Objectives The ultimate objective of the project is to increase the reliability of wind turbine blades through the development of proof-testing techniques, which we both identify developing problems before they become critical and improve the undemanding a damage processes. The proof-testing techniques will be developed during a series of static and fatigue tests on small and commercial scale blades and demonstrated on an in-service turbine. Acoustic emission (AE) we be used as the primary non-destructive test method, backed up by a combination of acousto-ultrasonics (AU) fibre optic (FO) strain sensing and infra red thermography (IRT). Real-time monitoring of these tests will contribute further to the understanding of failure processes in the blades and form the basis for feeding back information to designers for optimisation of the design and manufacturing processes.
The intermediate objectives are:
- reliable, real time, non-destructive damage characterisation during full scale laboratory testing of wind turbine blades by means of acoustic emission (e.g. the identification of threshold levels of activity or particular signal characteristics which can be directly related to the extent and type of damage in the structure);
- definition of acoustic emission and acousto-ultrasonic proof test procedures and quantifiable evaluation criteria (acceptance / rejection) during static and fatigue testing of wind turbine blades;
- demonstration of structural integrity assessment of an in-service blade by direct on-site proof testing.
Technical approach The basic approach will be first to look at the sensors available and Carry out a series of fundamental tests to characterise their behaviour with typical wind turbine blade materials and then to employ the appropriate sensors in a series of ten small scale blade tests to establish repeatability between blade samples and test rigs. Four of these blades will contain deliberately introduced flaws which will be characterised according to their AE "signatures". From these small scale tests, a set of drab procedures and assessment criteria will be produced. The assessment criteria will be supported by extensive data analysis and software development. The procedures will then be applied to a large scale blade static test and a large scale blade fatigue test The possibility to use AE proof testing in the field as a standard maintenance test will also be explored. Expected achievements and exploitation The major deliverables of the project will be a set of proof testing procedures and assessment criteria using AE and/or AU techniques for application during full scale blade tests. The project will also develop an unsupervised pattern recognition (UPR) software package to assist in the interpretation of AE measurements from such tests.
The project will therefore lead to improved certification procedures for full scale static and/or fatigue testing of blades. The defect location and characterisation possibilities offered by AE (and the associated non-destructive test techniques) will assist the designer in extracting more information from blade tests and hence lead to design improvements and future cost savings.
Funding SchemeCSC - Cost-sharing contracts
19009 Raphina (Pikeermi)
SN6 8LA Cranfield - Bedford
94370 Sucy En Brie
2628 CN Delft