Effects of Grain Size on Ultrasonic Attenuation in Type 316L Stainless Steel

Abstract

A lead bismuth eutectic (LBE) spallation target will be installed in the Target Test Facility (TEF-T) in the Japan Proton Accelerator Research Complex (J-PARC). The spallation target vessel filled with LBE is made of type 316L stainless steel. However, various damages, such as erosion/corrosion damage and liquid metal embrittlement caused by contact with flowing LBE at high temperature, and irradiation hardening caused by protons and neutrons, may be inflicted on the target vessel, which will deteriorate the steel and might break the vessel. To monitor the target vessel for prevention of an accident, an ultrasonic technique has been proposed to establish off-line evaluation for estimating vessel material status during the target maintenance period. Basic R&D must be carried out to clarify the dependency of ultrasonic wave propagation behavior on material microstructures and obtain fundamental knowledge. As a first step, ultrasonic waves scattered by the grains of type 316L stainless steel are investigated using new experimental and numerical approaches in the present study. The results show that the grain size can be evaluated exactly and quantitatively by calculating the attenuation coefficient of the ultrasonic waves scattered by the grains. The results also show that the scattering regimes of ultrasonic waves depend heavily on the ratio of wavelength to average grain size, and are dominated by grains of extraordinarily large size along the wave propagation path.

Comparison of Linear and Nonlinear Ultrasonic Parameters in Characterizing Grain Size and Mechanical Properties of 304L Stainless Steel

“…Characterizing the grain size can be used to monitor the changes in mechanical properties during the service of structures. Furthermore, the characterization also has potential for evaluating material degradation due to thermal aging or damage and for predicting the remaining service life of structures [7][8][9].…”

Effect of the Grain Sizes on the Ultrasonic Propagation and Attenuation on Different Types of Steels Microstructure During Non-Destructive Testing

“…Ultrasonic testing is one of the most useful non-destructive testing methods for inspection of fabricated structures and components [1,6,7]. Our ultrasonic transducer for ultrasonic testing is shown in Figure 9.…”

“…Metals grain size has significant influence on metallic structure properties and its elastic deformation. Determination of grain size in material manufacturing and service is important for characterization of microstructure [1,2,[6][7][8]. The mechanical waves created during Ultrasonic inspection were in the form of ultrasound and they have been transmitted and propagated through volume of parts or components which reflect when the waves meet with the existing interface such as flaws in the welds.…”

“…Furthermore, to obtain the data of the results, the attenuation coefficient follows the Rayleigh law for scattering and manifests a maximum at a frequency value that increases as the grain size decreases. The value of frequency akin to the attenuation maximum, converted in wavelength can be approximately compared as 3 -4 times the average grain size [1,2,7]. Our research it is focused on the investigation of the novel method which will be elaborated in details next, for analyzing the effect of grain size and determining microstructure evaluation of metals using non destructive testing.…”

Investigation of the Microstructural Evolution during Hot Stamping of a Carburized Complex Phase Steel by Laser-Ultrasonics

“…The attenuation of an ultrasound signal traveling through the material is caused by either grain scattering, diffraction, or internal friction [48]. Depending on the ratio between grain size and ultrasonic wavelength, the scattering of the ultrasonic signal can be associated with one of three different regimes, which influences the relationship between the attenuation coefficient and the grain size [49]. A more detailed description of the procedure for evaluating the grain scattering associated attenuation from raw data under consideration of other sources for attenuation can be found in [32].…”