基于有限元法的铝合金四通阀多向加载成形过程中的变形特征分析(英文)

采用数值模拟方法,研究7075铝合金四通阀体类零件在多向加载成形条件下成形过程中的材料变形特征。结果表明:四通阀多向加载成形过程中存在正挤、反挤、正挤和侧挤复合、反挤和侧挤复合等4种变形模式。在不同成形阶段,表现出的变形模式依赖于加载路径。一般在变形初期会发生正挤或反挤的变形行为;在变形中期以反挤变形模式为主;在变形终期一般会发生反挤、正挤和侧挤复合变形模式。为提高型腔填充稳定性和减少成形缺陷,在变形初期和中期,应增加侧挤变形行为;在变形终期应减少或避免正挤变形行为。     

FE analysis on Deformation and Temperature Nonuniformity in Forming of AISI-5140 Triple Valve by Multi-Way Loading

In triple valve forming process by multi-way loading severely nonuniform deformation and temperature distributions are prone to occur, which may lead to poor forming quality and macro-micro defects. A 3D coupled thermo-mechanical rigid-viscoplastic finite element (FE) model for multi-way loading forming of AISI-5140 steel equal diameter triple valve was developed based on DEFORM-3D. Through comprehensive simulation and analysis, the influences of main process parameters on the forming process and nonuniformity of deformation and temperature were studied. The results showed that: (1) the degree of deformation nonuniformity decreased with the increase of the punch loading speed, initial temperature of billet, or the decrease of the friction factor; (2) the average temperature of forming body increased as the punch loading speed, initial temperature of billet and the friction increased, while the degree of temperature nonuniformity decreased with the increase of punch loading speed or decrease of initial billet temperature.     

三通件多向加载成形热力耦合有限元分析

多向加载是通过在轴向和侧向同时或顺序地施加载荷,可以一次成形出多个方向上具有空腔的复杂构件,减少了加工工序,且提高了成形质量,为高效率、高质量成形复杂整体构件(如三通件)提供了有效途径。然而,三通件多向加载成形影响参数多、机理复杂,本文基于DEFORM-3D,建立了三通件多向加载成形热力耦合刚粘塑性有限元模型,并验证了其可靠性。在此基础上确定了加载方案,获得40Cr钢三通件多向加载成形过程中行程载荷曲线及速度场、温度场、应力-应变场的分布规律。结果表明,按本文确定的加载方案,成形初期在水平支管上出现明显的分流线,分流线处易出现裂纹;水平支管先于垂直支管成形完毕,在水平支管成形完毕时水平冲头的载荷迅速升高,而当整体成形快完毕时,水平冲头和垂直冲头的载荷都急剧升高;成形过程中坯料芯部为大变形区,变形速率大,塑性变形热使坯料芯部出现明显温升。该研究为三通件多向加载成形工艺参数的优化,以及缺陷的控制,提供了指导。     

AISI-5140三通阀多向加载成形开裂预测

三通阀体多向加载成形是一个多参数作用,多工步、多模具约束的高温变形过程,材料受力状态和流动行为复杂,变形不均匀性严重,易于产生开裂等缺陷。文章首先研究并确定了,适用于AISI-5140三通阀多向加载成形过程中的开裂预测准则为Cockcroft-Latham准则,计算出AISI-5140材料的临界损伤值为0.881;随后以材料损伤峰值为指标,采用正交试验设计与有限元模拟相结合,对发生开裂的趋势和区域进行了分析和预测。结果表明,成形末期三通阀肩部圆角偏上区域材料的损伤值达到峰值,易于发生开裂;成形过程中的开裂趋势随着凹模圆角减小和摩擦增大而增大;加载速度越大,发生开裂的趋势越小,该文条件下,当加载速度低于15mm/s时,易发生开裂。对于给定坯料成形内径不同的三通阀,损伤峰值随着三通阀内径的增大而增大,即开裂趋势增大;对于内外径比相同的三通阀,成形过程中的损伤峰值随着其外径的增大而降低,即开裂趋势减小。     

铝合金圆锥形零件粘性介质温成形研究

采用热力耦合有限元数值模拟方法对铝合金圆锥形零件粘性介质温成形过程进行了模拟分析,研究了成形过程粘性介质和板材的温度分布、不同温度条件下成形零件壁厚分布、成形载荷等.结果表明,圆锥形零件的底部圆角区域为成形危险区域.非等温粘性介质温成形过程中,在粘性介质内部形成的非均匀温度场影响了板材的温度分布.当粘性介质温度略低于板材温度时,坯料中心区域温度较低,有利于延迟底部圆角成形时的破裂,提高了零件壁厚的均匀性.分别进行了室温和加热时铝合金圆锥形零件粘性介质压力成形试验,试验结果与数值模拟具有相同的规律.     

