Ultrasonic NDT of wind turbine blades using contact pulse-echo immersion testing with moving water container

Wind turbine blades are complicated objects for inspection because they have a curved surface, are multi-layered, have variable thickness and are made from anisotropic materials. Ultrasonic contact pulse-echo immersion testing with moving water container has been selected for inspection of wind turbine blades, because this type of the inspection can be performed having access just from the one side of the wind turbine blade. The ultrasonic contact pulse-echo immersion testing technique with two types of ultrasonic transducers mounted into a moving water container was used for investigation of the artificial internal defects in a wind turbine blade. These defects (diameter 81 mm, 49 mm and 19 mm) were made on the internal side of the main spar. The contact pulse-echo immersion testing (using a moving water container) of the wind turbine blade was performed using two different transducers: focused 2.2 MHz and planar 400 kHz. From the ultrasonically obtained images it is possible to recognise the geometry of defects and to estimate their approximate dimensions.