Failure analysis of aircraft towbar shear pins

Abstract

This thesis addresses the effects of cyclic loads on the shear pins of aircraft towbars. The shear pins and the associated towbar head and attachment for the Boeing 737NG aircraft series were modeled in ANSYS Mechanical and a loading cycle block derived from the public domain was used to estimate the fatigue life of the shear pins. The models were validated against published work and the results obtained were compared with analytical calculations. The results indicate that fatigue may be a contributing factor to the premature failure of shear pins in operation. As an initial study, this work also identifies the need for further investigation into the actual load cycles experienced by the shear pins in operation to further verify the results obtained.