采用可移动凹模的板材液压成形技术

提出一种改进的板材液压成形新工艺,即采用可移动凹模,实现拉深与胀形的复合液压成形。在整个变形过程中,板材初始变形部分始终与可移动凹模接触,从而抑制已变形区进一步变形,使变形更加均匀,实现变形的顺序控制,板材成形极限得到提高。从试验和数值模拟两方面对可移动凹模板材液压成形技术进行了研究,分析各种工艺参数,如摩擦因数等对板材成形性的影响,并且分析了可移动凹模对板材成形极限的影响。     

汽车轻量化前沿制造技术的研究进展

分析了高强钢的液压成形、热成形和激光拼焊等先进轻量化成形工艺的研究进展及在车身上的应用现状,并指出了以计算机仿真为代表的有限元数值模拟技术在成形性设计、工艺参数优化、产品性能预测检测方面的应用及实现全面科学化、数字化、可控化的发展趋势。     

不同成形工艺对金属密封件坐封效果的影响

针对整体机械加工成形的新型桥塞金属密封件在坐封后密封面出现裂纹缺陷的现象展开了研究。通过坐封过程力学分析和不同状态下组织形貌观察,得出产生裂纹的原因。在此基础上,提出金属密封件的液压成形工艺。采用数值模拟完成液压成形模具和工艺参数的优化设计,并进行密封件的液压成形试验和坐封试验。试验结果表明,液压成形工艺设置成形压力为180MPa、保压时间为5s时,所得金属密封件表面质量较好,坐封后不产生裂纹。液压成形金属密封件密封面不同状态下的组织形貌观测和液压成形过程中的受力分析进一步表明,液压成形过程中的径向压应力能够改善晶界开裂等现象,因此与整体机械加工成形的密封件相比,液压成形工艺可以明显改善坐封效果。     

超高压管材液压成形控制系统的研制

介绍了管材液压成形工艺,根据液压成形原理,自主研制出具备高压发生器、阀门管路等配件的超高压液压系统,同时通过可编程控制器实现对电磁元件的控制,有效地解决了管材在液压成形过程中的端口密封、进给补料等关键问题,为管材液压成形的实验研究奠定了基础。     

基于多点成形的液压成形工艺关键技术的研究

介绍了基于液压成形和多点成形原理的板材成形新工艺.该工艺凸模用液体代替,凹模采用多点基本体调形而成.并用凹模垫技术提高多点成形技术中板材面轮廓度形状精度.对该工艺的液压系统、基本体的调形及压边圈等关键技术问题进行了深入研究.研制出了成形装置,并进行模拟试验.     

冲击液压载荷作用下双金属薄壁管内压力与型腔体积变化的关系

双金属薄壁管冲击液压胀形技术是在液压胀形与冲压成形基础上发展起来的一种复合成形技术。冲击液压载荷作用下的双金属薄壁管成形所需内压力源自于管坯型腔体积的压缩,其大小随液体体积压缩量变化而变化,为此提出了基于冲击液压载荷作用下双金属薄壁管的内压力形成机理的研究。首先介绍了双金属薄壁管冲击液压胀形的成形原理;然后,通过对内外管轴向冲击液压预成形与径向冲击液压成形过程中内压力形成的理论分析,构建了管坯型腔内压力与体积变化之间的数学模型;同时,利用Ansys Workbench有限元模拟技术获得了内外管轴向冲击液压预成形与径向冲击液压成形过程的内压力,通过有限元模拟与理论分析结果的对比发现,两者具有较好的一致性,并通过模型误差优化了内压力数学模型,为双金属薄壁管冲击液压胀形技术的进一步研究奠定了良好的理论与应用基础。     

复合管液压成形装置及残余接触压力预测

针对现有复合管制造工艺中存在的问题，研制开发了一种焊接不锈钢衬里复合管液压成形装置，介绍了该装置液压成形系统的工作原理及技术特点。阐述了复合管液压成形过程的原理，并采用弹塑性理论分析了其在液压成形过程中内管及外管的应力应变状态。推导出了复合管残余接触压力与成形压力之间关系的理论计算公式，通过实验对公式进行了验证。结果表明该装置结构及其计算方法适于工程应用。     

