When operating at high temperature and cyclic loading conditions, materials could potentially be subjected to a significant creep-fatigue degradation mechanism. Initiation is an assessment of the formation of a small crack from an initially defect-free condition under cyclic loading at high temperature conditions. Following the initiation of a defect, continued high temperature operation can lead to further crack growth and damage to the structure, leading to adverse safety implications and repair or replacement costs and plant downtime that could have easily been prevented through early detection of issues using a creep-fatigue crack initiation assessment.
Creep is a thermally activated, time dependent mechanism which can lead to formation of cavities in the material and possibly ultimate failure of a component under load. Creep can occur in plastics and metals.