流动应力计算对铝合金板材充液热成形性能影响

Effect of flow stress calculation on formability of aluminum alloy warm sheet hydroforming

为研究流动应力计算对铝合金板材充液热成形性能的影响,进行了板材热态胀形试验,得到了不同直径的胀形高度-压力曲线。结合三坐标测量仪测得的胀形零件轮廓数据,拟合出了最小二乘圆(LSCF)半径,发现在高径比(h/a)范围(0.18<h/a≤0.68)内,对应的曲率半径与圆形半径之间的圆形度误差为5%。为获取更为精确的应力-应变曲线,通过对现有曲率半径和厚度理论模型进行比较,结合流动应力计算,发现Hill及Panknin曲率半径模型的平均值及Kruglov-Hill厚度模型最符合试验数据。利用组合模型计算胀形试验所得到的胀形高度-压力曲线,得到了不同温度、不同压力率下的应力-应变曲线。结果表明,210℃时方向异性(轧制方向及垂直方向)对铝合金7075-O胀形件曲率半径的影响很小;同时,压力率可影响其应力-应变曲线。

In order to research the influence of flow stress calculation on formability of aluminum alloy warm sheet hydroforming,warm sheet bulging test was carried out to obtain bulging height-pressure curves with different bulging diameters in this study. Based on the data of bulging parts profile measured by three coordinate measuring machine,the least square circle fit（ LSCF） radius were fitted,and it was found that when the height-diameter ratio h/a was in the range of 0. 18 h/a≤0. 68,the corresponding value of roundness error between the radius of curvature and the circle radius was 5%. By comparing the existing theoretical models for radius of curvature and thickness,which is combined with flow stress calculation,it was found that the average value of radius of curvature model Hill and Panknin,and the thickness model Kruglov-Hill are in the most accordance with experimental data. The combination model was used to calculate the bulging height-pressure curves obtained by bulging test,and then the stress-strain curves with different temperatures and pressure rates were obtained. It was found that there was a little impact on radius of curvature for different directions（ rolling direction and vertical direction） of the bulging parts formed with 7075-O aluminum alloy at 210℃,while the pressure rate can affect the stress-strain curves.