基于逆向分析的铝合金板料塑性变形本构关系构建及成形极限预测

Warm forming technology of aluminum alloy sheet is an important method to achieve automotive lightweight. Reliable prediction of sheet metal formability considering temperature and strain rate effects is a key issue to improve sheet warm forming technology. To investigate the formability of 5086 aluminum alloy sheet, this project is supposed to establish a “time dependent” necking criterion, systematically study the influences of necking criterion, curvature, strain gradient and strain path on the forming limits determination, and build the forming limit diagrams under temperatures from 20℃ to 300℃ and strain rates from 0.01 to 10 (1/s). Based on inverse analysis, cruciform tests are carried out to identify the parameters of Yld2000-2d anisotropy yield function under different temperatures, and uniaxial tests are executed to build appropriate hardening laws that capable of describing temperature and strain rate effects on the flow stresses of researched material. With the implementation of ABAQUS material subroutine, the roles of hardening law, yield function and related model parameters on the prediction of forming limits are studied in the coupled-thermo-mechanical finite element models and FE M-K model. The reliability of the models on predicting forming limits with considering temperature and strain rate effects are obtained by comparing with experimental results. This project has important theoretical and engineering application significances on the improvement of aluminum alloy sheet warm forming technology and the development of China’s automotive lightweight.

铝合金板料温成形技术是实现汽车轻量化的重要手段，可靠预测温度/速率对成形极限的影响是实现板料温成形技术突破亟需解决的关键基础问题。本项目以5086铝合金板料成形性能为研究对象，建立“时间相关法”缩颈准则，深入研究缩颈准则、曲率、应变梯度、应变路径对判别成形极限的影响，构建常温至300℃、0.01至10 (1/s)下准确的成形极限图。基于逆向分析技术，开展十字双拉试验，建立不同温度下Yld2000-2d各向异性屈服准则，开展单向拉伸试验，建立包含温度/速率影响的准确描述材料流变力学行为的流动方程。开发ABAQUS用户材料子程序，建立热力耦合实物模拟有限元模型和FE M-K模型，系统研究屈服准则、流动方程和相关模型参数对预测成形极限的影响，建立包含温度/速率因素的板料成形极限可靠预测模型。项目的开展对提高铝合金板料温成形技术、推动我国汽车轻量化发展具有重要的理论意义和工程应用价值。

铝合金板料温成形技术是实现汽车轻量化的重要手段，可靠预测温度/速率对成形极限的影响是实现板料温成形技术突破亟需解决的关键基础问题。本项目以研究温度/速率对成形极限的影响为目的，通过成形极限试验研究、材料本构方程构建、预测模型开发三方面开展工作：1）开发了成形极限测试专用装置，构建了不同温度/速率下的板材成形极限并获得了相关因素对成形极限的影响及规律；2）构建了不同温度/应变速率下的AA5086的可靠流动方程，与试验值对比验证了模型的正确性；3）开展了单向拉伸试验、十字双拉拉伸试验以及Potier胀形试验，结合传统法识别和逆向识别法获得了不同试验法识别下的描述AA5086各项异性的Yld2000-2d屈服准则参数，并通过筒形件拉深制耳试验验证了各种识别方法的有效性；4）开展了理论M-K、FE M-K、FE Marciniak成形极限预测研究，通过编写Umat子程序导入前述构建的流动方程进行成形极限预测，与FLCs试验值对比，探讨了模型参数的影响，构建了包含温度/速率影响的成形极限可靠预测模型；5）研发了十字双向拉伸综合试验测试装置，为后续的双拉研究开展提供了试验基础。项目的研究对铝合金板材温热成形工艺的优化具有重要的理论指导意义和工程应用价值。