【摘要】 通过薄壁管复合加载实验及单向拉伸卸载组合实验,证明了Zn-22Al合金在超塑温度-速度条件下遵循Mises屈服条件,且与应变速度呈（σ₁-σ₂）²+（σ₂-σ₃）²+（σ₃-σ₁）²=2(σ=K_ε^m)²的关系。给出了该合金在250℃、应变速度为3.3×10^-2(sec^-1)时,平面应力且0.2％应变时的屈服椭圆方程为通过单向拉伸位置预置自动卸载组合实验及数学回归分析处理,可定量地确定关系式(变形一定时,σ=K_ε^m),且证明K、m与变形程度或变形速度有关。通过薄壁管复合加载实验和分析,还得到薄壁筒形件吹塑时的吹塑压力-应力图和压力-应变图,可为判断和选择类似的吹塑成型力学条件提供参考。更多还原

【Abstract】 There is evidence that for the typical fine-crystalline superplastic alloy Zn-22Al under tension-compression combined stress at superplastic temperature,much as the common plastic materials,the yielding strength σ0.2 obeys the Mises criterion,i.e.,where σz and σφ are the axial and tangential stress respectively.It follows from two proof tests——the gas-filling test for determining the combined tension-compression stress-strain relation which performed with thin-wall tube specimens,and the uniaxial tension test with preset elongation unloading.Both are at a superplastic temperature of 250℃.Besides,the relationship between stresses a and strain rate e is given aswhere m is the sensitivity factor relevant to strain rate and K a constant.The strained condition of gas-filling thin-wall tube during test is much the same with the plane strain since the radial stress σr is so much less than the tangential stress σφ Thus,a yielding ellipse can be obtained as follows when strain rate e=3.3×10-2 sec-1Regressively analyzing the experimental results,the relationship α=Kεmεn,or α=Kεm if the strain e is constant,may be quantitatively determined,where n is the hardening factor.The values K and m are therefore obviously proved to be dependent on strain and strain rate.With respect to the gas-filling pressure q in thinwall tube gas-filling forming,the q-ε and q-σ diagrams are plotted from the combined stress test results,thus giving a reference to the assessment and selection for the mechanical conditions in case of the similar forming process.更多还原