6111铝合金热变形行为及本构方程

利用Gleeble-1500热模拟机,研究6111铝合金在变形温度为350℃～550℃、应变速率为0.01s-1～10s-1的热变形流变应力行为。研究结果表明,6111铝合金为正应变速率敏感材料,且随着变形温度升高抗拉强度减小,其热变形经历了从应变硬化阶段过渡到稳态变形阶段的过程,软化机制主要为动态回复;采用Zener-Hollomon参数建立6111铝合金的本构方程,该方程可用于模拟6111铝合金材料一般加载情况下的热成形过程。     

5A06-O aluminium–magnesium alloy sheet warm hydroforming and optimization of process parameters

The uniaxial tensile test of the 5A06-O aluminium–magnesium (Al–Mg) alloy sheet was performed in the temperature range of 20–300 °C to obtain the true stress–true strain curves at different temperatures and strain rates. The constitutive model of 5A06-O Al–Mg alloy sheet with the temperature range from 150 to 300°C was established. Based on the test results, a unique finite element simulation platform for warm hydroforming of 5A06-O Al–Mg alloy was set up using the general finite element software MSC.Marc to simulate warm hydroforming of classic specimen, and a coupled thermo-mechanical finite element model for warm hydroforming of cylindrical cup was built up. Combined with the experiment, the influence of the temperature field distribution and loading conditions on the sheet formability was studied. The results show that the non-isothermal temperature distribution conditions can significantly improve the forming performance of the material. As the temperature increases, the impact of the punching speed on the forming becomes particularly obvious; the optimal values of the fluid pressure and blank holder force required for forming are reduced.     

钛合金筒形件真空热胀形壁厚效应的数值模拟

建立了钛合金筒形件真空热胀形的二维非线性热力耦合有限元模型。使用有限元软件MSC-Marc对钛合金简形件真空热胀形过程进行数值模拟。计算了钛合金筒形件真空热胀形过程的温度场和变形场，并进行了相应的实验验证。模拟结果与实验结果吻合较好。用建立的模型对真空热胀形过程中钛合金筒形件壁厚效应进行数值模拟，讨论了一定工艺条件下钛合金筒形件壁厚与弯曲角度、胀形量和残余应力之间的关系，为实际生产中制定和优化钛合金筒形件真空热胀形工艺参数提供理论与实践依据。     

二元合金非等温凝固过程的相场法模拟

基于Ginzburg-Landau理论,发展了一个新的相场模型.并利用该相场模型与溶质场、温度场进行耦合计算,以Al-6.5Cu合金为例模拟了二元合金非等温凝固和等温凝固的等轴枝晶生长过程.研究了凝固潜热对过冷合金熔液中的等轴枝晶生长以及溶质场和温度场的分布的影响.结果表明:潜热的释放在一定程度上抑制了枝晶的生长,使非等温凝固时枝晶没有等温凝固时发达,并且凝固界面的溶质浓度也会降低,但不会改变在枝晶生长过程中浓度分布情况.而且非等温凝固时的Peclet数值与Ivantsov理论值符合得更好.     

多向加载近净成形研究动态

通过主动控制不同方向、不同成形阶段的多向加载条件并配合模具、变形温度等成形条件,可有效控制变形,提高坯料的成形性能,以获得预期的结构形状及组织状态的零件,实现净成形或近净成形,为难变形材料的复杂整体构件的精确塑性成形提供了一条有效途径。多向加载技术在蒙皮拉形、管材挤胀、环件径轴向辗扩、多向模锻等塑性成形工艺中都得到体现,但其工艺通用性差,需要专门的设备,不同成形工艺甚至当成形零件不同时,其变形机理亦迥异。评述了目前多向加栽成形工艺的应用与国内外研究现状,指出了该工艺在体积成形中应用发展需要解决的关键技术问题。     

