Development of Multiaxial Fatigue Damage Assessment Methods Considering High Cycle Fatigue (HCF)/Low Cycle Fatigue (LCF) Interactions
Final rept. 18 Feb 2004-31 Mar 2006
NORTH DAKOTA STATE UNIV FARGO DEPT OF MECHANICAL ENGINEERING
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The objective of this study was to investigate the interaction between LCF highly damaging and HCF low damage cycles for a multiaxial stress state. This issue is of great importance in the development of reliable fatigue damage assessment methodologies, as aircraft mission spectra typically contain a large number of HCF cycles coupled with a much smaller number of LCF cycles. Past research in the areas of cycle interactions and damage accumulation have offered contrasting results. Some studies have indicated that small cycles at or near threshold levels have little effect on the total fatigue life and can be neglected, allowing for use of a linear damage accumulation Palmgren-Miner rule. Other studies, however, have demonstrated that linear damage summation methods may be highly nonconservative, indicating a strong interaction effect exists between LCF and HCF cycles, and the sequence of loading may be an important factor. The majority of these studies were conducted under uniaxial loading conditions, and thus may have limited applicability to multiaxial loadings where non-proportional load paths may alter the interaction. The consideration of cycle interactions within a multiaxial stress state gives rise to some additional challenges, such as cycle definition for non-proportional loadings and the load-path dependence on the interaction effect.
- Test Facilities, Equipment and Methods
- Statistics and Probability