Development of a novel vibration-based fatigue testing methodology

A novel testing methodology has been developed to determine the fatigue limit strength of structural materials at high frequencies. The procedure involves the use of a base-excited plate specimen driven into a high frequency resonant mode which allows completion of a fatigue test in a few hours. The use of a step-testing method allows determination of the fatigue limit strength of the material corresponding to a very large number of cycles, 106 or 107 in this case. The methodology consists of a topological design procedure, incorporating a finite element model, to produce the shape of the specimen necessary to achieve the required stress state/pattern, and a forced vibration-based fatigue procedure for conducting the high cycle fatigue experiments with variable-amplitude loading. The successful application of the methodology is demonstrated by the experimental results from steel, 6061-T6 aluminum, and Ti-6Al-4V plate specimens subjected to fully reversed uniaxial and biaxial bending stress states. Results are compared with existing data produced using traditional fatigue test machines.