充液成形技术在航天火箭整流罩成形中的应用

基于充液形成工艺的航天火箭整流罩零件,通过数值模拟的分析与试验结果进行对比,证明了数值模拟可以给试验提供正确方向,也说明数值模拟的准确性。根据现场的试验情况,基于实际制件过程出现的一些缺陷,调整液室压力与压边力加载曲线,根据零件的拉深高度进行合理匹配,最后达到控制整个冲液成形过程的起皱和破裂的问题。实现了充液拉深工艺在大尺寸薄壁整流罩构件上的工艺升级,大大提升了零件的表面质量,从而可以解决传统落压工艺的多道次拉深工序、多道次退火及多道次敲修导致的零件变形与表面质量差等问题,从而保证零件在生产过程中表面质量和成形精度的控制。     

复杂薄壁件多道次充液复合成形及变形量确定

针对大拉深比、阶梯锥形的航空发动机隔热罩薄壁件,基于塑性力学方法分析了其充液拉深的变形规律,并在此基础上提出了多道次充液复合成形方法,设计了等裕量函数法以快速、合理地确定各道次变形量的分配。通过数值模拟和工艺试验,研究了关键变形量——预成形高度对成形结果的影响规律,探讨了成形过程中起皱、破裂的失效形式。结果表明,提出的工艺方法可实现复杂薄壁隔热罩构件的整体精确成形,选择适当的预成形高度可获得壁厚均匀、成形质量较好的零件。     

充液拉深成形工艺与传统工艺的比较

以液体为介质成形零件已经有100多年的历史了.充液拉深成形与传统工艺相比具有许多优点,本课题从成形力、模具、拉深比及成形精度等几个方面阐述了充液拉深成形与传统工艺的区别.     

复杂型面零件充液拉深失效控制研究

对于普通拉深无法成形的复杂零件,充液拉深成形是一种有效的解决方法.在自行研制的充液拉深成形试验机上进行工艺验证实验,对复杂型面不锈钢零件充液拉深成形过程中出现的起皱、破裂和不贴模3种失效形式进行了研究,分析了液室压力、压边力和拉延筋深度等关键工艺参数对失效的影响和作用规律,优化了液室压力和压边力加载曲线以及拉延筋参数.结果表明,液室压力加载曲线应与板料悬空区变化趋势相协调,压边力加载路径应与液室压力相匹配,为消除悬空带过渡区的内皱,必须设置合适的拉延筋.     

航空发动机复杂型面罩子钣充液成形技术

利用先进的钣材冲压计算机仿真技术对零件成形中的关键问题进行了研究,并通过先进的充液成形技术进行了实际零件的成形试验,试验的结果与模拟结果基本一致。最后应用模拟得到的成形参数,利用钣充液成形工艺成形出了合格的零件。     

复杂凸凹曲率飞机蒙皮充液成形技术研究与应用

随着飞机气动、隐身等性能要求的提高,飞机外形曲率更加异形化,大量应用复杂凸凹曲率蒙皮,传统的拉伸成形方法已经不能完全满足新一代飞机蒙皮加工的要求。基于生产某型号飞机复杂凸凹曲率蒙皮这一背景,介绍了充液成形基本原理及关键技术,利用有限元数值模拟方法,分析板材充液成形过程中液室压力、厚度减薄率、板材失稳及贴胎度的变化规律,优化工艺参数,并且根据数值模拟结果指导工业生产。理论分析和现场实践证明:充液成形技术为复杂凸凹曲率蒙皮零件的制造提供了新的工艺方法,满足新一代飞机的凸凹曲率外形蒙皮的制造要求。     

双路径自然增压铝合金2A12O充液拉深

 基于铝合金等难成形板材的需要,提出了双路径自然增压充液拉深新技术。用有限元法对铝合金2A12O双路径自然增压充液拉深进行研究,探讨径向压力和液池压力单独变化时对壁厚分布的影响;得到合理的液池压力和径向压力加载路径以及合适匹配比;分析了该方法中液池压力和径向压力成比例变化时,壁厚分布的变化趋势。结果表明：采用15.0~20.0 MPa的液池压力,并将液池压力经增压活塞1.45倍增压后引到毛坯法兰边缘,可获得壁厚分布比较均匀、成形质量较高的零件,并能显著提高板料的极限拉深比;液池和径向压力的比例变化影响成形零件的壁厚分布,并且在不同的成形阶段其影响趋势不同。对模拟分析得到的压力加载路径和增压比进行实验,得到拉深比达2.65的铝合金2A12O杯形件,并建立其成形合理的压力区域。     

