A New Scatter Band Assessment Procedure for Multi-heat Fatigue Life Data

摘要

Two methods for fatigue life data assessment were introduced and verified for Low Cycle Fatigue tests od a 10%Cr-steel grade. With these methods mean fatigue life curves were calculated withrn1. regression analysis for single temperaturesrn2. temperature dependent approach on the basis of a cyde-temperature-paramelerrnA first method shows an acceptable fit of the experimental data. However, an unfavourable cross-over of mean curves could only be avoided with a graphical optimization, which affects the repeatability of the assessment procedure adversely. Further the description of the plastic strain amplitude is non satisfying. A second method represents a new procedure. This temperature dependent description of the fatigue lite behaviour is based on a cycle-temperaiure-parameter which is developed from the hysteresis loop at mid fatigue life time. The necessary data can be derived from the standard assessment of LCF tests. This second method delivers an acceptable description of multi-heat fatigue life in comparison to the first method. Summarizing it can be stated that an analytic procedure was developed which considers the influence of temperature in a suitable way and which allows to determine mean curves and scatter band parameters in a reproducible manner. Future work will focus on the influence of hold times and of strain rates. An extension of the assessment method for different materials and temperature ranges is also planed.