高功率密度发动机连杆热模锻工艺模拟与优化

目的研究某高功率密度发动机连杆的锻造工艺。方法首先采用传统设计方法设计了连杆模锻工艺,再通过有限元模拟分析优化工艺。结果根据有限元模型,分析了传统设计方法下的毛坯充型效果,直观地再现了终锻成形过程中的坯料外形演变和容易出现成形缺陷,在此基础上,优化了毛坯尺寸,满足了终锻充型要求。结论通过工艺试验进一步验证了模拟结果,获得的锻件没有出现缺肉、折叠等缺陷,微观组织较均匀,能够满足技术要求。     

复杂构件锻造预成形坯料设计综述

锻件预成形坯料设计是保证成形工艺顺利进行、获得无缺陷锻件、降低锻造载荷的关键环节。对于大型复杂构件,其预成形坯料形状影响到制坯工艺的周期、成本、预成形组织性能。分别从基于反向模拟技术的预成形坯料设计、基于优化设计方法的预成形坯料设计、基于正向过程分析的预成形坯料设计等方面,评述了复杂构件锻造预成形坯料设计的国内外研究现状,指出了大型筋板类构件的预成形坯料形状要求以及设计方法。     

连杆无飞边锻造工艺及模具系统研究

目的研究连杆无飞边锻造工艺,以及闭模锻造过程中中间工序件的设计和所需的模具系统。方法通过建立有限元模型,分析连杆的预锻和终锻过程中金属流动长度、成形载荷和模具寿命,为模具设计提供数据支持。结果数值模拟结果表明金属充模效果良好;连杆大端主要在预锻中成形,而连杆小端和杆部主要在终锻中成形;预锻和终锻的最大成形载荷分别为437 t和850 t;连杆大端的模腔圆角为模具失效危险区。结论通过辊锻制坯、预锻分配物料和终锻精密成形,实现了连杆的无飞边锻造。     

轴承环毛坯塔锻工艺的编制

详细阐述了轴承环毛坯塔锻成形工艺的编制方法;介绍了塔锻件公差、余量的选取,锻件图的制定、塔锻件、预成形件、镦粗件和坯料形状和尺寸的设计和计算.     

基于类等势场的粉末高温合金盘件预成形设计

根据能量最小原理和最小阻力原理,利用塑性变形过程中坯料的流动规律与静电场等势线分布类似这一特性,提出一种能够进行预成形设计的新方法——类等势场法,并采用该方法对粉末高温合金盘件进行预成形设计,从中优选出6组预成形形状,利用MSC/Super Form商用有限元软件对上述预制坯的等温成形过程进行了数值模拟,得到了6组粉末高温合金盘件在预锻到终锻过程中的应力率参数和应变率梯度.通过对盘件轮毂、辐板和轮缘3个部位6个典型单元体应力率参数g的比较与分析,以及整体盘件应变率梯度的比较,并参考预锻变形量和终锻变形量,认为选择3号预锻模为最佳方案.     

大截面差空心件内高压成形研究

截面周长差较大的空心零件的内高压成形需要解决膨胀区的轴向补料问题和预成形问题,才能获得壁厚分布较为均匀的合格零件.以某轿车转向节臂零件的成形过程为例,对上述问题进行了试验研究.首先设计、试制了瓶形预制件,在预成形中利用"有益起皱"实现了大量的补料,获得了壁厚分布符合要求的预制件;然后在终成形前使零件截面具有合理的形状,再进行终成形,既保证了圆角部位的外形尺寸,又提高了壁厚均匀性.采用本文介绍的方法实现了截面周长差达70%的瓶形预制件的制备,从而获得了壁厚、外形尺寸均满足设计要求的转向节臂零件.     

