**4. Performance of the apparatus constructed**

128 Tungsten Carbide – Processing and Applications

Impedance ΙZΙ[k

Ω] Impedance ΙZΙ[k

Ω]

**Figure 9.** Impedance characteristics of the shoe

Frequency *f* [kHz] (a)Impedance characteristics of B4 mode

Frequency *f* [kHz] (b)Impedance characteristics of L1 mode

Length of metal elastic body *l2* [mm]

**Figure 10.** Measured frequencies of two modes

Frequency

*fL1*, *fB4* [kHz]