复杂异形截面薄壁环形件动模液压成形研究

 液压成形技术是成形薄壁零件的一种有效的解决方法。针对具有异形截面结构的某型发动机高温合金薄壁环形件,提出了液压成形结合动模轴向加载的复合成形方法,依据塑性力学方法和增量理论对成形过程进行了应力应变特征分析,并建立了有限元模型。基于有限元模拟和工艺试验,研究了筒坯成形区高度和型腔液压加载路径等关键工艺参数对零件成形结果的影响,探讨了成形过程中壁厚过度减薄、材料堆积"折叠"、形状不对称等失效形式,提出了优化的工艺参数。结果表明,提出的工艺方法可实现复杂异形截面薄壁环形件的整体精确成形,采用优化的筒坯成形区高度和液压加载路径可获得壁厚分布均匀、成形质量较好的零件。     

TC1钛合金端盖零件热拉深成形工艺研究

针对TC1钛合金端盖零件的结构特点,分析了零件的成形难点,对热拉深工艺的模具材料、温度、压边间隙、拉深速度等对零件成形性能的影响进行了研究,提出了合理的工艺参数。结果表明,该工艺方法可实现薄壁、大拉深比的TC1钛合金零件的精确成形,采用空气脱模的方式可获得平面度满足设计要求的零件,为类似零件的取件提供了工艺参考。     

TA1钛合金板材高温颗粒介质成形试验研究

利用高温介质成形工艺对TA1钛合金板材进行了筒形零件拉深过程仿真计算及试验验证,模拟分析及高温条件下拉深试验结果表明,高温介质成形工艺适用于钛合金板材,并能显著提高钛合金薄壁零件的成形质量。     

航空发动机薄壁W形封严环动模外压成形

液压成形是复杂薄壁零件制造的一种有效方法。针对某航空发动机的薄壁高温合金W形封严环构件,提出动模外压成形方法,并建立了有限元模型。基于数值模拟和工艺实验,分析了不同成形阶段的变形规律和压缩失稳的控制机理,在此基础上研究了毛坯成形区高度和型腔液压加载路径等关键工艺参数对零件成形结果的影响,探讨了成形过程中环向失稳起皱、型面不对称、材料堆叠等失效形式,提出了优化的参数。结果表明,提出的工艺方法可实现W形封严环的整体精确成形,采用优化的毛坯成形区高度和液压加载路径可获得成形精度较高、表面平滑无褶皱的试件。     

Inner wrinkling control in hydrodynamic deep drawing of an irregular surface part using drawbeads

Inner wrinkling phenomenon is more likely to develop during hydrodynamic deep drawing （HDD） of complicated component-forms due to the higher demand for controlling deformation sequences. Aiming at the problems in control of inner wrinkling for an irregular surface part featured with both concavity and convex, this research proposes an optimal design method of drawbead parameters to change the material flow. According to theoretical analysis of the mechanism of inner wrinkling, optimizing cavity pressure only is unreasonable to form a wrinkle-free deep-drawn part, so semi-circular drawbeads are employed. The effects of layout and height of drawbeads on forming results are discussed, and a process window is established based on evaluation indicators including the anti-wrinkle coefficient and the minimum wall thickness. Experiments are carried out to validate the process window, and the wall thickness and the wrinkle height are measured and compared with numerical findings. The results show that the anti-wrinkle ability of drawbeads weakens with increasing oblique angle and distance from the die center, while the wall thickness increases with increasing oblique angle and distance, and the inner wrinkling can be completely suppressed by drawbeads arranged in zones I and II with optimum penetration.     

