內(nèi)外壓復(fù)合作用下5A02鋁合金管材的硬化行為Hardening behavior of 5A02 aluminum alloy tube under combined action of internal and external pressures

為了研究管材在內(nèi)外壓復(fù)合作用下的硬化行為，在中間自由脹形區(qū)為橢圓形輪廓線的假設(shè)條件下，理論推導(dǎo)得到內(nèi)外壓復(fù)合作用下管材的應(yīng)力/應(yīng)變分析模型；再利用薄壁5A02-O鋁合金管材在研制的內(nèi)外壓復(fù)合成形實(shí)驗(yàn)裝置上進(jìn)行外壓為85 MPa(1.0σ_s)的實(shí)驗(yàn)研究，得到5A02鋁合金管材在內(nèi)外壓復(fù)合作用下的應(yīng)力-應(yīng)變曲線。結(jié)果表明：5A02鋁合金管材在內(nèi)外壓復(fù)合作用下進(jìn)行脹形時(shí)，其脹形區(qū)輪廓形狀依然可以準(zhǔn)確地用橢圓函數(shù)進(jìn)行擬合，且最高點(diǎn)處壁厚與脹形高度符合線性關(guān)系；由內(nèi)外壓復(fù)合脹形得到的應(yīng)力-應(yīng)變曲線的硬化指數(shù)n值為0.274，低于單向拉伸時(shí)得到的n值(0.304)。

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(1.0σ_s). 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).

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