Attenuation measurements of high‐amplitude ultrasonic waves (macrosound) in metal crystals contribute to a better understanding of the physics of crystal plasticity, as has been shown in earlier experiments. The study of the interaction of high‐frequency mechanical waves with lattice structures (dislocations and grain boundaries) within the plastic range of acoustical stresses σ⩾ε′σ⩾τ (where τ is the shear stress necessary for extensive glide, ε′ the plastic strain, and σ the shear modulus) complements ordinary damping measurements at low amplitudes (a≲10−6) in metals after neutron (or other corpuscular) irradiation as well as the measurements during and after conventional plastic deformation. A satisfactory comparison and analysis of the data obtained at lower and higher amplitudes, respectively, was not possible as yet, owing to widely differing measuring techniques and materials. We therefore developed a new method of observation which provides continuous damping data ranging from low to high strain amplitudes, on high‐purity copper and aluminum single crystals. Also, the modulus defect was observed in correlation with the influence of high‐amplitude macrosound.

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