The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
S. Thuillier - One of the best experts on this subject based on the ideXlab platform.
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Calibration of anisotropic plasticity models using a Biaxial Test and the virtual fields method
International Journal of Solids and Structures, 2019Co-Authors: J. M. P. Martins, António Andrade-campos, S. ThuillierAbstract:Abstract The aim of the present study is to explore the combination of a Biaxial Test with a cruciform specimen and the virtual fields method to develop an efficient strategy for simultaneous identification of material parameters related with hardening and anisotropy in plasticity. In a first step, three cruciform geometries are evaluated as potential candidates to generate an experimental database for the calibration of the classical Hill’48 yield criterion and Swift’s hardening law. In a second step, the geometry with the best results is used to calibrate YLD2000-2d yield criterion and Swift’s hardening law. Numerical results are used as virtual experimental full-field measurements, which allows the comparison of the identified solution with the input material parameters. The accuracy of the identified material parameters is thoroughly assessed through the analysis of flow stress curve evolution, normalised yield stresses and plastic anisotropy coefficients, and for the last step, yield locus prediction. The results show the potential of this combination to identify simultaneously the material parameters related to hardening and anisotropy with a single Test.
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Potential of the Cross Biaxial Test for Anisotropy Characterization Based on Heterogeneous Strain Field
Experimental Mechanics, 2015Co-Authors: S. Zhang, Dominique Guines, Lionel Leotoing, S. ThuillierAbstract:The mechanical behavior in cross Biaxial tension was investigated for two metallic sheets, an aluminium alloy and a dual phase steel. The heterogeneous strain field in the central gauge area of a cruciform specimen was analyzed by digital image correlation. Minor and major strains were output along several paths, for a given load level just before necking, showing a wide range of strain states, from uniaxial tension to Biaxial state. The applied loads along the two loading directions were also recorded, the gap between the two signals being all the most important that the material anisotropy was significant. Moreover, the strain path ratio, defined as the ratio of the minor strain over the major strain, exhibited a sensible non-monotonic evolution along the transverse direction, compared to the rolling direction. Finally, a material parameter identification process with only Biaxial tensile Test for Bron and Besson anisotropic yield model was proposed, based on the minimization of experimental and numerical principal strains along a specified path in the gauge area of the cruciform specimen.
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Potential of the Cross Biaxial Test for Anisotropy Characterization Based on Heterogeneous Strain Field
Experimental Mechanics, 2015Co-Authors: S. Zhang, Dominique Guines, Lionel Leotoing, S. ThuillierAbstract:International audienceThe mechanical behavior in cross Biaxial tension was investigated for two metallic sheets, an aluminium alloy and a dual phase steel. The heterogeneous strain field in the central gauge area of a cruciform specimen was analyzed by digital image correlation. Minor and major strains were output along several paths, for a given load level just before necking, showing a wide range of strain states, from uniaxial tension to Biaxial state. The applied loads along the two loading directions were also recorded, the gap between the two signals being all the most important that the material anisotropy was significant. Moreover, the strain path ratio, defined as the ratio of the minor strain over the major strain, exhibited a sensible non-monotonic evolution along the transverse direction, compared to the rolling direction. Finally, a material parameter identification process with only Biaxial tensile Test for Bron and Besson anisotropic yield model was proposed, based on the minimization of experimental and numerical principal strains along a specified path in the gauge area of the cruciform specimen
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Calibration of anisotropic yield criterion with conventional Tests or Biaxial Test
International Journal of Mechanical Sciences, 2014Co-Authors: Shun Ying Zhang, Dominique Guines, Lionel Leotoing, S. Thuillier, Shun-lai ZangAbstract:Bron and Besson yield criterion has been used to model the plastic anisotropic behavior of an aluminum alloy series 5000. The parameters of this anisotropic yield model have been identified by two different methods: a classical one, considering several homogeneous conventional experiments and an exploratory one, with only one Biaxial Test. On one hand, the parameter identification with conventional experiments has been carried out with uniaxial tensile and simple shear Tests in different orientations to the rolling direction and with a hydraulic bulge Test, all of them considered at three equivalent plastic strain levels. On the other hand, Bron and Besson yield function has also been calibrated with inverse analysis from only a cross Biaxial tensile Test, since it was shown that the strain distribution in the center of the cruciform specimen is significantly dependent on the yield criterion. The principal strains along a specified path in the gauge area of the cruciform specimen have been analyzed and the gap between experimental and numerical values was minimized. Finally the yield contours obtained with the two methods have been compared and discussed.
