Abstract
Concepts for crack propagation as well as fatigue assessment under
variable mechanical and thermal loadings are unestablished. For variable
mechanical loadings, the damage parameter PJ is well
known, for thermal loadings the damage parameter DTMF is
established. Both parameters base on the effective cyclic J-Integral,
still the definition is different. The damage parameters
PJ considers the effective stress and strain ranges from
the upper reversal point of each load cycle to the point of crack
closure. Depending on the loading sequence the point of crack closure is
treated as a history variable. In addition, with a crack length
dependant fatigue limit, the most important sequence effects are
considered. A new PJ-based concept is developed by
considering additional sequence effects. In comparison to experimental
results, the developed concept is able to reduce scattering in the range
of constant amplitude loading tests.