| Popis: |
Metal spalling is a wear process where flakes of metal brake off a larger body. Spalling is typi-cal for gears and bearings so, to extend their service life, is it necessary to gain a better insight into the process itself, causes and effects. This paper deals with spalling of teeth on a gear shaft, part of a larger shipyard crane drivetrain. Wear analysis is performed as a combination of experimental and numerical research. Visual inspection revealed wear locations and wear propagation paths around the gear. Chem-ical composition of the material was determined by optical emission spectrometer with glow discharge source sample stimulation to reveal the type of stainless steel used for manufactur-ing the gear. To test the strength of the steel, tensile specimens were machined from the shaft and tensile test was performed. Additionally, hardness of the steel was tested. Optical and scanning electron microscopy was used to inspect damaged surfaces of the teeth, reveal possi-ble flaws and fine microstructure of the material. To gain better understanding of the wear process, a 3D finite element (FE) gear shaft model was built and stress analysis performed. All experimental procedures suggest it is a case of gear teeth spalling, probably caused by ex-cessive contact stresses. This was proved by FE stress analysis showing excessive contact stresses at the teeth contact area, especially in simulated mismatch of the gears. Mismatch was probably results of the crane overloading. In order to better understand spalling wear, proper analysis of the process needs to be per-formed. That way, causes of spalling can be determined and recommendations given to avoid failure scenarios of the structures prone to this type of wear. |