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Calibration of Material Parameters of Anisotropic Yield Criterion with Conventional Tests and Biaxial Test
Key Engineering Materials, 2013Co-Authors: Shun Ying Zhang, Dominique Guines, Lionel Leotoing, S. ThuillierAbstract:Bron and Besson yield criterion has been used to investigate the plastic anisotropic behavior of an aluminum alloy AA5086. The parameters of this anisotropic yield model have been identified by two different methods: a classical one, considering several homogeneous conventional experiments and an exploratory one, with only Biaxial Test. In this paper, the parameter identification with conventional experiments has been carried out with uniaxial tensile Tests and simple shear Tests in different orientations to the rolling direction and with a hydraulic bulge Test. For comparison's sake, Hill's 48 yield function has also been calibrated analytically from uniaxial tensile Tests. Numerical simulation for the cross Biaxial Test has been carried out with the anisotropic parameters identified from the conventional Tests. From this simulation, the principle strains along a specified path in the gauge area of the cruciform specimen have been evaluated. A good agreement is observed between experimental and numerical values of principal strains for a large range of strain paths.
Marc A. Simon - One of the best experts on this subject based on the ideXlab platform.
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Quantification of Coupled Stiffness and Fiber Orientation Remodeling in Hypertensive Rat Right-Ventricular Myocardium Using 3D Ultrasound Speckle Tracking with Biaxial Testing.
PloS one, 2016Co-Authors: Dae Woo Park, Andrea Sebastiani, Choon Hwai Yap, Marc A. Simon, Kang KimAbstract:Mechanical and structural changes of right ventricular (RV) in response to pulmonary hypertension (PH) are inadequately understood. While current standard Biaxial Testing provides information on the mechanical behavior of RV tissues using surface markers, it is unable to fully assess structural and mechanical properties across the full tissue thickness. In this study, the mechanical and structural properties of normotensive and pulmonary hypertension right ventricular (PHRV) myocardium through its full thickness were examined using mechanical Testing combined with 3D ultrasound speckle tracking (3D-UST). RV pressure overload was induced in Sprague–Dawley rats by pulmonary artery (PA) banding. The second Piola–Kirchhoff stress tensors and Green-Lagrangian strain tensors were computed in the RV myocardium using the Biaxial Testing combined with 3D-UST. A previously established non-linear curve-fitting algorithm was applied to fit experimental data to a Strain Energy Function (SEF) for computation of myofiber orientation. The fiber orientations obtained by the Biaxial Testing with 3D-UST compared well with the fiber orientations computed from the histology. In addition, the re-orientation of myofiber in the right ventricular free wall (RVFW) along longitudinal direction (apex-to-outflow-tract direction) was noticeable in response to PH. For normotensive RVFW samples, the average fiber orientation angles obtained by 3D-UST with Biaxial Test spiraled from 20° at the endo-cardium to -42° at the epi-cardium (Δ = 62°). For PHRV samples, the average fiber orientation angles obtained by 3D-UST with Biaxial Test had much less spiral across tissue thickness: 3° at endo-cardium to -7° at epi-cardium (Δ = 10°, P
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quantification of coupled stiffness and fiber orientation remodeling in hypertensive rat right ventricular myocardium using 3d ultrasound speckle tracking with Biaxial Testing
