On the thermal forming limit diagram (TFLD) with GTN mesoscopic damage model for AA7075 aluminum alloy: Numerical and experimental investigation
On the thermal forming limit diagram (TFLD) with GTN mesoscopic damage model for AA7075 aluminum alloy: Numerical and experimental investigation
复制标题
基于 GTN 细观损伤模型的 AA7075 铝合金热成形极限图 (TFLD)：数值和实验研究
DOI：
10.1016/j.jallcom.2019.05.342
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发表时间：
2019-09-25
影响因子：
6.2
通讯作者：
Hou, Wenbin
中科院分区：
文献类型：
--
作者：
Ying, Liang;Gao, Tianhan;Hou, Wenbin
高强度AA 7075铝合金的高温成形性能对汽车结构件的制造具有重要的指导意义。AA 7075在高温下的韧性断裂形成极限基本上是由热损伤演变。本文对AA 7075合金进行了300 ℃ ~ 450 ℃，应变速率0.1s（-1）~ 0.001s（-1）的热拉伸实验，并用Hensiel-Spittel（HS）本构方程拟合了相应的流变行为。采用GTN细观损伤模型，考虑了AA 7075合金在高温下的损伤演化现象。基于CCD参数设计-有限元反模拟-遗传算法（CCD-FEIS-GA）优化方法，对温度相关损伤孔隙体积分数（VVF）进行了精确识别。随后，基于GTN损伤参数计算了热成形极限图，并通过热Nakajima型胀形实验进行了验证。详细讨论了相应的损伤演化行为及临界成形参数的影响。结果表明，随着成形温度的升高，AA 7075的成形性能先增大后减小，在400 ℃时，TFLD 0达到最大值;随着应变速率的增大和表面摩擦系数的减小，成形性能也随之增大。所提出的模拟策略与细观GTN方法相结合，有助于准确预测AA 7075热成形过程中的TFLD和损伤断裂行为。(C)2019 Elsevier B. V.版权所有。
The formability of high strength AA7075 aluminum alloy under elevated temperatures is vital in guiding the fabrication of automobile structural parts. The ductile fracture forming limit of AA7075 at elevated temperatures is essentially governed by thermal damage evolution. In this paper, the hot tensile test (300 degrees C-450 degrees C, strain rate 0.1s(-1)-0.001s(-1)) for AA7075 was conducted and the corresponding flow behavior was fitted by Hensiel-Spittel (HS) constitutive equation. The GTN mesoscopic damage model was implemented to take account of the damage evolution phenomenon of AA7075 at elevated temperatures. The temperature-dependent damage void volume fractions (VVF) were identified accurately based on a novel inverse identification procedure, named the CCD parameters design-FEM inverse simulation-genetic algorithm (CCD-FEIS-GA) optimization method. Subsequently, the thermal forming limit diagram (TFLD) was calculated based on the GTN damage parameters and further validated by hot Nakajima-type bulging experiment. The corresponding damage evolution behaviors and effects of critical forming parameters were discussed in detail. The comparison of experimental and numerical results showed that the formability of AA7075 firstly increases and then decreases with the increasing forming temperature, the TFLD0 reaches its maximum value when the temperature is 400 degrees C, and the formability also increases with the increasing strain rate and the decreasing surface coefficient of friction. The proposed simulated strategy coupled with mesoscopic GTN approach conduces to the accurate prediction of TFLD and damage fracture behavior of AA7075 in the hot forming process. (C) 2019 Elsevier B.V. All rights reserved.