基于局部环向约束的内高压成形管坯有益皱调控

Useful wrinkle control of tube blank in hydroforming based on local circumferential constraints

在薄壁管通过压缩-胀形制备有益皱方法的基础上,提出一种通过局部环向约束调控薄壁管有益皱的新方法;建立局部环向约束条件下薄壁管压缩-胀形数值仿真模型,设计镶块式约束环和制皱模具并搭建压缩-胀形专用实验装置。结合数值仿真和实验结果讨论局部环向约束对起皱的影响规律。结果表明:受模具边界条件和局部约束的影响,管坯在模具入口、约束环两侧形成应力集中区,引起失稳起皱;半锥角为20°的入口锥面约束可显著提高薄壁管压缩-胀形的稳定性,有利于制备轴向对称的3个有益皱;中置中间约束将胀形区分为对称的两个变形区,有利于制备4个有益皱,进一步提高管坯材料预分配的合理性;偏置中间约束有利于获得轴向不对称的3个有益皱。因此,引入局部环向约束能够制备多种有益皱形式,满足变截面复杂管件内高压成形对管坯材料分布的需要。

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.