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François Hild - One of the best experts on this subject based on the ideXlab platform.
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Poynting Effects in Pantographic Metamaterial Captured via Multiscale DVC
Journal of Strain Analysis for Engineering Design, 2020Co-Authors: Patrick Auger, Thomas Lavigne, Benjamin Smaniotto, Mario Spagnuolo, Francesco Dell'isola, François HildAbstract:Metamaterials are often studied for their peculiar mechanical properties. However, few 4D studies were conducted on 3D printed pantographs. This study aims at analyzing an in situ torsion test in a lab tomograph. The acquired scans were used to Measure Displacement fields via digital volume correlation. The final goal was to analyze the deformation mechanisms of an Inconel pantograph and to rationalize potential Poynting effects.
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Mechanically Regularized FE DIC for Heterogeneous Materials
Experimental Mechanics, 2019Co-Authors: R. Naylor, Y. Renollet, B. Tranquart, Christian Fagiano, Martin Hirsekorn, François Hild, E. BarangerAbstract:In situ tensile tests in a scanning electron microscope (SEM) have been conducted on a 8-layer 5-harness satin carbon fibre and epoxy matrix composite to observe the first stages of damage at the scale of fibres and matrix. A speckle pattern based on a suspension of alumina particles was applied onto the surface of the specimen to facilitate the use of digital image correlation (DIC). Local and finite element (FE) DIC are compared on pictures acquired during the tensile tests, with and without a speckle pattern. FE DIC with mechanical regularization was found to be the only approach able to Measure Displacement fields at a fine enough resolution in both cases. This method, initially created for homogeneous materials, was then adapted to heterogeneous materials. First, a microstructure consistent mesh was created and used for correlation purposes. Second, the difference between the mechanical properties of the constituents is taken into account in the mechanical regularization. Last, the accuracy of the method is analysed. The adaptation presented herein was proved to be able to Measure Displacement fields in the matrix between fibres with an error of 10 nm (a fifth of a pixel) and to detect the initiation of the first damage mechanisms by means of the mechanical residuals.
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Mechanically Regularized FE DIC for Heterogeneous Materials
Experimental Mechanics, 2019Co-Authors: R. Naylor, Y. Renollet, B. Tranquart, Christian Fagiano, Martin Hirsekorn, François Hild, E. BarangerAbstract:In situ tensile tests in a scanning electron microscope (SEM) have been conducted on a 8-layer 5-harness satin carbon fibre and epoxy matrix composite to observe the first stages of damage at the scale of fibres and matrix. A speckle pattern based on a suspension of alumina particles was applied onto the surface of the specimen to facilitate the use of digital image correlation (DIC). Local and finite element (FE) DIC are compared on pictures acquired during the tensile tests, with and without a speckle pattern. FE DIC with mechanical regularization was found to be the only approach able to Measure Displacement fields at a fine enough resolution in both cases. This method, initially created for homogeneous materials, was then adapted to heterogeneous materials. First, a microstructure consistent mesh was created and used for correlation purposes. Second, the difference between the mechanical properties of the constituents is taken into account in the mechanical regularization. Last, the accuracy of the method is analysed. The adaptation presented herein was proved to be able to Measure Displacement fields in the matrix between fibres with an error of 10 nm (a fifth of a pixel) and to detect the initiation of the first damage mechanisms by means of the mechanical residuals.
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Digital Volume Correlation: Review of Progress and Challenges
Experimental Mechanics, 2018Co-Authors: Ante Buljac, T. Taillandier-thomas, B. Smaniotto, Amine Bouterf, Clément Jailin, Joseph Neggers, A Mendoza, François Hild, S. Le RouxAbstract:3D imaging has become popular for analyzing material microstructures. When time lapse series of 3D pictures are acquired during a single experiment, it is possible to Measure Displacement fields via digital volume correlation (DVC), thereby leading to 4D results. Such 4D analyses have been performed for almost two decades. The present paper aims at reviewing the achievements of and challenges faced by such Measurement technique. Ex-situ and in-situ experiments are discussed. A general and unified DVC framework is introduced. Various sources of Measurement bias and uncertainties are analyzed. The current challenges are studied and some propositions are given to address them.
