Influence of Impact Hammer on Parameter Acoustic Vibration Detecting Depth inside Wind Turbine Blade

Acoustic vibration has been applied in nondestructive examination of wind turbine blade because of its simplicity and applicability. In order to detect the deep defect, the dynamic procedure during the acoustic vibration of the wind turbine blade was simulated by finite element method (FEM). The influence of the hammer size and impact velocity on the stress wave energy radiation coefficient (SWERC) during the vibration was studied. The larger the radiation coefficient was, the deeper delamination could be recognized experimentally. The FEM analysis indicated that the parameters, such as the diameter and the length of the hammer, elastic modulus of the hammerhead and original impact velocity, had obvious influence on the SWERC. Based on the simulated results, two examples considering different hammering parameters were studied. The study indicates that an appropriate hammer could be designed to expand the detection depth.