Distribution of Metal Flowing into Unloaded Area in the Local Loading Process of Titanium Alloy Rib-Web Component

对于通过模具分区实现的等温局部加载成形,为了减少加载区对未加载区的不利影响,一般会采用筋上分区模式。由于局部加载特征,在成形过程中加载区部分材料会流向未加载区。流入未加载区材料的分配对成形过程分析、材料流动控制、成形质量改进都有着重要影响。从加载区流入为未加载区材料的分配主要由未加载区的形状和模具分区附近的几何参数所确定。若未加载区是已成形区,部分流向未加载区的材料充填分区筋型腔。应用偏最小二乘回归建立了流入分区筋型腔材料比率的预测模型。数值结果表明流向未加载区材料分配的分析和所建立的预测模型是合理的。     

钛合金多筋构件锻造成形筋槽充填一致性及影响因素

针对钛合金多筋构件锻造过程易发生的筋槽充填不满问题，首先应用Deform-3D模拟软件分析了TA15钛合金多筋薄腹特征构件锻造过程中不同筋槽的材料流动及充填特征，并采用物理模拟试验进行了验证。其次，基于正交试验研究了出模角度、圆角半径、坯料体积分配、加载速度、变形温度及摩擦因数这6个因素对充填的影响。结果表明，成形初期材料处于筋槽充填的自由流动状态，而当某区域筋槽充满后，上模继续下压导致模具型腔内两处发生材料流动转变，转变一是腹板处材料发生横向跨筋流动，二是筋槽处材料发生纵向逆流，不同区域筋槽充填的不一致是导致多筋构件充填不满的本质原因。坯料体积比对材料流动及筋槽充填的影响最大，摩擦因数有一定影响，而其他因素的影响很小。最后，基于优选的因素水平，获取了较好的充填效果，不同区域筋槽的充满趋于一致。     

大型钛合金隔框等温闭式模锻成形工艺优化

大型钛合金隔框锻件外形复杂,且要求尺寸精度高、内部质量稳定,然而在锻造过程中极易出现充填不满、折迭、流线紊乱等缺陷.针对这些成形缺陷,基于DEFORM有限元软件,采用数值模拟方法研究钛合金等温闭式模锻成形过程坯料和加载方式优化对锻件成形质量的影响.研究表明:基于隔框材料流动特性优化得到的不等厚坯料,能较好地改善材料的充填性,使锻件满足尺寸精度要求.而局部加载方式可以有效地控制材料的流动,提高锻件的变形均匀性,消除由于材料流动不良造成的成形缺陷.     

TA15合金H型构件等温局部加载成形工艺研究

基于DEFORM3D平台,建立筋板类构件等温局部加载宏微观有限元模型,对TA15钛合金H型构件等温局部加载成形工艺进行研究,揭示了局部加载过程中加载模式、分模面位置、加载次序及加载参数对筋的充填和初生α相晶粒尺寸的影响规律.结果表明:分模面位置设在筋上比设在腹板上的筋充填性好,初生α相晶粒尺寸分布均匀;相对于只采用局部加载成形,先局部加载后整体精整使得变形更均匀,筋的充填差较小并且流线分布更合理;改变局部加载成形参数,即增大横向筋和腹板、纵向筋和腹板之间的圆角半径,分模面处的纵向筋和横向筋的充填深度差增大;增加上模压下速度,使筋的充填深度减小,初生α相晶粒尺寸减小,但分布越来越不均匀;在两相区成形加载次序对初生α相的晶粒尺寸影响不显著.     

