What is the characteristic of injection mold of fatigue failure

Injection mould fatigue failure characteristics: after a certain of mold parts, sprouted a tiny crack, and gradually expand to the deep, expanded to a certain size, the bearing capacity of the severely weakened the mold caused by the rupture. Fatigue crack initiation in stress larger area, especially the stress concentration area, the fatigue crack fracture surface is divided into two parts, part of the formation of fatigue crack development by fatigue rupture section, presents the shells, fatigue source is located in the shell. The other part is all of a sudden rupture, appear uneven rough section.