FAILURE ANALYSIS OF NIGERIAN AIR FORCE BEETLE (ABT-18) NOSE WHEEL STRUT

Abstract

This research centres on failure analysis of the nose wheel strut of the Nigerian Air Force trainer aircraft, ABT-18, which collapsed especially during hard landings. Visual examination with the unaided eye and fractography revealed beach marks on the fracture surface which indicates fatigue failure characteristic of brittle fracture. The fractograph of the fracture surface shows high energy fracture. Chemical analysis of the as-received failed nose wheel strut was carried out. The results showed that the material is medium carbon steel of the tough grade and not the required spring steel. The experimental procedure consists in the characterization of fracture aspects of the standard and failed nose wheel struts using mechanical tests and metallographic methods of analysis. The results of the mechanical tests revealed that there is loss of strength and ductility in the failed sample as a result of fatigue. Micr0'structural examination revealed fatigue cracks in the failed sample, which led to failure. These cracks propagated from the dark inclusions present in the microstructure. Re-selection of spring steel material is a suggested appropriate solution.