Microstructure evolution in the local loading forming of TA15 titanium alloy under non-isothermal condition

In this paper, the microstructure evolution and processing–microstructure relationship in the non-isothermal local loading forming of TA15 titanium alloy were studied through an analog experiment. Some new microstructural mechanisms are found, which are different from those under isothermal local loading forming. In the non-isothermal local loading forming, the tri-modal microstructure consisted of equiaxed primary α, lamellar α and β transformed matrix is achieved. The lamellar α, not produced under isothermal condition, is generated by β → α transformation due to the decrease of component temperature. With the same processing parameters, the volume fraction and grain size of primary α are both greater than those processed isothermally. The content of lamellar α decreases with heating temperature decreasing and little lamellar α can be found when the heating temperature drops to 930 °C. Under small deformation degree, the lamellar α distributes randomly in each feature region. As deformation increases, the lamellar α in transitional region and second-loading region present a preferred orientation perpendicular to the compression direction. The primary α content almost decreases linearly with heating temperature, which is different from the regular that under isothermal condition. Non-isothermal local loading forming with a higher heating temperature (near-β region) offers a cost-efficient way for the manufacture of TA15 titanium alloy large-scale integral components.     

铝合金轧制成形的研究与现状

介绍了铝合金的几种体积成形方法,列举了目前的研究成果,重点介绍了楔横轧技术在铝合金材料成形中的可行性以及目前的研究现状,同时也提出了成形过程中需要解决的关键技术,为楔横轧技术在铝合金材料成形中的应用提供了一定的思路与方向。     

Microstructure prediction of two-phase titanium alloy during hot forging using artificial neural networks and FE simulation

The microstructural evolution of titanium alloy under isothermal and non-isothermal hot forging conditions was predicted using artificial neural networks (ANN) and finite element (FE) simulation. In the present work, the change in phase volume fraction, grain size, and the volume fraction of dynamic globularization were modelled considering hot working conditions. Initially, an ANN model was developed for steady-state phase volume fraction. The input parameters were the alloy chemical composition (Al, V, Fe, O, and N) and the holding temperature, and the output parameter was the alpha/beta phase volume fraction at steady state. The non-steady state phase volume fraction under non-isothermal conditions was subsequently modelled on the basis of 4 input parameters such as initial specimen temperature, die (or environment) temperature, steady-state phase volume fraction at die (or environment) temperature, and elapsed time during forging. Resulting ANN models were coupled with the FE simulation (DEFORM-3D) in order to predict the variation of phase volume fraction during isothermal and non-isothermal forging. In addition, a grain size variation and a globularization model were developed for hot forging. To validate the predicted results from the models, Ti-6Al-4V alloy was hot-worked at various conditions and then the resulting microstructures were compared with simulated data. Comparisons between model predictions and experimental data indicated that the ANN model holds promise for microstructure evolution in two phase Ti-6Al-4V alloy.     

铝合金大型复杂薄壁壳体旋压研究进展

大型复杂薄壁壳体是航空航天等高技术产业迅速发展的迫切需求,带横向内筋大型复杂薄壁壳体是其中的典型代表。然而,带横向内筋大型复杂薄壁壳体多道次复合旋压却是一个多因素耦合作用下的复杂塑性成形过程。作者采用数值模拟和实验相结合的方法,以铝合金带横向内筋大型复杂薄壁壳体为代表,建立大型复杂薄壁壳体复合旋压全过程仿真平台与模型,研究不同条件下大型复杂薄壁壳体复合旋压及其特征结构旋压过程中的不均匀塑性变形行为和成形缺陷的形成机理。揭示不同塑性变形行为对工件内筋质量的影响规律,获得对不同塑性变形行为有决定性影响的因素,确定合理的毛坯、工艺和旋轮参数的选择准则。研究结果对发展大型复杂薄壁壳体精确成形技术具有重要的理论意义和实际应用价值。     

车用铝合金板材回弹规律研究

在车用铝合金材料的成形加工过程中,回弹是主要的成形缺陷之一并且较难控制。本文对车用6061铝合金板材进行了室温拉伸试验获得其应力-应变曲线并建立改进的Johnson-Cook本构模型。该模型被应用于V形弯曲试验的有限元仿真中,研究不同各向异性屈服准则对板料回弹预测精度的影响,仿真结果表明应用YLD2000-2d屈服准则时其预测精度较高,同时也验证了该模型用于回弹分析的有效性。进一步探究不同因素如变形程度,冲压速度,摩擦条件,压边力等对铝合金板材回弹行为的影响规律,并应用于铝合金发罩内板的冲压成形过程,能够有效减小工件的回弹。     

