Noncontact measurement of ultrasonic attenuation during rotating fatigue test of steel

Acoustic resonance technique has been applied to monitor the fatigue damage process of steel pipes exposed to rotating bending fatigue. The technique incorporates a superheterodyne spectrometer and an electromagnetic acoustic transducer (EMAT). The EMAT was newly developed for this purpose, and uses the magnetostrictive mechanism of ferromagnetic metals and excites and detects axial shear waves traveling around the sample pipe with axial polarization. Noncontact ultrasonic spectroscopy permits the accurate determination of the resonant frequency and the attenuation coefficient throughout the fatigue life. The attenuation coefficient shows a sharp peak around 80%–90% of the life. The evolution is interpreted as reflecting dislocation multiplication, depinning, and formation of cell structures, which is supported by transmission electron microscopy observations.

[1]  Hirotsugu Ogi,et al.  Ultrasonic attenuation and grain‐size evaluation using electromagnetic acoustic resonance , 1995 .

[2]  A. Granato,et al.  Theory of Mechanical Damping Due to Dislocations , 1956 .

[3]  Z. G. Zhu,et al.  The relation between the variation of stress, energy loss, ultrasonic attenuation, and dislocation configuration in aluminium during the early stages of fatigue , 1993 .

[4]  Charles Elbaum,et al.  Ultrasonic Methods in Solid State Physics , 1969 .

[5]  C. Fortunko,et al.  Resonance techniques and apparatus for elastic-wave velocity determination in thin metal plates , 1994 .

[6]  A. Granato,et al.  Sensitivity of Ultrasonic Attenuation and Velocity Changes to Plastic Deformation and Recovery in Aluminum , 1956 .

[7]  Robert Pless,et al.  Ultrasonic spectroscopy of metallic spheres using electromagnetic-acoustic transduction , 1992 .

[8]  Katsuhiro Kawashima,et al.  Nondestructive characterization of texture and plastic strain ratio of metal sheets with electromagnetic acoustic transducers , 1990 .

[9]  H. Ogi,et al.  Resonance EMAT system for acoustoelastic stress measurement in sheet metals , 1993 .

[10]  R. B. Thompson.  Generation of horizontally polarized shear waves in ferromagnetic materials using magnetostrictively coupled meander‐coil electromagnetic transducers , 1979 .

[11]  J. Grosskreutz.  Fatigue Crack Propagation , 1967 .

[12]  A. Bhatia,et al.  Scattering of High‐Frequency Sound Waves in Polycrystalline Materials , 1959 .