Prediction of ductile fracture on 6016-T4 aluminum alloy sheet metal forming considering anisotropic plasticity
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(2020) 42:593
TECHNICAL PAPER
Prediction of ductile fracture on 6016‑T4 aluminum alloy sheet metal forming considering anisotropic plasticity Saijun Zhang1 · Kun Zhang1 · Kangzhen Li1 · Huazhao Ye1 Received: 5 June 2020 / Accepted: 5 October 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract 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. Keywords Aluminum alloy · Ductile fracture · Anisotropy · Plasticity · Metal forming List of symbols a, b, c, d1, d2, d3 Material constants for fracture models c′1 , …, c′4 , c Material constants in anisotropic Drucker yield function J2′ , J3′ Second and third stress invariants K Strength coefficient L Lode parameter n Strain hardening exponent r0 , r45 , r90 Lankford r-values of 0°, 45° and 90° rb Lankford r-value of biaxial tension s′ Stress tensor in anisotropic Drucker yield function
Technical Editor: Marcelo Areias Trindade. * Saijun Zhang [email protected] 1
Guangdong Provincial Key Laboratory of Precision Equipment and Manufacturing Technology, School of Mechanical and Automotive Engineering, South China University of Technology, Wushan RD, Tianhe District, Guangzhou 510640, People’s Republic of China
X′ , X′′ Deviatoric stress tensors in Yld2000-2d yield function 𝜏max Maximum shear stress X1′ , X2′ Principal values of deviatoric stress tensor X′ ′′ ′′ X1 , X2 Principal values of deviatoric stress tensor X′′ 𝛼1 , …, 𝛼8 , m Material constants in Yld2000-2d yield function 𝜀̄ , 𝜀̄ f Equivalent plastic
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