An Advanced Vibrothermography Approach for Wind Turbine Applications

The reliability of a wind turbine system is greatly impacted by hidden defects. An improved method of inspection is sought for manufactured composite materials. Also, field inspection methods to assure quality during and after installation are required. The ultimate goal of this project is to provide a reliable, portable, instrumentation deployment system that can be utilized during wind turbine composite members manufacturing, at the time of installation, and throughout the lifetime of a wind turbine system. An advanced Vibrothermography technique developed by this work will be designed to detect and characterize the manufacturing flaws and the damage done to turbine blades and supporting structures thought their service life. Algorithms will be derived to distinguish and determine the types of manufacturing defects, shipping damage, and fatigue related failure flaw types. The feasibility to generate heat in embedded flaws, surface flaws, surface cracks, and subsurface cracks in glass/epoxy composite samples and to thermographically detect those flaws was demonstrated. The energy and transmissibility of the sound waves used to excite the flaws was demonstrated at a flaw to excitation transducer distance of 24 inches for samples up to 2 inches thick. The Phase II project goal is a prototype development platform capable of demonstrating the technology on actual wind turbine components. The information from the demonstration/qualification test will be compared to other test methods, which are being explored through the Sandia led wind blade reliability collaborative for the DOE EERE Wind and Water program. Commercial Applications and Other Benefits: Yearly operation and maintenance costs are approximately 30% of the total cost of a wind turbine. The proposed improved inspection technology can reduce manufacturing flaws, improved detecting field flaws during operation, and generally improve system reliability and therefore reduce maintenance costs. The overall net benefit to the public will be lower operating cost resulting in lower customer rates. An additional benefit of the proposed technology is that a final commercial system will include software algorithms for