薄壁管数控弯曲过程中失稳起皱的主要影响因素

 针对薄壁管数控弯曲精确成形过程在多因素交互作用下可能发生失稳起皱这一复杂物理问题, 基于起皱能量准则和有限元方法相结合, 提出了预测该过程起皱发生的能量( 数值) 方法, 研究了影响薄壁管数控弯曲成形过程起皱发生的主要因素及影响机制。结果表明, 弯曲半径、相对管径、芯棒伸长量和摩擦因素是影响薄壁管数控弯曲精确成形过程起皱发生的主要因素, 而材料的应力强度系数和加工速度等对起皱发生影响较小。研究结果为薄壁管数控弯曲精确成形过程参数的确定和优化创造了条件。     

Plastic wrinkling prediction in thin-walled part forming process:A review

The precision forming of thin-walled components has been urgently needed in aviation and aerospace field. However, the wrinkling induced by the compressive instability is one of the major defects in thin-walled part forming. The initiation and growth of the wrinkles are interac-tively affected by many factors such as stress states, mechanical properties of the material, geometry of the workpiece and boundary conditions. Especially when the forming process involves compli-cated boundary conditions such as multi-dies constrains, the perturbation of clearances between workpiece and dies and the contact conditions changing in time and space, etc., the predication of the wrinkling is further complicated. In this paper, the current prediction methods were summa-rized including the static equilibrium method, the energy method, the initial imperfection method, the eigenvalue buckling analysis method, the static-implicit finite element method and the dynamic-explicit finite element method. Then, a systematical comparison and summary of these methods in terms of their advantages and limitations are presented. By using a combination of explicit FE method, initial imperfection and energy conservation, a hybrid method is recommended to predict plastic wrinkling in thin-walled part forming. Finally, considering the urgent requirements of com-plex thin-walled structures’ part in aviation and aerospace field, the trends and challenges in wrin-kling prediction under complicated boundary conditions are presented.     

薄板拉深过程中的起皱与防皱的探讨

冲压工艺应用十分广泛，拉深是一种常规的冲压工艺方法。失稳起皱是拉深过程中的主要障碍，而压边力是板料成形过程中的重要参数之一，如何有效地防止失稳起皱是从业人员最为关注的问题。论述了薄板拉深过程中常规的防皱措施，提出了在拉深过程中压边力的变化趋势，指出理想的压边力可以随拉深起皱的变化规律而合理变化，并引人变压边力的优化技术概念。     

虑及板坯几何和性能波动的薄壁件塑性成形数值模拟研究进展

用于塑性成形的大型金属板坯存在不可避免的几何以及性能波动,其参数波动呈现很强的分散性和随机性,难以准确地定量表征。金属板坯几何和性能的波动会显著增加其在塑性成形中变形的复杂性,导致成形质量及成形极限下降,尤其是在具有强烈不均匀变形特征的薄壁件拉深、旋压等塑性成形中表现得更加明显,极大制约了大型薄壁件的精确成形。从板坯几何和性能波动的表征方法,虑及几何和性能波动的薄壁件塑性成形有限元模型建立、成形质量的影响规律、工艺参数设计及调控等方面综述了相关研究进展,并提出虑及几何和性能波动的薄壁件塑性成形研究中仍面临的难题与挑战,对发展薄壁件塑性成形理论与技术具有重要指导意义和参考价值。     

Design of an innovative multi-stage forming process for a complex aeronautical thin-walled part with very small radii

In this paper, an aeronautical thin-walled part with a complex geometry which has several sharp bends and curvatures in different directions was investigated. This kind of part is difficult to be manufactured only in one stage. Therefore, an innovative multi-stage active hydroforming process assisted by the rigid forming method was designed. In addition, an optimized blank geometry is obtained. In fact, the main focused point of this paper is to propose a new small radius rounded corner forming technique and analyze the mechanism. Two kinds of forming modes of changing a big rounded corner into a small one, which are related to different tangential positions of the die in the process of calibration, are analyzed theoretically. Meanwhile, the stress and strain states of the deformation region are compared. The relationships between the minimum relative radii of rounded corners I and II in the first stage and the hydraulic pressure are calculated by the bending theory. Finally, the influences of the tensile-bulging effect and the interface condition of the double-layer sheet on the forming quality of the specimen are investigated. The achieved results can make a foundation for utilizing the proposed method in forming of thin-walled parts with very small radii.