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Lianxiang Yang - One of the best experts on this subject based on the ideXlab platform.

  • Recent developments in digital Shearography for nondestructive testing
    Materials evaluation, 2020
    Co-Authors: Lianxiang Yang
    Abstract:

    Recently there has been considerable research activity in the development of digital Shearography for nondestructive testing (NDT) in production/field environments. The research has shown that digital Shearography has great potential in identifying discontinuities in objects and especially in the detection of delaminations in composite materials such as honeycomb structures. This paper is a review of the state of the art of digital Shearography for NDT. Recent developments of digital Shearography and its potentials and limitations for NDT will be demonstrated by examples of nondestructive testing for different materials.

  • double imaging mach zehnder spatial carrier digital Shearography
    Journal of Modern Optics, 2019
    Co-Authors: Yonghong Wang, Lianxiang Yang
    Abstract:

    ABSTRACTThis paper presents a Double Imaging Mach–Zehnder Spatial Carrier Digital Shearography (DIM-SCDS) system. Compared to traditional Spatial Carrier Mach–Zehnder Shearography, DIM-SCDS has two...

  • Digital Shearography for NDT: Phase Measurement Technique and Recent Developments
    Applied Sciences, 2018
    Co-Authors: Qihan Zhao, Yonghong Wang, Sijin Wu, Lianxiang Yang
    Abstract:

    Composite materials have seen widespread use in the aerospace industry and are becoming increasingly popular in the automotive industry due to their high strength and low weight characteristics. The increasing usage of composite materials has resulted in the need for more effective techniques for nondestructive testing (NDT) of composite structures. Of these techniques, digital Shearography is one the most sensitive and accurate methods for NDT. Digital Shearography can directly measure strain with high sensitivity when combined with different optical setups, phase-shift techniques, and algorithms. Its simple setup and less sensitivity to environmental disturbances make it particularly well suited for practical NDT applications. This paper provides a review of the phase measurement technique and recent developments in digital shearographic NDT. The introduction of new techniques has expanded the range of digital Shearography applications and made it possible to measure larger fields and detect more directional or deeper defects. At the same time, Shearography for different materials is also under research, including specular surface materials, metallic materials, etc. Through the discussion of recent developments, the future development trend of digital Shearography is analyzed, and the potentials and limitations are demonstrated.

  • Double Imaging Mach–Zehnder Spatial Carrier Digital Shearography
    Journal of Modern Optics, 2018
    Co-Authors: Yonghong Wang, Lianxiang Yang
    Abstract:

    ABSTRACTThis paper presents a Double Imaging Mach–Zehnder Spatial Carrier Digital Shearography (DIM-SCDS) system. Compared to traditional Spatial Carrier Mach–Zehnder Shearography, DIM-SCDS has two...

  • polarized digital Shearography for simultaneous dual shearing directions measurements
    Review of Scientific Instruments, 2016
    Co-Authors: Junrui Li, Lianxiang Yang, Boyang Zhang
    Abstract:

    The selection of the direction of sensitivity for digital Shearography is determined by its shearing direction. As a result, directionally shaped defects could be missed in non-destructive testing using a digital Shearography system with only one shearing direction. This paper reports a polarized digital Shearography system based on two Mach–Zehnder interferometers, which can create two orthogonal shearing directions and record shearograms in the two orthogonal directions simultaneously. The two shearograms are separated from each other by proper polarization design so that no cross interference occurs. The phase maps of the shearograms are generated by spatial phase shift methods through the introduction of different carrier frequencies in the two orthogonal shearograms and use of the Fourier transform method. This enabled simultaneous dual directional non-destructive testing during continuous loading. Theory derivation, spectrum analysis, and non-destructive testing application results are shown in detail.

Roger M. Groves - One of the best experts on this subject based on the ideXlab platform.

