中文摘要：

为了研究管材在内外压复合作用下的硬化行为,在中间自由胀形区为椭圆形轮廓线的假设条件下,理论推导得到内外压复合作用下管材的应力/应变分析模型;再利用薄壁5A02-O铝合金管材在研制的内外压复合成形实验装置上进行外压为85 MPa（1.0σs）的实验研究,得到5A02铝合金管材在内外压复合作用下的应力-应变曲线。结果表明：5A02铝合金管材在内外压复合作用下进行胀形时,其胀形区轮廓形状依然可以准确地用椭圆函数进行拟合,且最高点处壁厚与胀形高度符合线性关系;由内外压复合胀形得到的应力-应变曲线的硬化指数n值为0.274,低于单向拉伸时得到的n值（0.304）。

英文摘要：

In order to investigate the hardening behavior of tubes under the combined action of internal and external pressures, the analytical models of stress and strain for the tubes bulged under the combined action of internal and external pressures were deduced firstly based on the assumption that the free bulging zone can be fitted perfectly using the elliptic equation. Moreover, an experimental investigation was conducted that the thin-walled 5A02-O aluminum alloy tubes were bulged under double-sided pressures using self-developed double-sided tube hydroforming equipment at the same external pressure of 85 MPa（1.0σs）. Then, the stress-strain curve of 5A02 aluminum alloy tube under double-sided pressures was obtained. The results show that the free bulging area of 5A02 aluminum alloy tubes can be fitted perfectly using the elliptic equation. The thickness at the highest point（P） has a linear relation with the bulging height. In addition, the strain hardening exponent n obtained from double-sided free bulging（0.274） is lower than that obtained from uniaxial tension（0.304）.