Abstract
To investigate the influence of loading frequency in high speed fatigue of metals, a pneumatic machine for fatigue testing at frequencies ranging from 150 to 2000 cycles per second has been designed.
Method for excitation used is an air nozzle system of so-called flutter type, in which the specimen vibrates in a direction transverse to the air stream, and it does not require complicated control system to maintain resonant condition.
Specimens are thin reeds of 1.2mm in thickness and 4 or 5mm in width at the test section, and are vibrated in the fundamental mode of cantilever beam.
Strain amplitude of the loaded specimen was measured by electrical resistance strain meter, and certain considerations about measurement were made with respect to gauge length, thickness of gauge base and temperature increase during test.
Cyclic strain fatigue tests were made at room temperature on an annealed 0.23% carbon steel, and it was found that the endurance limit increased with increasing test speed in this range of frequencies.
