Stress analysis of fibrous composites using moiré interferometry

McDonach, A.; McKelvie, James; Walker, C.A.

doi:10.1016/0143-8166(80)90002-0

Cited by 20 publications

(7 citation statements)

References 8 publications

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“…While certain microcracks open under tensile loads, neighboring cracks close under compressive loads. For the randomized case, where cracks are in no preferred direction, factors such as crack inclination/orientation and their response to internal shearing forces can conceivably lead to secondary intensity-based response mechanisms that are not accounted for in eq (6). However, as the results presented in the following sections show, the intensity-to-strain response is relatively linear (the form of eq (6) when ec > > ~).…”

Section: Io Domentioning

confidence: 77%

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Full-field strain measurement using a luminescent coating

Hubner

Ifju

Schanze

et al. 2003

Experimental Mechanics

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ABSTRACT--In this paper we describe an optical-based technique, called strain sensitive skin ($3), for measuring in-plane strain data on structural members under static load. The technique employs a coating consisting of a luminescent dye and polymer binder that is applied to the surface of a test part via conventional aerosol techniques. Proper illumination stimulates the dye, which in turn emits higher wavelength luminescence. The excitation and emission intensities have different wavelengths; therefore, enabling optical filtering to separate the two signals. The optical strain response is intensity based. A network of randomized microcracks within the binder scatters the waveguided luminescence from the excited dye molecules. The amount of scattered luminescence is related to the changes in the microcrack openings and orientations via mechanical strain. Various calibration tests show the optical strain response to be proportional to the sum of in-plane principal strains. With this new experimental testing tool, fullfield high-resolution strain measurements can be acquired.The optical strain response of this new sensor is minimally dependent on viewing and lighting directions, rendering the technique viable to imaging and determining strain fields for three-dimensional complex geometries.

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Section: Io Domentioning

confidence: 77%

“…4. Equation (6) fits the data where A = 0.162 and ec = 1448 t~e. For values of *c >> g, eq (6) approaches a linear functional form with A/ec representing the relative intensity-to-strain sensitivity.…”

Section: Io Domentioning

confidence: 98%

Full-field strain measurement using a luminescent coating

Hubner

Ifju

Schanze

et al. 2003

Experimental Mechanics

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“…There are several strengths of this technique that make it highly suitable for measuring displacement and strain distributions in biscuits. First of all, the method is non-contacting and does not require modification of the specimen, such as the preparation of a grating on the specimen surface as in grid (Parks 1982;Haynes & Coates 1996) and moiré (McDonach et al 1980;Post 1991) techniques. It therefore enables determination of the required displacement and strain information without any physical contact with the sample or reinforcement of it.…”

Section: Speckle Interferometrymentioning

confidence: 99%

Improved understanding of biscuit checking using speckle interferometry and finite-element modelling techniques

et al. 2005

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For almost a century, manufacturers have tried to understand and predict the appearance of small hairline cracks in biscuits and crackers, an effect known as ‘checking’. Results are presented here from a combined experimental and numerical study of the phenomenon. Experimentally determined material properties of semi-sweet biscuits were used as inputs to an axisymmetric finite-element model, which predicts that, at low relative humidities (RHs), the rim of the biscuit expands and the centre contracts. The expansion is caused by uptake of moisture at the rim, which is initially dry after baking, and the contraction is attributable to loss of moisture from the more moist centre. The finite-element predictions were validated by strain measurements of freshly baked biscuits using speckle interferometry. These measurements are the most sensitive and the first whole-field measurements yet made of strains in biscuits. Experiments using a range of storage conditions enable us to confirm that it is the presence of moisture gradients, in combination with a low environmental RH, which increases the chance of checking. These results will aid biscuit manufacturers in the development of more effective strategies to avoid the damaging phenomenon of checking, potentially enabling consumers to benefit from fewer broken biscuits.

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“…Today, moiré interferometry is used for many studies [1]. It has been applied for studies of composite materials [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], polycrystalline materials [1,19], piezoelectric materials [20], fracture mechanics [21][22][23][24][25][26][27][28], biomechanics [29], structural elements [30,31], structural joints [32][33][34][35], residual stress measurement [36][37][38][39][40][41][42] and strain gauge calibration [1,43]. More recently, it has been practised extensively in the microelectronics industry to measure thermally induced deformation of electronic packages [44][45][46]…”

Section: Introductionmentioning

confidence: 99%

Moiré interferometry for engineering mechanics: Current practices and future developments

Han

Post

Ifju

2001

The Journal of Strain Analysis for Engineering Design

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In the past decade, the optical method called moiré interferometry has matured rapidly to emerge as an invaluable tool, proved by many industrial and scientific applications. It has been applied to numerous problems in engineering mechanics. It measures in-plane displacement fields with high sensitivity and high spatial resolution. This paper reviews current practices of moiré interferometry and its extensions. Applications in diverse fields are addressed to demonstrate the wide applicability of the method, especially the recent applications for thermal deformation analyses of microelectronics devices. Speculation on future developments and practices is presented.

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Stress analysis of fibrous composites using moiré interferometry

Cited by 20 publications

References 8 publications

Full-field strain measurement using a luminescent coating

Full-field strain measurement using a luminescent coating

Improved understanding of biscuit checking using speckle interferometry and finite-element modelling techniques

Moiré interferometry for engineering mechanics: Current practices and future developments

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