Failure analysis of a lifting platform for tree pruning

The paper presents an analysis of the failure in service of a lifting platform used for tree pruning. Different fracture mechanics techniques were used to reveal the causes of failure such as analysis of the fracture surface, mechanical and microstructural characterization of the material and fracture mechanics tests to determine the critical value of the stress intensity factor and to characterize the subcritical crack growth under fatigue. Results yield do conclude that the platform failure cause was the subcritical crack growth in the welded joint where the welding was discontinuous, thereby producing a stress concentration effect similar to that of a crack.