Vibration analysis by digital shearography

Wolfgang Steinchen; Lian Xiang Yang; Gerhard Kupfer

doi:10.1117/12.248666

23 August 1996 Vibration analysis by digital shearography

Wolfgang Steinchen, Lian Xiang Yang, Gerhard Kupfer

Proceedings Volume 2868, Second International Conference on Vibration Measurements by Laser Techniques: Advances and Applications; (1996) https://doi.org/10.1117/12.248666
Event: Second International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 1996, Ancona, Italy

Abstract

This paper describes the recent developments of the digital shearography for vibration analysis, i.e. real time observation of the time-average digital shearogram with refreshed reference frame and stroboscopic illumination in conjunction with the phase shifting technique for quantitative evaluation of the digital shearogram. Time- average method is by far the most usual technique for qualitative vibration analysis. In the conventional technique for real time observation of the time-average interferogram, the fringe contrast is poor because the fringe pattern is modulated by 1-J₀ ((Omega) ). In addition, the fringe is very sensitive against ambient noises such as thermal air waves or lower frequency vibrations. With the introduction of the refreshing reference frame technique, the fringe pattern is modulated by J²₀ ((Omega) ) and the fringe contrast becomes much better. Furthermore, the low frequency ambient noises are greatly suppressed by the technique. It is suited well for qualitative vibration analysis such as NDT and qualitative modal analysis. For quantitative vibration analysis, the stroboscopic technique in conjunction with the phase shifting method is applied, the accurate phase map of digital shearogram for a vibrating object can be obtained. Therefore, the dynamic deformation and strain fields of the vibrating object can be determined.

Citation Download Citation

Wolfgang Steinchen, Lian Xiang Yang, and Gerhard Kupfer "Vibration analysis by digital shearography", Proc. SPIE 2868, Second International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, (23 August 1996); https://doi.org/10.1117/12.248666

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