基于局部环向约束的内高压成形管坯有益皱调控

Based on the method of forming useful wrinkles for thin-walled tubes by compression-bulging, a novel method to control the useful wrinkle of thin-walled tube using local circumferential constraints was proposed. A numerical simulation model of compression-bulging for thin-walled tube under the condition of local circumferential constraints was established. The insert type constraint rings and wrinkling die were designed and a special experimental device for compression-bulging was established. Effect of local circumferential constraints on wrinkling was discussed combined with numerical simulation and experimental results. The results show that under the influence of the die boundary conditions and local constraints, the stress concentration zones are formed at the die entrance and on both sides of the constraint ring, which causes instability and wrinkling. The compression-bulging stability of thin-walled tube can be improved significantly by the entrance conical constraint with half conical angle of 20°, which is beneficial to the preparation of three axially symmetric useful wrinkles. The center constraint divides the bulging zone into two symmetric deformation zones, which is beneficial to the preparation of four useful wrinkles, and further improves the reasonability of predistribution of tube blank material. The offset-center constraint is beneficial to obtain three axially asymmetric useful wrinkles. Therefore, a variety of useful wrinkle types can be prepared by introducing local circumferential constraints, which can meet the requirement of tube material distribution for complex pipe parts with complex variable section.