The use of a lock-in amplifier to apply digital image correlation to cyclically loaded components

Fruehmann, R.K.; Dulieu-Barton, J.M.; Quinn, Simon; Tyler, J.P.

doi:10.1016/j.optlaseng.2014.12.021

Cited by 22 publications

(16 citation statements)

References 21 publications

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“…Specifically, the authors generally use SDIC with high-speed cameras to analyze dynamic tests with a harmonic excitation [34,38,15], a shock [34,18] or a random excitation [34,18,39,5,32]. From full field displacement measurements, different mode shapes are extracted by using e.g.…”

Section: Introductionmentioning

confidence: 99%

“…From full field displacement measurements, different mode shapes are extracted by using e.g. Fourier analysis and modal curve fitting [34,32] or using lock-in amplifiers [15] in a post-processing phase. In [38], the authors use an a posteriori sinusoidal fitting method to increase the accuracy of the displacement measurement of fatigue crack growth tests.…”

Section: Introductionmentioning

confidence: 99%

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A Space-Time PGD-DIC Algorithm:

2018

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The aim of this study is to develop a new regularized Digital Image Correlation (DIC) method for time dependent measurements. The correlation problem is written as a minimization problem over the space-time domain in a general formulation including 2D-DIC and Stereo DIC (SDIC). The unknown time-resolved displacement field is found as a sum of products of space and time functions, similarly to the Proper Generalized Decomposition in computational mechanics. It is shown that the space fields are less sensitive to noise as time regularity acts as a physical regularization of the space fields. The proposed method is illustrated by vibration measurement under harmonic excitation in 2D-DIC and SDIC.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Space-Time PGD-DIC Algorithm:

2018

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“…An approach for DIC that utilises low-cost cameras and can be used during fatigue loading has been developed in [20], known as LIDIC (lock-in DIC), similar to that used in [10,11]. The approach captures a series of white-light images over multiple loading cycles.…”

Section: Automated Image Capture Methodologymentioning

confidence: 99%

Data-rich characterisation of damage propagation in composite materials

Battams

Dulieu-Barton

2016

Composites Part A: Applied Science and Manufacturing

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A novel methodology for the synchronised capture of high resolution white-light and infra-red (IR) images during a fatigue test is described. The approach allows digital image correlation (DIC) and thermoelastic stress analysis (TSA) to be applied practically simultaneously without the requirement to pause the cyclic load. The methodology is demonstrated on cross-ply carbon-epoxy specimens that have experienced damage induced by intermediate strain rate loading. Similar undamaged specimens are studied and the results from each compared.Various damage types are identified which include transverse cracking, delaminations and longitudinal splitting. The results are verified using X-ray computed tomography (CT).

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“…There is significant overlap, at least in terms of broad principles, between the approach described here and the lock-in DIC approach developed by Fruehmann et al [9], who describe the use of a low-speed DIC system to capture cyclic strain data using a lock-in amplifier. As with Fruehmann et al, the images for DIC processing are captured here at a lower frequency than that of the vibration or cyclic loading, resulting in an undersampled set of data.…”

Section: Introductionmentioning

confidence: 99%

“…Unlike that approach however, the generation of the quadrature signal in the present work is performed using hardware (and errors in the π/2 phase shift are corrected in software), a lock-in amplifier is not used, and a xenon stroboscopic lamp (in the form of a high-powered photographic flash unit), in conjunction with very short exposure, is used to Bfreeze^the images rather than using a steady light source. The present work also covers higher frequencies (exceeding 1 kHz) than those reported in references [9][10][11], and may be regarded as being based on asynchronous rather than synchronous lock-in principles [12].…”

Section: Introductionmentioning

confidence: 99%

Digital Image Correlation Vibrometry with Low Speed Equipment

Warburton

Buss

et al. 2016

Exp Mech

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A low-cost method is presented which enables digital image correlation (DIC) with conventional cameras (i.e. not high-speed) to be used for determination of vibration deflected shapes via the use of a stroboscopic lamp and some simple ancillary circuits. For each natural frequency of the structure under consideration, a sequence of images is captured asynchronously with the vibrations using the DIC system and the resulting displacement fields are correlated with the excitation signal driving the vibration using a least-squares approach. Three approaches for performing this correlation are outlined, one of which is developed into the algorithm used for processing the present results to obtain the amplitude and phase of the vibration at each point on the specimen, allowing the deflected shape to be reconstructed. This process is illustrated using the example of a vibrating aluminium plate. The resulting shapes and frequencies agree well with finite element modal analyses of the plate.

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The use of a lock-in amplifier to apply digital image correlation to cyclically loaded components

Abstract: An approa

Cited by 22 publications

References 21 publications

A Space-Time PGD-DIC Algorithm:

A Space-Time PGD-DIC Algorithm:

Data-rich characterisation of damage propagation in composite materials

Digital Image Correlation Vibrometry with Low Speed Equipment

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