Linked from
The 10 pages that link to Stress concentration, each with the reason it gives.
Stress (mechanics)Related: Notches and holes can make local stress far higher than nominal stress.
FatigueRelated: Notches and defects raise local stresses where fatigue cracks often begin.
Brittle fractureRelated: Crack tips and flaws concentrate stress, making local failure likely.
BrittlenessRelated: Crack tips concentrate stress, helping brittle fractures propagate.