Non-destructive testing of large wind turbine blades
As such, the market for electricity generation harnessing the power of wind is growing. In order to meet the expected demand, wind turbine blade (WTB) manufacturers have turned to glass-reinforced plastics rather than metal to increase the size and output of the wind turbines while saving on cost and weight. However, suitable non-destructive testing (NDT) techniques for rapid and accurate inspection of very large areas are lacking, resulting in increased manufacturing and maintenance costs as well as downtime. The EU-funded ‘Development of new and novel automated inspection technology for glass reinforced plastic wind turbine blades’ (Renewitt) project was initiated to develop the necessary NDT techniques in order to enable European WTB manufacturers to use the optimal materials with cost savings. Thus, the project sought to maximise the efficiency of WTBs while increasing the competitiveness of European WTB manufacturers. The Renewitt project team successfully developed four NDT techniques for application to glass-reinforced plastic WTBs, enabling early detection of defects or damage. First, the researchers applied digital radiography which has revolutionised the field of X-ray imaging using digital sensors instead of traditional radiographic film. They also applied laser shearography, extending its conventional capabilities for out-of-plane deformation and enabling in-plane detection as well. The investigators also used pulsed thermography that essentially relies on a brief pulse or flash of energy applied to a surface and subsequent detection of non-uniformities during cooling. Finally, the team employed two different types of ultrasound detection. The researchers incorporated all of these NDT methodologies into a single system that was software controlled and mounted on a robot scanner to produce the Renewitt WTB inspection system. The system is capable of reaching all areas of the blade, is operated by a single technician and is applicable during both the manufacturing and the maintenance processes. In summary, the Renewitt project developed the necessary NDT methods for inspection of glass-reinforced plastic WTBs and the means to apply them. Commercialisation of the technology has the potential to significantly enhance the competitiveness of Europe’s WTB manufacturers while reducing GHG emissions and Europe’s dependence on fossil fuels.
