Hello, in a recent lecture on introductory engineering, our professor made reference to a stress concentration factor that pops up due to inconsistencies or changes in the shape of a material subject to a load. The introduction he gave referenced a method of stopping cracks by drilling a hole in them, and this point didn't settle well with me. It seems counterintuitive--the only way I was able to reconcile with this idea is in--say a steel rectangular bar, that the hole's added area to the bar creates a larger surface for the crack to attempt to propagate along (the area I mean is (pi*diameter)(depth of material). Is this an incorrect way of thinking about this situation? Or does it just mean that the stress concentration factor of a crack in a member under load is greater than one with a hole in it--and why?