  • EXTREME Shearography : Development of a high-speed Shearography instrument for measurements of the surface strain components during an impact event
    Speckle 2018: VII International Conference on Speckle Metrology, 2020
    Co-Authors: Andrei G. Anisimov, Roger M. Groves
    Abstract:

    This work presents the design and preliminary results of a high-speed Shearography instrument in development for surface strain components measurements during an impact event. Composite materials are vulnerable to extreme dynamic loadings such as blade off events or foreign object damage as their mechanical properties are strain rate dependent. The development of new instruments to reconstruct extreme dynamic events will provide important insight into the understanding of the behaviour of composites. Shearography provides a quantitative measurement of the surface strain components with a high sensitivity as it is a non-contact interferometric technique. The current configuration of the Shearography instrument realises measurements of the out-of-plane surface strain components during an impact using a double frame approach. The first experimental results reveal phase maps registered during an impact event with μs temporal resolution. Later the experimentally measured surface strain components will be used as input and validation data for new numerical and analytical models of the impact response of composites. The overall set of technical parameters of the developing Shearography instrument makes it one of the most extreme applications of Shearography for material characterisation.

  • EXTREME Shearography: high-speed Shearography instrument for in-plane surface strain measurements during an impact event
    Optical Measurement Systems for Industrial Inspection XI, 2019
    Co-Authors: Andrei G. Anisimov, Roger M. Groves
    Abstract:

    This work presents the design and the latest experimental results on the surface strain measurements during an impact event obtained with the EXTREME high-speed Shearography instrument. The Shearography technique is used in this project to provide a quantitative measurement of the surface strain development at the first moments of the impact event (μs time scale) which may reveal the initiation of the failure mechanisms in composite materials. Experimentally measured surface strain components over the field of view will be used as input and validation data for new numerical and analytical models of the impact response of composites. The new configuration of the Shearography instrument realises measurements of the in- and out-of-plane surface strain components to improve coupling with the numerical models. Two viewing directions (shearing interferometers) with a double-frame approach are used to capture the interferograms during the impact. The interferometers realise a double-imaging Mach-Zehnder scheme for the spatial phase-shifting with independent control of the shearing amount and the carrier frequency. The set of technical parameters of the developed Shearography instrument makes it one of the most extreme applications of Shearography for material characterisation. The framework for this work is the “EXTREME Dynamic Loading – Pushing the Boundaries of Aerospace Composite Material Structures” Horizon 2020 project.

  • 3d shape Shearography technique for surface strain measurement of free form objects
    Applied Optics, 2019
    Co-Authors: Alexander G. Anisimov, Mariya G Serikova, Roger M. Groves
    Abstract:

    Shearography is a non-destructive testing technique that provides full-field surface strain characterization. Previous inspection of flat objects or simple geometric shapes has been reported. However, real-life objects especially in aerospace, transport, or cultural heritage are not flat, but their inspection with Shearography is of interest for both hidden defect detection and material characterization. Accurate strain measurement of a highly curved or free-form surface needs to be performed by combining in-line object shape measuring and processing of the Shearography data in 3D. Previous research has not provided a general solution for that. This paper presents a new approach of 3D shape Shearography which is based on the integration of a structured light projector for in-line shape measuring with 3D Shearography. For the experimental part, a 3D shape Shearography system prototype was developed and its performance was evaluated with a cylinder specimen loaded by internal pressure and compared with strain gauges.

  • 3D shape Shearography with integrated structured light projection for strain inspection of curved objects
    Optical Measurement Systems for Industrial Inspection IX, 2015
    Co-Authors: Alexander G. Anisimov, Roger M. Groves
    Abstract:

    © 2015 SPIE. Shearography (speckle pattern shearing interferometry) is a non-destructive testing technique that provides full-field surface strain characterization. Although real-life objects especially in aerospace, transport or cultural heritage are not flat (e.g. aircraft leading edges or sculptures), their inspection with Shearography is of interest for both hidden defect detection and material characterization. Accurate strain measuring of a highly curved or free form surface needs to be performed by combining inline object shape measuring and processing of Shearography data in 3D. Previous research has not provided a general solution. This research is devoted to the practical questions of 3D shape Shearography system development for surface strain characterization of curved objects. The complete procedure of calibration and data processing of a 3D shape Shearography system with integrated structured light projector is presented. This includes an estimation of the actual shear distance and a sensitivity matrix correction within the system field of view. For the experimental part a 3D shape Shearography system prototype was developed. It employs three spatially-distributed shearing cameras, with Michelson interferometers acting as the shearing devices, one illumination laser source and a structured light projector. The developed system performance was evaluated with a previously reported cylinder specimen (length 400 mm, external diameter 190 mmm) loaded by internal pressure. Further steps for the 3D shape Shearography prototype and the technique development are also proposed.

