非等温模具对2024铝合金弯曲回弹和残余应力的影响

主要研究了2024铝合金在差温模具下弯曲成形时回弹和残余应力的变化规律。实验中选取板坯温度为25℃室温,凸模和凹模温度分别选取25,200,300和400℃共16组温度组合进行V型弯曲;然后进行板坯、凸模和凹模均为200℃的等温弯曲,并与差温弯曲进行对比分析。研究结果表明:分别提高凸模和凹模的温度均能够减小回弹角和残余应力;在成形结束后,当差温弯曲板坯和等温弯曲板坯开始回弹前的温度相接近时,由于温度梯度和贴模后温升的影响,差温弯曲件的回弹角和内、外表面残余应力及其差值能够达到与等温弯曲数值相近或更小的效果;通过合理控制凸、凹模温度能够使室温板坯获得与高温等温成形时同样较小的回弹和残余应力。

Influence of non-isothermal dies on bending springback and residual stress for aluminum alloy 2024

The regulations of springback and residual stress in non-isothermal dies bending process of aluminum alloy 2024 were re-searched. The V-shape bending tests were conducted that the blank was set at 25 ℃ (room temperature), and the punch and the die were set at 25 ℃, 200 ℃, 300 ℃, 400 ℃ respectively. Then the isothermal bending of blank and die at 200 ℃ was conducted to com-pare with the non-isothermal bending. The results show that the springback and residual stress decrease when the punch and die tempera-tures rise. When the blank temperatures of non-isothermal bending after processing before springback is close to that of isothermal ben-ding, the springback and the residual stress of inner and outer layers and their difference with non-isothermal bending are close to the val-ue with isothermal bending or even less due to the temperature gradient during processing and the influence of the temperature rise after hydroforming. By controlling the temperature of punch and die properly, the springback and residual stress of blank with room temperature are as small as those of the high temperature isothermal bending.