Before running any SOLIDWORKS simulation study, you need to make sure there is no interference between different components of a multibody part or an assembly. This can be done using the SOLIDWORKS interference detection tool available under Evaluate > Interference Detection.
If any volumetric interference is found within the model, it needs to be fixed prior to creating your simulation study. The only exception of this rule is for shrink fit problems. If you are creating a shrink fit study, the shrink fit faces can have volumetric interference since after the shrink fit contact is applied, these faces will come in contact to be coincident either by expanding or shrinking (therefore, there is not actually a volumetric interference in this case). That is the reason for the internal stresses created due to the shrink fit contact.
After checking for volumetric interference, you want to check for coincident faces by checking the option “Treat coincident as interference” withing the Interference Detection command.
These coincident faces are important since the global contact condition and the component contact will be applied to initially touching faces in your model.