How materials fail

Rarely by simply being overloaded.

The mechanisms

Fatigue from repeated loading, creep from sustained load at temperature, corrosion, wear, and brittle fracture from a small flaw. Each has its own warning signs and timescale.

Fatigue cracks start at surface flaws and holes, and grow invisibly for years.
Cold makes many steels brittle, which sank ships and cracked pipelines.

Designing against it

Rounded corners rather than sharp ones, surface finish, inspection intervals and a safety factor sized to the uncertainty. Failure analysis is a discipline of its own.