Environmental Engineering Reference
In-Depth Information
Fig. 9.31 The damage
acuteness index J at the
failure time of the structure
for different PZT sensors
16
14
12
10
8
6
4
2
0
3
4
5
6
7
8
The number of Sensors
which means the structure is failed. Before the structure was failed, the damage
index fluctuates at similar value, which means the damage developed with similar
acuteness. The results indicate that the proposed method is able to assess the
damage development in the composite wind blade.
The damage acuteness index J for different PZT sensors at the failure time of
the structure is shown in Fig.
9.31
. It is demonstrated that sensor 5 has the largest
value which indicates the structure failed close to sensor 5. As the distance from
the failure location become larger, the value of J becomes smaller.
9.5 Conclusions and Future Work
Three kinds of damage detection methods, vibration-based, BOTDA-based, and
PZT-based methods, are employed to implement structural health monitoring of
wind turbine blades. Above methods have their advantages, respectively. Vibra-
tion-based method is able to detect the damage of the large structure with few
sensors. BOTDA-based techniques show their distributed sensing ability over
extremely long distance with increasingly high accuracy. They can measure the
structural strain directly. While PZT-based techniques can detect the tiny local
damage with high sensitivity.
(1) For the vibration-based damage detection method, a PCA-based method was
introduced to implement the damage detection of rotational blades. The finite
element modal analysis of the wind blade indicates that the modal parameters
(frequencies and mode shapes) of the rotational blade depend on the rota-
tional speed. The detailed theory foundation and operating procedures of the
PCA-based method are introduce. Then, it was tested on a detailed FE model
of a wind turbine blade. The results indicate that the algorithm is able to
detect the simulated damage in the blade in operational condition despite the
weak nonlinear relationship between modal frequencies. Subsequently, an
experiment was designed to obtain the modal parameters under the rotational