PLOS ONE, 2016Co-Authors: Dae Woo Park, Andrea Sebastiani, Marc A. SimonAbstract:Mechanical and structural changes of right ventricular (RV) in response to pulmonary hypertension (PH) are inadequately understood. While current standard Biaxial Testing provides information on the mechanical behavior of RV tissues using surface markers, it is unable to fully assess structural and mechanical properties across the full tissue thickness. In this study, the mechanical and structural properties of normotensive and pulmonary hypertension right ventricular (PHRV) myocardium through its full thickness were examined using mechanical Testing combined with 3D ultrasound speckle tracking (3D-UST). RV pressure overload was induced in Sprague–Dawley rats by pulmonary artery (PA) banding. The second Piola–Kirchhoff stress tensors and Green-Lagrangian strain tensors were computed in the RV myocardium using the Biaxial Testing combined with 3D-UST. A previously established non-linear curve-fitting algorithm was applied to fit experimental data to a Strain Energy Function (SEF) for computation of myofiber orientation. The fiber orientations obtained by the Biaxial Testing with 3D-UST compared well with the fiber orientations computed from the histology. In addition, the re-orientation of myofiber in the right ventricular free wall (RVFW) along longitudinal direction (apex-to-outflow-tract direction) was noticeable in response to PH. For normotensive RVFW samples, the average fiber orientation angles obtained by 3D-UST with Biaxial Test spiraled from 20° at the endo-cardium to -42° at the epi-cardium (Δ = 62°). For PHRV samples, the average fiber orientation angles obtained by 3D-UST with Biaxial Test had much less spiral across tissue thickness: 3° at endo-cardium to -7° at epi-cardium (Δ = 10°, P<0.005 compared to normotensive).
Nele Famaey - One of the best experts on this subject based on the ideXlab platform.
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Constrained mixture modeling affects material parameter identification from planar Biaxial Tests
Journal of the mechanical behavior of biomedical materials, 2019Co-Authors: Lauranne Maes, Heleen Fehervary, Julie Vastmans, S. Jamaleddin Mousavi, Stéphane Avril, Nele FamaeyAbstract:Abstract The constrained mixture theory is an elegant way to incorporate the phenomenon of residual stresses in patient-specific finite element models of arteries. This theory assumes an in vivo reference geometry, obtained from medical imaging, and constituent-specific deposition stretches in the assumed reference state. It allows to model residual stresses and prestretches in arteries without the need for a stress-free reference configuration, most often unknown in patient-specific modeling. A finite element (FE) model requires material parameters, which are classically obtained by fitting the constitutive model to experimental data. The characterization of arterial tissue is often based on planar Biaxial Test data, to which nonlinear elastic fiber-reinforced material parameters are fitted. However, the introduction of the constrained mixture theory requires an adapted approach to parameter fitting. Therefore, we introduce an iterative fitting method, alternating between nonlinear least squares parameter optimization and an FE prestressing algorithm to obtain the correct constrained mixture material state during the mechanical Test. We verify the method based on numerically constructed planar Biaxial Test data sets, containing ground truth sets of material parameters. The results show that the method converges to the correct parameter sets in just a few iterations. Next, the iterative fitting approach is applied to planar Biaxial Test data of ovine pulmonary artery tissue. The obtained results demonstrate a convergence towards constrained mixture compatible parameters, which differ significantly from classically obtained parameters. We show that this new modeling approach yields in vivo wall stresses similar to when using classically obtained parameters. However, due to the numerous advantages of constrained mixture modeling, our fitting method is relevant to obtain compatible material parameters, that may not be confused with parameters obtained in a classical way.