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Experimental-Numerical Validation Framework for Micromechanical Simulations
2018Co-Authors: Ante Buljac, Joseph Neggers, Modesar Shakoor, Marc Bernacki, Pierre-olivier Bouchard, Lukas Helfen, Thilo F. Morgeneyer, François HildAbstract:A combined experimental-numerical framework is presented in order to validate computations at the microscale. It is illustrated for a flat specimen with two holes, which is made of cast iron and imaged via in situ synchrotron laminography at micrometer resolution during a tensile test. The region in the reconstructed volume between the two holes is analyzed via Digital Volume Correlation (DVC) to Measure Displacement fields. Finite Element (FE) simulations, whose mesh is made consistent with the studied material microstructure, are driven by Measured Dirichlet boundary conditions. Damage levels and gray level residuals for DVC Measurements and FE simulations are assessed for validation purposes.
Robert J. Wood - One of the best experts on this subject based on the ideXlab platform.
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IROS - An ultra-high precision, high bandwidth torque sensor for microrobotics applications
2011 IEEE RSJ International Conference on Intelligent Robots and Systems, 2011Co-Authors: Benjamin M. Finio, Kevin C. Galloway, Robert J. WoodAbstract:Motivated by the need for torque sensing in the µNm range for experiments with insect-sized flapping-wing robots, we present the design, fabrication and testing of a custom single-axis torque sensor. The micorobots in question are too large for MEMS force/torque sensors used for smaller live insects such as fruit flies, but too small to produce torques within the dynamic range of commercially available force/torque sensors. Our sensor consists of laser-machined Invar sheets that are assembled into a three dimensional beam. A capacitive Displacement sensor is used to Measure Displacement of a target plate when the beam rotates, and the output voltage is correlated to applied torque. Sensor bandwidth, range, and resolution are designed to match the criteria of the robotic fly experiments while remaining insensitive to off-axis loads. We present a final sensor design with a range of ±130µNm, a resolution of 4.5nNm, and bandwidth of 1kHz.
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An ultra-high precision, high bandwidth torque sensor for microrobotics applications
IEEE International Conference on Intelligent Robots and Systems, 2011Co-Authors: Benjamin M. Finio, Kevin C. Galloway, Robert J. WoodAbstract:Motivated by the need for torque sensing in the µNm range for experiments with insect-sized flapping-wing robots, we present the design, fabrication and testing of a custom single-axis torque sensor. The micorobots in question are too large for MEMS force/torque sensors used for smaller live insects such as fruit flies, but too small to produce torques within the dynamic range of commercially available force/torque sensors. Our sensor consists of laser-machined Invar sheets that are assembled into a three dimensional beam. A capacitive Displacement sensor is used to Measure Displacement of a target plate when the beam rotates, and the output voltage is correlated to applied torque. Sensor bandwidth, range, and resolution are designed to match the criteria of the robotic fly experiments while remaining insensitive to off-axis loads. We present a final sensor design with a range of ±130µNm, a resolution of 4.5nNm, and bandwidth of 1kHz.
Benjamin M. Finio - One of the best experts on this subject based on the ideXlab platform.
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IROS - An ultra-high precision, high bandwidth torque sensor for microrobotics applications
2011 IEEE RSJ International Conference on Intelligent Robots and Systems, 2011Co-Authors: Benjamin M. Finio, Kevin C. Galloway, Robert J. WoodAbstract:Motivated by the need for torque sensing in the µNm range for experiments with insect-sized flapping-wing robots, we present the design, fabrication and testing of a custom single-axis torque sensor. The micorobots in question are too large for MEMS force/torque sensors used for smaller live insects such as fruit flies, but too small to produce torques within the dynamic range of commercially available force/torque sensors. Our sensor consists of laser-machined Invar sheets that are assembled into a three dimensional beam. A capacitive Displacement sensor is used to Measure Displacement of a target plate when the beam rotates, and the output voltage is correlated to applied torque. Sensor bandwidth, range, and resolution are designed to match the criteria of the robotic fly experiments while remaining insensitive to off-axis loads. We present a final sensor design with a range of ±130µNm, a resolution of 4.5nNm, and bandwidth of 1kHz.
