Preliminary evaluation of the loading characteristics of biaxial tests at low and very high frequencies

The very high cycle region of the S-N fatigue curve has been the subject of intensive research on the last years, with special focus on axial, bending, torsional and fretting fatigue tests. This can be achieved using ultrasonic exciters which allow for frequency testing of up to 30 kHz. Still, the multiaxial fatigue analysis is not yet developed for this type of fatigue analyses, mainly due to conceptual limitations of these testing devices. In this paper, a specimen is tested at 20 kHz on a bi-axial loading condition, with axial and torsional components on the specimen throat. The behavior of the specimen is measured by rotational and axial laser transducers at the bottom of the specimen and by strain gauges applied at its throat. Strain gauge data from very high frequency excitation is compared to strain gauge data obtained from equivalent specimen geometry at 0.5 Hz. Results indicate good correlation between both low and very high frequency tests. This data will serve as groundwork for future research on this field.