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development of an improved parameter fitting method for planar Biaxial Testing using rakes
International Journal for Numerical Methods in Biomedical Engineering, 2019Co-Authors: Heleen Fehervary, Jos Vander Sloten, Nele FamaeyAbstract:A correct estimation of the material parameters from a planar Biaxial Test is crucial since they will affect the outcome of the finite element model in which they are used. In a virtual planar Biaxial experiment, a difference can be noticed in the stress calculated from the force measured experimentally at the rakes and the actual stress at the center of the sample. As a consequence, a classic parameter fitting does not result in a correct estimation of the material parameters. This difference is caused by the boundary conditions of the set-up and is among others dependent on the sample material. To overcome this problem, a new parameter fitting procedure is proposed that takes this difference into account by calculating a finite element-based correction vector. This paper describes the methodology to apply this new parameter fitting procedure on real experimental data from a planar Biaxial Test using rakes. To this end, image processing is used to extract the experiment characteristics. This information is used to construct a finite element model. Two variations of the new parameter fitting procedure are investigated using two human aortic samples: a basic approach and an image-based approach. The performance of the method is assessed by the difference between the force measured at the rakes during the experiment and the force at the rakes obtained from the finite element simulation. Both approaches of the new parameter fitting procedure lead to an improved estimation of the sample behavior compared with the classic approach.
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How important is sample alignment in planar Biaxial Testing of anisotropic soft biological tissues? A finite element study.
Journal of the mechanical behavior of biomedical materials, 2018Co-Authors: Heleen Fehervary, Julie Vastmans, Jos Vander Sloten, Nele FamaeyAbstract:Abstract Finite element models of biomedical applications increasingly use anisotropic hyperelastic material formulations. Appropriate material parameters are essential for a reliable outcome of these simulations, which is why planar Biaxial Testing of soft biological tissues is gaining importance. However, much is still to be learned regarding the ideal methodology for performing this type of Test and the subsequent parameter fitting procedure. This paper focuses on the effect of an unknown sample orientation or a mistake in the sample orientation in a planar Biaxial Test using rakes. To this end, finite element simulations were conducted with various degrees of misalignment. Variations to the Test method and subsequent fitting procedures are compared and evaluated. For a perfectly aligned sample and for a slightly misaligned sample, the parameters of the Gasser-Ogden-Holzapfel model can be found to a reasonable accuracy using a planar Biaxial Test with rakes and a parameter fitting procedure that takes into account the boundary conditions. However, after a certain threshold of misalignment, reliable parameters can no longer be found. The level of this threshold seems to be material dependent. For a sample with unknown sample orientation, material parameters could theoretically be obtained by increasing the degrees of freedom along which Test data is obtained, e.g. by adding the data of a rail shear Test. However, in the situation and the material model studied here, the inhomogeneous boundary conditions of the Test set-ups render it impossible to obtain the correct parameters, even when using the parameter fitting method that takes into account boundary conditions. To conclude, it is always important to carefully track the sample orientation during harvesting and preparation and to minimize the misalignment during mounting. For transversely isotropic samples with an unknown orientation, we advise against parameter fitting based on a planar Biaxial Test, even when combined with a rail shear Test.
Dae Woo Park - One of the best experts on this subject based on the ideXlab platform.
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Quantification of Coupled Stiffness and Fiber Orientation Remodeling in Hypertensive Rat Right-Ventricular Myocardium Using 3D Ultrasound Speckle Tracking with Biaxial Testing.
