Failure analysis of a pinion of the jacking system of a jack-up platform

Component analysis, metallographic examination and hardness test were performed respectively for a failed pinion and a new rack of the jacking system of a jack-up platform. Experiment results showed that the superficial heat treatment of the pinion was not uniform and there was no hardened layer at the tooth root. At the same time, the hardened layer near the pitch circle had been worn out for long-term service, thus the surface hardness of the failed pinion was lower than that of the rack. Considering that each pinion bears different load during service, the exact load that each pinion bears under the action of self-weight, variable loads and wind loads, was deduced firstly. As per the deduced bearing load of the failed pinion, elastic FEM analysis was performed and the distribution of stresses on the rack and pinion was simulated when the platform was under preload condition. By comparing the Von mises stresses and contact stresses with those calculated according to the formula, the accuracy of FEM analysis was verified. Then elastic–plastic FEM analysis was performed for pinion models with hardened layer and without hardened layer respectively, the results were used to explain the failure of the pinion.