双层异质金属波纹管液压胀形过程变形协调机制研究

In hydroforming of bi-layered metal bellows with different materials, the structural characteristic and material inhomogeneity cause significant constraint effects and complicated stress states, and thus sensitively reduce to failures, such as excessive thickness thinning, wrinkling and bursting, etc. Therefore, investigating on deformation compatibility mechanism and failures control are the fundamental key problems for realizing precision forming. The project aims to establish a finite element model for the hydroforming process with considering the constraint effects. Based on the model, the stress and strain constraint effects between the two layers and the deformation compatibility mechanism are addressed. Further, failure modes are analyzed and indices are proposed to evaluate forming quality of the formed bellow. By carrying out influence studies on the failure indices, multi-objective optimization for the process parameters is implemented to obtain the stable deformation zone and finally realize the failures control. The study plays a fundamental role in enriching and developing of the precision hydroforming technology, and also provides a guideline for precision hydroforming of the bi-layered metal bellows with different materials used for aerospace and aviation.

双层异质金属波纹管液压胀形过程中“双层”结构特性和“异质”材料特性导致各层管材约束效应显著，应力状态复杂，极易出现材料过度减薄、起皱、破裂等缺陷，因此研究材料变形协调机制、进行成形缺陷控制是实现精确成形的关键基础问题。本项目通过建立考虑约束效应的双层异质金属波纹管液压胀形全过程有限元仿真模型，研究成形过程各层材料的应力、位移约束效应，揭示各层材料的变形协调机制；在此基础上，分析变形协调失效形式和缺陷产生的原因，提炼成形缺陷评估指标；开展工艺研究和多目标优化计算，获得稳定成形区间并实现缺陷的控制。为丰富和发展双层异质金属波纹管精确成形技术奠定基础，并可为航空航天用双层异质金属波纹管精密制造提供依据。

双层异质金属波纹管具有高补偿能力、耐高压、耐高低温、可用于特殊工况等优点的弹性元件，广泛应用于航空、航天、石油、电力、化工等工业领域。而液压胀形是实现该类零件精确化、柔性化、高效率的重要成形制造技术。本项目以双层异质金属波纹管成形过程为主要研究对象，采用计算机数值模拟并与理论分析和试验研究相结合的研究方法，获得了与波纹管液压成形过程应力状态接近一致的筒材双向应力应变关系，以此作为开展波纹管液压胀形过程仿真分析的基础，通过对比研究不锈钢、高温合金四种材料，多种规格波纹管液压胀形过程，通过对比单层、双层同质、双层异质波纹管应力应变分布、壁厚变化、轮廓变化，揭示了波纹管成形特征，揭示了工艺参数、材料参数、几何参数对成形质量（壁厚减薄率、胀形高度、壁厚不均匀度、回弹后波高/波距变化量）的影响规律，开展了工艺参数优化研究，获得了优化的加载路径，基于仿真分析了波纹管起皱、破裂等缺陷出现的原因，提出了评估缺陷的量化指标，获得了稳定的成形窗口，加工出了合格的试验样件，验证了研究成果的有效性，为后续生产提供了参考和借鉴。研究成果在本领域著名期刊IJAMT、中国有色金属学报、塑性工程学报等发表期刊论文6篇（其中SCI期刊1篇，EI论文1篇）并在国内国际会议上发表会议论文2篇；申请发明专利1项，实用新型专利1项。