A method of determining test load for full-scale wind turbine blade fatigue tests
- 32 Downloads
Full-scale fatigue test is an effective method for validating the fatigue performance of wind turbine blade. Its primary problem is how to design the test load. The conventional approach to determine test load requires a complicated and time-consuming process. Thus, a simplified method for directly converting load spectrum of blade into test load is proposed in this paper. Firstly, beam theory is used to obtain the relationship between stress, strain and bending moment of blade cross section. Based on the assumption of local stress concentration and linear relationship between stress and strain, M-N curves (applied moment vs. allowable number of cycles to failure) is defined. Secondly, based on Miner's linear cumulative damage theory and constant life diagram, the equivalent fatigue cumulative damage of load spectrum which is equal to the damage of full-scale fatigue test is obtained. Then, in the case of the selected test load ratio and cycles, the mean and amplitude of test load can be solved. Finally, the validity of the proposed method is verified by an illustrative example. The result indicates that the error of the calculated results between this method and the traditional method is close to 5 %, and it can be used for fatigue test and improve the efficiency of test load design.
KeywordsFatigue damage Full-scale fatigue test Load spectrum Test load Wind turbine blade
Unable to display preview. Download preview PDF.
- Caithness Windfarm Information Forum, Summary of wind turbine accident data to 31 March 2017, Available at: http://www.caithnesswindfarms.co.uk.Google Scholar
- International Electrotechnical Commission, IEC 61400–1 Wind turbines part 1: Design requirements (2005).Google Scholar
- International Electrotechnical Commission, IEC 61400–23 Wind turbines Part 23: Full–scale structural testing of rotor blades (2014).Google Scholar
- G. Freebury and W. Musial, Determining equivalent damage loading for full–scale wind turbine blade fatigue tests, Proceedings of the 19th American Society of Mechanical Engineers (ASME) Wind Energy Symposium, Reno, Nevada, USA (2000) 50.Google Scholar
- S. Larwood and W. Musial, Comprehensive testing of Nedwind 12–Meter wind turbine blades at NREL, Proceedings of the 19th American Society of Mechanical Engineers (ASME) Wind Energy Symposium, Reno, Nevada, USA (2000) 51.Google Scholar
- R. P. L. Nijssen, Fatigue life prediction and strength degradation of wind turbine rotor blade composites, Contractor Report SAND2006–7810P, Sandia National Laboratories, Albuquerque, New Mexico, USA (2006).Google Scholar
- P. R. Greaves, Fatigue analysis and testing of wind turbine blades, Doctoral Dissertation, Durham University (2013).Google Scholar
- Germanischer Lloyd, Guideline for the certification of wind turbines (2010).Google Scholar
- S. Larwood, W. Musial, G. Freebury and A. G. Beattie, NedWind 25 blade testing at NREL for the European standards measurement and testing program, National Renewable Energy Lab., Golden, Colorado, USA (2001).Google Scholar