The application of pulsed thermography in the inspection of wind turbine blades

Wind power is a very promising source of environmentally safe, renewable, and the fast-growing energy source over the past several years. The blades of a wind turbine are considered to be an important component in wind turbine generator. Currently, bigger and more powerful wind blades are being built to increase the swept area of the turbine and extract more energy from the wind. Correspondingly, more capital cost is invested in manufacture and service. In order to reduce damage possibility and extend the wind turbine blades life, there are increasing demands for the inspection of wind turbine blades in the manufacturing factory and on site inspection. The regular inspections of wind turbine blades are done normally by using visual inspection and tapping test. To improve the safety of wind turbine blades, nondestructive testing technique using pulsed thermography is being investigated in this study. This technique utilized an active pulsed heating source that is applied on the outer surface of wind turbine blades, and an infrared camera to monitor the surface temperature distribution controlled by a computer. Reflective pulsed thermography was directly applied on several full scale wind blades, surface and subsurface defects, such as air bubbles, pin holes, edge bonding, etc. were clearly detected. Several specimens were intentionally manufactured to simulate the glue faults between supporting spars and glass fiber reinforced plastic (GFRP) shells with different thickness. Afterwards they were inspected by using pulsed thermography in laboratory. The current test results indicated that pulsed thermography has the potential for the detection of glue faults at least about 15mm thickness GFRP shell. It is shown that pulsed thermography maybe provide a powerful non-contacting technique for the inspection of wind turbine blades as well in the workshop just after the production or in the field that before and after installation of the wind blades and during reparation.