管件液压成形技术在汽车制造中的应用研究

阐述了管律液压成形的基本概念及其优点，介绍了在汽车制造领域中的应用，综述了管件液压成形技术的研究成果，重点介绍材料、塑性失稳、加载路径优化、预成形等问题；讨论了应用研究中进一步的发展方向。     

《快速成形技术》

本书系统地介绍了快速成形技术的知识。其基础部分包括成形原理、主要成形工艺、国内外发展现状、成形理论、成形过程数学描述、零件变形理论及零件精度问题等。随后介绍了快速成形制造中的几个核心技术，即材料技术，包括各成形工艺（尤其是光固化成形工艺）材料的性能、供料系统、材料的后处理等；能源技术，包括SL及SLS中的光学技术、FDM及LOM中的加热系统及3DP工艺中的喷墨系统.     

对向液压拉深模液压系统的设计

对向液压拉深是现代拉深成形工艺中的一项新技术。它利用凹模腔内液压室油液不可压缩的高弹性和油膜的高支撑强度及润滑性能,能有效地提高拉深件的形状精度、尺寸精度、成形件表面质量,提高成形极限,抑制侧壁起皱等拉深工艺缺陷。文章主要对对向液压拉深的液压系统设计及液压系统工作过程作了介绍。     

液压成形管件中心轴线抽取算法

管材液压成形技术是一个相对新颖的技术，其在应用过程中仍然有许多问题需要研究和解决。基于有限元法的管材液压成形数值模拟技术发展的时间更短，有待进一步研究和发展。针对这种发展要求，提出了管材液压成形数值模拟中分析模型的构造方法，并且重点介绍了逆向构造中管件中心轴线的抽取算法即边界递进搜寻法，这个算法不仅运行速度快，实现简单，而且具有较强的适应性。     

液压成形管件中心轴线抽取算法

管材液压成形技术是一个相对新颖的技术,其在应用过程中仍然有许多问题需要研究和解决。基于有限元法的管材液压成形数值模拟技术发展的时间更短,有待进一步研究和发展。针对这种发展要求,提出了管材液压成形数值模拟中分析模型的构造方法,并且重点介绍了逆向构造中管件中心轴线的抽取算法即边界递进搜寻法,这个算法不仅运行速度快,实现简单,而且具有较强的适应性。     

Prediction of necking of high strength steel tubes during hydroforming—multi-axial loading

This article studies tubular hydroforming of high strength low alloy (HSLA) and dual phase (DP600) straight tubes under the action of end feeding loads. Experiments demonstrate that higher end feed loads enhance the formability of the tubes and increase the internal fluid pressure for onset of necking and bursting. Because of the action of the internal pressure and the axial compressive load, the onset of localization (necking) is due to a complex three-dimensional state of stress. Using free expansion experiments, approximate upper and lower bound strain-based forming limit curves are determined for the tube materials. These limit curves, in turn, are used to derive upper and lower bound extended stress-based forming limit curves [Simha et al., Prediction of necking in tubular hydroforming using an extended stress-based FLC. Transactions of the ASME Journal of Engineering Materials and Technology 2007;129(1): 36-47]. In conjunction with finite element computations that use solid elements to model the tube, these stress-based limit curves are used to predict upper and lower bound necking pressures under the action of end feed loading. These predictions of necking pressures, when an appropriate coefficient of tube-die friction is used, are found to bracket the experimentally measured necking pressures. Computations using plane stress shell elements to model the tubes are shown to give erroneous results, since the plane stress approximation is not valid when tubes are hydroformed in a die.     

波动加载管材液压成形系统关键问题的研究

分析了液压成形设备的组成以及在研发波动加载管材液压成形系统过程中涉及的关键问题,并对每个问题都提出了合理的解决方案,实现了系统的设计要求。     

Analysis and finite element simulation of the tube bulge hydroforming process

To investigate the effect of the loading path on the forming result and get the reasonable range of the loading path in tube bulge hydroforming process, a mathematical model considering the forming tube as an ellipsoidal surface is proposed to examine the plastic deformation behavior of a thin-walled tube during the tube bulge hydroforming process in an open die, and thus different loading paths are gained based on this model. The finite element code Ls-Dyna is also used for simulating the tube bulge hydroforming process. The effect of the loading paths on the bulged shape and the wall thickness distribution of the tube are discussed, and then the reasonable range of the loading path for the tube bulge hydroforming process is determined.     

