Creep is defined as plastic (permanent) deformation occurring at high temperature under a constant load over a long time period. For pressurised components operating in the high-temperature regime creep is the governing damage mechanism. Thus design and lifetime assessment have to be based on the correct understanding of the basic phenomena of creep but also on the specific relationship to e.g. material conditions and the interaction to other relevant damage mechanisms.
Part 1 of the presentation refers to the basics of creep. By means of uniaxial creep tests the creep behaviour and rupture characteristics will be gained. The main stages: development of plastic creep deformation and the link to the changes in the microstructure, formation of creep cavities mainly at grain boundaries and subsequent micro cracks, creep crack growth and failure will be described. The main influencing parameters as material state and the temperature and their impact on creep strength will be shown. The problem of long-term extrapolation and creep rupture data scattering will be discussed, as well as the use of these data in the formulation of the “user models” in the non-linear FE-analysis.
In Part 2 the problem of transferability to components will be treated. This relates to the possibilities and limitations of detection of the first stages of creep damage by means of non-destructive methods but also to the risk of premature creep failure in the heat affected zone of fully weldments.
Part 3 deals with creep laws and models for the FE simulation and numerical (FE) computation of creep loaded components considering the effects of multiaxial stress state and creep damage development.
Introduction and CCOPPS Update
Prof. Aleksandar Jovanovic, Director of Steinbeis Advanced Risk Technologies
Creep Loading of Pressurized Components - Phenomena and Evaluation
Prof. Karl Maile, MPA University of Stuttgart
Q & A Session