CRACK INVESTIGATION IN A FRAME OF A PASSENGER AIRPLANE STRUCTURE MADE OF ALUMINUM ALLOY 7075-T6.

This study presents investigation of a cracked piece of a passenger aircraft fuselage frame made of aluminum alloy 7075-T6. Investigation method includes chemical analysis, hardness and tensile tests in order to determine mechanical properties of the alloy, metallography and microstructural analysis, scanning electron microscopy of the fracture surface and energy dispersive spectroscopy of the precipitates and corrosion debris at grain boundaries. Although from striations observed in SEM images of the fracture surface, it is found that fatigue is the main cracking reason but other evidences prove that precipitates and corrosion pits accelerated cracks nucleation. [ABSTRACT FROM AUTHOR]