Holographic Measurement of Wave Propagation in Axi-Symmetric Shells.
Abstract
Holography is a lensless imaging technique which allows the reconstruction of three dimensional images. A related technique, called holographic interferometry, allows one to measure static or dynamic displacement on the order of a wavelength of light. The present report deals with the use of pulsed, double exposure holographic interferometry to record the propagation of transverse waves in thin walled axisymmetric shells. The report is Subdivided into sections dealing with (1) Wave propagation in circular cylindrical shells (2) Wave propagation past cut outs and stiffeners and (3) Wave propagation in conical shells. Several interferograms are presented herein which show the waves reflecting from the shell boundaries, from cut outs, and from stiffening rings. The initial response of the shell was nearly axisymmetric in all cases, but nonsymmetric modes soon appeared in the radial response. This result suggests that the axisymmetric response of the shell may be dynamically unstable, and thus may preferentially excite certain circumferential harmonics through parametric excitation. Attempts were made throughout this study to correlate the experimental data with analysis. For the most part, good agreement between theory and experiment was obtained. Occasional differences were attributed primarily to simplifying assumptions used in the analysis. As faster and more economical computer analyses of wave propagation become available, it is hoped that the experimental data given herein will serve to verify computer solutions. From the standpoint of engineering applications, it is clear that pulsed laser holography can be used to obtain quantitative engineering data. Areas of dynamic stress concentration, stress concentration factors, local anomalies, etc. can be readily determined by holography.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1972
- Accession Number
- ADA307523
Entities
People
- David A. Evensen
- Jerold L. Jacoby
- Robert Aprahamian
Organizations
- TRW Inc.