Defense Technical Information Center Compilation Part Notice ADP 014084 TITLE : Recognition and Correction of Sonic Fatigue Damage in Fighter Aircraft DISTRIBUTION : Approved for public release , distribution unlimited
High performance aircraft that fly aggressive low altitude or high-angle of attack maneuvers will experience high acoustic loading, especially in the presence of external stores. These high acoustic loadscan lead to rapid sonic fatigue in thin gage metallic structure. As a means of prolonging fatigue life, while at the same time restoring structural load carrying capability in damaged structure, composite bonded repairs which incorporate damping layers have been developed. These damped composite bonded repairs are installed on F-15 flight test aircraft. This paper describes ways to recognize sonic fatigue damage, and the design and flight test results of represeintative damped patches.
Life extension of F/A 18 intake nacelle using add-on dampers
Acoustic fatigue is due to very high intensity excitation as a result of pressure waves caused by either engine/or aerodynamic effects. Currently a large portion of the F/A-18 fleet has suffered from acoustic fatigue cracking in skin panel on the lower external surface of the inlet nacelle. There has been a long history of cracking in this region, which is attributed to fatigue caused by acoustic excitation of the panel during the operation of the aircraft. Efforts to alleviate these fatigue crack growth with traditional boron/epoxy patches was not successful. This paper seek to select a set of damping material suitable for the reinforcement/damping treatment to alleviate the acoustic fatigue damage of the nacelle panel of the F/A-18 aircraft. This experimental study will address the relevance of constrained layer damping reducing the incidence of acoustic fatigue problems in the nacelle region.
Impact of Nuclear Data Uncertainties on Transmutation of Actinides in Accelerator-Driven Assemblies
Abstract The potential impact of nuclear data uncertainties on a large number of performance parameters of reactor cores dedicated to the transmutation of radioactive wastes is discussed. An uncertainty analysis has been performed based on sensitivity theory, which underlines the cross sections, the energy range, and the isotopes that are responsible for the most significant uncertainties. To provide guidelines on priorities for new evaluations or validation experiments, required accuracies on specific nuclear data have been derived, accounting for target accuracies on major design parameters. The required accuracies (mostly in the energy region below 20 MeV), in particular for minor actinide data, are of the same order of magnitude of the achieved accuracies on major actinides. Specific requirements also concern the improvement of minor actinide data related to decay heat and effective delayed-neutron fraction assessment.