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An ultra-high precision, high bandwidth torque sensor for microrobotics applications
IEEE International Conference on Intelligent Robots and Systems, 2011Co-Authors: Benjamin M. Finio, Kevin C. Galloway, Robert J. WoodAbstract:Motivated by the need for torque sensing in the µNm range for experiments with insect-sized flapping-wing robots, we present the design, fabrication and testing of a custom single-axis torque sensor. The micorobots in question are too large for MEMS force/torque sensors used for smaller live insects such as fruit flies, but too small to produce torques within the dynamic range of commercially available force/torque sensors. Our sensor consists of laser-machined Invar sheets that are assembled into a three dimensional beam. A capacitive Displacement sensor is used to Measure Displacement of a target plate when the beam rotates, and the output voltage is correlated to applied torque. Sensor bandwidth, range, and resolution are designed to match the criteria of the robotic fly experiments while remaining insensitive to off-axis loads. We present a final sensor design with a range of ±130µNm, a resolution of 4.5nNm, and bandwidth of 1kHz.
Stephane Roux - One of the best experts on this subject based on the ideXlab platform.
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Mode-enhanced space-time DIC: Applications to ultra high-speed imaging
Measurement Science and Technology, 2018Co-Authors: Myriam Berny, Amine Bouterf, Clément Jailin, François Hild, Stephane RouxAbstract:Digital Image Correlation (DIC), which consists in registering image pairs to Measure Displacement fields, can be tailored to analyze image sequences from videos taking advantage of a common reference image. In the present study it is no longer the first image of the sequence but rather a computed image from the entire video. The sought kinematics, which is separated in space and time, offers the opportunity to extract "modes," each of which is a spatial Displacement field multiplied by a scalar function of time only. These modes are not chosen a priori but rather computed from a specific formulation of DIC so that they capture the Displacements at best. The exploited mathematical technique to achieve this modal representation is a form of Proper Generalized Decomposition (PGD) that makes use of the DIC variational formulation, where both spatial and temporal regularizations can be included. Two image videos acquired with an ultra-high speed camera at 5 and 10 million frames per second are analyzed to illustrate the proposed technique. Very large computation time gains are obtained with no noticeable differences in the kinematic Measurements. Moreover, it is shown that motions have a lower complexity, i.e., require less modes, than the direct Proper Orthogonal Decomposition (or Principal Component Analysis)
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In situ observation of strained bands and ductile damage in thin AA2139-T3 alloy sheets
Procedia IUTAM, 2017Co-Authors: Ante Buljac, T. Taillandier-thomas, Stephane Roux, Lukas Helfen, Thilo Morgeneyer, François HildAbstract:The interactions between plasticity and damage mechanisms are not clearly established concerning the fracture of ductile sheet materials (e.g., flat to slant transition). The question addressed herein is to elucidate which mechanism is responsible for localized phenomena leading to the final failure. A mechanical test carried out on a notched plate made of 2139-T3 aluminum alloy is imaged thanks to synchrotron laminography at micrometer resolution. Ductile damage (i.e., void nucleation, growth and coalescence) is analyzed via reconstructed volumes. Although the low volume fraction of secondary phases in the tested alloy is challenging, digital volume correlation is also utilized to Measure Displacement fields and estimate strain fields in the bulk of the alloy during the whole test. In the first part of this study, the resolution of the Measurement technique is assessed under such conditions. Then strained bands are shown to occur very early on in what will be the slant region of the fracture path. Conversely, damage grows at very late loading steps.
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Slip activities in polycrystals determined by coupling DIC Measurements with crystal plasticity calculations
International Journal of Plasticity, 2016Co-Authors: Adrien Guery, Felix Latourte, François Hild, Stephane RouxAbstract:The role of crystallographic grain size and microstructure of an austenitic stainless steel (A316LN) is studied via in-situ mechanical testing in an SEM and digital image correlation to Measure Displacement and strain fields. The latter ones are directly Measured on a mesh supported by the grain boundaries as imaged by EBSD. This experimental analysis is applied to five microstructures of the same cast material but subjected to different heat treatments. Differences in the strain distributions that can be attributed to the grain size are observed. The full-field Measurements allow in turn for a direct, local and quantitative comparison with crystal plasticity finite element simulations of the same experiments based on the same mesh. A weak correlation between the plastic strain and the Schmid's factors, which are computed with macroscopic or even local stress evaluations, emphasizes the role of inter-grain strain incompatibilities or grain boundaries. However, a good agreement in the major slip system evaluation between experimental observation and computations is observed.