Analysis and finite element simulation of the tube bulge hydroforming process

To investigate the effect of the loading path on the forming result and get the reasonable range of the loading path in tube bulge hydroforming process, a mathematical model considering the forming tube as an ellipsoidal surface is proposed to examine the plastic deformation behavior of a thin-walled tube during the tube bulge hydroforming process in an open die, and thus different loading paths are gained based on this model. The finite element code Ls-Dyna is also used for simulating the tube bulge hydroforming process. The effect of the loading paths on the bulged shape and the wall thickness distribution of the tube are discussed, and then the reasonable range of the loading path for the tube bulge hydroforming process is determined.     

基于Dynaform三通管液压成型分析

提出改进液压成型工艺,并通过Dynaform软件仿真及实际生产验证。该方法舍弃了通常管材液压成形中所需的超高压供给系统以及平衡冲头,进而大大降低设备费用。在验证工艺正确基础上,通过Dynaform软件仿真分析影响三通管液压成型因素。仿真模拟分析为模具设计方案和液压成形工艺方案设计提供了科学的依据,提高了设计效率。     

激光焊管内高压成形焊缝有限元建模方式

为明晰焊管内高压成形焊缝的合理有限元建模方式,针对激光焊接接头的材料性能分布特点提出三种焊缝建模方式,分别为完整焊缝模型、粗略焊缝模型和无焊缝模型。通过与试验结果对比,从壁厚分布和几何形状两方面,分析不同焊缝简化方式对送料区、过渡区和胀形区模拟精度的影响情况。指出焊缝对模拟精度有影响,受影响区域不超过3倍焊缝宽度。只有建立焊缝模型才能模拟出靠近焊缝部位壁厚过渡减薄的变形特征,但建立完整焊缝模型和建立粗略焊缝模型的模拟精度相差不大,最大误差均小于6.5%。在综合考虑误差大小和典型变形特征模拟准确性后,给出适合激光焊管内高压成形的焊缝有限元建模方式。     

The effect of tube material, microstructure, and heat treatment on process responses of tube hydroforming without axial force

In this paper, the influence of tube material, microstructure, and heat treatment on process responses of tube hydroforming has been studied. One of the most important parameters in performing a successful tube hydroforming process is the selection of appropriate material for tubes. In the analysis section, effective parameters for the selection of an appropriate tube material for the hydroforming process have been investigated; it was concluded that higher strain hardening exponent (n), elasticity modulus (E), and anisotropy index (R) can enhance formability in this process; and the effects of microstructure and heat treatment on the formability of ASTM C11000 copper and ASTM AA1050 aluminum have been investigated. Consequently, four different heat treatment processes, which had different heating temperatures and durations, were selected, in addition to different cooling methods for each of the materials. In the experimental tests, the effects of these heat treatment methods on maximum bulging height, thickness strains, and final forming pressures were scrutinized. The effects of heat treatment on copper microstructure were also studied through metallographic tests; on the other hand, the effects of microstructure on tube hydroforming process were justified. As a result of these analyses, two heat treatment methods, namely, heating to 450 and 350 °C for 15 min and cooling in water, were recommended for copper and aluminum, respectively. Using these methods and due to their consequent fine and homogenous microstructure, higher mechanical strength and increase in material formability was achieved by attaining higher thickness strain and bulging height values. Finally, after extracting the mechanical properties of the two materials and comparing them with each other, parameters of strength coefficient and strain hardening exponent were reported as two effective factors that would improve tube deformation by tube hydroforming process.     

An investigation of the optimal load paths for the hydroforming of T-shaped tubes

This paper proposes a new method to design the optimal load curves for hydroforming T-shaped tubular parts. In order to assess the mathematical models, a combination of design of experiment and finite element simulation was used. The optimum set of loading variables was obtained by embedding the mathematical models for tube formability indicators into a simulated annealing algorithm. The adequacy of the optimum results was evaluated by genetic algorithm. Using this method, the effect of all loading paths was considered in hydroforming of T-shaped tubes. Eliminating of variables with lower effect could simplify the problem and help designers to study the effect of other parameters such as geometrical conditions and loading parameters. Applying the optimal load paths obtained with the proposed method caused an improvement in the thickness distribution in the part as well as a decrease in maximum pressure.