“…The value of 10 MJ/m 3 is well-within the saturated regime. Similar findings are reported in the authors’ previous work on AA6013 [ 65 ].…”
Section: Plastic Anisotropysupporting
confidence: 93%
“…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%
“…The experiment is performed four times, and an average is taken for the yield function parameter calibration: the value is = 0.958 with standard deviation of 0.043. This deviation is slightly higher (but still acceptable) than the authors’other works, e.g., [ 65 , 71 , 72 ], possibly due to experimental errors caused by the thinner and softer material condition. This value is included in Table 1 .…”
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 value of 10 MJ/m 3 is well-within the saturated regime. Similar findings are reported in the authors’ previous work on AA6013 [ 65 ].…”
Section: Plastic Anisotropysupporting
confidence: 93%
“…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%
“…The experiment is performed four times, and an average is taken for the yield function parameter calibration: the value is = 0.958 with standard deviation of 0.043. This deviation is slightly higher (but still acceptable) than the authors’other works, e.g., [ 65 , 71 , 72 ], possibly due to experimental errors caused by the thinner and softer material condition. This value is included in Table 1 .…”
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.
“…It is noted that the critical elements chosen to compare the strain evolution between simulation and experimental results were all in the middle region (i.e., element A marked in Fig. 12a-c) because the large deformation at the edge of specimen cannot be calculated successfully by DIC near the fracture stroke, which is also stated in the work of Lou and Huh [49] and Ha et al [45]. The comparison of strain evolution reveals that finite element models provide sufficient accuracy for the simulation of these specimens.…”
Section: Parameters Calibration For Fracture Criteriamentioning
confidence: 97%
“…First, seven material parameters ( 0 , 45 , 90 , b , r 0 , r 45 r 90 ) were used to calibrate the Yld1996 yield function, and then we could predict that r b is equal to 1.79 for AA6016-T4. The same way had also been successfully used in the research of Ha et al [45], who successfully employed Yld2000-2d yield function to generate enough data to calibrate Yld2004-18p yield model.…”
Section: Calibration Of Anisotropic Yield Functionmentioning
This study is aimed to predict ductile fracture of sheet metal forming for 6016-T4 aluminum alloy (AA6016-T4). Six shapes of tension tests in three directions with respect to the rolling direction have been carried out up to fracture to measure ductile fracture for the sheet. Since the fracture-related parameters determined by finite element simulation are sensitive to plasticity model, the Yld2000-2d and anisotropic Drucker yield functions with a combined Swift-Voce hardening model were firstly identified for AA6016-T4 and then used to compare the prediction accuracy. These constitutive models are implemented into ABAQUS for plane stress condition and S4R shell elements are set for the finite element model. Comparison of the experimental and simulation results indicates that the anisotropic Drucker yield function is more suitable for AA6016-T4 by considering both the computational accuracy and efficiency. Based on these results, fracture loci for AA6016-T4 were represented by four common ductile fracture criteria (Cockcroft-Latham, Rice-Tracey, Clift and DF2012). Three kinds of specimen were employed to calibrate the fracture models by using a hybrid experimental-numerical method. The results show that the DF2012 criterion is more flexible and accurate for AA6016-T4 with the comparison of force-displacement curves. For further validation, these four ductile fracture criteria are also applied to predict the fracture of an automobile inner panel in drawing forming, and the results show that the DF2012 criterion provides sufficient prediction precision for AA6016-T4.
The paper discusses a thermodynamically consistent anisotropic continuum damage model for ductile metals. It takes into account different elastic potential functions to simulate the effect of damage on elastic material behavior. In addition, a yield condition and a flow rule describe plastic behavior whereas a damage criterion and a damage rule characterize various damage processes in a phenomenological way. To validate the constitutive laws and to identify material parameters different experiments have been performed where specimens have been taken from thin metal sheets. As an example, the X0-specimen is tested under different biaxial loading conditions covering a wide range of stress states. Results for proportional and corresponding non-proportional loading histories are discussed. During the experiments strain fields in critical regions of the specimens are analyzed by digital image correlation (DIC) technique while the fracture surfaces are examined by scanning electron microscopy (SEM). Corresponding numerical simulations have been performed and numerical results are compared with available experimental ones. In addition, based on the numerical analyses stress states as well as plastic and damage fields can be predicted allowing explanation of different damage processes on the micro-level. The results also elucidate the effect of loading history on damage and fracture behavior in ductile metals.
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