FATIGUE LIFE OPTIMIZATION FOR GEAR CRITICAL ACTUATION SYSTEMS BY LOAD SPECTRUM SYNTHESIS AND AN ALGORITHM FOR S-N-R CURVE GENERATION

The purpse of this project is to develop a method to synthesize the load spectrum for a gear critical machine in order to obtain its maximum life capability. An algorithm able to predict the fatigue life of any cyclic load based on a few known S-N curves is developed first. This algorithm can also generate the S-N curve of any stress ratio. The following two advantages are identified for this algorithm: (1) It imposes minimum restraints to the shape of the constant life curves in the constant life diagram. (2) All the constant life curves and S-N curves generated by this algorithm pass through their data points. These two features improve the accuracy of te life prediction for cyclic loads. Therefore, this algorithm is not only developed for the usage in this project, but it also can be very useful for general fatigue analysis, espcially for cumulative damage problems.;Computer programs are developed for the above algorithms. This can greatly reduce the problem solving time and enhance the applicability of the two algorithms.;A second algorithm is then developed to synthesize the load spectrum of gear critical machinery to maximize the machine life capability. Based on the author's knowledge, this type of work has not been done in a systematic way before.