大型弯头无模整体液压胀形新工艺的实验研究

提出了一种旨在用于大型管路系统的无模整体液压胀形制造弯头新工艺，成功地获得了一个厚度3．0mm，口径531．0mm，弯曲半径1310．0mm 的45．0°弯头实验件，其材料为Q235A该弯头初始结构为截面为正六边形的焊接扇形环壳结构，成形压力约为2．5MPa，实验表明，无模整体液压胀形法制造大型弯头造价低廉，简单可行。     

高精度17-4PH不锈钢隔碗拉深液压胀形复合成形工艺参数优化

目的 针对17-4PH不锈钢冷成形回弹大、贴模性差等问题,研究17-4PH不锈钢隔碗零件的拉深成形和液压胀形规律,确定隔碗零件拉深液压胀形复合成形的最佳工艺及参数.方法 利用有限元方法确定并优化了拉深预成形和液压胀形中的工艺参数.基于优化后的结果设计并制造了相关的模具,最终通过试验验证了有限元方法的有效性.结果 结合数值模拟和试验的方法,提出了零件先拉深预成形、后液压胀形的多步成形方案,逐步优化了成形工艺参数,最终成形出了满足尺寸和精度要求的高精度隔碗零件.结论 通过数值模拟获得了最佳的坯料直径及多步成形中的关键工艺参数,基于数值模拟优化为主和试验验证为辅的设计制造理念,解决了17-4PH不锈钢冷成形回弹大和贴模性差的问题.     

32面足球式球形容器的整体液压成形过程非线性有限元模拟

球形容器整体胀形制造技术是一项新的造球工艺。而32面足球式球形容器则是最早应用这种工艺开发出的一种球形容器。本文应用非线性有限元程序对这种球壳的整体液压成形过程进行了数值模拟,分析了壳体外形与位移的变化过程和胀后的弹复变形规律,并与实验结果进行了对比。有限元模拟中采用了全量Lagrange理论的四边形八节点三维Kirchhoff薄壳等参单元,考虑了棱边交汇点的位移和板面的弯曲效应影响。有限元方法较好地模拟了壳体的液压胀球过程,与实验结果吻合较好。     

带壁厚偏差管坯液压胀形加载路径的研究

建立了带壁厚偏差管坯液压胀形的力学模型,揭示了不同轴向应力状态下壁厚偏差对管坯成形的影响规律,给出了带壁厚偏差管坯液压胀形加载路径设计的标准.针对某重型卡车桥壳预成形管坯的液压胀形工艺,进行了3种不同壁厚偏差管坯在不同典型加载路径下的有限元模拟,结果表明:内压升高至最大保持恒定,管坯薄壁侧均在合模前发生开裂且薄壁侧与厚...     

Spherical-cymbal换能器端帽自由胀形回弹预测与控制

为更经济地制造出质量更高的Spherical-cymbal换能器端帽,在其成形中用自由液压胀形工艺取代传统的冲压工艺,并对其自由胀形中的回弹问题进行了重点研究。采用ANSYS/LS-DYNA软件对端帽的自由胀形回弹量进行了预测,并根据约束条件及有限元模拟结果提出了回弹控制措施。实验结果验证了采用有限元数值模拟进行Spherical-cymbal换能器端帽自由胀形回弹预测与控制的可行性。     

铝合金马鞍形件充液成形工艺模拟分析

目的研究板材充液成形柔性制造高精度、高质量马鞍形件的工艺方法。方法利用有限元动力学显示分析方法,对充液拉深和液压胀形两种成形工艺方案进行分析,并对比分析减薄率和成形极限图判断工艺方案的合理性。结果针对铝合金马鞍形件,通过对比分析2种方案,充液拉深工艺中的最大减薄率达到14.3%,液压胀形最大减薄率为7.2%,位置均在型面补充件的顶部,2种方案的成形极限都在安全区域内,未见破裂现象。结论通过工艺模拟分析,得到对铝合金马鞍形件,采用一模两件液压拉深成形工艺较合理,成本较低,加工周期短,加工效率高,成形精度高。     