PloS one, 2016Co-Authors: Dae Woo Park, Andrea Sebastiani, Choon Hwai Yap, Marc A. Simon, Kang KimAbstract:Mechanical and structural changes of right ventricular (RV) in response to pulmonary hypertension (PH) are inadequately understood. While current standard Biaxial Testing provides information on the mechanical behavior of RV tissues using surface markers, it is unable to fully assess structural and mechanical properties across the full tissue thickness. In this study, the mechanical and structural properties of normotensive and pulmonary hypertension right ventricular (PHRV) myocardium through its full thickness were examined using mechanical Testing combined with 3D ultrasound speckle tracking (3D-UST). RV pressure overload was induced in Sprague–Dawley rats by pulmonary artery (PA) banding. The second Piola–Kirchhoff stress tensors and Green-Lagrangian strain tensors were computed in the RV myocardium using the Biaxial Testing combined with 3D-UST. A previously established non-linear curve-fitting algorithm was applied to fit experimental data to a Strain Energy Function (SEF) for computation of myofiber orientation. The fiber orientations obtained by the Biaxial Testing with 3D-UST compared well with the fiber orientations computed from the histology. In addition, the re-orientation of myofiber in the right ventricular free wall (RVFW) along longitudinal direction (apex-to-outflow-tract direction) was noticeable in response to PH. For normotensive RVFW samples, the average fiber orientation angles obtained by 3D-UST with Biaxial Test spiraled from 20° at the endo-cardium to -42° at the epi-cardium (Δ = 62°). For PHRV samples, the average fiber orientation angles obtained by 3D-UST with Biaxial Test had much less spiral across tissue thickness: 3° at endo-cardium to -7° at epi-cardium (Δ = 10°, P
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quantification of coupled stiffness and fiber orientation remodeling in hypertensive rat right ventricular myocardium using 3d ultrasound speckle tracking with Biaxial Testing
PLOS ONE, 2016Co-Authors: Dae Woo Park, Andrea Sebastiani, Marc A. SimonAbstract:Mechanical and structural changes of right ventricular (RV) in response to pulmonary hypertension (PH) are inadequately understood. While current standard Biaxial Testing provides information on the mechanical behavior of RV tissues using surface markers, it is unable to fully assess structural and mechanical properties across the full tissue thickness. In this study, the mechanical and structural properties of normotensive and pulmonary hypertension right ventricular (PHRV) myocardium through its full thickness were examined using mechanical Testing combined with 3D ultrasound speckle tracking (3D-UST). RV pressure overload was induced in Sprague–Dawley rats by pulmonary artery (PA) banding. The second Piola–Kirchhoff stress tensors and Green-Lagrangian strain tensors were computed in the RV myocardium using the Biaxial Testing combined with 3D-UST. A previously established non-linear curve-fitting algorithm was applied to fit experimental data to a Strain Energy Function (SEF) for computation of myofiber orientation. The fiber orientations obtained by the Biaxial Testing with 3D-UST compared well with the fiber orientations computed from the histology. In addition, the re-orientation of myofiber in the right ventricular free wall (RVFW) along longitudinal direction (apex-to-outflow-tract direction) was noticeable in response to PH. For normotensive RVFW samples, the average fiber orientation angles obtained by 3D-UST with Biaxial Test spiraled from 20° at the endo-cardium to -42° at the epi-cardium (Δ = 62°). For PHRV samples, the average fiber orientation angles obtained by 3D-UST with Biaxial Test had much less spiral across tissue thickness: 3° at endo-cardium to -7° at epi-cardium (Δ = 10°, P<0.005 compared to normotensive).
J. Huetink - One of the best experts on this subject based on the ideXlab platform.
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influence of stress state and strain path on deformation induced martensitic transformations
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Emin Semih Perdahcioglu, H J M Geijselaers, J. HuetinkAbstract:The mechanically induced transformation behavior of 12Crsingle bond9Nisingle bond 4Mo (ASTM A 564) austenitic stainless steel is investigated in different stress states. This phenomenon is studied experimentally on a plane-stress Biaxial Test facility. The facility can load a sheet specimen simultaneously in shear and tension which enables us to investigate the effect of stress state on transformation kinetics. The martensite fraction is monitored via a magnetic sensor while the strain is measured using a camera and a dot-tracking software.
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Non-proportional tension-shear experiments in a Biaxial Test facility
2006Co-Authors: M. Van Riel, A.h. Van Den Boogaard, J. HuetinkAbstract:This paper discusses the results obtained from experiments on DC06 mild steel with a Biaxial Test facility. The two presented Tests are non-proportional Tests consisting of a two stage strain path. First the samples are deformed in the tensile direction after which simple shear deformation is applied. In the one case elastic unloading is applied after the tensile deformation, while in the other case the tensile deformation is directly followed by the simple shear deformation. For the Test with elastic unloading a peak in the shear stress appears directly after the strain path change, while in the Test without elastic unloading the shear stress gradually increases to a uniform stress-strain curve. The difference in the result is explained with reference to the microstructure evolution.