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INTERACTION OF HIGH‐STRAIN AND HIGH‐CYCLE FATIGUE IN TURBINE MATERIALS
Author(s) -
Suhr R. W.
Publication year - 1992
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1992.tb01281.x
Subject(s) - strain (injury) , cycling , structural engineering , low cycle fatigue , fatigue testing , materials science , cycle count , turbine , engineering , mechanical engineering , medicine , operations management , archaeology , history
— An investigation has been conducted to examine the interaction between high‐strain and high‐cycle fatigue under combined cycling conditions on 2% NiCrMoV and a 12% CrNiMo alloy. The results reveal that the application of high‐strain fatigue cycles prior to low‐strain high‐cycle fatigue is significantly less damaging than the equivalent number of single high‐strain cycles applied between periods of high‐cycle fatigue, indicating a much greater damaging interactive effect under the combined cycling condition. A damage summation, based on high‐strain and high‐cycle fatigue initiation curves and calculated at various endurances, was found to approach zero under combined cycling conditions indicating that a prediction of damage using the Palmgren‐Miner linear damage rule is inapplicable. Cumulative damage curves, based on an assessment of hypothetical crack growth behaviour under high‐strain and high‐cycle fatigue conditions, can be constructed to explain the large departure from the Palmgren‐Miner prediction of unity. Such curves, however, fail to predict the more damaging interactive effect observed under combined cycling conditions. The apparent contradiction between experimental results and theoretical assessment is discussed and a mechanism proposed to account for the observed interactive effect.