An Analytical and Experimental Study of Stresses in Turbine Blades Using Holographic Interferometry.
Final rept. 23 Jun 70-23 Jun 71,
TRW SYSTEMS GROUP REDONDO BEACH CALIF
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The applicability of laser holographic interferometry to the determination of stresses in turbine blades was investigated. Experiments included continuous wave holographic interferometry of a statically loaded blade at both room and elevated temperatures 1400F and a vibrating blade at room temperature. A finite element computer model of the blade was used to calculate deflections, strains and stresses in the blade in response to the experiment loads. The holographically measured deflections were compared to the computed deflections and found to be in good agreement. Actual stresses were then taken to be those calculated by the computer program. The applicability of holographic techniques to the detection of flaws in hollow turbine blades was also investigated. The methods used did not reveal localized flaws but did reveal the presence of out of tolerance wall thicknesses. The feasibility of obtaining holograms of blades rotating at high speed was investigated analytically and experimentally. Analysis showed that certain optical arrangements or shortened laser pulses were required. Experiments were performed in which holograms were successfully recorded, confirming the analysis and demonstrating that high rates of rotation do not necessarily degrade holographic images. Author
- Test Facilities, Equipment and Methods
- Jet and Gas Turbine Engines