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发表于 2009-2-23 21:06:44
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Fatigue Testing of Wind Turbine Blades
Content: Wind turbine blades are designed for 20 years of virtually maintenance free
operation. Therefore, fatigue is often design driving for wind turbine blades. In verifying the
final structural design of new prototype blades, full-scale fatigue testing is an inherent part
of the test program. Traditionally the design and setup of blade fatigue testing comprise a
difficult task, where many aspects both practical and theoretical must be considered.
Typically, the procedure is to calculate an equivalent loading (a constant cyclic loading at
e.g. 3·106 cycles) of the blade, where the material in the blade is subject to the same
accumulated damage as during 20 years in operation. To achieve the correct loading
level, the blade is fitted with a number of discrete masses at predefined location and set to
vibrate at the systems resonant frequency at a given amplitude.
In a resent M.Sc. project carried out at Vestas Wind Systems A/S, a computer program for
determining the optimal location and size of masses as well as the desired amplitude has
successfully been developed. In short, the program (written in Matlab) uses a simple 2D
FE beam model for solving an eigenvalue problem, where the natural frequency along with
the eigenmode of the system is determined. Based on this, a moment distribution is
determined, and using an optimization algorithm the next guess on an optimal solution for
amplitude, location and size of masses is obtained.
In the present project, it is proposed to further develop this program. The aim is to include
3D transient dynamic analysis of the blade. Thus taking into account both transient
behaviour and damping. During the project, it will be possible to test the performance of
the program in full-scale testing of a prototype wind turbine blade.
Due to the nature of the project it will be advantageous to have the student(s) spend part
of the project time at Vestas Wind Systems A/S. |
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