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Evaluation of fatigue crack network growth in cast iron for different biaxial loading paths via full-field Measurements
International Journal of Fatigue, 2016Co-Authors: Zvonimir Tomicevic, Stephane Roux, François HildAbstract:This paper proposes a new method for monitoring fatigue crack network initiation and growth based on Digital Image Correlation (DIC) , and reports on in-plane biaxial fatigue experiments with two dierent loading paths and two amplitudes on nodular graphite cast iron. The central thinned part of cross-shaped samples is observed on two scales. Regularized Digital Image Correlation (DIC) is used to Measure Displacement elds and to reveal DIC residuals, i.e., image dierences that cannot be accounted for with registration. The detailed strain histories are compared at dierent scales and for the dierent loading regimes. DIC and mechanical residuals, i.e., local deviations of the Displacement eld from being the solution to an elastic problem, enable for the crack network detection and quantication with respect to the number of cycles. The relative damage severity and fatigue lifetime of different loading paths experiencing identical load magnitudes are analyzed for the tested material.
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On the use of regularized DVC to analyze strain localization
2015Co-Authors: T. Taillandier-thomas, Stephane Roux, Thilo F. Morgeneyer, François HildAbstract:For an in-depth understanding of the failure of structural materials the study of the deformation mechanisms in the bulk is fundamental. In situ synchrotron radiation computed laminography provides 3D images of thin plates subsequently processed by digital volume correlation to Measure Displacement and strain fields by using the natural contrast of the material. Difficulties arise from the lack of data, which is intrinsic to laminography and leads to several artifacts, and the weak absorption contrast in the 3D image texture of the studied material. To lower uncertainty levels and to have a better mechanical admissibility of the Measured Displacement fields, a regularized digital volume correlation procedure is introduced and applied to analyze localized Displacement and strain fields.
Kevin C. Galloway - One of the best experts on this subject based on the ideXlab platform.
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IROS - An ultra-high precision, high bandwidth torque sensor for microrobotics applications
2011 IEEE RSJ International Conference on Intelligent Robots and Systems, 2011Co-Authors: Benjamin M. Finio, Kevin C. Galloway, Robert J. WoodAbstract:Motivated by the need for torque sensing in the µNm range for experiments with insect-sized flapping-wing robots, we present the design, fabrication and testing of a custom single-axis torque sensor. The micorobots in question are too large for MEMS force/torque sensors used for smaller live insects such as fruit flies, but too small to produce torques within the dynamic range of commercially available force/torque sensors. Our sensor consists of laser-machined Invar sheets that are assembled into a three dimensional beam. A capacitive Displacement sensor is used to Measure Displacement of a target plate when the beam rotates, and the output voltage is correlated to applied torque. Sensor bandwidth, range, and resolution are designed to match the criteria of the robotic fly experiments while remaining insensitive to off-axis loads. We present a final sensor design with a range of ±130µNm, a resolution of 4.5nNm, and bandwidth of 1kHz.
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An ultra-high precision, high bandwidth torque sensor for microrobotics applications
IEEE International Conference on Intelligent Robots and Systems, 2011Co-Authors: Benjamin M. Finio, Kevin C. Galloway, Robert J. WoodAbstract:Motivated by the need for torque sensing in the µNm range for experiments with insect-sized flapping-wing robots, we present the design, fabrication and testing of a custom single-axis torque sensor. The micorobots in question are too large for MEMS force/torque sensors used for smaller live insects such as fruit flies, but too small to produce torques within the dynamic range of commercially available force/torque sensors. Our sensor consists of laser-machined Invar sheets that are assembled into a three dimensional beam. A capacitive Displacement sensor is used to Measure Displacement of a target plate when the beam rotates, and the output voltage is correlated to applied torque. Sensor bandwidth, range, and resolution are designed to match the criteria of the robotic fly experiments while remaining insensitive to off-axis loads. We present a final sensor design with a range of ±130µNm, a resolution of 4.5nNm, and bandwidth of 1kHz.