Hiroaki Hatanaka

Examination of Flaw Detection near the Surface by the Ultrasonic TOFD Method

Nobukazu Ido, Hiroaki Hatanaka, Takahiro Arakawa, Kenji Katou and Hiroyuki Furuta 1 Research & Development Ishikawajima-Harima Heavy Industries Co., Ltd 1 Shin-Nakahara-cho, Isogo-ku, Yokohama 235-8501, Japan 2 Energy & Plant Ishikawajima-Harima Heavy Industries Co., Ltd. 3-2-16 Toyosu, Koto-ku, Tokyo 135-8733, Japan 3 Trunkline Maintenance Group Distribution Planning & Administration Dept. Toho Gas Co., Ltd. 19-18 Sakurada-cho, Atsuta-ku, Nagoya 456-8511, Japan

Ultrasonic testing with advanced signal processing for concrete structures

This paper proposes an ultrasonic test method for detecting flaws inside concrete structures. The ultrasonic testing can be valuable in locating flaws in materials. However, there are lots of coarse aggregates inside concrete and reflections from these aggregates influence ultrasonic test results. To reduce noise due to aggregates, an advanced signal processing method using the wavelet transform was applied to the ultrasonic signals. As-received ultrasonic signals were decomposed into several frequency components, which vary in width. From the decomposed result, significant frequency components, which include flaw signals, were chosen. To emphasize the flaw signals, products of chosen frequency components were calculated. The components were weighted according to these products, and signals were reconstructed. Flaws in the 3-dimensional image become increasingly evident by processing chosen frequency components. This signal processing using the wavelet transform could be a valuable method for increasing the reliability and should help in the interpretation of the test results.

Ultrasonic Creep Damage Detection by Frequency Analysis for Boiler Piping

Boiler piping of fossil-fuel combustion power generation plants are exposed to high-temperature and high-pressure environments, and failure of high-energy piping due to creep damage has been a concern. Therefore, a precise creep damage assessment method is needed. This paper proposes a nondestructive method for creep damage detection of piping in fossil-fuel combustion power generation plants by ultrasonic testing. Ultrasonic signals are transformed to signals in a frequency domain by Fourier transform, and a specific frequency band is chosen. To determine the creep damage, the spectrum intensities are calculated. Calculated intensities have a good correlation to life consumption of the weld joints, and this method is able to predict the remaining life of high-temperature piping, which has been already installed.

Towed Marine Dipole Source for Shear Wave Generation

In this paper, we focused on the generation of the shear wave using a dipole source in water. We first made a scaled model of a deep-tow seismic survey using solid material with a set of reflectors and an overlain water layer and conducted an exploration experiment as a feasibility study. For the model, we performed both an acoustic experiment as well as numerical simulations to see if the shear reflection could be generated by a source in water without any contact to the solid surface. As a result, we confirmed that shear waves are generated at the liquid-solid interface and are reflected at the interface of material heterogeneities even with a hydrophone streamer. Numerical simulation indicates that the amplitudes of the S-to-S or S-to-P reflected would be emphasized if we use horizontal seismic sensors on the liquid-solid interface. Our experiment has encouraged us to fabricate a mock-up of Marine Seismic Vibrator (MSV) to confirm seismic signal generation and to verify that the source could be distended to multi-pole setup for shear wave generator.

Application of Ultrasonic Technique for Precipitate Detection and Viscosity Measurement of Molten Glass at Elevated Temperature

This paper describes the results of ultrasonic examination of molten glass in the glass melter for the vitrification process of high-level radioactive liquid waste (HLW). The propagation and the attenuation of ultrasound in the molten glass were measured to study feasibility of detecting noble metal precipitates and the viscosity measurement of glass melter.The ultrasonic propagation experiment at 2.25MHz were carried out in a simulant fluid (glycerin) at room temperature and the molten glass at 1000°C using ultrasonic wave guide rods. The wave guide rod materials used in this research are a nickel-based heat resistant alloy 690 and a high density isotropic graphite T-6 (Ibiden Co., Ltd.) with a corrosion resistant coating. Although the nickel-based alloy 690 has a favorable property such as superior structural integrity or corrosion resistant against molten glass at high temperatures, the ultrasonic attenuation was quite large thereby not suited for the wave guide rod. On the other hand, the wave guide rod made of high density isotropic graphite showed good capabilities of ultrasonic propagation both in glycerin and the molten glass at 1000°C.The changes in ultrasonic intensity of reflecting echoes vs. distance were measured both in glycerin and the molten glass to obtain attenuation coefficient of ultrasound. Then, the viscosity of glycerin and molten glass was calculated from the result of ultrasonic attenuation measurement. The viscosity of glycerin and molten glass thus obtained showed good agreement with those obtained by ordinary viscous test.Copyright

Study of the exploration focused on shear waves generated by a dipole source

In this paper, we focused on the generation of the shear wave using a dipole source in water. We made a scaled model of a deep-tow seismic survey using solid material with a set of reflectors and an overlain water layer. Two dilatational sources with the opposite phase to each other are simultaneously excited to form a point force in the water parallel to solid-water interface. The sound field generated by the dipole in water creates a stress field tangential to the solid-water interface so that the shear wave is generated in the solid. For the model, we performed both acoustic experiment and numerical simulations to see both compressional and shear reflection profiles. Numerical simulation indicates that the amplitudes of the S-to-S or S-to-P reflected would be emphasized if we use horizontal seismic sensors on the fluid-solid interface. Although the signal-to-noise ratio of the acoustic experiment is not sufficiently high, we confirmed that shear reflection profile could be produced. It should be noted that shear waves could be produced in water using multipolar sources fired close to the seafloor, and that some improvements to increase shear wave energy more than the compressional wave need to be pursued for practical use of multipolar sources.

Ultrasonic Examination of Noble Metal Precipitate Detection in Glass Melter

This paper describes the results of ultrasonic examination of the build-up of noble metal precipitates in the glass melter using a wave guide rod. The glass melter is used for the vitrification process of high-level radioactive liquid waste (HLLW).A high density isotropic graphite T-6 (Ibiden Co., Ltd.) and a nickel-based corrosion and heat resistant alloy 690 were selected as candidate materials of wave guide rod. Ultrasonic propagation experiment with the frequency 0.5, 1.0 and 2.25 MHz was performed using the wave guide rods. The T-6 graphite wave guide rod in the simulant fluid (glycerin) showed a good capability of ultrasonic propagation and signal detection. However, the propagation of ultrasonic wave into molten glass was not possible due to the poor wetting of molten glass with the graphite. On the other hand, it was possible to propagate the ultrasonic wave into molten glass with the wave guide rod made of the nickel-based alloy 690. However, the intensity of reflecting echo signal was very small due to the large ultrasonic attenuation in the nickel-based alloy. The simulation study on the ultrasonic wave propagation using the three dimensional finite element method code ComWave showed good agreement with the experimental results.Copyright