Failure of an Al-alloy tail wheel trunion of a combat vehicle

Systematic material failure of wheel suspension assemblies was observed on several combat vehicles after about 10 years of continuous operation under severe cross-country route and environmental conditions. The present study focuses on the failure of the trail wheel trunion, cast from an Al-alloy. Visual inspection, macrographic examination and microscopic observations revealed that cracking was initiated at the inner micromachined surface of the alignment lugs and propagated towards the external surface, during long term vehicle operation. Similar findings were observed on the conjugate trunion piece, where intergranular cracking was extended in a significant depth beneath the fracture surface. Failure is attributed to the existence of a stress gap, due to the different fixation configurations of the attachment pin on the alignment lug.