Mechanical failure analysis of a rubber drying machine speed reducer output shaft

The aim of this analysis is to identify and to study the phenomena which have produced the failure of a rubber drying machine speed reducer output shaft. The machine has suffered several failures during its operating life and different materials for the same shaft have been tested. At the time of initiation of the analysis there was no evidence that a change of material or a change of geometry could avoid the appeared problem. An experimental analysis and a theoretical evidence study have been made from the knowledge of the machine operating conditions. The observations of the laboratory have identified the mechanisms which have produced the fracture of the shaft and have verified the quality of the used material. Through this identification, a study which justifies the failure in regards to the initiation and propagation phenomena implied in the fracture has been performed. The analysis of laboratory has included hardness tests, optical microscopy and SEM. The theoretical study has been based in the fatigue and fracture methodology recently developed by the European Fitness-for-Service Network [1]. The laboratory observations and the theoretical study are consistent and both demonstrate the same causes of failure and justify the life cycle of the shaft subject to its actual operating conditions. (c) 2009 Elsevier Ltd. All rights reserved.