6016铝合金板成形极限NADDRG模型优化及验证

Optimization and verification of NADDRG theoretical prediction model for 6016 aluminum alloy sheet forming limit test

成形极限曲线是反映材料冲压性能的方法,在选材、工艺优化方面有着重要的应用。使用Nakajima测试法和NADDRG预测模型得到6016铝合金板材成形极限曲线,通过对比发现:采用NADDRG模型预测6016铝合金板材成形极限曲线结果比较接近实际测试的,但实测得到曲线的最低点次应变明显向右偏移,其主应变与预测结果基本一致;曲线最低点的应变路径明显分为两个阶段,第一阶段为双向等拉伸应变状态,第二阶段次应变基本保持不变直至试样失效,故曲线最低点位置发生偏移;笔者针对这一现象对NADDRG模型进行修改,并采用不同厚度的6016铝合金板进行验证,修改后模型预测结果与实测结果更加吻合。

The forming limit curve(FLC)is a way to express the stamping performance of materials.It is very important for material selection and process optimization.We use Nakajima test method and NADDRG prediction model to obtain the actual test curve and theoretical prediction curve of 6016 aluminum alloy sheet.Through comparison,we find that the result of using the NADDRG model to predict the forming limit curve of the 6016 aluminum alloy sheet is close to the result of the actual test,but the secondary strain at the lowest point of the measured curve is obviously shifted to the right,while the principal strain is basically consistent with the prediction.The strain path at the lowest point of the curve is clearly divided into two stages.The first stage is in the bidirectional equal-tensile-strain state,and in the second stage,the secondary strain remains basically unchanged until the specimen fails,so the strain point position deviates.In response to this phenomenon,the author modified the NADDRG model and verified the results with 6016 aluminum alloy sheets of different thicknesses.After the modification,the predicted results of the model are more consistent with the measured results.