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Microscopic digital volume correlation (DVC) and finite element precoalescence strain evaluations are compared for two nodular cast iron specimens. Displacement fields from \textit{in-situ} 3D synchrotron laminography images are obtained by DVC. Subsequently the microstructure is explicitely meshed from the images considering nodules as voids. Boundary conditions are applied from the DVC measurement. Image segmentation-related uncertainties are taken into account and observed to be negligible with respect to the differences between strain levels. Macroscopic as well as local strain levels in coalescing ligaments between voids nucleated at large graphite nodules are compared. Macroscopic strain levels are consistently predicted. A very good agreement is observed for one of the specimens, while the strain levels for the second specimen presents some discrepancies. Limitations of the modeling and numerical framework are discussed in light of these differences. A discussion of the use of strain as coalescence indicator is initiated.

International audience; This paper presents and compares two combined experimental-numerical techniques for the investigation of fracture properties of additively manufactured polymer parts using digital image correlation (DIC) measurements. The first method only uses measured kinematic fields, and the second is based on Finite Element simulations driven by measured boundary conditions. A mini Single Edge Notched Tensile sample manufactured by fused filament fabrication with ABS is studied. It is shown that both methods locally extract J-integrals, and the crack tip is accurately located by the FE-based method. By comparing computed displacements to those measured via DIC, it is possible to locally check the validity of the numerical model. The initiation and propagation stages are analyzed independently thanks to two different magnifications of acquired image series.

International audience; In the field of structural health monitoring, the use of Digital Image Correlation (DIC) on relevant surfaces offers remarkable advantages. Such a method is presented herein. The statistically stationary nature of usual loads makes it possible to determine, by training with DIC, a reduced kinematic basis (composed of "modes") and a statistical amplitude distribution for each mode. Further, a specific DIC technique is proposed to deal with such particular kinematics by introducing an extractor per mode that operates on images after a filtering step. This per-mode DIC measurement is reduced to a simple scalar product between the image and the corresponding extractor, which allows for very fast and noniterative processing. As an illustration, this methodology is deployed on a test case of fatigue crack propagation.

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International audience; Fused silica is prone to damage under ultraviolet laser irradiation. Because they are key components to achieve fusion on high energy laser facilities, final fused silica optics are analyzed after each laser shot. The quantification of damage sites is limited by the image resolution. Measurements of scattered light by damage sites allow for sub-pixel detection and growth monitoring after a calibration step based on time-consuming measurements laser facilities. It is proven herein that modeling laser damage size monitoring based on light scattering is efficient to link gray levels to damage diameters, thereby avoiding any experimental calibration based on a reference optics on the facility

The authors would like to acknowledge Claude Verliac and Joachim Magnier for technical advice on the manufacturing process of the mechanical loading system. A mini-compression jig was built to perform in situ tests on bovine trabecular bone monitored by micro-MRI. The MRI antenna provided an isotropic resolution of 78 microm that allows for a volume correlation method to be used. Three-dimensional displacement fields are then evaluated within the bone sample during the compression test. The performances of the correlation method are evaluated and discussed to validate the technique on trabecular bone. By considering correlation residuals and estimates of acquisition noise, the measured results are shown to be trustworthy. By analyzing average strain levels for different interrogation volumes along the loading direction, it is shown that the sample size is less than that of a representative volume element. This study shows the feasibility of the 3D-displacement and strain field analyses from micro-MRI images. Other biological tissues could be considered in future work.

International audience; A preliminary application of the digital image correlation (DIC) is presented aiming to detect and analyze crack networks which are induced by stresses arising during curing and drying (CD) of MgO containing refractory castable slabs. Surface images of castable samples placed in a specially designed climatic chamber were recorded over the CD stages with a digital camera and processed by the DIC technique to measure the displacement fields. Post-processing DIC results were carried out to estimate the length, orientation and opening of cracks in the networks. The methodology is highlighted and first experimental results are shown pointing out its future potential to better understand the effect of the physical aspects (particle size, chemical analysis, temperature, etc.) and the structural ones (slab shape and size) on processing and performance of advanced refractory castables.