“…These observations justify the additional investment in calibrating and implementing more advanced yield criterion, instead of resorting to classical J 2 plasticity. Similar examples for other materials can be found in [ 65 , 66 , 67 , 71 , 72 ]. Figure A2 KBK anisotropy evaluation of ( a ) Yld2000-2d and ( b ) von Mises models.…”
Section: Figure A1supporting
confidence: 60%
“…Hence, obtaining the stress as simply “force/area” only provides an average stress, which is not work-conjugate to the strains at the center of the test-section, as extracted from the DIC. The authors have proposed and applied on a large variety of materials a stress correction technique that is based on FE analysis [ 64 , 66 , 67 , 68 ]. Here, a FE model of 1/8 of the plane-strain tension specimen is created in Abaqus/Standard version 2018 (implicit solver), and meshed with quadratic, reduced integration elements (C3D20R).…”
Section: Plastic Anisotropymentioning
confidence: 99%
“…As the last plasticity characterization test, the plastic strain ratio of the RD and TD at the equibiaxial stress state, termed , i.e., , is determined using the disk compression experiment [ 27 , 69 ]. A well-lubricated, coin-shaped specimen of 8 mm diameter is compressed in the thickness direction using an Instron 1350 servo-hydraulic testing machine (Norwood, MA, USA) [ 66 , 67 , 70 , 71 ]. The experiment is interrupted at several levels of compressive thickness strain and in each step, the lengths along the RD and TD are measured manually using a micrometer.…”
The plasticity and formability of a commercially-pure aluminum sheet (AA1100-O) is assessed by experiments and analyses. Plastic anisotropy of this material is characterized by uniaxial and plane-strain tension along with disk compression experiments, and is found to be non-negligible (e.g., the r-values vary between 0.445 and 1.18). On the other hand, the strain-rate sensitivity of the material is negligible at quasistatic rates. These results are used to calibrate constitutive models, i.e., the Yld2000-2d anisotropic yield criterion as the plastic potential and the Voce isotropic hardening law. Marciniak-type experiments on a fully-instrumented hydraulic press are performed to determine the Forming Limit Curve of this material. Stereo-type Digital Image Correlation is used, which confirms the proportional strain paths induced during stretching. From these experiments, limit strains, i.e., the onset of necking, are determined by the method proposed by ISO, as well as two methods based on the second derivative. To identify the exact instant of necking, a criterion based on a statistical analysis of the noise that the strain signals have during uniform deformation versus the systematic deviations that necking induces is proposed. Finite element simulation for the Marciniak-type experiment is conducted and the results show good agreement with the experiment.
“…These observations justify the additional investment in calibrating and implementing more advanced yield criterion, instead of resorting to classical J 2 plasticity. Similar examples for other materials can be found in [ 65 , 66 , 67 , 71 , 72 ]. Figure A2 KBK anisotropy evaluation of ( a ) Yld2000-2d and ( b ) von Mises models.…”
Section: Figure A1supporting
confidence: 60%
“…Hence, obtaining the stress as simply “force/area” only provides an average stress, which is not work-conjugate to the strains at the center of the test-section, as extracted from the DIC. The authors have proposed and applied on a large variety of materials a stress correction technique that is based on FE analysis [ 64 , 66 , 67 , 68 ]. Here, a FE model of 1/8 of the plane-strain tension specimen is created in Abaqus/Standard version 2018 (implicit solver), and meshed with quadratic, reduced integration elements (C3D20R).…”
Section: Plastic Anisotropymentioning
confidence: 99%
“…As the last plasticity characterization test, the plastic strain ratio of the RD and TD at the equibiaxial stress state, termed , i.e., , is determined using the disk compression experiment [ 27 , 69 ]. A well-lubricated, coin-shaped specimen of 8 mm diameter is compressed in the thickness direction using an Instron 1350 servo-hydraulic testing machine (Norwood, MA, USA) [ 66 , 67 , 70 , 71 ]. The experiment is interrupted at several levels of compressive thickness strain and in each step, the lengths along the RD and TD are measured manually using a micrometer.…”
The plasticity and formability of a commercially-pure aluminum sheet (AA1100-O) is assessed by experiments and analyses. Plastic anisotropy of this material is characterized by uniaxial and plane-strain tension along with disk compression experiments, and is found to be non-negligible (e.g., the r-values vary between 0.445 and 1.18). On the other hand, the strain-rate sensitivity of the material is negligible at quasistatic rates. These results are used to calibrate constitutive models, i.e., the Yld2000-2d anisotropic yield criterion as the plastic potential and the Voce isotropic hardening law. Marciniak-type experiments on a fully-instrumented hydraulic press are performed to determine the Forming Limit Curve of this material. Stereo-type Digital Image Correlation is used, which confirms the proportional strain paths induced during stretching. From these experiments, limit strains, i.e., the onset of necking, are determined by the method proposed by ISO, as well as two methods based on the second derivative. To identify the exact instant of necking, a criterion based on a statistical analysis of the noise that the strain signals have during uniform deformation versus the systematic deviations that necking induces is proposed. Finite element simulation for the Marciniak-type experiment is conducted and the results show good agreement with the experiment.
“…The eight anisotropic parameters α i=1∼8 are determined using the Levenberg-Marquardt nonlinear least-square algorithm. For the plane-strain tension, only the major stress component along the loading direction can be identified in the experiment (using the procedure detailed in [28][29][30][31]) and the minor one, transverse to the loading direction, is determined by the optimization with α i=1∼8 , with the plane-strain assumption (i.e., zero minor strain, transverse to the loading) [28][29][30]. The calibrated parameters for Calib1 and Calib2 are listed in Table 2.…”
Section: Calibration Of Yld2000-2d Parametersmentioning
confidence: 99%
“…A quantitative assessment of the performance of Calib1 and Calib2 in capturing all the experiments is shown in Figure 3, using the representation proposed by [34]. See also [27,29,30,35]. For each experiment, the orientation of the stress state with respect to a reference direction is computed as cos ω.…”
Section: Calibration Of Yld2000-2d Parametersmentioning
The influence of yield function parameters on hole-expansion (HE) predictions are investigated for an anisotropic AA6022-T4 aluminum sheet. The HE experiment is performed in a fully-instrumented double-action hydraulic press with a flat-headed punch. Full strain fields are measured by a stereo-type digital image correlation (DIC) system. The stress state gradually changes from uniaxial to plane-strain tension to biaxial tension in the radial direction. Besides HE, the plastic anisotropy of AA6022-T4 is characterized by uniaxial tension and plane-strain tension experiments. Uniaxial tension is considered as the most important, since it is the stress state along the hoop direction in the hole. For the finite element (FE) simulation, the Yld2000-2d non-quadratic anisotropic yield function is used with two different parameter sets, calibrated by: (1) uniaxial tension only (termed Calib1) and, (2) both uniaxial and plane-strain tension (Calib2). The strain field predictions show a good agreement with the experiments only for Calib2, which takes into account plane-strain as well uniaxial tension. This indicates the importance of biaxial modes, and in particular plane-strain tension, for the adopted yield function to produce accurate HE simulations.
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