Fatigue: Fatigue is a phenomenon in which a metal material is subjected to alternating loads for a long time (i.e. loads with repeated changes in shape and direction) and breaks suddenly without obvious plastic deformation, which is called fatigue. Fatigue index includes fatigue limit and fatigue strength.




Fatigue limit: The maximum stress that a metal material can bear without repeated fracture after repeated (N) stress cycle is called fatigue limit.


FATIGUE STRENGTH: The maximum stress that a metal material can withstand after repeated (N) fracture under repeated or alternating stresses is called fatigue strength. At this time, N is called the fatigue life of materials. Some metal materials have no obvious fatigue limit under repeated or alternating stresses, which is usually expressed by fatigue strength.