超音波重畳によるアルミニウムの静的変形応力低下

抄録

The change in static flow stress caused by superimposed ultrasonics (17.8 kHz) during testing was studied at 77 and 300 K under the strain rates and oscillatory stress amplitudes from 8.3×10^-6 to 8.3×10^-4/s and from 0.2 to 11 MPa respectively. The temperature rise due to application of ultrasonics is smaller than 6 K, when the application time is less than 10 s. The decrements in static flow stress Δσ are independent of strain rates, temperatures and stresses at which the stress superimposition is carried out. The relation between Δσ and stress amplitude Δσ_v°is empirically expressed;Δσ=qΔσ_v°, where q is a constant equal to 0.7, although the theory based on the stress superimposition mechanism predicts that the value of q is equal to unity. The reason for this discrepancy between the theory and experiments is discussed.