The stress below which a material can endure unlimited load cycles without failing.
Some steels have a genuine fatigue limit — below about 40% of tensile strength they survive indefinitely. Aluminium and most non-ferrous metals do not, and their fatigue strength must be quoted at a specified number of cycles, usually 10⁷ or 5×10⁸.
The practical asymmetry matters: a steel part can be designed for infinite life, and an aluminium part cannot. It is a large part of why aircraft structures are life-limited rather than infinite-life.
Assuming aluminium has an endurance limit like steel. It does not — specify a fatigue strength at a cycle count instead.
This site uses Google Analytics to count visits and see which pages are useful. It sets cookies only if you agree. See the privacy policy.