A flow liner used in the propulsion system on the space shuttle was under evaluation to determine whether vibrations could result in cracking. The liner could be subject to a range of vibration frequencies, and it was not known which would produce the greatest vibratory strains.
The specimen under test was complex, which meant that the overall response of the part would be impossible to predict. It was also fairly lightweight, which meant that any contact with the specimen could be expected to alter its response. Although the areas of primary concern were not very large, they included geometric features which made it difficult to predict the location of peak strains. It was also difficult to know whether the areas of peak strain would be large enough to be identified with strain gages. This test was further complicated by the high frequencies required to simulate flight conditions. Vibration response was measured at frequencies up to 6kHz.
Correlated Solutions provided a Vic-3D system and a vibration synchronization module designed to accurately capture data from vibrating specimens without the expense of high-speed cameras. Because the measurements do not require contact with the specimen, the specimen’s movement was not affected by the measurement system. Strain measurements were obtained over the entire image area, allowing the true location of the maximum strain to be identified. Because of Vic-3D’s high spatial resolution, researchers were able to obtain accurate measurements even when peak strains were concentrated in a very small area.
Click here to see an animation of the 3D plot shown above.
Read about the Vibration Fatigue Module for more information on this technology.