Failure of a Landing Gear Steel Pin

A transverse cross-section through the fracture initiation site was examined by metallography. The fracture surface profile was found to be relatively flat and there was no crack branching. The microstructure showed dark-etching-tempered martensite. Further no plastic deformation was observed at the fracture initiation site. 

It is concluded that the pin failed due to fatigue initiated at the outside cylindrical surface where wear and pitting corrosion occurred. The fracture initiated at a shallow circumferential groove and corrosion of the fracture occurred after the rupture. There was no evidence of stress-corrosion cracking. 

Zamanzadeh, E. Larkin and D.Gibbon, A Re-Examination of Failure Analysis and Root Cause Determination, Mateo Associates, Pittsburgh, Pennsylvania, December 2004. 

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Failure of a Landing Gear Steel Pin A landing gear pin failure occurred in the cylindrical part of the pin whose outer surface was corroded (Sastri et al. (19), p. 515, Fig. 7.78). The fracture surface with convergent chevron patterns at the initiation site and a cover of corrosion product on the surface is shown in Sastri et al. (19, p. 516, Fig. 7.80). Corrosion pits were present at the exterior surface of the cylindrical pin. Pitting corrosion was also present at the fracture initiation site. 

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