To keep the safety of the nuclear reactor and prevent the destruction of the environment, it is important to evaluate integrity of piping used in the nuclear power plant. Many kinds of the non-destructive testing methods for the nuclear components have been developed. Especially, measurement techniques using laser
provide the high accuracy, the high speed, and the convenience. ESPI and shearography are well known techniques as the optic-based non-destructive measurement method. The goal of this paper is to present the standard of measurement technique using laser for the wall-thinned pipes. In order to achieve this goal, the out-of-plane deformation of the wall-thinned pipes is quantitatively measured by using ESPI and shearography and the results are compared each other. Various kinds of specimen which have respect to the
minimum thickness, the width, and the length of a wall-thinning defect are prepared. The size and the shape of a wall-thinning defect are measured by using ESPI and shearography. According to the comparison results, the applicability for the piping used in the nuclear power plant is verified and the measurable range is
Mostly piping which is using for the nuclear power plants are made up of carbon steel pipes. The wall thinning defects
occurs by the effect of the flow accelerated corrosion of fluid that flows in carbon steel pipes. The defects could be found
on the welding part and anywhere in the pipes. The infrared thermography technique which is one of the non-destructive
testing method has used for detecting the defects of various kinds of materials over the years. There is a limitation for
measuring the defect of metals that have a big coefficient of thermal diffusion. However, a technique using lock-in
method gets over the difficulty. Consequently, the lock-in infrared thermography technique has been applied to the
various industry fields. In this paper, the defect thickness of the straight pipe which has an artificial defect the inside of
the pipes was measured by using the lock-in infrared thermography technique and the result could be utilized in detecting
defects of carbon steel pipes.
A decoupled dual servo (DDS) stage for ultra-precision scanning system is introduced in this paper. The proposed DDS consists of a 3 axis fine stage for handling and carrying workpieces and a XY coarse stage. Especially, the DDS uses three voice coil motors (VCM) as a planar actuation system of the fine stage to reduce the disturbances due to any mechanical connections with its coarse stage. VCMs are governed by Lorentz law. According to the law and its structure, there are no mechanical connections between coils and magnetic circuits. Moreover, the VCM doesn't have force ripples due to imperfections of commutation components of linear motor systems - currents and flux densities. However, due to the VCM's mechanical constraints the working range of the fine is about 5mm<sup>2</sup>. To break that hurdle, the coarse stage with linear motors is used for the fine stage to move about 200mm<sup>2</sup>. Because of the above reasons, the proposed DDS can achieve higher precision scanning than other stages with only one servo. Using MATLAB's Sequential Quadratic Programming (SQP), the VCMs are optimally designed for the highest force under conditions and constraints such as thermal dissipations due to its coil, its size, and so on. For linear motors, Halbach magnet linear motor is proposed and optimally designed in this paper. In addition, for their smooth movements without any frictions, guide systems of the DDS are composed of air bearings. And then, precisely to get their positions, linear scales with 0.1um resolution are used for the coarse's XY motions and plane mirror laser interferometers with 20nm for the fine's XYθz. On scanning, the two stages have same trajectories and are controlled. The control algorithm is Parallel method. The embodied ultra-precision scanning system has about 100nm tracking error and in-positioning stability.
The paper proposes an evaluation technique for the elastic modulus of a cantilever beam by vibration analysis based on time average electronic speckle pattern interferometry (TA-ESPI) and Euler-Bernoulli equation. General approaches for the measurement of elastic modulus of a thin film are the Nano indentation test, Buldge test, Micro-tensile test, and so on. They each have strength and weakness in the preparation of the test specimen and the analysis of experimental results. ESPI is a type of laser speckle interferometry technique offering non-contact, high-resolution and whole-field measurement. The technique is a common measurement method for vibration mode visualization and surface displacement. Whole-field vibration mode shape (surface displacement distribution) at resonance frequency can be visualized by ESPI. And the maximum surface displacement distribution from ESPI can be used to find the resonance frequency for each vibration mode shape. And the elastic modules of a test material can be easily estimated from the measured resonance frequency and Euler-Bernoulli equation. The TA-ESPI vibration analysis technique can be used to find the elastic modulus of a material requiring simple preparation process and analysis.
A high-speed FM demodulation method for measuring mechanical vibration using a homodyne laser interferometer is presented. The Doppler frequency, which represents the surface velocity of a vibrating object, is obtained by using the homodyne laser interferometer, and converted to a voltage signal by using the proposed analogue FM demodulation circuit. The dc offsets of the interference signals obtained from the homodyne laser interferometer are eliminated by using simple subtraction. The new method for compensation of the asymmetry of each interference signal is presented. The laser power variation of the interferometer is normalized by using an auto-gain controller (AGC). The performance of the proposed FM demodulation algorithm is proved by using theoretical methods, and validated by using experimental results. In the experiments, the proposed FM demodulation algorithm is compared with a conventional demodulation method.