3-D RIGID PLASTIC FEM SIMULATION OF EXTRUDING-BULGING PROCESS OF TEE TUBES

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Φ508mm等径三通拉拔工序数值模拟与实验研究

大口径挤压三通的成形是管件制造工艺技术的难点,其中支管的拉拔工序更是三通最终成形的关键所在。文章通过有限元数值模拟与实验,对大口径高钢级(X80)Φ508mm等径三通热挤压成形工艺过程中支管拉拔工序进行研究。通过数值模拟对拉拔道次和成形载荷进行分析,确定出合理的工艺参数,并通过实验对数值模拟结果进行验证。其研究结果对实际生产有一定的指导作用。     

弹塑性大变形有限元法在直缝焊管成型中的应用

采用弹塑性大变形有限元法研究了直缝焊管成型过程,针对边界非线性问题,首次导出了位移边界条件的迭代方法,分析了33.5mm×2mm双半径焊管管坯表面的应变分布规律。该方法也适用于冷弯过程。     

Deformation Behavior of 6061 Aluminum Alloy Through Tube Channel Pressing: Severe Plastic Deformation

The deformation behavior of solid solution-treated AA6061 tubes in a novel severe plastic deformation process named Tube Channel Pressing has been assessed. In order to do so, an analysis based on the finite element method and dislocation density model is utilized, and microhardness measurement is carried out to verify the trends of analysis results. By comparing FEM results with experimental data, the optimized geometrical parameters controlling the deformation behavior of the tube in tube channel pressing are determined to obtain the best strain homogeneity and minimum dimensional changes in tube.     

3D FEM simulations and experimental validation of plastic deformation of pure aluminum deformed by ECAP and combination of ECAP and direct extrusion

Rigid-viscoplastic 3D finite element simulations (3D FEM) of the equal channel angular pressing (ECAP), the combination of ECAP + extrusion with different extrusion ratios, and direct extrusion of pure aluminum were performed and analyzed. The 3D FEM simulations were carried out to investigate the load–displacement behavior, the plastic deformation characteristics and the effective plastic strain homogeneity of Al-1080 deformed by different forming processes. The simulation results were validated by microstructure observations, microhardness distribution maps and the correlation between the effective plastic strain and the microhardness values. The 3D FEM simulations were performed successfully with a good agreement with the experimental results. The load–displacement curves and the peak load values of the 3D FEM simulations and the experimental results were close from each other. The microhardness distribution maps were in a good conformity with the effective plastic strain contours and verifying the 3D FEM simulations results. The ECAP workpiece has a higher degree of deformation homogeneity than the other deformation processes. The microhardness values were calculated based on the average effective plastic strain. The predicted microhardness values fitted the experimental results well. The microstructure observations in the longitudinal and transverse directions support the 3D FEM effective plastic strain and microhardness distributions result in different forming processes.     

大口径三通成形冷却区数值模拟与实验研究

通过数值模拟与实验,对大口径高钢级三通管件热挤压成形工艺过程中关键工序--压包工序的冷却区进行研究,对冷却参数给出了合理定性、定量分析.确定了冷却区温度,分析了不同的冷却区参数对压包成形的影响,获取了合适的冷却区占压扁后工件长轴尺寸的百分比数.其研究结果对实际生产有一定的指导作用.     

金属管接头复合成形过程有限元模拟及实验研究

针对凸筋类金属管接头提出了一种新的管接头复合成形工艺：“缩口－轴压－胀形”复合成形工艺,分析了该复合成形的工艺特点,利用刚塑性有限元方法对复合成形过程进行了模拟,得出了不同时刻的网格变形图和等效应变的等值线分布图,讨论了缩口半锥角和摩擦因子对成形极限的影响,将刚塑性有限元计算的结果与实验结果进行了比较,并得出了一些对生产实际有价值的结论     

