キャビテーション気泡崩壊圧の伝ぱ挙動と壊食量 : 三層型制振材料を用いた結果

抄録

Cavitation erosion was analyzed from the propagation of stress waves in 3-layer damping materials (first layer : metal, second layer : plastic, third layer : metal). The metals used were SS400 steel, pure copper and pure aluminum. The thickness of the first layer T_i varied from 1mm to 20mm. The damping materials were exposed to vibratory cavitation. The cavitation impact load acting on the surface decreased as T_i decreased below the critical thickness T_c, which is about 3 mm irrespective of kind of metals. This is because the intensity of the compression wave is reduced by the reflected tension wave emitted from the boundary between the first layer and the damping sheet. Therefore, the critical thickness T_c also observed in terms of mass loss rate. The T_c for both impact load and mass loss rate is calculated by T_c=Δt·c/4, where Δt is the time interval of impact load and c is the longitudinal wave velocity. The mass loss rate m, when T_i is less than T_c, is given by m={1+α-4·α·T_i/(Δt·c)}²×m_o, where α is the reflection coefficient between the first layer and the damping sheet, and m_o is the constant mass loss rate when T_i is greater than T_c. The calculated values of T_c and m correspond well with the experimental results.