薄壁管轴压胀形关键工艺参数及成形极限

利用粘性介质传压,对薄壁管轴压胀形进行了研究;基于塑性理论和分散性失稳理论,推导了轴对称胀形内压力分布规律,得出了内压加载区间和轴向加载关系;建立了基于载荷控制的加载函数,提出了送料控制方法,优化了加载模式;基于集中性失稳理论,计算了胀形压力极限,建立了均匀变形极限和极限应力比的概念,形成了零件可成形性的基本判据;分析了管材成形过程中应力变化特点,揭示了管材胀形区由拉-压应力状态迅速发展到双向受拉的机理.通过实验并利用有限元方法对薄壁管轴压胀形过程进行了模拟计算和研究,验证了理论分析结果.

Process parameters and limits in tube hydro-forming with axial feeding

By using the viscous media,tube hydro forming with axial feeding was investigated.Based on the diffusion instability and plasticity theory,the distribution rules of the internal pressure were indicated and the relationship between the internal pressure and the axial loading were obtained with axial symmetrical part.After creating the loading function to control the loads,the method to control the axial feeding was proposed and the loading mode was optimized.Based on the localized instability theory,the limits of the internal pressure were calculated,and the UDL(uniform deformation limitation) and the concept of LSR(limited stress ratio) were proposed to check the basic workability of parts.After analyzing the features of stress variation during forming,the mechanism that the stress state changes quickly from the tension-compression to the dual-tension was carried out.Through the experiment and numerical simulation,the forming process of the tube hydro forming with axial feeding was conducted and it proves that the results from the theoretical analysis keep a reasonable agreement with the reality.