筒形件正旋旋压力及位移分布规律的有限元分析

筒形件强力旋压时旋压力三个分量及其分布规律是确定设备功率及结构参数的重要依据。本文采用三维弹塑性有限元法对筒形件强力旋压工艺进行了分析 ,得到了正旋时变形区接触面上旋压力 3个分量的分布规律 ,计算结果与叶山实测结果吻合较好 ;同时得到毛坯内表面各节点的位移分布规律 ,为合理选择工艺参数 ,提高产品的尺寸精度提供了理论依据     

Equal channel angular extrusion of NiTi shape memory alloy tube

As a new attempt, equal channel angular extrusion (ECAE) of nickel–titanium shape memory alloy (NiTi SMA) tube was investigated by means of process experiment, finite element method (FEM) and microscopy. NiTi SMA tube with the steel core in it was inserted into the steel can during ECAE of NiTi SMA tube. Based on rigid-viscoplastic FEM, multiple coupled boundary conditions and multiple constitutive models were used for finite element simulation of ECAE of NiTi SMA tube, where the effective stress field, the effective strain field and the velocity field were obtained. Finite element simulation results are in good accordance with the experimental ones. Finite element simulation results reveal that the velocity field shows the minimum value in the corner of NiTi SMA tube, where severe shear deformation occurs. Microstructural observation results reveal that severe plastic deformation leads to a certain grain orientation as well as occurrence of substructures in the grain interior and dynamic recovery occurs during ECAE of NiTi SMA tube. ECAE of NiTi SMA tube provides a new approach to manufacturing ultrafine-grained NiTi SMA tube.     

局部加载控制不均匀变形与精确塑性成形研究进展

局部加载控制不均匀变形与精确塑性成形关键理论与技术研究,既是先进塑性成形学科前沿领域中的关键和挑战性课题,又是航空航天高技术发展的迫切需求。文章以局部不均匀加载实现通常极难的板面内弯曲成形为切入点,发展了控制不均匀变形以实现精确塑性成形的理论与技术,为我国先进飞机发展面临的大型复杂整体钛框成形制造难题的解决,提供了启示。建立了薄壁管数控弯曲失稳起皱、回弹、截面畸变预测和成形极限分析的模型、过程仿真和优化设计的方法;揭示了其关键影响因素和影响规律;实现了难度很大的薄壁管小弯曲半径数控弯曲精确成形。建立了多道次普旋、曲母线和带内筋件强旋等复杂过程三维仿真模型,提出了解决不均匀变形导致的复杂成形缺陷和旋轮轨迹优化设计难题的方法。解决了大型铝型材先进等温挤压中迫切需要解决的多场耦合作用下温度与速度效应和控制的重大难题。发展了复杂环件辗扩过程和控制仿真的三维有限元模型以及临界摩擦系数确定的解析-数值方法;总结了冷辗扩3种塑性变形行为及多因素耦合对辗扩过程的影响;提出了率相关晶体塑性模型在有限元中实现的稳健算法,实现了冷辗扩宏观变形行为的细观响应描述。     

汽车副架液压胀形预成形工艺设计的数值模拟

对汽车副架液压胀形预成形工艺设计进行了数值模拟研究。应用建立在刚塑性有限元法 (FEM)基础上的HydroFORM 3D软件与Oyane延性断裂准则相结合的数值模拟方法 ,重点针对管料初始尺寸的确定 ,给出了汽车副架液压胀形预成形工艺的数值模拟结果。分析表明 ,确定适合预成形工艺条件的管材初始尺寸有利于汽车副架液压胀形工艺的实施     

Y型异径三通管热态内高压成形研究

基于Dynaform软件平台,建立了Y型异径三通管三维弹塑性有限元模型。运用数值模拟方法,研究了AZ31镁合金Y型异径三通管热态内高压成形过程、成形缺陷、等效应变分布。探讨了初始管坯长度、左右冲头轴向进给量与成形支管高度之间的关系;研究得到了相同支管长度下成形不同Y型夹角三通管所需的左右冲头进给量。结果表明：随着初始管坯长度减小,支管高度随之增加;在左右进给量相同的情况下,左侧金属流向支管阻力更小,支管高度增加明显;随着Y型夹角的增大,右侧冲头进给增加,轴向补料比减小,总补料比增加,当夹角为90°时,左右补料相同。     