A356铝合金轮毂半固态挤压铸造成形数值模拟

通过建立A356铝合金的半固态表观粘度模型,采用计算机模拟方法对A356铝合金轮毂半固态挤压铸造成形工艺进行了研究.通过分析挤压速度、半固态浆料充填温度及模具预热温度对铝合金轮毂半固态成形性能的影响,探讨了不同条件下的金属流动特点和温度分布规律.结果表明,对该尺寸铝合金轮毂的最佳成形工艺:半固态浆料充填温度为600℃,模具预热温度为300℃,挤压速度为5 mm/s,保压时间为25 s.     

Microforming of superplastic 5083 aluminum alloy

The mechanical behavior of superplastic 5083 aluminum alloy during microforming process was investigated by finite element analysis.A micro V-groove die was modeled to analyze the effects of forming time,load and temperature on the microformability of the 5083 aluminum alloy.First,the microformability of the 5083 aluminum alloy was estimated using a microformability index.The simulation results show that the microformability increases with the forming load,time and temperature increasing.Superplasticity of the 5083 aluminum alloy during microforming using the V-groove die was also investigated in terms of the effective strain rate.The results show that the superplasticity of the 5083 aluminum alloy occurs in a specific part of the material for a specific period during the microforming process depending on the forming conditions and the microformability index.     

固溶成形工艺对6016铝合金组织及力学性能的影响

针对铝合金在室温下塑性差等问题,结合铝合金固溶处理特点,采用了固溶成形工艺制备零件。为获得6016-T6铝合金固溶成形最优工艺参数,利用电子拉伸试验机对6016-T6铝合金板进行不同加热温度及冷却方式的研究,分析了不同固溶工艺参数对其组织与力学性能的影响规律。结果表明,冷却速度对材料的组织性能影响较大,固溶工艺参数为550℃×5 min,水冷时,其抗拉强度可达到300 MPa以上。采用了上述工艺参数对铝合金后风档下横梁进行了测试验证,试制出合格的成形件,热冲压件力学性能可达308 MPa。     

Prediction of Forming Limit Diagrams for 22MnB5 in Hot Stamping Process

Hot stamping of ultra-high strength steels possesses many superior characteristics over conventional room temperature forming process and is fairly attractive in improving strength and reducing weight of vehicle body product. However, the mechanical and failure behavior of hot stamping boron steel 22MnB5 are both strongly affected by strain hardening, temperature, strain rate, and microstructure. In this paper, the material yield and flow behavior of 22MnB5 within the temperature and strain rate range of hot stamping are described by an advanced anisotropic yield criterion combined with two different hardening laws. The elevated temperature forming limit diagram (ET-FLD) is constructed using the M-K theoretical analysis. The developed model was validated by comparing our predicted result with experimental data in the literature under isothermal conditions. Based on the verified model, the influence of temperature and strain rate on the forming limit curve for 22MnB5 steel under equilibrium isothermal condition are discussed. Furthermore, the transient forming limit diagram is developed by performing a transient forming process simulation under non-isothermal transient condition.     

镁合金板材的固体颗粒介质拉深工艺参数

提出基于固体颗粒介质成形(SGMF)工艺的镁合金板材差温拉深工艺,并展开试验研究。通过对AZ31B镁合金薄板进行差温拉深成形试验,研究了成形温度、拉深速度、压边力、压边间隙、凹模圆角和润滑条件对拉深性能的影响,确定AZ31B镁合金板料最佳成形工艺参数。结果表明:该工艺可显著提高镁合金板材的成形性能,成形温度及拉深速度对板料拉深性能影响较大,板料最佳成形温度区间为290～310℃,颗粒介质与板料理想温差为110～150℃;压边力和压边间隙对拉深性能产生联合影响;此外,凹模圆角和润滑条件也对拉深性能有一定的影响。当上述工艺参数达到最佳值时成功拉深出极限拉深比(LDR)为2.41的工件。