New concept to crack growth at high temperature creep and creep-fatigue

ABSTRACT A new parameter, the Q* parameter is proposed for the characterization of high temperature creep crack growth. Using this parameter, the data on SUS 304 stainless steel and Cr-Mo-V steel were well characterized covering the initial or so-called tail part of da/dt diagram except the threshold part. The experimental formulation of the Q* parameter and the physical and mechanical. meaning were explained. Then the relation of the Q* parameter and C* or Δ was derived. Finally, the Q* was shown to be applied to high temperature creep-fatigue and fatigue. For creep-fatigue, it was suggested to treat the problem as composed of the two different thermal activated processes in order to get more exact expression of the Q* parameter.