钛合金整体隔框等温成形局部加载分区研究

钛合金大型整体隔框在航空航天领域得到了越来越广泛的应用,等温局部加载为这类构件的成形提供了新的途径。等温局部加载过程复杂并且存在着加载区、未加载区和过渡区以及不同加载区之间的转换,合理的局部加载分区,是保证成形过程实施和成形质量的关键,文章研究并提出了局部加载分区的总体原则,随后基于DE-FORM3D有限元软件,采用数值模拟方法研究了局部加载分区(大小、位置)对TA15钛合金整体隔框成形过程的影响规律。结果表明,局部加载分区对未加载区材料错移的影响是短程效应,合理的分区可有效控制未加载区材料错移和降低总体成形载荷;分区对材料总体变形量和变形均匀性影响不大;采用筋上分区有利于提高筋的充填性能并可避免毛刺的产生,从而可提高了过渡区成形质量。     

铝合金锻件成形工艺及三维有限元分析

为了揭示叶轮件模锻成形过程中金属的变形流动规律,采用有限元模拟对不同形状坯料成形过程的塑性变形流动行为进行对比分析.结果表明:叶片处是较难以充填成形的部位,且随着截面位置的下移,金属向该处型腔充填流动的趋势更为显著;与圆柱形坯料相比,阶梯形坯料成形过程中叶片部位更易于被充填成形,金属流动的均匀性也较好;通过工艺实验验证了利用阶梯形坯料可一次性成形出尺寸精度和性能均符合设计要求的叶轮锻件.     

TA15钛合金大型复杂构件等温局部加载过渡区宏微观变形研究

基于DEFORM3D平台,针对大型复杂构件建立了等温局部加载有限元模型,模拟分析了成形参数对过渡区成形和微观组织演化的影响规律.结果表明:随过渡区宽度的增加,过渡区纵向筋和横向筋之间的凹陷增大,平均晶粒尺寸减小;随加载道次的增加,过渡区纵向筋和横向筋之间的凹陷减小,平均晶粒尺寸减小;随锻造温度的升高,加速度的减小其平均晶粒尺寸增大;只采用局部加载成形方式时,过渡区纵横筋充填不均匀,平均晶粒尺寸较小:采用先局部加载后精整的变形方式时,过渡区纵横筋的充填较好,平均晶粒尺寸较大.     

钛合金筋板件等温局部加载模具应力分析

等温局部加载成形技术为航空航天复杂筋板类大型整体构件的成形提供了一种新的途径,但由于构件尺寸大,其成形温度高、时间长、载荷大等工艺特点,对模具提出了更高的要求。文章针对TA15钛合金典型环形高筋薄腹特征结构件等温局部加载成形,分析了等温局部加载模具的结构特点和可能的失效形式,并在此基础上采用DEFORM 3D有限元软件,对成形时模具应力进行了研究,获得了模具载荷和应力分布规律,并进一步分析了模具凹圆角半径和锻件筋条宽度对模具应力的影响。结果表明,等温局部加载成形模具的失效形式,主要为应力集中引起的脆性断裂;加载分区边界附近模具应力较小,离分区边界越远模具应力越大,且应力峰值出现在宽度较小的环形筋型腔凹角处;模具型腔各部分材料填充能力的不一致,是导致模具应力不均匀、局部出现应力集中的主要原因;增大模具凹圆角半径,模具应力降低程度较小,而通过合理的锻件几何尺寸设计,可以改善模具型腔的充填性,能更有效地降低模具应力的不均匀性和应力峰值。文章的研究结果可为等温局部加载成形模具的设计提供参考。     

基于BP-GA的大锻件过渡区宏观成形性能优化

针对铝合金大型锻件局部加载成形工艺下过渡区筋部充填不满的问题,借助于BP神经网络和GA遗传算法与数值模拟技术相结合的策略对锻件的局部加载成形工艺参数进行了研究。以锻件过渡区填充性作为质量评价目标,建立了坯料温度、压力机加载速度、第1道次压下量、进给量与质量指标之间的关系模型,利用遗传算法求解得到了合理的工艺参数:坯料温度为435℃,压力机加载速度为5 mm·s-1,第1道次压下量为18 mm,进给量为1165 mm,并将得到的工艺参数进行再模拟,并应用于生产试制,生产后的锻件筋部过渡区充填完整,对比模拟结果,表明所提出的策略能有效对大型锻件局部加载成形过渡区充填问题进行控制。     

筋板类锻件等温精密成形技术研究

主要研究筋板类锻件等温精密成形技术.针对典型筋板类锻件,设计了不同形式的局部加载垫板进行局部加载,通过局部加载技术控制腹板处多余金属的流动方向和距离,避免产生折迭、充不满等缺陷,并且利用等温变形条件改善金属充填质量和降低模压力.实验结果表明局部加载等温成形技术可以有效地控制金属的变形流动,提高筋板类锻件的成形质量.     

