Interferometric strain gage and rosettes extended to out-of-plane deformation measurements

Keyu Li

doi:10.1117/12.211888

14 June 1995 Interferometric strain gage and rosettes extended to out-of-plane deformation measurements

Keyu Li

Proceedings Volume 2544, Interferometry VII: Techniques and Analysis; (1995) https://doi.org/10.1117/12.211888
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

Abstract

This paper extends an optical strain gage/rosette technique to measure derivatives of out-of- plane displacements. The principle of the technique is interference of light reflected and diffracted from two or three closely spaced indentations on a specimen surface. The technique measures derivatives of in-plane and out-of-plane displacements simultaneously through analyzing the phase shift of the interference fringes. Movement of the interference fringes is monitored by a photodiode system and collected via a microcomputer in real time to obtain the specimen deformations. There are a variety of the indentation configurations. The configuration of two pyramidally shaped indentations enables measurements of one derivative of in-plane and one derivative of out-of-plane displacements. Three indentations with six or eight reflective faces allow determination of three derivatives of in-plane and three derivatives of out-of-plane displacements. The derivatives are with respect to the directions of the indentation separations. The theory of the technique is presented. Associated instrumentation for data acquisition and analysis is also described. Experiments are conducted on a cantilever beam to verify the capability of the technique to measure small deflection angles. The comparative results between measurements and theoretical predictions show that the method is feasible to measure derivatives of out-of-plane displacements.

Citation Download Citation

Keyu Li "Interferometric strain gage and rosettes extended to out-of-plane deformation measurements", Proc. SPIE 2544, Interferometry VII: Techniques and Analysis, (14 June 1995); https://doi.org/10.1117/12.211888

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