管轴压精密成形过程中管坯脱模点的预测

管轴压精密成形过程中 ,存在着管坯脱离模具而由约束变形到自由变形的转变 ,因而明确管坯脱模点的位置 ,将对整个成形过程的研究具有重要意义。本文采用有限元数值模拟 ,对成形过程中管坯的脱模特性及其影响因素进行了研究 ,结果表明 :管轴压成形过程中管坯的脱模状况 ,受到变形几何参数和材料参数的共同作用 ,其中几何参数是影响管坯脱模点位置的决定因素 ,材料参数则对脱模时的成形力影响很大     

上机匣锻造时径向筋条成形过程的数值模拟

采用三维刚塑性有限元法模拟了上机匣锻造时径向筋条的成形过程，得到了各主要变形场量的分布及金属流动规律，为合理地确定锻造工艺方案提供了依据。     

Study of the buckling mechanism in laser tube forming with axial preloads

The buckling mechanism of a thin metal tube during laser forming with axial preloads was investigated numerically and experimentally in this study. Metal tubes made of 304 stainless steel were heated by a CO₂ Gaussian laser beam, which induced the buckling phenomenon on the tube surface due to elastic–plastic deformation. This uncoupled thermal–mechanical problem was solved using a 3D finite element method (FEM) and was subsequently satisfactorily verified with axial force measurements. The transient force response and residual stress of the thin metal tube under specific operation conditions were also studied.     

板材单点渐进成形工艺数值模拟与成形缺陷研究

工具头运动轨迹的动态加载是建立板材渐进成形有限元模型的难题。首先基于DYNAFORM建立基本的有限元模型,而后直接提取数控代码中工具头的位移坐标信息并添加至关键字文件,从而实现任意复杂运动曲线的加载;数控代码规划的加工轨迹存在起刀区域集中和加工方向单一的问题,容易造成破裂和失稳缺陷。起刀区域塑性变形大,累积效应使该区域板材严重减薄,采用均布策略,并保证均布后相邻起刀点的空间距离大于塑性变形区的最大半径可避免此缺陷。同时,运用顺逆相间的加工方式避免了单一方向加工方式存在的材料堆积引起的形状失稳和棱纹缺陷。     

筒形件错距旋压缺陷的有限元仿真研究

筒形件的错距旋压是一个非常复杂的塑性变形过程，在生产实践中，常伴有旋压缺陷的产生。本文采用三维弹塑性有限元仿真的方法，对旋压变形过程中的韧性损伤、不贴芯模、隆起等典型缺陷的起因进行研究，并提出相应的预防措施，这对旋压件的生产具有良好的理论指导意义。     

铝合金管材无芯模冲切过程的有限元模拟

对铝合金管的冲切过程进行了有限元模拟,刀具采用刚体模型,工件采用弹塑性模型,材料断裂破坏采用Normalized Cockcroft＆Latham破坏准则。分析了冲切过程中冲切力、等效应力的变化,得出了弹性变形、塑性变形、塑性变形至裂纹扩展、断裂始终贯穿于整个冲切过程之中。通过模拟切口与实际切口的对比、模拟切屑形状与实际切屑形状的对比,说明了模拟过程的有效性。     

钛合金连接管件内径滚压成形的数值模拟

采用有限元软件DEFORM3D对U型套管形状钛合金连接管件内径滚压成形过程进行了三维刚塑性有限元模拟，得到变形区的速度场，以掌握管壁金属产生塑性变形填入套管凹槽的成形行为。井对影响连接件性能的齿槽尺寸、压下量进行了模拟，这对分析连接件密封质量具有一定的指导意义。     

等速万向节滑套温挤成形工艺缺陷分析

针对滑套精锻成形中，存在的反挤压冲头弯曲失效及精锻件表面出现折叠等问题，建立了弹塑性热力耦合有限元模型。通过对滑套的镦挤和反挤过程进行数值模拟分析，找出了出现上述问题的原因，提出了改进措施。