• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.6
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• pp.643-648
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• 2002

In this study, shearography and ESPI have been used for quantitative analysis of an inside crack of pipeline and both of them appeared suitable to qualitatively detect inside crack. However, shearography needs several effective factors including the amount of shearing, shearing direction and induced load for the quantitative evaluation of the inside crack. In this study, the factors were optimized for the quantitative analysis and the site of cracks has been determined. Although the effective factors in shearography has been optimized, it is difficult to determine the factors exactly because they are related to the details of tracks. On the other hand, ESPI is independent on the details of a crack and only the induced load plays an important role. The out-of-plane displacement was measured under the optimized load and the measured were numerically differentiated, which resulted in an equivalent to the shearogram. The size of cracks can be determined quantitatively without any detail of a crack.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.1
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• pp.59-66
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• 2013

The measuring of internal defects of objects using the shearography has many advantages. It is a non-contact and non-destructive method and It has a real time measurement speed and no constraints of object shape. Compared to ESPI(Electronic Speckle Pattern Interferometry), Shearography has a very low error rate by vibration and air turbulence. So shearography provides possibilities of industrial application. In this paper, Image processing algorithm that is measurement of out-of-plane deformation using the shearography is proposed by developed using the LabVIEW 2010 and measurement result of out-of-plane ESPI and Shearography are compared quantitatively.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.686-692
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• 2013

Today, environmental issues have become a matter of worldwide concern. In particular, automobile industries engage in considerable research and investment to develop high-efficiency and ecofriendly cars. Most ecofriendly cars use natural gas or hydrogen gas instead of fossil fuels. In this regard, low-weight and high-pressure vessels have gradually been developed to increase the driving distance of a car. However, most pressure vessels installed in cars develop many defects over time owing to shocks sustained when the car is being driven. Such defects can cause the explosion of the pressure vessel. Therefore it is important to prevent such explosions due to internal defects. The use of shearography for measuring the internal defects of objects afford many advantages. It is a non-contact and non-destructive method, and it is not limited by the object shape. In this study, the internal defect deformation and strain of an aluminum liner that is used in a CNG bus for the fuel storage tank is measured using shearography. It is important to measure the strain and deformation in order to detect defects and repair the pressure vessel. To verify the accuracy of the shearography measurement method, the measurement results of shearography, out-of-plane ESPI, and FEM are compared quantitatively.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.3
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• pp.302-308
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• 2008

Composite materials are widely used as structural materials for aerospace engineering because of its excellent mechanical properties such as light weight, high stiffness, and low thermal expansion. In driving, impact damage is one of the common but dangerous damages, caused by internal failure of the laminas interface which is not detected by in the surface. Many techniques to detect defects or delaminate between laminates have been reported. Shearography is a kind of laser speckle pattern interferometry with the advantages of non-destructive, non-contact, high resolution and displacement slope measurement. In this paper, the shearography is used to evaluate non-destructively impact damaged surface of the composite material and a measuring method using shearography for the thermal deformation of a impact damaged composite material is discussed. The basic principles of the technique are also described briefly.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.1
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• pp.97-104
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• 2009

There is a many kinds with nondestructive testing such as RT and UT representatively. Referred before two testing methods there is a limit which is spatial such as nuclear pipe, small vessel, sealing up vessel. So a new technique needs to overcome the limit which is spatial. shearography will be able to overcome the limit which is spatial. This paper introducing shearography which was known as non-contact full-field testing method and It is an interferometric technique for measurement of surface deformation such as displacement or displacement gradient. Also, a research about internal defect of the flange welding zone was accomplished. About variation with method pressurized with the Gaseous Nitrogen. Phase map where is various were measured according to changing a sheared direction, size of crack and loaded pressure. Consequently, crack quantitatively to be detected qualitatively was measured by using shearography.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.6
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• pp.563-575
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• 2007

This contribution contained the classical work of an open-hole tensile plate to demonstrate the performance of grating shearography and to compare with the results obtained by other full-field measurement techniques, The isotropic plate with an open-hole has often appeared in the previous contributions introducing novel full-field method and system. Grating shearography directly provided six quantitative measurands about the specimen's surface kinematics by using a single measurement set: three in-plane strains, in plane rotation, and two out-of-plane slopes. The quasi-plane wavefront of grating metrology led to high signal-to-noise ratio (SNR) and thus neither fitting nor filtering was applied, and the small shearing distance of $101{\mu}m$ could be used. The small shearing distance provided the outstanding spatial resolution of $80{\mu}m$ and sensitivity appropriate for experimental mechanics. Finally, the grating shearography enabled the visualization of the complex surface deformation around the hole and also detected parasitic flexions of the specimen in the micrometer regime during the tensile test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.400-403
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• 2002

This paper presents a shearographic technique for measuring in-plane strains. During the measurement, the test object is illuminated alternately with two laser beams, symmetrically with respect to the viewing direction. Employing a phase shift technique, the phase distributions due to object deformation for each beam are obtained separately. The difference of the two phase distributions depicts the derivative of in-plane surface displacements. The technique is equivalent to a system of many strain gages.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.35-38
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• 2002

Real defects in composite structures were detected by using laser measuring system. Four types of specimens, that is, a composite laminate, a honeycomb structure, a free-edge delamination and an adhesive joint, were used to study the applicability of ESPI and Shearography to composite structures. Thermal loading method, which can easily induce the surface deformation of specimen, was used to detect defects. Experimental results show that defects in composite structures can be easily detected by ESPI and Shearography. Moreover, it shows that ESPI and Shearography can be usefully applied to the detection of defects in various kinds of composite structures.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.298-303
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• 2003

In recent years, shearogrpahy has significantly improved capabilities in the areas of unbond and separation detection in tires. Although shearography has many advantages for qualitative evaluation, the technique remains the problem of quantitative analysis of inside defects, because shearography needs several effective factors including the amount of shearing, shearing 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.195-198
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• 2001

Backside defect of plate structure may grow due to fatigue or overload to cause critical failure during operation, so it is important to detect this kind of defect in line. For this purpose, nondestructive, non-contact and highly sensitive method is required. ESPI and Shearography are considered as useful method to satisfy these requirements. In this paper, the possibility of application of ESPI and Shearography to detect the backside defect of steel plate and to quantify the defect size was tested. For the experiment, some steel plates with defect on the backside were prepared. Experimental results for these plates showed that location and size of defect could be detected correctly by both of ESPI and Shearography.