Abstract
A high speed dynamic strain measurement test of a vibrating mechanical element in liquid hydrogen was carried out using a fiber Bragg grating sensor (FBG sensor). The object for easement was the mechanical element made of stainless steel which supports an outer ring of a ball bearing. The test temperature was 26 K. The object vibrated with rotations of the ball bearing of 30,000 rpm. Signals from the FBG sensor were recorded at the sampling frequency 50 kHz. Although the dynamic-strain root-mean-square level was small under 10x10^<-6>, the vibration of the mechanical element was able to be measured successfully using the FBG sensor. The frequency analysis revealed that the FBG signals corresponded well with the rotation speed of the bearing. The peak frequencies were the same as the 1st order frequencies of the rotation speeds of the bearing. The test results show that FBG sensors are available to mechanical measurements for liquid fuel space rocket jpnines' operational tests.
