Fusion analyses of lifecycle safety and damage tolerance for cracked structures

The important problem of damage detectability is proposed and the relationship between fatigue life and damage detectability of cracked structures is elucidated through cracked gear tooth models with detailed analyses of the fatigue fracture properties and vibration modes and frequencies. It is shown that the detectability of the damage or faults in a large portion of fatigue life of the structures is poor, where the crack is relatively small. The damage detectability of a structure depends not only on the size of the crack, but also on the location and structure details of the crack and the diagnosis techniques used. It is pointed out that damage monitoring or diagnosing techniques can only be used to structures with enough damage tolerant capability and enough long detectable life duration for safety guarantee. Through the whole text, an integrated description on fusion technology of lifecycle safety guarantee of mechanical structures is provided.