Analysis of local loading forming for titanium-alloy T-shaped components using slab method

A large-scale rib-web component may be considered as a combination of many T-shaped components which can reflect forming characteristics of large-scale rib-web components by local loading. So exploring the material flow and filling law of the T-shaped components local loading forming is important for parameter optimization and process control of local loading forming processes of rib-web components. With the help of reasonable assumptions and simplifications, the slab method (SM) is used to analyze the isothermal forming process of titanium-alloy T-shaped components under local loading in this paper. The process of local loading forming and the characteristics of material deformation are analyzed, and two deformation patterns under local loading are found by using the physical experiment. Mathematical models of loading force, rib height (depth of cavity filling) and the position of neutral layer in loading process are established by using the slab method. Calculation-program for models is developed under MATLAB environment, and then the loading force, rib height and position of neutral layer are predicted. The comparison of the SM results with the experimental and FEM results indicates that the models established based on the slab method are reliable. The reasonable parameters determined by using the mathematical models, such as the width of punch, the thickness of billet, the reduction amount etc., may provide a basis for analysis of local loading forming for large-scale rib-web components.     

Effects of Parameters on Inhomogeneous Deformation and Damage in Isothermal Local Loading Forming of Ti-Alloy Component

Isothermal local loading (ILL) forming technology provides a new way to form largescale rib-web (LSRW) components of Ti-alloy, widely used in the aero-space fields as key load-bearing structures. However, the metal undergoes complex plastic inhomogeneous deformation and microstructural evolution, this will lead to macroscopical forming defects and further damage due to multi-process parameters and local loading method, making the process and forming quality hard to control. Using numerical simulation, combined with experiment, influences of various process parameters on forming process, inhomogeneous deformation and damage have been explored for ILL of LSRW components, such as the types of die-forging mode, frictional conditions, and local loading parameters (partitioning of the loading zone, constraint conditions, and loading pass). Then the reasonable forming conditions for LSRW components of Ti-alloy to be studied are proposed. The practical forming experiment of TA15 LSRW component was achieved successfully and the forging with good forming quality, excellent microstructure, and comprehensive mechanical properties was obtained, which indicates the reliability and practical value of results obtained in this article.     

Preparation and thixoforging of semisolid billet of AZ80 magnesium alloy

Semisolid billet of AZ80 magnesium alloy was prepared by new strain induced melt activated (new SIMA) process and thixoforging experiment was performed. The results show that after as-cast AZ80 magnesium alloy is processed by equal channel angular extrusion, microstructure is refined well due to heavy dynamic recrystallization occurring in severe plastic deformation. Compared with semisolid isothermal treatment and conventional SIMA, semisolid billet with fine and spheroidal grains are achieved in new SIMA. Thixoforging process of semisolid billet prepared by new SIMA has many advantages such as good surface quality of final component, high ability to fill cavity and net-shape. The fine and spheroidal grains and high mechanical properties such as tensile strength of 298 MPa and elongation of 28% can be developed in final part thixoforged.     

H型钢坯水冷金属型铸造充型凝固过程数值模拟

提出了处理水冷铸型边界条件的等效换热系数法，该法综合考虑了铸件与铸型问的辐射换热、间隙热阻及水冷铸型边界条件。获得了H型钢的充型流动过程及凝固过程的温叟场，并采用Xue判据预测了H型钢的缩松缺陷位置。为进一步改进H型钢水冷金属型铸造工艺提供了理论依据。     

管坯生产工艺路线的分析研究

论述了各种管坯生产工艺路线的特征,分析了连铸圆坯优于用钢锭轧制的轧制坯;指出选择圆形,空心圆形截面连铸坯是管坯生产的发展方向,并提出了连铸大方坯,CC－HDR生产小直径管坯的方案。