A numerical and experimental approach to the design and failure analysis of a pinion shaft for wheel loaders

The present paper deals with the failure analysis and consequent design tips regarding a pinion shaft belonging to a differential gear for offroad machinery applications, namely wheel loaders. The motivations of the study arise from some in-field failures, which resulted in the fracture of the pinion shaft, originated at an external groove located at the end of its threaded portion. The issue has been tackled by means of analytical, numerical and experimental tools. The observed failures have been demonstrated to be due to the in-service loosening of a ring nut, whose function is to preload the tapered rolling bearings, which support the shaft. The weak points of the shaft design are highlighted and possible approaches to overcome the observed occurrence are presented at the end of the study.