13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- 3. Data Analysis and Discussion 3.1. Calibration of Acoustic Emission Measurements For wood, the wave velocities are very dependent on propagation direction. Consequently, conventional AE source location techniques such as 2D planer location mode, which assume isotropic velocity, cannot easily be used for wood. Thus, AE source location, the most identifiable and beneficial factor of the AE technique for homogenous materials, is difficult to use on wood. In order to overcome these difficulties, we adopted in this study a liner location mode combined with a specific calibration procedure. The value of effective AE wave velocity (5350 m/s) was evaluated by the conventional pencil lead breaking. y = 1,21x - 1,19 R² = 0,99 y = 1,36x - 1,67 R² = 1,00 0 2 4 6 8 10 12 0 2 4 6 8 10 X position of pencil lead breaking (cm) X location by EA (cm) 1-2 Sensors 3-4 Sensors (a) (b) y = 80,50e-4,00x R² = 0,92 y = 86,83e-4,31x R² = 0,94 0 10 20 30 40 50 60 70 80 90 100 0,00 0,02 0,04 0,06 0,08 0,10 Measured amplitude with AST source of 99dB X position of the AST signal (m) 1-2 Sensors 3-4 Sensors (c) (d) Figure 3. Calibration of Acoustic Emission Measurements. a) Photography of the pencil lead break method. b) calibration curve of the acoustic emission location. c) Photography of the AST method for attenuation measurements. d) Attenuation profile of the AE response on the wood sample.
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