[en] Welding residual stress was measured by Barkhausen noise method. The calibration experiment was done for the quantitative analysis. The specimen for the calibration experiment must has the same thermo-mechanical history as the actual material to be tested. The Barkhausen noise were analysed by the pulse-height distribution. The results show that the distribution and magnitude of welding residual stress from Barkhausen noise method are in good agreement with those from blind hole method

[en] DC potential drop(DCPD) measurement system was made and the optimum measuring conditions have been studied. The room temperature resistivity of commercially available medium carbon steel(S45C) was measured using this technique. DCPD was measured in the specimens which were hardened and tempered at different temperatures. It was found that DCPD reflected the change of the microstructure during tempering very sensitively. It was possible to monitor the stage of tempering of S45C steel nondestructively using DCPD measurement

[en] Welding residual stress was measured by ultrasonic birefringence technique. Acoustoelastic constant was taken by averaging the values in the literature. The initial birefringence from preferred orientation of grains was measured. The EMAT transducers were used to remove couplant effect. The results show that the distribution and magnitude of welding residual stress from ultrasonic measurement are in good agreements with those from semi destructive hole drilling measurement

[en] A system for EMAT, which generates ultrasound by electro-magnetic forces and performs nondestructive testing in noncontact, was established. By linking it with a 3 axis scanning system and a data acquisition and processing system the automation of EMAT testing was attempted. A EMAT sensor was fabricated and the directivity pattern of it was measured. To be suitable automation, it has a transmitter and a receiver in one case and the main beam direction of it can be controlled by the frequency of driving signal. A program which controls the EMAT system, the 3 axis scanner and the data acquisition and processing system was developed. It also processes acquired data and displays the processing results. IBM-PC/AT compatible PC was used as main controller and the stratage of the program is emulation of real devices on the PC monitor. To provide the performance of the established EMAT system, two aluminium blocks containing artificial flaws and a welded aluminium block were tested. The result of the tests were satisfactory

[en] Plastic anisotropy is one of important factors which determine the drawability of a steel sheet. It has been mainly measured by mechanical tensile test. From the ultrasonic velocities propagating along the relative directions to the rolling direction, CODF(crystallite orientation distribution function) can be measured and ODC's(orientation distribution coefficients) has some correlations with the plastic anisotropy. In this study the correlations between the plastic anisotropy and ODC's of the cold rolled steel sheet were measured. From the results of ultrasonic velocity measurements the average normal anisotropy, γ and the average planar anisotropy, Δγ could be predicted within the accuracy of ±0.082 and ±0.096, respectively. Acoustic resonance method was applied to measure the ultrasonic velocities and EMAT's were used for generating and detecting the ultrasonic waves

[en] The specific strength of the fiber reinforced composite material is closely related to the anisotropy of the material. For the quantitative characterization of the anisotropy in the composite material, applied was CODF concept which was extensively used in the metallic material. As the results, the anisotropy of the material could be quantitatively analysed from the measurement of the phase velocities of the angular dependent SH_o waves

[en] Ni nanoparticles were grown on a n-Si(111) substrate by using pulsed electrodeposition in a non-aqueous NiCl₂ + methanol solution. In this solution, the Ni/Si interface showed rectifying characteristics due to the formation of a Schottky barrier, and the reduction of Ni²⁺ was the dominant process rather than the oxidation. We confirmed that the average size of the Ni nanoparticles obtained by using pulsed electrodeposition depended on the frequency of the applied potential pulse. When the frequency was varied from 20 Hz to 900 Hz, the average size of Ni nanoparticles varied in the ranges from 48 nm to 130 nm. In the case of 600 Hz, the Ni nanoparticles were found to undergo a 3-dimensional instantaneous nucleation followed by diffusion-limited growth. Vibrating sample magnetometer (VSM) measurements showed that the coercivity of the as-deposited samples depended significantly on the size of Ni nanoparticles. The coercivity of the Ni nanoparticles increased up to an average size of 86 nm, and a maximum coercivity of 203.5 Oe was obtained at an average size of 86 nm. Above this value, the coercivity began to decrease again and was 96.3 Oe at an average size of 131 nm.

[en] The eddy current probe was designed for the test of fin tubes that have uneven outer and inner surfaces to enhance the efficiency of heat emission. Because of the surface roughness of the fin tube, it needs much care to detect flaws in the tube employing eddy current test(ECT). We made ECT probes with different coil lengths and performed eddy current test using these probes for artificially flawed specimens. By the fast Fourier transform and digital filtering, signals from these probes were processed to characterize frequency spectra. From the analysis of eddy current signals and their frequency spectra, we concluded that, for the effective testing of the tubes with the fins of 1mm pitch, 4mm coil length gave the highest S/N ratio

[en] Iron thin films were grown directly on n-Si(111) substrates without any buffer layer by using pulsed electrodeposition in a non-aqueous solution. The electrical and the electrochemical characteristics of the Fe²⁺/n-Si(111) interface in the electrolyte solution were characterized by using a cyclic voltammogram (CV) and the Mott-Schottky (MS) relation. CV results indicated that the Fe²⁺/n-Si(111) interface showed a good diode behavior by forming a Schottky barrier. The flat band potential of the n-Si(111) substrate and the equilibrium redox potential of Fe²⁺ ions were - 0.526 V and - 0.316 V, respectively. The nucleation and growth kinetics at the initial stages of Fe²⁺/n-Si(111) interface formation studied by current transients were indicative of an instantaneous nucleation mode rather than a progressive one. According to this model, the estimated nucleus density and diffusion coefficient were on the order of magnitude of ∼ 10¹⁰cm^-2 and ∼ 10^-9 cm²s^-1, respectively. From the as-deposited sample obtained using a potential pulse of 1.4 V and 300 Hz, Fe nuclei in early deposition stages were found to grow to three dimensional islands with an average size of about 100 nm. As the deposition time was increased, the sizes of the Fe nuclei increased progressively and by a coalescence of the nuclei, continuous Fe films were grown on the Si surfaces. In this case, the Fe films showed a highly oriented columnar structure, and X-ray diffraction patterns reveal that the α-Fe phase was grown on the n-Si(111) substrates.

[en] It is inevitable to evaluate the life of turbine rotor because the operating periods of power plants need to be extended. The magnetic methods utilizing magnetic barkhausen noise curve were applied to detect the degradation caused by thermal aging. The magnetic property of material depends on the domain dynamics and it is affected by the microstructure of material. Therefore the magnetic property is very sensitive to the microstructure change of the material. It is, thus, very useful to detect the state of degradation of varying materials. The test specimen made of 1Cr-1Mo-0.25V steel was used widely for turbine rotor material, and seven kinds of specimens with different degradation levels were prepared by the isothermal heat treatment at 630 .deg. C. With the increase of degradation, BHN was decreased. The result was compared with coercive force and vickers hardness