1973 年 29 巻 12 号 p. 713-718
Many experiments have been performed by various investigators concerning the erosion of metals caused by the ultrasonic cavitation, there being many factors which affect this phenomenon. The authors conducted the following experiment in this paper. The cylindrical testpiece of aluminum, 18 mm in diameter and 20 mm in length, is set in front of the radiating surface of a stainless-steel solid-horn driven by a bolt-clamped Langevin-type piezoelectric (PZT) transducer. The dc voltage or the dc pulse voltage is applied between the testpiece and the radiating surface of the horn, with the testpiece as cathode or anode. The weight loss of the testpiece by erosion under irradiation of ultrasound and application of voltage, is measured. The erosion first increases slightly then decreases rather sharply with the increase of the dc current in case the testpiece is cathode (Fig. 3). The behavior is more complex when the testpiece is anode : the erosion first increases slightly, then decreases and finally increases almost linearly as the dc current increases (Fig. 7). Also an experiment with dc pulse current has been performed with the testpiece as cathode, but no difference is observable between the dc current and the dc pulse current, provided that the total amount of current is the same (Fig. 3 and Fig. 6). When the dc voltage is applied, with the testpiece as anode and without ultrasonic irradiation, a linear increase in erosion is observed with the increase of the dc current (Fig 7). It is concluded that the large difference in erosion of the aluminum testpiece acording as the testpiece is cathode or anode, is mainly due to the effect of the electrolytic erosion, while the mechanical effect of the cavitation is equally reduced in both cases the testpiece is cathode and anode. Although the mechanism is not ascertained as yet, the reduction of the mechanical effect of cavitation is presumably due to the electrolytic production of large gas bubbles preventing cavitation.