T型管的液压成形研究及模拟分析

为更好地了解T型管液压成形过程中,内液压力、轴向推力以及加载路径对T型管的极限液压胀形深度的影响,本研究选用2.5mm壁厚的QSTE340钢管为研究对象,采用解析法和数值模拟分析相结合的方式进行了较为详细的研究。首先结合解析法获得T型管胀形的理论最佳内液压力和轴向推力参数,而后结合有限元软件Abaqus对比了不同内液压力和轴向推力对管成形的贡献,利用解析法获得的内液压力和轴向推力可以获得较好的T型管胀形效果,同时加载路径的变化会对T型管的胀形效果有较大影响。上凸型加载路径的轴向推力和下凹型加载路径的内液压力可提高T型管胀形的极限深度。     

金属板材成形的静力隐式有限元分析与程序设计

阐述了用于板材成形过程静力隐式数值模拟的弹塑性大变形有限元方法,基于给出的方法编制了板材成形过程数值模拟软件,并对矩形板的液压胀形进行了有限元分析,计算结果与典型的实验结果吻合很好.对球形模具拉伸成形过程进行了数值模拟,给出了计算结果.     

刚塑性有限元法求解护环的液压胀形问题

本文用刚塑性有限元法分析了护环的液压胀形问题。研究了对于外载荷作用边界上位移速度不能给定问题如何求解的方法。计算出了胀形全过程中护环的应力、应变分布,外形尺寸和载荷的变化,以及最佳工具参数。计算结果和实验符合较好。     

等边双圆锥台壳体端部约束胀形的实验研究

针对等边双圆锥台壳体在自由胀形过程中,赤道环焊缝处产生失稳起皱现象,提出了壳体的内约束胀形工艺,实验证明,壳体端部加约束后成形过程中没有起皱现象发生.     

Effect of Prestrain on Formability and Forming Limit Strains During Tube Hydroforming

The tube hydroforming process is a relatively complex manufacturing process; the performance of this process depends on various factors and requires proper combination of part design, material selection and boundary conditions. In manufacturing of automotive parts, such as engine cradles, frames rails, sub-frames, cross members, and other parts from circular tubes, pre-bending and per-forming operations are often required prior to the subsequent tubular hydroforming process to fit the tubular blank in the complex die shape. Due to these pre-- hydroforming operations, some of the strains are already developed before going to the actual hydroforming process. Such developed strains before hydroforming process in the part is called as prestrain. In this paper the study of effect of prestrain on formability and forming limit strains during tube hydroforming is done by simulation by taking the material prestrain value. The forming limit strains of pre-strained tube during hydroforming are predicted. A series of tube bulge tests for tube hydroforming are simulated by a commercial finite element solver to predict the limit strains. Numerical simulation of forming limit strains in tube hydroforming with different internal pressure and different simulation set up with or without axial feeding are considered to develop wide range of strain paths in the present work. The effects of process conditions on the forming limit strains are detailed. In this paper the forming limit strains during tube hydroforming are simulated for prestrain and compared with zero prestrain. Prediction of limits strains is based on a novel thickness based necking criterion.     

Limit Strains Comparison during Tube and Sheet Hydroforming and Sheet Stamping Processes by Numerical Simulation

Hydroforming is a manufacturing process that uses a fluid medium to form a component by using high internal pressure. Tube and sheet hydroforming has gained increasing interest in the automotive and aerospace industries because of its many advantages such as part consolidation, good quality of the formed parts etc. The main advantage is that the uniform pressure can be transferred to every where at the same time. Forming limit is the limit of the component up to that extent it can be formed safely. While analyzing hydroforming process, it is often assumed that the limit strains are identical as that of stamped sheet metal of equivalent material properties. It is not clear if such an assumption is valid. In this paper the forming limit strains during hydroforming is predicted. A series of tube bulge tests for tube hydroforming and limiting dome height test for sheet hydroforming and sheet stamping processes are simulated by a commercial finite element solver to predict the limit strains. Numerical simulation of forming limit strains in tube hydroforming with different internal pressure and different simulation set up with or without axial feeding, while in sheet hydroforming and sheet stamping, by changing the specimen geometry are considered to develop wide range of strain paths in the present work. The effects of process conditions on the forming limit strains are detailed. The comparison of limits strains during hydroforming and stamping processes is presented. Prediction of limits strains is based on a novel thickness based necking criterion.     

