Structural components used in equipment operating at high temperatures, such as much of that used in the petrochemical industry, typically undergo operational cycles that give rise to coupled thermal-mechanical loadings, often in an aggressive environment. These cyclic loadings cause damage or degradation in the material that eventually culminates in crack nucleation and growth. In the advanced state of this damage process--crack growth--the service capacity of the structure may be reduced. Ultimately, unless the component is removed from service during the crack growth period, it may fail catastrophically causing an untimely loss in production and damaging other parts of the structure. Clearly, it is worthwhile to design against thermal-mechanical fatigue damage that culminates in cracking. Design against this damage mechanism involves the judicious combination of experience, prototype testing in advanced stages of the design/analysis cycle, and fatigue analysis during the preliminary stages of the design/analysis cycle. This paper examines important considerations in the thermal-mechanical fatigue evaluation of metallic materials, an essential part of the fatigue analysis phase in design against cracking in petrochemical components.