  • Shearography technology and applications a review
    Measurement Science and Technology, 2010
    Co-Authors: Ralph P Tatam, D. Francis, Roger M. Groves
    Abstract:

    Shearography is a full-field speckle interferometric technique used to determine surface displacement derivatives. For an interferometric technique, Shearography is particularly resilient to environmental disturbances and has hence become an invaluable measurement tool outside of the optics laboratory. Furthermore, the inclusion of additional measurement channels has turned Shearography from a qualitative inspection tool into a system suitable for quantitative surface strain measurement. In this review article we present a comprehensive overview of the technique, describing the principle of operation, optical configurations, image processing algorithms and applications, with a focus on more recent technological advances.

Y Y Hung - One of the best experts on this subject based on the ideXlab platform.

  • Shearography in Experimental Mechanics and Nondestructive Testing
    IUTAM Symposium on Advanced Optical Methods and Applications in Solid Mechanics, 2020
    Co-Authors: Y Y Hung
    Abstract:

    This paper reviews Shearography and its applications in experimental mechanics and nondestructive testing. Shearography is an interferometric method for measuring surface displacement derivatives. Unlike holography, it does not require special vibration isolation; hence it can be employed in field/factory environments. The technique has already received wide industrial acceptance for nondestructive testing. Other applications include strain measurement, material characterization, residual stress evaluation, vibration studies and 3D shape measurement.

  • non destructive evaluation nde of composites digital Shearography
    Non-Destructive Evaluation (NDE) of Polymer Matrix Composites, 2013
    Co-Authors: Y Y Hung, L X Yang, Y H Huang
    Abstract:

    Abstract: The increasing usage of composite materials has called for more effective techniques for inspecting the integrity of composite structures, as composite materials generally have higher likelihood of having material imperfections. This chapter reviews Shearography and its applications in non-destructive testing. Shearography is an interferometric technique for full-field, non-contacting measurement of surface deformation (displacement or strain). It was developed to overcome several limitations of holography by eliminating the reference beam. Consequently, it is less sensitive to environmental disturbances and is a practical tool that can be used in field/factory settings. In non-destructive testing, Shearography reveals defects in an object by identifying defect-induced deformation anomalies. Shearography has already received considerable industrial acceptance, in particular, for nondestructive testing of tires and aerospace structures. Other applications of Shearography include strain measurement, material characterization, residual stress evaluation, leak detection, hermetic seal evaluation, vibration studies and 3D shape measurement. This chapter focuses on its application in non-destructive testing with an emphasis on composite materials.

  • review and comparison of Shearography and active thermography for nondestructive evaluation
    Materials Science & Engineering R-reports, 2009
    Co-Authors: Y Y Hung, Y H Huang, Y S Chen, S P Ng, R W L Ip, Chiman Lawrence Wu, Po Sheun Chung
    Abstract:

    Abstract Shearography and thermography are optical techniques, both proven to be valuable tools for material nondestructive evaluation. Papers on these topics, however, are scattered and mainly appeared in optical journals. For the convenience of the materials community, this paper aims to present a comprehensive review of Shearography and active thermography and their applications in nondestructive evaluation of materials. Both techniques enjoy the merits of full-field, non-contact and allowing speedy detection of material defects in metal, non-metal as well as composites materials. However, they are fundamentally different in flaw detection mechanisms. Shearography measures materials’ mechanical response to stresses, whereas active thermography measures material's heat-transfer response to an instantaneous thermal excitation. A comparison of the advantages and limitations of two techniques for nondestructive evaluation will also be presented.

  • Characterization of Flaws Embedded in Externally Bonded CFRP on Concrete Beams by Infrared Thermography and Shearography
    Journal of Nondestructive Evaluation, 2009
    Co-Authors: C. S. Poon, S P Ng, W. F. Tsang, Y Y Hung
    Abstract:

