What is Metal Low-Cycle Fatigue Fracture?

Parts that experience low-cycle fatigue fracture are subjected to forces that are close to or exceed the yield strength of the material, with a relatively low loading rate, usually measured in minutes, hours, or even longer periods.

One characteristic of low-cycle fatigue is the presence of multiple fatigue origins on the macroscopic fracture surface.

The fracture surface is relatively rough, somewhat resembling a static tensile fracture. The microscopic feature of low-cycle fatigue is that the fatigue striations are relatively coarse.

For ultra-high-strength steel, if the loading frequency is low and the amplitude is large, fatigue striations may not appear on the low-cycle fatigue fracture surface.

Sometimes, microscopic features resembling tire patterns can be observed in the fracture propagation zone.