Failure analysis of fifth wheel coupling system

This work presents a failure analysis study of a fifth wheel coupling system that failed in service. The first part of the study presents the failure analysis conducted to determinate the reasons for failure. A finite element analysis was conducted to simulate the coupling in service. The results of the numerical analysis was compared with fatigue S–N curves given in the British Standard BS 7608 – Fatigue design and assessment of steel structures. Finally, corrective actions are presented to prevent similar events. The investigation concluded that the failure occurred by fatigue initiated at a welded joint. The presence of defects in the weld toe created the condition for crack initiation. The adoption of better welding procedures and careful inspection are vital to prevent similar failures.