The rotor blades of a helicopter are subjected to high speeds and varying weather conditions, which could lead to fatigue failure - Leaving Cert Engineering - Question i - 2017

Fatigue failure refers to the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. This type of failure is particularly pertinent in components subjected to varying stress levels, such as the rotor blades of a helicopter.

The process begins at a microscopic level, where small cracks may form due to repeated stress cycles. These cracks typically initiate at points of high stress concentration and grow incrementally with each load cycle. Over time, the propagation of these cracks can lead to significant weakening of the material, eventually resulting in catastrophic failure.

In summary, fatigue failure is characterized by its gradual onset due to cyclic loading, starting from minute cracks that develop into larger fractures under fluctuating stress conditions.