塑性変形におけるAEの振幅分布
1977 年 41 巻 9 号 p. 897-904
詳細
1977 年 41 巻 9 号 p. 897-904
The amplitude distribution of acoustic emission due to plastic deformation was studied in relation to deformation properties of Al, Cu, Al-Mg, Al-Si, α-Brass, α-Fe and SUS 304. The integrated distribution function of AE amplitudes can be given by
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oindentwhere I(Vt) shows the cumulative number of ringdown countings, whose amplitude are equal to or greater than a given threshold voltage Vt, m and k are constants defined as the threshold exponent and the threshold pre-exponent respectively. The threshold exponents may be classified to three categories: 0.5, 1 and 2, respectively. The case of m=2, which represents Gaussian distribution, was observed in high purity Cu and Al, and corresponds to the so-called continuous-type of AE. The case of m=0.5, on the other hand, corresponds to the burst-type of AE and was observed in SUS 304 and Al-Si alloy. The case of m=1 shows the mixture mode of continuous and burst-type of AE, and was observed in Al-Mg, α-Brass and α-Fe.
These threshold exponent m values are strongly connected with the metallurgical factors, which control the flow deformation, such as Peierls potential, solute atoms, dispersion particles, and stacking fault energy. The variation of m values between 0.5 and 2.0 can be explained by simple AE models, characterized by the terms of stress concentration and the frictional stress.
The stress concentration (elastic stored energy) controls the magnitude of discontinuos deformation. The frictional stress controls the relaxation rate of the energy release.
