Ejection-Seat-Quick-Release-Fitting Quantitative Fractography and Estimation of the Local Toughness using the Topography of the Fracture Surface
BUNDESWEHR RESEARCH INST FOR MATERIALS EXPLOSIVES FUELS AND LUBRICANTS ERDING(GERMANY)
Pagination or Media Count:
A Quick-Release-Fitting of an Ejection Seat broke and investigations were made to estimate the fracture mechanism on the basis of fracture surface characteristics. Fractographic based investigations normally use qualitative characteristics to purify the cause of the failure. Generally the determination of the fracture location and its origin, the kind of fracture and special features on the fracture surface are enough to describe the cause of the fracture. The aim of this investigation is to use quantitative fractography as a tool to get more information about crack propagation mechanism and also to get an estimation concerning striations, fracture topography and stretched zone. This results in a correlation to fracture mechanic concepts. During crack propagation striations were created on the fracture surface caused by the service induced load changes The distance of the striations were measured to estimate crack propagation and remaining life time. In addition a plastic stretched zone could be found on the tip of the cracks. The width of these zones gave information about local fracture toughness. The 3-dimensional zone symmetry was measured on cross sections by using stereographical methods to get more information about the crack tip and the crack propagation. To complete the failure analysis nondestructive evaluation, metallographic examination and chemical investigations were carried out. No additional cracks could be found. Most of the failed parts showed that the microstructure, the hardness and the chemical composition of the Al-alloy were within the specification, but some of the cracked parts were manufactured with an other material as specified.
- Fabrication Metallurgy