Digital shearography: state of the art and some applications

Chen, Fanglin

doi:10.1117/1.1329336

Cited by 17 publications

(7 citation statements)

References 137 publications

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“…The techniques include: pulse thermography [27], lock-in thermography [28], thermosonics [29], and digital shearography [30]. Digital shearography has a broad application field to provide information about flaws in materials such as discontinuities and separations, dimensions, as well as stress and dynamic response.…”

Section: Shearographymentioning

confidence: 99%

A feasibility study on different NDT techniques used for testing bond quality in cold roll bonded Al-Sn alloy/steel bimetal strips

2017

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-This paper presents non-destructive testing (NDT) results for the detection of bond defects in aluminiumtin (Al-Sn) alloy/steel bimetal strips. Among all types of bimetal strip that are used in the automotive industry for plain journal engine bearings, Al-Sn alloys cold roll bonded (CRB) onto steel backing is the most common type. The difficulty to evaluate the metallurgical bond between the two dissimilar metals is a major industrial concern, which comprises the risk that bearings fail in the field. Considering the harsh performance requirements, 100% online non-destructive testing would be desirable to significantly reduce the business risk. Nowadays bimetal strip manufacturers still rely on destructive testing through different peel-off tests. This work offers the results from four independent NDT studies, using active thermography, shearography, ultrasound and guided wave electromagnetic acoustic transducers (EMATs) and samples with different artificially implanted defects, to explore the feasibility to qualitatively indicate the occurrence of bond defects. A destructive peel off test was used to correlate the NDT results with known bond quality. The studies were done under laboratory conditions, and in case of ultrasound also online under production conditions. During the ultrasound online test, the requirements that a NDT technique has to fulfil for online inspection of Al-Sn alloy/steel bimetal strip were established. For active thermography, shearography and guided wave EMAT techniques, it was theoretically analysed, if the laboratory test results could be transferred to testing under production conditions. As a result, guided waves using EMATs, among the four tested methods, are best suited for online inspection of Al-Sn alloy/steel bimetal strip. This research was carried out in collaboration with MAHLE Engine Systems UK Ltd., an Al-Sn alloy/steel bimetal strip manufacturer for the automotive industry.

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Section: Shearographymentioning

confidence: 99%

A feasibility study on different NDT techniques used for testing bond quality in cold roll bonded Al-Sn alloy/steel bimetal strips

2017

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“…Noting that (1) the random phase field ϕ is uniformly distributed from 0 to 2π and (2) ϕ ∆ usually varies slower than ϕ and can be assumed constant in a local area, a local averaging yields [3] ( )…”

Section: Principlementioning

confidence: 99%

“…Incorporating digital techniques in conventional shearography makes the measurement faster and more flexible, resulting in new techniques and applications. [2][3][4]. A good example of opto-digital wedding is the determination of curvature (second order derivatives of the displacement) for plate-bending problems.…”

Section: Introductionmentioning

confidence: 99%

OS01W0134 Digital shear for curvature determination in speckle shearography

Kemao

Soon

Asundi

2003

ATEM

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Shearography provides whole-field derivatives of displacement. In many plate-bending problems, stresses are proportional to curvatures. A novel digital scheme is proposed to digitally shear the shearographic fringes to obtain second derivatives or curvature contours over the whole field. Since differentiation is noise-prone, a novel filtering approach is proposed to obtain good results. Examples of the method for different shear amounts are shown to reveal the advantages and capabilities of this approach.

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“…By contrast, shearing interferometry (SI) is an effective way to obtain relative phase information without additional reference waves because SI is a method to make an interferogram with self-interference 40 – 42 . There have been several effective methods to perform SI 43 – 52 . One of them is to use a double-frequency grating (DFG) to shear the diffracted waves when the wavefront passes through a designed grating, and is referred to as double-frequency grating shearing interferometry (DFGSI) 53 , 54 .…”

Section: Introductionmentioning

confidence: 99%

Double-frequency grating shearing interferometer with built-in phase-shifting function for robust multi-level phase retrieval

Hou

Yang

et al. 2022

Sci Rep

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In this paper, we propose and demonstrate a novel interferometer and signal process to retrieve two-dimensional signals with multilevel phases. The interferometer is based on a shearing interferometry with double-frequency grating, and phase-shifting interferometry is derived as a built-in function of the lateral displacement of the grating. The interferometer not only retrieves the multilevel phase signals but also eliminates slow-varying phase errors wherever they occur. Owing to the common path algorithm, the new interferometer is more robust in dynamic circumstances for optical testing and data processing. We propose a pre-integral signal process for two-dimensional (2D) data processing to prevent post-phase-integral due to shearing interferometry. The simulation and experiment showed that the proposed interferometer with a pre-integral process has various advantages in signal processing for multilevel phase retrieval, and will be useful for higher data rates in optical data storage and free-space communication.

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Digital shearography: state of the art and some applications

Cited by 17 publications

References 137 publications

A feasibility study on different NDT techniques used for testing bond quality in cold roll bonded Al-Sn alloy/steel bimetal strips

A feasibility study on different NDT techniques used for testing bond quality in cold roll bonded Al-Sn alloy/steel bimetal strips

OS01W0134 Digital shear for curvature determination in speckle shearography

Double-frequency grating shearing interferometer with built-in phase-shifting function for robust multi-level phase retrieval

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