Nonlinear Acoustics

Creep-Induced Microstructural Evolution and Acoustic Characterization in Tempered Martensitic Stainless Steel

“…[19] This problem is especially serious for attenuation measurement, because mechanical contacts allow the probing ultrasonic waves to propagate in the sample, as well as in the transducers, couplant, and buffer, where a significant fraction of the acoustic energy is absorbed during wave propagation. Therefore, noncontact measurement with electromagnetic acoustic transducers (EMATs) [20,21,22] is preferable, but low transduction efficiency prevents us from accurately measuring the ultrasonic characteristics. To overcome this dilemma, we combined an EMAT with the resonant technique, so as to superimpose many signals coherently and compose large signal amplitudes.…”

“…To overcome this dilemma, we combined an EMAT with the resonant technique, so as to superimpose many signals coherently and compose large signal amplitudes. This is the electromagnetic-acoustic-resonance (EMAR) [20,21,22] method developed for the contactless measurement of phase velocity and attenuation.…”

“…Type-403 is similar to 410, but the chemical composition is adjusted to prevent the formation of dferrite in heavy sections. It is used extensively for steamturbine rotor blades and gas-turbine compressor blades operating at a temperature of up to 753 K. [29] In the present work, a bulk-wave EMAT [20,21,22] was used to measure the ultrasonic attenuation and velocity in the thickness direction of specimens as creep progressed.…”