13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- ( ) ( ) 2 2 2 2 2 2 2 1 2 1 2 1 1 s su s s A D A D ζ ζ ω ω ⎛ ⎞ − + − − ⎜ − ⎟ ⎝ ⎠ = − . (6) Since 1 ζ= , ( ) 1/ 1 / sl s sA D ω ω = + , ( ) 1/ 1 / su s sA D ω ω = − . Therefore, 1 2 1 sl sl s s f f A D ω π = = + , (7) 1 2 1 su su s s f f A D ω π = = − . (8) When fs = 11 Hz, As = 1.4 mm (0-peak) and D = 4.5 mm, fsl and fsu are calculated to be about 9.6 Hz and 13.3 Hz, respectively. V V V V V V D = 4.5 D = 30 xs x PZT-T-IMP PZT-B-IMP Proof Poling direction + + + + Poling direction N S N N N S S S ⊗⊗⊗⊗⊗⊗⊗ ⊗⊗⊗⊗⊗⊗⊗ ⊗⊗⊗⊗⊗⊗⊗ ⊙⊙⊙⊙⊙⊙⊙ ⊙⊙⊙⊙⊙⊙⊙ ⊙⊙⊙⊙⊙⊙⊙ PZT-T-IMP PZT-B-IMP Bottom frame Top frame PZT-T-EX V Impact body Coil vibration Coil vibration PZT-B-EX (a) (b)
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