三销轴叉精整底部裂纹产生和防护

三销轴叉精锻件是汽车等速传动系统中的关键零件,其头部内、外腔形状复杂,尺寸精度要求高,故一般采用温锻预成形+冷精整成形复合成形技术,而预成形温锻件设计不合理,在冷精整成形中,存在内腔底部薄壁处出现裂纹的问题。利用数值模拟技术,分析了三销轴叉冷精整型腔底部区域成形过程的成形力、应力、应变的变化,对预成形温锻件进行了优化,设计了不同的入模角,入模角的起始点位于内腔基准平面之上。工程实践后,优化后的预成形温锻件在冷整形后,口部内腔底部没有裂纹产生,流线连续,获得较为理想的精锻件。证明优化后的预成形温锻件,经冷精整成形后,精锻件产品质量显著提高,可有效防止裂纹产生。     

发动机泵体精密热模锻成形工艺研究

目的为了提高发动机泵体综合机械性能和降低制造成本,采用精密热模锻技术来实现泵体的精确成形。方法通过确定锻件分模面位置,建立了泵体精密热模锻几何实体模型;在此基础上,建立了泵体热模锻过程三维有限元模型和模拟参数,实现了精密热模锻过程有限元模拟模型。结果通过数值模拟,获得了成形过程中坯料的速度场、等效应变场和温度场及载荷-行程曲线,揭示了泵体热模锻过程中金属充填模具型腔的情况及其变形机理,获得了温度场应变分布以及载荷、打击能量随行程的变化规律,优化了预成形时拍方坯料长度等参数,为确定成形工艺参数提供了科学依据。结论经试验验证,新工艺成形的锻件非加工外形面尺寸精度达到了零件要求,数值模拟结果与实验结果一致。     

轿车左转向节锻造工艺的模拟研究

针对轿车左转向节是带细杆的叉形件,同时兼有叉类、盘类和杆类零件的外形特点,分析其成形的工艺特点,进行工艺计算,确定工艺方案为头部镦粗—杆部拔长—预锻—终锻.利用有限元软件对成形过程进行模拟,得到飞边均匀的终锻成形件,并对模拟得到的应力场、应变场和载荷等信息进行分析.结果表明,各工序变形较为均匀,应力变化正常,没有出现破坏现象;最终锻件完全充满终锻模膛,没有出现缺料、折叠等缺陷,而且飞边均匀.     

6700 转向直臂成形过程设计及微观组织预测

通过对锻件结构的分析,设计了辊锻制坯+终锻的生产工艺。 运用有限元分析技术,通过对比分析,重点研究了新过程终锻成形时金属流动情况、等效应力应变分布,并对锻件的晶粒度进行了预测。 通过对锻件成形、载荷及质量等的综合评定表明,新的生产工艺在改善锻件质量、提高材料利用率与模具寿命等方面具有明显优势。     

Microstructure optimization design methods of the forging process and applications

A microstructure optimization design method of the forging process is proposed. The optimization goal is the fine grain size and homogeneous grain distribution. The optimization object is the forging process parameters and the shape of the preform die. The grain size sub-objective function, the forgings shape sub-objective function and the whole objective function including the shape and the grain size are established, respectively. The detailed optimization steps are given. The microstructure optimization program is developed using the micro-genetic algorithm and the finite element method. Then, the upsetting process of the cylindrical billet is analyzed using a self-developed program. The forging parameters and the shape of preform die of the upsetting process are optimized respectively. The fine size and homogenous distribution of the grain can be achieved by controlling the shape of the preform die and improving the friction condition.     

ANALYSIS OF AXISYMMETRIC FORGING OF POROUS MATERIALS BY THE FINITE ELEMENT METHOD

Axisymmetric forging of powdered-metal preforms was analyzed by the finite element method neglecting the effect of temperature on deformation. A remeshing program based on the area-weighted-average technique was developed and tested by simulating forging of the flange-hub shape. Then the analysis was performed for forging of a pulley blank. The detailed deformation characteristics for the different preform shapes under the two frictional conditions were obtained. A comparison between the prediction and the experiment regarding proper preform design to forge defect-free pulley blank demonstrates that the finite element analysis is useful for further developments in preform design in powdered-metal forging.     

Shape optimization of preform tools in forging of aerofoil using a metamodel-assisted multi-island genetic algorithm

Preform design plays an important role in improving the material flow, mechanical properties and reducing defects for forgings with complex shapes. In this paper, a study on shape optimization of preform tools in forging of an airfoil is carried out based on a multi-island genetic algorithm combined with a metamodel technique. An optimal Latin hypercube sampling technique is employed for sampling with the expected coverage of parameter space. Finite element (FE) simulations of multistep forging processes are implemented to obtain the objective function values for evaluating the forging qualities. For facilitating the optimization process, a radial basis function surrogate model is established to predict the responses of the hot forging process to the variation of the preform tool shape. In consideration of the compromise between different optimal objectives, a set of Pareto-optimal solutions are identified by the suggested genetic algorithm to provide more selections. Finally, according to the proposed fitness function, the best solution of multi-objective optimization on the Pareto front is confirmed and the corresponding preform tool shape proves optimal performances with substantially improved forging qualities via FE validation.     

