AZ31マグネシウム合金円管の冷間プレス曲げにおける変形挙動に及ぼす引張・圧縮変形抵抗の影響

抄録

The deformation behavior of a magnesium alloy tube during press bending is investigated to clarify the effect of the difference between tensile and compressive stress-strain curves of magnesium alloy experimentally and theoretically. The bending experiments using a mandrel of wires are carried out at room temperature. An AZ31 magnesium alloy circular tube with 25mm outer diameter and 1.5mm wall thickness is used in the experiment. The unique deformation behavior of the AZ31 tube is discussed in detail and compared with the press bending deformation of a 6063-TD aluminum alloy tube. In the bending experiments, the AZ31 tube was able to be bent without wrinkling or splitting under the ratio of bending radius to outer diameter, R₀/D₀, of 3. A formula on the neutral surface position of a tube under pure bending is derived in this study. For an AZ31 tube having a low average flow stress and a low r-value in the compression range, the neutral surface position is predicted to move to the tensile side of the bend. The theoretical results are in good agreement with the experimental results. From these results, it is found that the high bendability of AZ31 is attributable to its unique deformation behavior with low average flow stress and a lower r-value in compression.