ステップ状応力変化に対する超音波伝ぱ速度の応答について

概要

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In an experimental study of acousto-elastic effect, some anomalous phenomena in ultrasonic velocity, that could not be interpreted by the lattice anharmonicity, have been observed. In this paper, we have observed in detail the behaviors of an ultrasonic velocity propagating in a copper specimen (99.98% of purity) perpendicularly to the stress axis, as the uniaxial tensile and compressive stresses exceeding the range of plastic deformation were applied or released stepwisely. The results obtained are summarized as follows: (1) The decrease of the traveling time (in a traveling path of 10 mm) after one minute of stress application under a constant stress level (ΔT_m) seems to be related with the pinning of dislocation lines similar to the Koster effect. (2) The difference between the traveling time at To and that after stress release (ΔT_<or>) increased with the plastic strain (ε_<ply>). The dislocation is in un-stable state when the plastic strain appears, so that its mobility becomes larger. Even in the elastic range, ΔT_<or> was observed. (3) The change in traveling time (ΔT_a) during stress application increased parabolically with the stress in the elastic range, similar to (ΔT_r) during stress release. When some plastic strain pre-existed, they decreased at first depending on the amount of the plastic strain, reached a minimum, and then increased with the stress.
社団法人日本材料学会の論文
1978-11-15