    Carbon fiber-reinforced polymer (CFRP) has become an important material to rehabilitate deteriorating concrete structures. The quality of the bond between the externally-bonded CFRP and concrete elements is crucial to durability and structural integrity of the rehabilitated concrete structure. However, flaws between CFRP and concrete interfaces can reduce the effective contact area significantly and therefore, the overall bond strength at these interfaces. Such flaws are not readily noticed by naked eyes, but can be detected and quantified non-destructively and effectively by using full-field and non-contact infrared thermography (IRT) and laser Shearography. Flaw and sound areas presented within the FRP-concrete interfaces manifest very different thermal decay and mechanical fingerprints. In this paper, we report a study which tested, with IRT and Shearography, the sizes and shapes of 17 round-shaped and artificial flaws embedded in 6 CFRP-concrete specimens; and then compared the results with the actual flaw sizes and shapes. In general, the results show that IRT underestimated the actual flaw sizes by 6.1% on average, whilst Shearography overestimated the actual flaw sizes by 9.4% on average. These results demonstrated that both IRT and Shearography are promising non-destructive evaluation techniques that can be used to define flaw boundaries and determine flaw sizes within the CFRP-concrete composites.

  • Shearography an optical measurement technique and applications
    Materials Science & Engineering R-reports, 2005
    Co-Authors: Y Y Hung, H P Ho
    Abstract:

    This article reviews Shearography and its applications. Shearography is a laser-based technique for full-field, non-contacting measurement of surface deformation (displacement or strain). It was developed to overcome several limitations of holography by eliminating the reference beam. It does not require special vibration isolation; hence, it is a practical tool that can be used in a field/factory environment. Shearography has already received considerable industrial acceptance, in particular, for non-destructive testing. In non-destructive testing, Shearography reveals defects in an object by identifying defect-induced deformation anomalies. Other applications of Shearography include strain measurement, material characterization, residual stress evaluation, leak detection, vibration studies and 3-D shape measurement.

Ralph P Tatam - One of the best experts on this subject based on the ideXlab platform.

  • quantitative Shearography error reduction by using more than three measurement channels
    Applied Optics, 2011
    Co-Authors: Thomas O H Charrett, Daniel Francis, Ralph P Tatam
    Abstract:

    Shearography is a noncontact optical technique used to measure surface displacement derivatives. Full surface strain characterization can be achieved using Shearography configurations employing at least three measurement channels. Each measurement channel is sensitive to a single displacement gradient component defined by its sensitivity vector. A matrix transformation is then required to convert the measured components to the orthogonal displacement gradients required for quantitative strain measurement. This transformation, conventionally performed using three measurement channels, amplifies any errors present in the measurement. This paper investigates the use of additional measurement channels using the results of a computer model and an experimental Shearography system. Results are presented showing that the addition of a fourth channel can reduce the errors in the computed orthogonal components by up to 33% and that, by using 10 channels, reductions of around 45% should be possible.

  • Shearography technology and applications a review
    Measurement Science and Technology, 2010
    Co-Authors: Ralph P Tatam, D. Francis, Roger M. Groves
    Abstract:

    Shearography is a full-field speckle interferometric technique used to determine surface displacement derivatives. For an interferometric technique, Shearography is particularly resilient to environmental disturbances and has hence become an invaluable measurement tool outside of the optics laboratory. Furthermore, the inclusion of additional measurement channels has turned Shearography from a qualitative inspection tool into a system suitable for quantitative surface strain measurement. In this review article we present a comprehensive overview of the technique, describing the principle of operation, optical configurations, image processing algorithms and applications, with a focus on more recent technological advances.

  • surface strain measurement using multi component Shearography with coherent fibre optic imaging bundles
    Measurement Science and Technology, 2007
    Co-Authors: Daniel Francis, Stephen W. James, Ralph P Tatam
    Abstract:

    Shearography is a full-field interferometric speckle technique used to determine displacement derivatives. Measurement of surface strain is possible using Shearography if six components of displacement gradient are calculated. This can be achieved using Shearography instrumentation that incorporates at least three measurement channels combined with two orthogonal shear directions. This paper presents a laser Shearography instrument that utilizes coherent imaging fibre bundles to port four spatially multiplexed speckle images to a single CCD camera via a shearing Michelson interferometer. The four images are spatially multiplexed onto the sensor of a CCD camera. Wrapped phase maps are derived from the recorded speckle interferograms using temporal phase stepping. The unwrapped phase maps are combined with the measurement channel sensitivity vectors using a matrix operation to determine the required displacement derivatives. Results from an out-of-plane displacement of a flat aluminium plate are presented and compared with a computational model. Results from a second test object that show in-plane and out-of-plane strain components are also shown.

