| Abstract: | The Damage Line of the Wöhlerdiagram Sometimes, Wöhlerdiagrams are supplemented by so-called damage lines or French-lines, synonymously. Due to the statistical nature of fatigue events, however, Wöhlerdiagrams more and more are statistically ascertained and described by curves which commonly are referred as to probability-stress-cycle curves (P-S-N). Accordingly, it was to find out, whether the feature “damage” might be described in a similar way, aiming at Pd-S-N curves (Pd = Probability of damage) within the expected damage field. Using the steels Ck 35 and 34 CrMo 4 quenched and tempered, the statistically planned and evaluated investigations showed that within the Wöhlerdiagrams of these steels large damage fields can be defined which extend from far before the ranges of finite life till far into these ranges (of scatter). Pd-S-N curves are given. Satisfactory shortcut-methods for estimating such curves using features as specimens' temperature and deformation during cyclic pre-loading could not be developed. By progressively increasing and – another sample – decreasing load tests to the same account of 0,34 Palmgren-Miner-damage specimens showed remarkable differences when compared within French's concept of damage. |
