https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Tue, 14 Apr 2026 00:27:26 GMT 2026-04-14T00:27:26Z http://hdl.handle.net/10985/8648 Assessment of Digital Image Correlation Measurement Accuracy in the Ultimate Error Regime: Main Results of a Collaborative Benchmark AMIOT, Fabien; BORNERT, Michel; DOUMALIN, Pascal; DUPRE, Jean Christophe; FAZZINI, Marina; ORTEU, Jean José; POILANE, Christophe; ROBERT, Laurent; ROTINAT, René; TOUSSAINT, Evelyne; WATTRISSE, Bertrand; WIENIN, Jean Samuel We report on the main results of a collaborative work devoted to the study of the uncertainties associated with Digital image correlation techniques (DIC). More specifically, the dependence of displacement measurement uncertainties with both image characteristics and DIC parameters is emphasised. A previous work [Bornert et al. (2009) Assessment of digital image correlation measurement errors: methodology and results. Exp. Mech. 49, 353–370] dedicated to situations with spatially fluctuating displacement fields demonstrated the existence of an ‘ultimate error’ regime, insensitive to the mismatch between the shape function and the real displacement field. The present work is focused on this ultimate error. To ensure that there is no mismatch error, synthetic images of in-plane rigid body translation have been analysed. Several DIC softwares developed by or in use in the French community have been used to explore the effects of a large number of settings. The discrepancies between DIC evaluated displacements and prescribed ones have been statistically analysed in terms of random errors and systematic bias, in correlation with the fractional part τ of the displacement component expressed in pixels. Main results are as follows: (i) bias amplitude is almost always insensitive to subset size, (ii) standard deviation of random error increases with noise level and decreases with subset size and (iii) DIC formulations can be split up into two main families regarding bias sensitivity to noise. For the first one, bias amplitude increases with noise while it remains nearly constant for the second one. In addition, for the first family, a strong dependence of random error with τ is observed for noisy images. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8648 2013-01-01T00:00:00Z AMIOT, Fabien BORNERT, Michel DOUMALIN, Pascal DUPRE, Jean Christophe FAZZINI, Marina ORTEU, Jean José POILANE, Christophe ROBERT, Laurent ROTINAT, René TOUSSAINT, Evelyne WATTRISSE, Bertrand WIENIN, Jean Samuel We report on the main results of a collaborative work devoted to the study of the uncertainties associated with Digital image correlation techniques (DIC). More specifically, the dependence of displacement measurement uncertainties with both image characteristics and DIC parameters is emphasised. A previous work [Bornert et al. (2009) Assessment of digital image correlation measurement errors: methodology and results. Exp. Mech. 49, 353–370] dedicated to situations with spatially fluctuating displacement fields demonstrated the existence of an ‘ultimate error’ regime, insensitive to the mismatch between the shape function and the real displacement field. The present work is focused on this ultimate error. To ensure that there is no mismatch error, synthetic images of in-plane rigid body translation have been analysed. Several DIC softwares developed by or in use in the French community have been used to explore the effects of a large number of settings. The discrepancies between DIC evaluated displacements and prescribed ones have been statistically analysed in terms of random errors and systematic bias, in correlation with the fractional part τ of the displacement component expressed in pixels. Main results are as follows: (i) bias amplitude is almost always insensitive to subset size, (ii) standard deviation of random error increases with noise level and decreases with subset size and (iii) DIC formulations can be split up into two main families regarding bias sensitivity to noise. For the first one, bias amplitude increases with noise while it remains nearly constant for the second one. In addition, for the first family, a strong dependence of random error with τ is observed for noisy images. http://hdl.handle.net/10985/27084 Development of a custom commingled flax/PLA wrapped yarn for additive manufacturing of long-fibre biocomposites QUEREILHAC, Delphine; CAILLAULT, Thomas, Raphaël; TEREKHINA, Svetlana; BAR, Mahadev; MOREL, Guillaume; FAZZINI, Marina; ABIDA, Marwa; DE LUYCKER, Emmanuel; OUAGNE, Pierre Plant fibres are promising reinforcements for bio-composites in additive manufacturing, but their use as long fibres remains limited, often reduced to short particles that underuse their potential. This study presents a customised yarn design that not only maintains fibre alignment parallel to the yarn axis but also ensures core resin impregnation. Commingling and wrap spinning techniques were used to produce four flax/PLA yarns with varying compositions. The manufacturing process and printing of unidirectional composite specimens are detailed. Tomography revealed up to 3.3 times lower intra-yarn porosity thanks to commingling, and tensile tests showed a modulus increase by a factor of 2.1 compared to similar previous works using conventional twisted yarns. These results pave the way for broader use of long flax fibres in 3D printing. Mon, 25 Aug 2025 00:00:00 GMT http://hdl.handle.net/10985/27084 2025-08-25T00:00:00Z QUEREILHAC, Delphine CAILLAULT, Thomas, Raphaël TEREKHINA, Svetlana BAR, Mahadev MOREL, Guillaume FAZZINI, Marina ABIDA, Marwa DE LUYCKER, Emmanuel OUAGNE, Pierre Plant fibres are promising reinforcements for bio-composites in additive manufacturing, but their use as long fibres remains limited, often reduced to short particles that underuse their potential. This study presents a customised yarn design that not only maintains fibre alignment parallel to the yarn axis but also ensures core resin impregnation. Commingling and wrap spinning techniques were used to produce four flax/PLA yarns with varying compositions. The manufacturing process and printing of unidirectional composite specimens are detailed. Tomography revealed up to 3.3 times lower intra-yarn porosity thanks to commingling, and tensile tests showed a modulus increase by a factor of 2.1 compared to similar previous works using conventional twisted yarns. These results pave the way for broader use of long flax fibres in 3D printing.