Wind turbine blades testing

Griffin, D.A. and AshwUl, T.D. (2003), Alternative composite materials for mega-watt-scale wind turbine blades Design considerations and recommended testing , Journal of Solar Energy Engineering, Vol. 125, p. 515. 

In order to evaluate the capability of the integrated CFY sensor networks for the SHM, the small wind turbine blade is mounted horizontally in a fuU-scale semi-beam test rig. Considering its subsequent load case at the wind turbine, the aerodynamically effective suction side of the blade is aligned in a way that the so-called pressure and compression side is subject to tensile stress by normal forces and compressive stress, respectively. 

Larsen EM, Sorensen T. New lightning qualification test procedure for large wind turbine blades. In Proceedings of international conference on lightning and static electricity, Blackpool, UK September 2003. 

Having completed the design, the component can be manufactured and tested under the appropriate service loads. Noteworthy examples of this approach include glider wings, wind turbine blades and leaf springs. 

Transient overloads create damage which can cause premature failure they thus need to be considered during the design stage. If these cannot be eliminated by design then the tests should be carried out to determine the reduction in life. Examples of such overloads include water hammer in cooling pipes (as above) and gust turbulence for wind turbine blades. 

This provides the justification and a means for screening materials by testing at a higher frequency (or loading rate) than that encountered in practice. Notable examples of such applications include those of leaf springs and wind turbine blades. 

Agastra, P. Mandell, J. F. Testing and Simulation of Damage Growth at Ply Drops in Wind Turbine Blade Laminates. Presented at the Society lor the Advancement of Material and Process Engineering, Seattle, Washington (USA), May 17-20,2010 Paper 398. 

Today the coin-tap test is a widely used technique on wind turbine rotor blades for inspection of thin GFRP laminates for disbonded and delaminated areas. However, since the sensitivity of this technique depends not only on the operator but also on the thickness of the inspected component, the coin-tap testing technique is most sensitive to defects positioned near the surface of the laminate. Therefore, there has been an increasing demand for alternative non-destmctive testing techniques which is less operator dependent and also more sensitive to delaminations and disbonded areas situated beyond thicker GFRP-laminates. 

Bechly ME, Clausen PD, Snaith H. Structural Design, Manufacture, and Testing of Resin Transfer Moulded Blades for Small Wind Turbines. Bury St Edmunds, UK Mechanical Engineering Publications, 1997. ISBN 1-86058-034-3. 

Kensche, C.W. and Kalkul, T. (1990) Fatigue testing of Gl-ep in wind turbine rotor blades, Proc, EWEC 90 Conference Madrid. 

The vertical spindle, three blade machine [Fig. 12.11 and curve (E) in Fig. 12.10] is a high-speed wind turbine having blades in the shape of airfoil sections like an aircraft propeller. However, instead of having vertical blades, they are bowed to form a catenary thus eliminating the bending moments that straight vertical blades would experience. The peak efficiency of the three blade machines is about 42% at a speed ratio of about six. This means that great care of construction is required for these machines, as in the case of conventional two blade horizontal-axis propellers. A 14 ft diameter machine, tested in a wind tunnel, had an output of 0.65 hp at 130 rpm with a wind speed of 18.2 fps. 

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