But a simple idea like "factor of safety" isn't very useful for "high tech" rotating machines. It's more about doing a risk analysis of the consequences of failure, and designing the machine to mitigate those consequences.
As a simple example, if a helicopter rotor blade tries to pick a fight with a large bird (e.g. a swan) with mass say 8 pounds, the blade will lose every time. The "factor of safety" comes from not picking the fight, not from design of the blade.