NONDESTRUCTIVE EVALUATION USING REAL-TIME SHEAROGRAPHY
type: CreativeWork
description: This thesis begins with an account on the development of shearography as background. The conventional double-exposure shearography for static testing and the commonly adopted time-average shearography for vibration study have been credited for their particular contributions and evaluated for their shortcomings. Real-time shearography, though receiving only limited qualitative attention from researchers in the past, stands out as a most flexible shearographlc technique. This project aims to provide a sound theoretical basis for real-time shearography and to explore in depth its potential applications in nondestructive testing and vibration analysis. The development of a simple and effective technique for determining fractional fringe order is also another primary objective in this project. The principle behind the formation of high resolution "live" fringe patterns by real-time shearography is presented. It is shown that both linear and nonlinear photographic recordings yield instantaneous fringe patterns which depict instantaneous surface displacement gradient of the deformed object. It is found that real-time shearography, coupled with static stressing, produces fringe patterns of uniform fringe contrast whereas shearogram resulting from vibration stressing has fringe visibility which decreases with increasing surface displacement gradient. In either case, real-time shearography requires a simpler optical setup and eliminates the need for Fourier filtering during fringe read-out. Nondestructive testing using real-time shearographic technique hiss achieved significant success in detecting sub-surface delamination in composite plates. Under partial vacuum stressing, the depth of flaw can be calculated with high accuracy and consistency at any easily-readable maximum fringe order or convenient partial vacuum pressure. Using vibration stressing, the flaw depth in a component can be determined without having to determine the fringe orders. Vibration analysis performed o…
abstract: This thesis begins with an account on the development of shearography as background. The conventional double-exposure shearography for static testing and the commonly adopted time-average shearography for vibration study have been credited for their particular contributions and evaluated for their shortcomings. Real-time shearography, though receiving only limited qualitative attention from researchers in the past, stands out as a most flexible shearographlc technique. This project aims to provide a sound theoretical basis for real-time shearography and to explore in depth its potential applications in nondestructive testing and vibration analysis. The development of a simple and effective technique for determining fractional fringe order is also another primary objective in this project. The principle behind the formation of high resolution "live" fringe patterns by real-time shearography is presented. It is shown that both linear and nonlinear photographic recordings yield instantaneous fringe patterns which depict instantaneous surface displacement gradient of the deformed object. It is found that real-time shearography, coupled with static stressing, produces fringe patterns of uniform fringe contrast whereas shearogram resulting from vibration stressing has fringe visibility which decreases with increasing surface displacement gradient. In either case, real-time shearography requires a simpler optical setup and eliminates the need for Fourier filtering during fringe read-out. Nondestructive testing using real-time shearographic technique hiss achieved significant success in detecting sub-surface delamination in composite plates. Under partial vacuum stressing, the depth of flaw can be calculated with high accuracy and consistency at any easily-readable maximum fringe order or convenient partial vacuum pressure. Using vibration stressing, the flaw depth in a component can be determined without having to determine the fringe orders. Vibration analysis performed o…
author: SIM CHAY WHATT
date published: 1995
date modified: 2026-07-24T03:33:34Z
provider: National University of Singapore
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: National University of Singapore