fails.