Simulation And Analysis Of Detceting Blade Delamination Based On Vibration Testing

This paper first summarized non-destructive testing method for detecting delamination in composite material at home and abroad. Then, the method of vibration testing in blade delaminating was elaborated and carried on deep research.The principle of percussion method in wind turbine blade delamination was analysed firstly. When delaminates are appeared, the stiffness of defects is decreased and the duration of tap stress is increased during detection. Based on this principle, the research uses dynamic simulation module LS-DYNA of the finite element software ANSYS to simulate the whole process of collision, the signal of nodes’ acceleration was output to simulate the vibration information of the actual digital hammer with Time Hist Postpro(POST26). Then, intercept time history curve with MATLAB to obtain the impact duration.The simulated signal of percussion was carried on the preliminary analysis. In the time domain, the rate of signal’s amplitude attenuation which belongs to delamination in shallow is slower and signal’s amplitude will exists longer than these delamination in deeper locations. In the frequency domain, the first order frequency increase gradually with the increase of delaminating depth, and the delaminating depth has a linear relationship with the first order frequency within a certain range.Subsequently, the relationship between duration of the stress and delaminating depth was studied. It is concluded that the stress duration is different when rapping the specimen with and without delaminating. And the duration of stress will decrease when the delaminating depth becomes deeper, so the duration of stress can be used in judging delaminating and its’ depth. However, the depth of the delaminating cannot be deeper than the maximum depth that the percussion method can detect. In order to improve the effects of percussion method in detecting the maximum delamination depth practically, the position of piezoelectric sensor and energy radiation ratio were improved and we develop a set of new collision scheme, this scheme can significantly improve the delamination maximum depth of detection.Finally, Microsoft SQL Server was used to store all the simulation results and build a judging system of delamination based on software of C#. The delamination depth will be given if you input duration of tap stress.