Electronic Resonant Fatigne Testing Apparatus and Some Testing Results

Abstract

Resonant fatigue testing apparatus, which are applicable to wide extent of loading capacity, type of stressing, and size and shape of specimens, are newly devised and constructed. An apparatus is composed of the following five blocks arranged in a closed loop:
(1) Power amplifier (electron tube type, 5KVA or 70VA)
(2) Exciter (moving coil type, see Figs. 4 and 5)
(3) Mechanical vibrating system (composed of a test specimen, weights and sometimes springs, Figs. 2, 3 and 4)
(4) Load detecting device (strain gages or unbonded type wire strain gage accelerometers)
(5) Automatic amplitude control device (almost-zero method using an a-c-powered bridge and a carrier amplifier system).
Some results of the plane-bending tests on unnotched and notched mild steel specimens are reported, in which size of the test section of the specimens extends from 100(height)×20(breadth) mm to 4×18mm, loading capacity from 1 t-m to 0.5kg-m, and loading speed is 50-70c/s.