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Nakajima T.,IHI Inspection and Instrumentation Co.
Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A | Year: 2013

A self-temperature compensating strain-measurement technique is proposed using a single fiber Bragg grating (FBG) sensor for a cyclic loaded testing-object heated moderately by itself. The technique adopts a moving-averaging method using the forward and backward Bragg wavelength data from an FBG sensor. One case was considered: a sinusoidal strain-change and a linear-functional temperature-change are assumed. In the case, it was derived that the self-temperature compensating strain-measurement is possible. The technique was applied to a test result, which is a strain-measurement result of a rotating aluminum-beam using an FBG sensor. The attempt was significantly successful. The self-compensated maximum and minimum strains were kept almost same values for about 1 hour, although the non-compensated strains shifted to the tensile strain side as testing-time. These results indicate that FBG sensors are appropriate for applying to measuring dynamic phenomena than for applying to measuring quasi-static phenomena. The self-temperature compensating technique will be applicable to fatigue testing of metal materials, strain-measurements in vibration-tests, and strain measurements of rotating mechanical elements in machineries. © 2013 The Japan Society of Mechanical Engineers. Source


Nakajima T.,IHI Inspection and Instrumentation Co.
Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A | Year: 2013

A vibration measurement of a mechanical element in liquid hydrogen was conducted using a fiber Bragg grating (FBG) sensor. The monitored mechanical element was an 8-mm diameter stainless-steel rod connected to a bearing cartridge of a ball-bearing, which is an element of a liquid rocket engine. The rotation of the ball-bearing vibrates both the cartridge and the rod to be monitored. The vibration was measured during a rotational test where the test temperature and the maximum rotational speed were 26 K and 30,000 rpm, respectively. The FBG-sensor signals were recorded at the sampling frequency of 50 kHz. The vibration of the rod was measured successfully up to 25 kHz despite the root-mean-square level of the dynamic strain smaller than 10x10 -6. The frequency analysis revealed that the FBG-sensor signal corresponded well with the rotational speed of the ball bearing. The peak frequency agreed with the first-order frequency of the rotational speed of the ball-bearing. The experiment demonstrates that FBG sensors are available to mechanical measurements of liquid rocket engines during operational tests, and also seem to be useful for mechanical measurements of fuel cell cars and hydrogen engine cars. © 2013 The Japan Society of Mechanical Engineers. Source


Nakajima T.,IHI Inspection and Instrumentation Co.
Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A | Year: 2012

A structural health monitoring system using multiple fiber Bragg grating sensors (FBG sensors) was developed. The system was designed to measure a large and a fast strain change and also to measure acoustic emissions (AE) simultaneously. The strain up to 1% and up to 100 kHz was considered. A multiple fiber ring laser was adopted as a light source, which consists of a multiple erbium-doped fiber amplifier (EDFA), an optical circulator, optical couplers and FBG sensors. Multiple fiber ring lasing wavelengths depended on strains loaded to FBG sensors. A CFRP beam bending test was carried out to confirm the possibility of simultaneous measurement of both strain and AE signals from a single FBG sensor. In the test, signals from a conventional electric resistive strain gage and a piezo-electric AE sensor were revealed equivalent to those from the FBG sensor. The system will be applied to development of composite structures in aerospace field such as Epsilon Launch Vehicle. © 2012 The Japan Society of Mechanical Engineers. Source


Patent
Ihi Inspection And Instrumentation Co. | Date: 2010-05-11

An L-mode guided wave sensor


Patent
IHI Inspection and Instrumentation Co. | Date: 2015-02-19

An ultrasonic transmitter

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