Comparison of Shearography to Scanning Laser Vibrometry as Methods for Local Stiffness Identification of Beams

Zastavnik, Filip; Pyl, Lincy; Gu, Jun; Sol, Hugo; Kersemans, Mathias; Paepegem, Wim Van

doi:10.1111/str.12069

Cited by 12 publications

(12 citation statements)

References 40 publications

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“…If the shearing angle α x is constant and the distance d 0 is changing, according to equation (12) x mm for this case). The correction of applying the calibration maps, by using equation (13), is thus also small, in the interval [−2.0%, 1.6%] for this case.…”

Section: Resultsmentioning

confidence: 92%

“…First the varying shearing distances δ x and δ y are computed from the measured average shearing distances δ x and δ y by applying the calibration map in equations (13). From two measurements of the same experiment with distinct shearing distances, by using equation (9), the exact deformation gradient can be computed.…”

Section: Resultsmentioning

confidence: 99%

“…Shearography is generally considered to be less susceptible to environmental vibrations than the other interferometric techniques, as the gradient measurement is not affected by the rigidbody translations. However, our previous work [13,14,21] has shown that vibration isolation can greatly benefit noise reduction in the measurements. The refraction between zones of air with different temperatures can cause transient optical distortion.…”

Section: Errors In Shearographymentioning

confidence: 99%

“…Another application of quantitative shearography is the full-field stiffness identification using displacement gradients of vibrating surfaces. An example of local stiffness identification of vibrating beams [13,14] is shown in figure 1(b).…”

Section: Introductionmentioning

confidence: 99%

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Calibration and correction procedure for quantitative out-of-plane shearography

Zastavnik

Pyl

et al. 2015

Meas. Sci. Technol.

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Quantitative shearography applications continue to gain practical importance. However, a study of the errors inherent in shearography measurements, related to calibration of the instrument and correction of the results, is most often lacking. This paper proposes a calibration and correction procedure for the out-of-plane shearography with a Michelson interferometer. The calibration is based on the shearography measurement of known rigidbody rotations of a flat plate and accounts for the local variability of the shearing distance. The correction procedure further compensates for the variability of the sensitivity vector and separates the two out-of-plane deformation gradients when they are coupled in the measurement. The correction procedure utilizes two shearography measurements of the same experiment with distinct shearing distances. The effectiveness of the proposed calibration procedure is demonstrated in the case of a static deformation of a centrally loaded plate, where the discrepancy between experimental and finite element analysis results is minimized.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Errors In Shearographymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Calibration and correction procedure for quantitative out-of-plane shearography

Zastavnik

Pyl

et al. 2015

Meas. Sci. Technol.

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“…An example of quantitative application of shearography is also the identification of local stiffness values in beam specimens shown in figure 1b [15].…”

Section: Introductionmentioning

confidence: 99%

Errors in shearography measurements due to the creep of the PZT shearing actuator

Zastavnik¹,

Pyl²,

Sol³

et al. 2014

Meas. Sci. Technol.

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Shearography is a modern optical interferometric measurement technique. It uses interferometric properties of coherent laser light to measure deformation gradients on the µm/m level. In the most common shearography setups, the ones employing Michelson interferometer, the deformation gradients in both x-and y -direction can be identified by setting angles on the shearing mirror. One of the mechanisms for setting the desired shearing angles in the Michelson interferometer is using the PZT actuators. This paper will reveal that the time-dependent creep behaviour of the PZT actuators is a major source of measurement errors. Measurements at long time spans suffer severely from this creep behaviour. Even for short time spans, which are typical for shearographic experiments, the creep behaviour of the PZT shear actuator induces considerable deviation in the measured response. In this paper the mechanism and the effect of the PZT creep is explored and demonstrated with measurements. For long time-span measurements in shearography, noise is a limiting factor. Thus, the time-dependent evolution of noise is considered in this paper, with particular interest in the influence of the external vibrations. Measurements with and without the external vibration isolation are conducted and the difference between the two setups is analyzed. At the end of the paper some recommendations are given for minimizing and correcting the here studied time-dependent effects.

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Application of cubic spline interpolation with optimal spatial sampling for damage identification

Pedroso

Arco

Figueiras

et al. 2021

Structural Contr & Hlth

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This paper aims to explore a new technique for structural damage identification using cubic spline interpolation. The method is based on the interpolation of modal rotations measured with shearography, making use of the analytical derivative of the spline to compute the modal curvature, which is known to be very sensitive to damage. As a means of reducing noise and measurement uncertainty propagation to a minimum, an expression for an optimal spatial sampling is derived. Furthermore, a baseline-free damage factor, allied with an optimal sampling, is also introduced. The proposed identification method is validated using experimental data of a beam. Using a damage localisation quality index, a comparison between the present method and one using finite differences is carried out, showing that the differentiation of spline interpolation leads to better damage identifications. The results obtained with the proposed approach show robustness and consistency in the localisations. Additionally, the hurdles of identifying small and multiple damage are tackled with the proposed method, yielding a good performance.

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Comparison of Shearography to Scanning Laser Vibrometry as Methods for Local Stiffness Identification of Beams

Cited by 12 publications

References 40 publications

Calibration and correction procedure for quantitative out-of-plane shearography

Calibration and correction procedure for quantitative out-of-plane shearography

Errors in shearography measurements due to the creep of the PZT shearing actuator

Application of cubic spline interpolation with optimal spatial sampling for damage identification

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