Failure analysis of fretting fracture in frame rails of heavy duty trucks – Case study

Abstract

This paper analyzed fatigue fracture of a frame rail during accelerated endurance test of a heavy duty truck. This fracture was noted in an area of high shear stresses where contact and fretting fatigue was suspected. A cross section through the fracture initiation site showed areas of surface contact wear in the microstructure. Fretting wear resulted in crack initiation and propagated to form a through crack under reverse bending fatigue crack growth mechanism. A combination of crack growth simulation tool (FRANC3D) and finite element analysis solver (MSC NASTRAN) was used and automated to handle multiple crack growth iterations. The simulation results obtained showed good correlation to failure crack path and cycles to failure. These simulation results were also used to understand the root cause of failure, identify critical parameters causing failure and recommend design modifications to prevent fretting fatigue in frame of heavy duty trucks. A modified design using the proposed simulation methodology was identified and was shown to provide improved frame durability.