Special virtual fields for the direct determination of material parameters with the virtual fields method. 1––Principle and definition

Grédiac, Michel; Toussaint, Evelyne; Pierron, Fabrice

doi:10.1016/s0020-7683(02)00127-0

Cited by 143 publications

(121 citation statements)

References 24 publications

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“…1 It has to be underlined that, normally, the virtual fields are chosen automatically to ensure their maximum independence as explained in [46,47]. But since this automatic procedure has not been implemented for dynamic cases yet, the two fields are chosen manually here.…”

Section: Field Nmentioning

confidence: 99%

Full-Field Strain Measurement and Identification of Composites Moduli at High Strain Rate with the Virtual Fields Method

et al. 2010

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Abstract The present paper deals with full-field strain measurement on glass/epoxy composite tensile specimens submitted to high strain rate loading through a split Hopkinson pressure bar (SHPB) device and with the identification of their mechanical properties. First, the adopted methodology is presented: the device, including an Ultra-High Speed camera, and the experimental procedure to obtain relevant displacement maps are described. The different full-field results including displacement, strain and acceleration maps for two mechanical tests are then addressed. The last part of the paper deals with an original procedure to identify stiffnesses on this dynamic case only using the actual strain and acceleration maps (without the applied force) by using the Virtual Fields Method.

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Section: Field Nmentioning

confidence: 99%

Full-Field Strain Measurement and Identification of Composites Moduli at High Strain Rate with the Virtual Fields Method

et al. 2010

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“…Later, the stability of the linear system Eqn. (13) was improved by means of a special virtual fields selection strategy [10]. The selection can be implemented so that the integrals corresponding to the unknown stiffness components take their turn to be 0 or 1, so that matrix M in Eqn.…”

Section: Selection Of Virtual Displacement and Strain Fieldsmentioning

confidence: 99%

“…In this example, the number of cosine/sine terms in the Fourier series (7) was chosen as N = 32, which leads to a total number of unknown Fourier coefficients of N F = 2177 by Eqn. (10). Total computation time for 1600×1000 pixels input strain was ~8.5×10 3 s on an Intel® Core™ i7 CPU 2.79 GHz machine with 8GB of memory, using the MATLAB programming language with pinv operator to perform the inversion of Eqn.…”

Section: Layered-pattern Stiffness Distributionmentioning

confidence: 99%

A Fourier‐series‐based virtual fields method for the identification of 2‐D stiffness distributions

Nguyen

Huntley

Ashcroft

et al. 2014

Numerical Meth Engineering

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The Virtual Fields Method (VFM) is a powerful technique for the calculation of spatial distributions of material properties from experimentally-determined displacement fields. A Fourier-series-based extension to the VFM (the F-VFM) is presented here, in which the unknown stiffness distribution is parameterised in the spatial frequency domain rather than in the spatial domain as used in the classical VFM. We present in this paper the theory of the F-VFM for the case of elastic isotropic thin structures with known boundary conditions. An efficient numerical algorithm based on the 2-D fast Fourier transform is presented, which reduces the computation time by 3-4 orders of magnitude compared to a direct implementation of the F-VFM for typical experimental dataset sizes. Artefacts specific to the F-VFM (ringing at the highest spatial frequency near to modulus discontinuities) can be largely removed through the use of appropriate filtering strategies. Reconstruction of stiffness distributions with the F-VFM has been validated on three stiffness distribution scenarios under varying levels of noise in the input displacement fields. Robust reconstructions are achieved even when the displacement noise is higher than in typical experimental fields.

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“…Full-field strain measurements recently took a major place in experimental mechanics [1,2]. However, these methods do not apply to uni-dimensional objects, such as wires or beams images, whose width can be of the order of one pixel.…”

Section: Introductionmentioning

confidence: 99%

Identification of the Shape of Curvilinear Beams and Fibers

François

Semin

Auradou

2010

AMM

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Abstract. This work concerns the shape identification of curvilinear objects, for example bent beams or wires in mechanics. The beam's digital picture is analyzed with the introduced Virtual Image Correlation method. This one consists in finding the optimal correlation between the beam's image and a virtual beam, whose curvature field is described by a truncated series. The gray level and amplitude of the virtual beam does not need to reproduce exactly the ones of the physical beam image. The analytical form of the optimal shape allows one to derive mechanical properties: the identification of the Young's modulus of a bar is given as an example. We will also show the robustness of the method with regards to the quality of the image.

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Special virtual fields for the direct determination of material parameters with the virtual fields method. 1––Principle and definition

Cited by 143 publications

References 24 publications

Full-Field Strain Measurement and Identification of Composites Moduli at High Strain Rate with the Virtual Fields Method

Full-Field Strain Measurement and Identification of Composites Moduli at High Strain Rate with the Virtual Fields Method

A Fourier‐series‐based virtual fields method for the identification of 2‐D stiffness distributions

Identification of the Shape of Curvilinear Beams and Fibers

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