Electromagnetic acoustic resonance for studying dislocation formation in polycrystalline pure copper during deformation

In this paper, the ultrasonic velocity and attenuation are continuously measured during deformation of a polycrystalline pure copper by means of the electromagnetic acoustic resonance (EMAR). The EMAR is a combination of an electromagnetic acoustic transducer (EMAT) and the ultrasonic resonant technique, in which the noncontact transduction allows absolute measurement of the phase velocity and attenuation. This technique enables the simultaneous determination of the velocity and attenuation of the shear wave polarized parallel to the stress, propagating in the thickness direction. For the explanation of the observed responses, the traditional string model is modified by incorporating the resonant frequency shift due to the acoustoelasticity.