Experimental and numerical investigation of failure during bending of AA6061 aluminum alloy sheet using the modified Mohr-Coulomb fracture criterion
Experimental and numerical investigation of failure during bending of AA6061 aluminum alloy sheet using the modified Mohr-Coulomb fracture criterion
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DOI：
10.1007/s00170-019-04549-6
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发表时间：
2019-11
期刊：
影响因子：
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通讯作者：
H. Talebi-Ghadikolaee;H. Moslemi Naeini;M. J. Mirnia;M. Mirzai;S. Alexandrov;H. Gorji
中科院分区：
文献类型：
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作者：
H. Talebi-Ghadikolaee;H. Moslemi Naeini;M. J. Mirnia;M. Mirzai;S. Alexandrov;H. Gorji
采用修正的莫尔-库仑（MMC）韧性断裂准则，对AA 6061-T6铝合金板材U形弯曲过程中的断裂行为进行了分析。采用适当的校准程序，使用各种张力测试。使用商业有限元程序Abaqus/Explicit建立了一个有限元（FE）模型，其中包含校准的MMC断裂准则。结果发现，MMC标准校准的单轴，平面应变，缺口，和修改后的面内剪切拉伸试验可以预测在U形弯曲过程中的断裂发生具有合理的精度。裂缝位移预测值与实验值的误差在2%左右。由于断裂预测精度依赖于应力状态，工艺参数对应力三轴度和归一化矿脉角参数的影响进行了研究。工艺参数对应力状态的影响可以忽略不计，证实了校准断裂准则（MMC）能够以相同的精度预测不同成形条件下的断裂。此外，在U形弯曲过程中的比例应力和应变状态表明，除了MMC的损伤累积函数的高断裂预测精度，断裂形成极限图（比例加载假设下）可以作为一个可靠的工具，用于估计在U形弯曲过程中的断裂发生。因此，也进行了一系列的研究损伤演化，裂纹扩展，主应变，断裂位移在不同的成形条件下的U形弯曲过程中。
In this paper, the modified Mohr-Coulomb (MMC) ductile fracture criterion was adopted to analyze the fracture behavior of the AA6061-T6 aluminum alloy sheet during the U-bending process. Appropriate calibration procedures were employed using various tension tests. A finite element (FE) model was built using the commercial FE code Abaqus/Explicit incorporating the calibrated MMC fracture criterion. It was found that the MMC criterion calibrated by the uniaxial, plane strain, notched, and modified in-plane shear tension tests can predict the onset of fracture in the U-bending process with reasonable accuracy. The error of the predicted fracture displacement was about 2% as compared to experiments. Due to the dependency of the fracture prediction accuracy on the stress state, the effects of process parameters on stress triaxiality and normalized Lode angle parameter were investigated. The negligible effect of process parameters on the stress state confirmed that the calibrated fracture criterion (MMC) was able to predict fracture in different forming conditions with equal accuracy. Also, the proportional stress and strain state in the U-bending process indicate that, besides the high fracture prediction accuracy of the MMC’s damage accumulation function, the fracture forming limit diagram (under proportional loading assumption) can serve as a reliable tool for estimating the onset of fracture in the U-bending process. Therefore, a series of studies were also conducted on damage evolution, crack propagation, principal strains, and fracture displacement during the U-bending process under various forming conditions.