  • Multicomponent laser Shearography for the investigation of defects in rotating machinery
    Optical Metrology in Production Engineering, 2004
    Co-Authors: Roger M. Groves, Stephen W. James, Stuart E. Barnes, Shan Fu, Domenico Furfari, Philip E. Irving, Ralph P Tatam
    Abstract:

    Shearography is a full-field interferometric optical technique that is usually used for the qualitative investigation of defects in non-destructive testing applications. The optical configuration is sensitive directly to displacement gradient, a parameter closely related to the surface strain. The component of the displacement gradient that is measured is determined by the illumination and viewing directions and by the direction of the applied shear. The sensitivity is governed by the magnitude of applied shear and by the optical wavelength. Full characterisation of the surface strain requires a measurement of six-components of displacement gradient; this is achieved in Shearography by forming a number of distinct measurement channels using multiple illumination, or viewing, directions. In this paper the authors discuss the quantitative measurement of the strain field around a fatigue crack, using a time-division-multiplexed diode laser Shearography instrument. To investigate moving objects, a pulsed laser provides a method of freezing the object position at two points in the loading cycle. A Shearography instrument incorporating two frequency doubled pulsed Nd:YAG lasers, with a common injection seeder is described. The measurement channels are spatially-multiplexed by viewing from four directions using an optical fibre imaging bundle, with optical processing at a remotely located interferometer head. Preliminary experimental measurements are presented.

  • Multicomponent Shearography using optical fiber imaging-bundles
    Optical Measurement Systems for Industrial Inspection III, 2003
    Co-Authors: Roger M. Groves, Stephen W. James, Ralph P Tatam
    Abstract:

    ABSTRACT Shearography is a full-field non-contact optical technique usually used for the investigation of defects in non-destructive testing. In Shearography interferometric speckle patterns recorded before and after object deformation arecorrelated, often by subtraction, to yield correlation fringes sensitive to displacement gradient, a parameter closelyrelated to surface strain. Shearography is sensitive to the component of displacement gradient that is determined by thedirection of the illumination and viewing directions, the optical wavelength and by the magnitude and direction of theapplied shear. To perform a multi-component measurement requires illumination, or viewing, from a minimum of threedirections, followed by a coordinate transformation to obtain the in-plane and out-of-plane displacement gradientcomponents. This would normally require the use of either multiple optical sources or multiple interferometer heads andmultiple cameras. In this paper the authors use a single laser source, a single interferometer head and camera, with fourviews of the object ported from the camera lenses to the interferometer using a four-leg optical fibre imaging bundle.This approach allows four components of displacement gradient to be recorded simultaneously. Experimental resultsfrom the multi-component Shearography instrument are presented.Keywords: Shearography, optical fibre imaging-bundle, multi-component measurement, surface strain measurement

D. Francis - One of the best experts on this subject based on the ideXlab platform.

  • Non-destructive evaluation (NDE) of composites: introduction to Shearography
    Non-Destructive Evaluation (NDE) of Polymer Matrix Composites, 2014
    Co-Authors: D. Francis
    Abstract:

    Abstract: Shearography is an optical technique that relies on interference of laser speckle patterns to visualise variations in surface strain. As it provides full-field measurements and is particularly robust against external vibrations for an interferometric system, it is well suited to industrial non-destructive testing. This chapter discusses the principle of operation of Shearography, explaining the process of fringe formation and interpretation and the use of phase analysis to provide quantitative data and improve fringe contrast and measurement sensitivity. The application of Shearography for non-destructive evaluation of composite materials is then considered and is compared with other well-established techniques.

  • Shearography technology and applications a review
    Measurement Science and Technology, 2010
    Co-Authors: Ralph P Tatam, D. Francis, Roger M. Groves
    Abstract:

    Shearography is a full-field speckle interferometric technique used to determine surface displacement derivatives. For an interferometric technique, Shearography is particularly resilient to environmental disturbances and has hence become an invaluable measurement tool outside of the optics laboratory. Furthermore, the inclusion of additional measurement channels has turned Shearography from a qualitative inspection tool into a system suitable for quantitative surface strain measurement. In this review article we present a comprehensive overview of the technique, describing the principle of operation, optical configurations, image processing algorithms and applications, with a focus on more recent technological advances.