Abstract: Mechanical failures in general can appear because of weak design, wrong handling, and problems during the manufacturing process, material problems etc. This paper is dealing with failures in lifting machinery gearboxes which appear because of material stresses and tribological problems. The study conducted is based on theoretical analysis and analysis of inspection results for failures that have appeared in cranes and other lifting machinery in southern part of Sweden. Investigation shows that besides the surface damages like abrasive and adhesive failures also cracks in the material in different parts appear. Since these types of gearboxes are made in short series, gearbox housings and sometimes also gears are made of welded steel. Hence welding process makes the weld joints brittle; cracks do start and developed until the part fails. Another problem that happens due to welding is wrapping which leads to changes in the geometrical tolerances and that does affect the parallelism of the shafts and the functionality of the gearbox.
Keywords: mechanical failures, material stresses, tribology, lifting machinery, failures in gearboxes