Experimental determination of vibration characteristics of turbine blades with an immunity digital speckl interferometer

Abstract

The paper notes the wide possibilities and high efficiency of vibration diagnostics of parts and assemblies of power units by the method of electronic speckle interferometry (ESI), shows the feasibility of developing and improving methods for obtaining speckle interferograms of vibrating objects. A patented by the authors' scheme of a digital speckle interferometer (DSI) for determining the dynamic parameters of products is presented. The diffuse reference wave greatly simplifies its alignment, mainly the aligned channels of propagation of interfering beams determine the resistance to mechanical and thermal disturbances, and the separate beam splitter and diffuser make it easy to optimize the optical scheme for the object under study. Speckle interferograms are obtained by speckle correlation methods and a developed method for determining the contrast of the dynamic speckle pattern. It does not impose special requirements on the parameters of the video system, does not require the use of a specialized video camera, and allows, by using a rotary platform, to organize a panoramic view of the oscillatory forms of asymmetric structures. The use of this method in combination with the proposed optical scheme provides an express analysis of products in off-bench conditions. The increased noise immunity of the installation allows the determination of the spectrum of frequencies and vibration modes (SFVM) of samples under free boundary conditions, which is rarely realized in interferometry. The paper presents examples of such speckle interferograms, the expediency of obtaining which is important in the resonance study of the elastic properties of the material and vibration resonance flaw detection. The implemented software and hardware solutions increase the resolution and visibility of the band patterns; facilitate their quantitative interpretation and the extraction of numerical information on the distribution of vibration amplitudes. The area of scientific interests and the specificity of the author's developments have determined the preferential adaptation of the proposed device with a complex of software and methodological developments for vibration testing of gas turbine engine (GTE) blades.

Keywords

• спекл-интерферометрия
• голография
• рабочая лопатка гтд
• резонансные частоты
• интерферограмма