Simulation results are only as good as the information entered in by the end user, so no software vendor will take on the liability of saying a part will not fail when they have no control of the data being entered or any understanding of the parts operating environment.
As far as material properties go, the yield stress is the ideal stress at which a part will start to fail. If you perform an analysis and the maximum stress is below the yield stress, ideally it will not fail. Since the real world is not ideal we typically apply reduction factors to the Yield stress to determine the allowable stress. For example, if you perform a static analysis on an engine mount you need to account for the vibration in the operating environment. Typically high cycle vibration will reduce the yield stress by 50%. Variability in how the part is machined or cast could reduce the yield by another 10-15%. Higher temperatures will reduce the Yield stress, as does being in a corrosive environment such as salt air.
So depending on how the part is used, its operating environment and a host of other factors, determines the allowable stress, and these are factors you cannot model. A36 Steel has a yield stress of 220 MPa. In some cases the allowable stress may be close to 220 MPa. However, it you are designing an engine mount for an ocean going vessel teh maximum allowable stress could be around 100 MPa or less.
If you are working on a specific problem right now and are trying to figure out if something will fail or not, please provide us with more detail and we will see how we can help you out.
I hope this helps.