Very High Speed Plane Bending Fatigue Test : (1st Report, On The Fatigue Testing Machine)

Abstract

In order to investigate the effect of the speed of stress reversal on the endurance limit, and to reduce the time necessary for a fatigue test, a high speed pneumatic fatigue testing machine has been developed. Ultrasonic siren (air interruptor) is used as an exciter for a plane bending type testing machine for the frequency range of 3 to 20 kc/sec. Specimen is a uniform bar of the rectangular cross section vibrating in the first free-free mode, and is supported by steel wires at the nodal points. Tests were made on normalized carbon steels at frequencies up to 18 kc/sec. In order to compare the endurance limit at high speed with that at ordinary speed, the same materials were tested by the ordinary plane bending machine and the rotary bending machine. Speed dependence of the endurance limit obtained from these tests is notable, and the endurance limit at the highest frequency was 43% higher than that in the ordinary frequency range.