基于恒应变率控制的椭圆凹模胀形试验方法

为确定2A16-O铝合金板材在不同温度及应变率下的成形极限曲线(FLCs),应用改进Hollomon公式获取满足外插可靠度的拟合应力应变,通过有限元分析(FEA)不同椭圆度的椭圆凹模胀形破裂位置,优化工艺参数得到指定应变路径下的成形极限点,建立了液体压力与等效应变及应变率的公式,推导出压力变化率与应变率的定量关系。以应变率控制的椭圆凹模胀形与单拉试验相结合,获得2A16-O铝合金板材在不同温度及应变率下的FLCs,为定量分析应变率的影响规律和评判理论预测方法的准确性提供了依据。

Test method of elliptical hydraulic bulging based on constant strain rate

To determine the forming limit curves (FLCs) of 2A16-O aluminum alloy sheet at various temperatures and strain rates, a modified Hollomon equation is put forward to acquire the fitted true stress-true strain curve. Through finite element analysis (FEA), the fracture position in elliptical hydraulic bulging with different ovality was obtained. The forming limit data in specified strain path were determined by optimizing the process parameters. The quantitative relation between pressure rate and strain rate was derived by establishing the formula of liquid pressure, equivalent strain and strain rate. By combining the uniaxial tensile with elliptical hydraulic bulging which is controlled by the constant strain rate, the FLCs of 2A16-O aluminum alloy sheet at different temperatures and strain rates were acquired. The above method provides the criterion for quantitatively analyzing the influence rule of strain rate on FLCs and evaluating which theoretical method is more accurate to predict FLCs.