一种深孔钻成形工艺设计及数值模拟

目的 根据深孔钻的结构特点,进行零件工艺分析和成形工艺方案设计,通过工艺试验结果验证深孔钻成形工艺的可行性。方法 首先,利用高温热压缩试验得到不同形变条件下深孔钻所用材料42CrMo合金钢的真应力-真应变曲线,并加以分析。其次,将试验数据导入Deform-3D材料库中,利用Deform-3D有限元模拟软件对深孔钻热挤压成形工艺方案进行数值模拟,分析成形过程中冲头的载荷-行程曲线以及形变过程中金属的流动规律、应力场分布、温度场分布和最终锻件的金属流线分布情况。最后,优化模拟结果进而得到成形工艺参数,进行深孔钻模具结构设计及工艺试验。结果 试验模拟得到的深孔钻充填饱满,金属流线分布合理,与实际金属流线分布基本一致。在成形过程中,上冲头的最大载荷为4.43×10³ kN,工艺试验得到的锻件尺寸一致性较好,没有锻造缺陷。结论 提出的深孔钻成形工艺是可行的,模具结构设计合理,可对该类型锻件的实际生产提供指导。     

航空锻件常见表观缺陷及其控制研究

目的 揭示服役寿命长、工况苛刻、锻造成本高、质量控制难度大的航空结构件与发动机盘件用钛合金、高温合金等锻件外观缺陷的产生原因及控制措施。方法 按照航空锻件锻造流程(开坯、制坯、模锻和锻后热处理),分别研究裂纹、折叠、错移等锻造缺陷产生的原因。结果 航空锻件产生表观质量缺陷的原因一般由工艺设计不合理、锻造操作不当、工装设备保障不到位等导致,需结合锻件材料、形状、变形过程等采取对应措施进行优化解决。结论 对航空锻件缺陷产生原因进行了研究,给出了行之有效的解决措施,对于航空锻件质量的提高,尤其是新材料、大尺寸、复杂结构的航空锻件研制具有重要的工程指导意义。     

3D preform shape optimization in forging using reduced basis techniques

Three-dimensional preform shape optimization of complex forgings with a weighted summation of multiple basis shapes is presented in this article. Currently, 2D preform shape optimization is well developed; however, in cases in which the parts are neither axisymmetric nor plane strain, 2D assumptions do not hold well. The number of design variables required to define the 3D preform shape is high, making most iterative design methods impractical for shape optimization. The goal here is to make design optimization practical and efficient by developing reduced-order modeling techniques for 3D preform shape optimization. The preform shape is treated as a linear combination of various billet shapes, called basis shapes, with the weights for each basis shape used as design variables, thereby reducing the number of design variables. It is very difficult to obtain the necessary gradient information for 3D forging simulations, so a non-gradient method is used to build the surrogate model on which optimization is performed. The optimization problem is formulated to minimize strain variance while placing constraints on underfill. Representative problems are used to demonstrate the effectiveness of the approach.     

连杆断裂失效分析及锻造折叠缺陷控制研究

目的 确定连杆断裂失效模式、机理和原因,找到有效预防连杆锻造缺陷的措施。方法 针对连杆断裂失效问题,在对连杆合格件和故障件进行符合性对比试验分析的基础上,对故障件进行断裂失效模式、机理和原因分析,并对连杆锻造折叠缺陷产生类型、机理、原因、条件和时段进行分析。结果 只有在连杆制坯坯料形状与尺寸不合理、制坯坯料在预锻模膛中位置不合理、预锻形状与尺寸不合理、预锻成形打击力或变形速度不合理、终锻形状与尺寸不合理、锻模导向功能失效等多种极端不利因素同时存在的条件下,才具有产生复合型锻造折叠缺陷的可能性。结论 通过连杆锻造过程控制和锻造首锻控制,可有效预防锻造折叠缺陷产生,满足锻件高优质性、高可靠性和高有效性要求。