Digital image correlation for surface deformation measurement: historical developments, recent advances and future goals

An overview of layerwise theories for composite laminates and structures: Development, numerical implementation and application

Three-dimensional Digital Image Correlation (3D-DIC) is a non-contact optical-numerical technique for evaluating the dynamic mechanical behavior at the surface of structures and materials, including biological tissues. 3D-DIC can be used to extract shape and full-field displacements and strains with high resolution, at various length scales. While various commercial and academic 3D-DIC software exist, the field lacks 3D-DIC packages which offer straightforward calibration and data-merging solutions for multi-view analysis, which is particularly desirable in biomedical applications. To address these limitations, we present MultiDIC, an open-source MATLAB toolbox, featuring the first 3D-DIC software specifically dedicated to multi-view setups. MultiDIC integrates robust two-dimensional subset-based DIC software with specially tailored calibration procedures, to reconstruct the dynamic behavior of surfaces from multiple stereo-pairs. MultiDIC contains novel algorithms to automatically merge meshes from multiple stereo-pairs, and to compute and visualize 3D shape and full-field motion, deformation, and strain. User interfaces provide capabilities to perform 3D-DIC analyses without interacting with MATLAB syntax, while stand-alone functions also allow proficient MATLAB users to write custom scripts for specific experimental requirements. This paper discusses the challenges underlying multi-view 3D-DIC, details the proposed solutions, and describes the algorithms implemented in MultiDIC. The performance of MultiDIC is tested using a low-cost experimental system featuring a 360° 12-camera setup. The software and system are evaluated using measurement of a cylindrical object with known geometry subjected to rigid body motion and measurement of the lower limb of a human subject. The findings confirm that shape, motion, and full-field deformations and strains can be accurately measured, and demonstrate the feasibility of MultiDIC in multi-view in-vivo biomedical applications.

MultiDIC: An Open-Source Toolbox for Multi-View 3D Digital Image Correlation

/pdf/a-review-of-surface-deformation-and-strain-measurement-using-3tb8linch1.pdf

A Review of Surface Deformation and Strain Measurement Using Two-Dimensional Digital Image Correlation

The goal of the present study is to illustrate the full integration of sensor and imaging data into numerical procedures for the purpose of identification of constitutive laws and their validation. The feasibility of such approaches is proven in the context of in situ tests monitored by tomography. The bridging tool consists of spatiotemporal (i.e., 4D) analyses with dedicated (integrated) correlation algorithms. A tensile test on nodular graphite cast iron sample is performed within a lab tomograph. The reconstructed volumes are registered via integrated digital volume correlation (DVC) that incorporates a finite element modeling of the test, thereby performing a mechanical integration in 4D registration of a series of 3D images. In the present case a non-intrusive procedure is developed in which the 4D sensitivity fields are obtained with a commercial finite element code, allowing for a large versatility in meshing and incorporation of complex constitutive laws. Convergence studies can thus be performed in which the quality of the discretization is controlled both for the simulation and the registration. Incremental DVC analyses are carried out with the scans acquired during the in situ mechanical test. For DVC, the mesh size results from a compromise between measurement uncertainties and its spatial resolution. Conversely, a numerically good mesh may reveal too fine for the considered material microstructure. With the integrated framework proposed herein, 4D registrations can be performed and missing boundary conditions of the reference state as well as mechanical parameters of an elastoplastic constitutive law are determined in fair condition both for DVC and simulation.

/pdf/toward-4d-mechanical-correlation-2xe6ii1fif.pdf

Toward 4D mechanical correlation

A new calibration procedure is proposed for a stereovision setup It uses the object of interest as the calibration target, provided the observed surface has a known definition (eg, its CAD model) In a first step, the transformation matrices needed for the calibration of the setup are determined assuming that the object conforms to its CAD model Then the 3D shape of the surface of interest is evaluated by deforming the a priori given freeform surface These two steps are performed via an integrated approach to stereoDIC The measured 3D shape of a machined Bezier patch is validated against data obtained by a coordinate measuring machine The feasibility of the calibration method’s application to large surfaces is shown with the analysis of a 2-m2 automotive roof panel

/pdf/cad-based-calibration-and-shape-measurement-with-stereodic-16dwsbrdao.pdf

CAD-based calibration and shape measurement with stereoDIC

A new displacement measurement technique is proposed in a stereovision setup, which uses the object of interest as the support of the correlation process. This procedure leads to a global approach to stereocorrelation. The method is presented in its general formulation and is then particularized to the case of non uniform rational B-splines (NURBS). The displacement field is directly measured as a 3D field expressed in a NURBS basis consistent with the existing geometric model. The kinematic measurements are validated against prescribed displacements of a machined Bezier patch. The feasibility in an industrial context is shown with the analysis of 3D displacement fields of a 2- m2 automotive roof panel during a welding operation.

/pdf/cad-based-displacement-measurements-with-stereo-dic-5ap5cligu2.pdf

CAD-based Displacement Measurements with Stereo-DIC

It is proposed to develop a multiview framework to perform stereocorrelation by resorting to isogeometric descriptions of the observed three-dimensional surfaces. Once the three-dimensional surface...

/pdf/shape-displacement-and-mechanical-properties-from-38s5rkod29.pdf

Shape, displacement and mechanical properties from isogeometric multiview stereocorrelation

https://hal.archives-ouvertes.fr/hal-00947401/document

Integrated Digital Image Correlation for the Evaluation and Correction of Optical Distortions

https://hal.archives-ouvertes.fr/hal-01303516/document

John-Eric Dufour

Papers

CAD-based calibration and shape measurement with stereoDIC

CAD-based Displacement Measurements with Stereo-DIC

Shape, displacement and mechanical properties from isogeometric multiview stereocorrelation

Integrated Digital Image Correlation for the Evaluation and Correction of Optical Distortions

Integrated Digital Image Correlation considering gray level and blur variations: Application to distortion measurements of IR camera