Materials Engineering: Fatigue and Its Types

A set of vocabulary flashcards defining fatigue, its various types (LCF, HCF, Thermal, Corrosion, Fretting), and the sequence of fatigue failure stages.

Fatigue

The progressive failure of a material due to repeated or fluctuating stresses below its yield strength.

Low Cycle Fatigue (LCF)

Fatigue that occurs below $105$ cycles, involving high stress levels and plastic deformation, resulting in short fatigue life; it is common in pressure vessels.

High Cycle Fatigue (HCF)

Fatigue that occurs above $105$ cycles where low stress levels are involved and elastic deformation predominates, leading to long fatigue life; common in aircraft structures.

Thermal Fatigue

Fatigue caused by cyclic temperature changes and repeated expansion and contraction, which develop thermal stresses and initiate cracks; common in turbine blades.

Corrosion Fatigue

Fatigue caused by cyclic stress in a corrosive environment, leading to decreased fatigue strength, an increased crack growth rate, and significantly reduced service life; common in marine structures.

Fretting Fatigue

Fatigue caused by small relative motion between surfaces, leading to surface wear and accelerated crack initiation; common in bolted and riveted joints.

Stages of Fatigue Failure

A five-stage process consisting of crack initiation, crack growth, crack propagation, reduction in strength, and final sudden fracture.