• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.2
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• pp.177-181
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• 2001

Nondestructive testing(NDT) is one of the fundamental tools to improve the quality of commercial and industrial products. NDT is potentially a major application of interferometry. Interferometry(ESPI, Shearography, ect) has successfully been applied in various industrial environments such as high performance aircraft, home appliance, automotive, and laminates on engine structures, etc. Today's industry demands high performance components with toughest mechanical features and ultimate safety standards. Especially in automotive and aircraft industry the development process focuses on tailor-made design and solutions to meet customer specifications. To reconcile economy, ligh-weight construction has become a key issue. Many companies are looking for new advanced NDT techniques to archive cost efficiency over the limitations of classical methods. ESPI and shearography allow a rapid, full field and 3D-measurement without contact. In this paper recent applications of ESPI and shearography for NDT are described. Advanced features of classical techniques are specified and new applications in material and component testing are presented.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.211-214
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• 2001

Electronic Speckle Pattern Interferometry(ESPI) is one of optical technique to measure displacement precisely, uses CCD camera to show result image in real time. General ESPI system measures in-plane or out-of-plane displacement. Shearography is one of electronic speckle pattern interferometric methods which allow full-field observation of surface displacement derivatives and it is robust in vibration. The shearography provides non-contacting technique of evaluating defects nondestructively. In this study, the shearography was used to evaluate defects in Carbon Fiber Reinforced Plastic(CFRP). Various sizes of artificial defects were embedded in various depths of woven CFRP plate. Effects due to the variation of size and depth of defects were evaluated in this study.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.245-251
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• 2002

Electronic Speckle Pattern Interferometry(ESPI) is one of optical technique to measure displacement precisely, uses CCD camera to show result image in real time. General ESPI system measures in-plane or out-of-plane displacement. Shearography is one of electronic speckle pattern interferometric methods which allow full-field observation of surface displacement derivatives and it is robust in vibration. The shearography provides non-contacting technique of evaluating defects nondestructively In this study, the shearography was used to evaluate defects in Carbon Fiber Reinforced Plastic(CFRP). Various sizes of artificial defects were embedded in various depths of woven CFRP plate. Effects due to the variation of size and depth of defects were evaluated in this study.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.1
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• pp.33-39
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• 2008

Dual-function interferometer is an interferometer that has all features of ESPI (electronic speckle pattern interferometry) and shearography in one interferometer setup. The deformatiou of an object is directly obtained by ESPI while the slope of the deformation of an object is obtained by shearography. If the result of shearography is divided by shearing amount and integrated by numerical analyzing, then finally the reconstructed deformation of an object that is the same as the results directly obtained by ESPI can be measured by shearography. In this study, rubber and alruminum plates are used as specimen and its out-of-plane deformation is measured by ESPI and shearography setup of the dual-function interferometer. Each of the results obtained by ESPI and shearography is compared by using numerical integration to the result of shearography. From this study, it is confirmed that the reconstructed deformation results obtained by numerical integration good agree with the results obtained by ESPI.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.623-624
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1077-1078
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• 2013

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.772-776
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• 2004

The paper describes the quantitative determination of out-of-plane displacement from result of Shearogrpahy, which can measure the first-order partial derivative of out-of-plane displacement directly. However, the differential sensitivity of Shearography is related to the amount of shearing, which is manually adjustable in optical interferometer and affects the quantitative determination. The relationship between those is inspected by comparing ESPI with Shearography. From the result, the amount of shearing plays a modulation factor of out-of-plane displacement and small amount of shearing gives good agreement with out-of-plane displacement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.140-143
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• 2001

Digital shearography, a speckle pattern method is based on the superposition of two laterally sheared images. Therefore, object points which are positioned in some distance from each other are superposed in the image plane. This shearography, one of NDT methods without contact, is able to inspect defects in pipelines and pressure vessels that are used in nuclear power plants. This is can inspect whole fields and has a low sensitivity to environmental noise. Because optical setting is very simple, it has a little exhaustion of time, cost and man power. And also it can find a defect position through real time monitoring of a part. This paper, finds out the relationship among shearing quantity image quality and defect size with this method.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.251-254
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• 2003

In recent years, shearogrpahy has significantly improved capabilities In the areas of unbend and separation detection in tires. Although shearography has many advantages fur qualitative evaluation, the technique remains the problem of quantitative analysis of inside defects, because shearography needs several effective factors including the amount of shearing, shearine direction and induced load, which exist as barrier for the quantitative analysis of inside defects. Since the factors are highly dependent on inspectors skill and also affect the in-situ workability. The factors were optimized and the size of cracks inside of pipeline and tire has been quantitatively determined.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.8-13
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• 2004

We presented the method to obtain four speckle interferograms with relative phase shift of $\pi$/2 by passive devices such as waveplate and polarizer, calculate the phase at each point of the speckle interferogram in shearography using Wollaston prism, and theoretically demonstrated the feasibility of the unposed method by Jones matrix.