Hydroforming a small scale aluminum automotive component using a layered die

The aim of this study is to investigate the possibility of manufacturing an aluminum automotive component (a small sized car door panel) using a highly reconfigurable and cheap forming process. Specifically, the sheet hydroforming process and rapid tooling technique were combined, with the objective of making the resulting process more flexible and less expensive.Sheet hydroforming experiments were carried out using a layered die created assembling 2D laser cut layers and testing three Al alloys (AA2024, AA5754, AA7475); process parameters (Closing Force and Pressure) were evaluated by means of finite element simulations, mainly focused on the curve defining the Closing Force as a function of the forming Pressure and on friction conditions, which have a significant effect on the distribution of sheet thickness in formed parts.Both numerical simulations and experimental tests highlighted that sound parts could be obtained if a hard enough sheet material together with the appropriate Closing Force and forming Pressure are used. The proposed approach, combining the hydroforming process with a rapid tooling technique, proved to be effective in rapidly manufacturing prototypes and thus in shortening the product design process.     

轻量化结构内高压成形技术

内高压成形适用于制造汽车 ,航空航天等领域中使用的各类轻体构件 .用其加工的零件具有重量轻 ,刚度好 ,零件数量少 ,可减少后继机械加工和组装焊接量 ,成本低等优点 .本文综述了内高压成形原理、优点、应用范围、适用材料、国内外工业应用情况及研究现状 ,并详细介绍了作者进行的部分研究结果 .     

异形截面管不均匀膨胀充液成形数值模拟

目的对低碳钢不均匀膨胀率异形截面弯管零件充液成形工艺参数进行研究。方法利用有限元方法对低碳钢异形截面管零件的充液成形过程进行有限元仿真,对影响圆角破裂的关键工艺参数进行分析及优化。结果液室压力过小,弯管圆角内侧不易贴模;压力过大,圆角内侧会因材料过度减薄而发生破裂。推头轴向进给量合适时,可以在圆角处形成"有益皱纹",防止材料不均匀膨胀发生破裂。结论成形压力在300 MPa,推头的轴向进给量为50 mm时,可以成形出合格零件。     

FEM Simulation of the Hydroforming Process of Spherical Vessels from Combination Frustum Shells

The dieless hydroforming of spherical vessels from combination frustum shells is put forward in thepresent paper,and the forming process is developed by means of elastoplastic finite element methodand experiments.In this paper the principle and experimental procedure of the new technology areintroduced,the simulation method and the calculating assumptions are presented,the deformationprocess and the deformation characteristics of the shells are discussed,as well as the stress and straindistributions of the shell during bulging are analysed.     

肘形挠性接管冲击特性试验研究

针对肘形挠性接管特殊结构形式,提出了两根相同挠性接管对称或反对称安装测量方案,用于测量其不同坐标方向上的冲击特性。采用阶跃松弛释放法,测量了不同工况下肘形挠性接管冲击振荡的固有频率与阻尼比,从被测试件对应工况时机械阻抗测试曲线中获取了肘形挠性接管的端部等效质量,用于冲击刚度的计算,进而计算出阻尼系数。通过分析不同工况下冲击特性的变化规律,得到了一些初步结论,为抗冲击设计和计算提供了参考依据。     

Wirkmedienbasierte Herstellung hybrider Metall‐Kunststoff‐Verbundbauteile mit Kunststoffschmelzen als Druckmedium

Working media based manufacturing of hybrid metal‐plastic‐compounds by using thermoplastic melt as pressurized media This paper presents an alternative manufacturing process for metal plastic hybrid parts. The focus is placed on the integration of injection moulding technology with hydroforming technology. The forming of bulging geometry and cup geometry from Aluminium and Steel sheets was examined. Particularly, the process parameters involved in forming such geometries including Injection pressure, volume flow rate, were measured, and their influence on the final shape of product as well on the strain distribution was analyzed.