Multiobjective optimization design of porthole extrusion die using Pareto-based genetic algorithm

The extrusion die plays a crucial role in aluminum alloy profile production, which influences product quality and service life of extrusion die directly. In this paper, a profile with irregular shape was taken as an analysis example, and multiobjective optimization for porthole extrusion die based on modern intelligence algorithm was carried out. Aiming at achieving the uniform velocity distribution in the cross-section of the profile as well as decreasing the maximum stress on the extrusion die and the deflection of the mandrel, the angle between port bridges, the position of die orifice, and the height of welding chamber were considered as the design variables. Then Kriging model was established on the basis of Latin hypercube samplings, and above design variables were optimized using Pareto-based genetic algorithm. Finally, an optimal die structure is gained. Compared with the initial scheme, the velocity distribution in the extrudate was more even, and the stress on the die and the deflection of the mandrel were decreased obviously in the optimal scheme. The optimal design method for porthole die has strong commonality, thus, it could give useful guidelines for practical production of the same kind of aluminum profile.     

多腔壁板铝型材挤压过程数值模拟及模具优化

挤压模具在铝型材挤压生产中起着至关重要的作用,挤压模具设计的优劣直接影响挤压产品的质量。然而实际生产中,挤压模具的设计更多依赖传统设计经验,需要多次试模和修模,无法满足产品开发需求。以典型的多腔壁板铝型材为例,应用UG建立分流组合模几何模型,采用基于任意拉格朗日—欧拉(Arbitrary Largrang-Euler,ALE)算法的HyperXtrude软件对多腔壁板铝型材的挤压成形过程进行数值模拟,获得挤压过程中速度场、温度场、应力场及金属流动情况。针对初始模具设计的不足,提出多腔壁板铝型材挤压模具优化三步曲(开设引流槽、增设阻流块、优化工作带),有效地解决了初始模具设计中速度分布不均的问题。利用数值模拟方法可以优化模具结构,提出的多腔壁板铝型材挤压模具优化三步曲对同类铝型材挤压模具结构设计具有一定的指导意义。     

Analysis and porthole die design for a multi-hole extrusion process of a hollow,thin-walled aluminum profile

The appropriate die design for multi-hole extrusion is still a challenging task because of the complicated circumstances and large material deformation during extrusion process. In the present study, the material flow during multi-hole extrusion process for producing a hollow and thin-walled profile was revealed by means of numerical simulation based on the Arbitrary Lagrangian Eulerian (ALE) method. The effects of eccentricity ratio, shape of the second-step welding chamber, and uneven bearing length on the exit velocity distribution of extrudate were synthetically investigated, and a two-hole porthole die was designed accordingly. The exit velocity and temperature on the extrudate in this optimized die were analyzed and compared with the initial die, and it was found that both of them exhibit better uniformity, which is beneficial for the enhancement of product quality. Through performing the current work, a logical and effective route for designing multi-hole porthole die was proposed as the guidance for die designers.     

分流组合模挤压过程数值模拟及模具应力分析

采用有限体积数值模拟方法研究分流组合模中焊合室的深度对铝型材挤压过程的影响,分别采用21mm、26mm和31mm三种焊合室深度对挤压过程进行了模拟,得到了应力、应变、挤压力等各种物理场量的变化规律,并采用有限元法对模具受力及变形情况进行了分析。研究结果表明,焊合室深度对载荷影响不大,但焊合室深度为26mm时质点流速最均匀。模具变形分析结果表明,随着焊合室深度增加,模芯变形程度增大,对应力分布来说,存在一个最佳的焊合室深度。从型材产品质量和模芯变形量综合考虑,应合理设计焊合室深度。     

阻流块对薄壁空心铝型材挤压过程材料流速的影响

采用基于任意拉格朗日—欧拉(Arbitrary Largrang-Euler,ALE)算法的HyperXtrude软件模拟带有细小特征的薄壁空心铝型材挤压过程,以模孔出口处材料流速均方差作为衡量其均匀性的指标,通过设计一系列阻流块有效控制材料流速及型材变形。研究阻流块对流速均匀性的影响规律,提出阻流块设计的一般原则。结果表明,阻流块的截面形状对流速控制起着关键作用,应保证阻流块截面形状合理,再调整阻流块高度及其到模孔的距离,可有效控制材料流速及型材的变形,获得形状和尺寸符合要求的型材。在阻流块高度的一定范围内,增加其高度可增加型材整个截面上材料流速的均匀性,但阻流块的宽度对平衡材料流速作用不大。     

Optimization of an aluminum profile extrusion process based on Taguchi’s method with S/N analysis

Taguchi’s design of experiment and numerical simulation were applied in the optimization of an aluminum profile extrusion process. By means of HyperXtrude, the extrusion process was simulated and the effects of process parameters on the uniformity of metal flow and on the extrusion force were investigated with the signal to noise ratio and the analysis of variance. Through analysis, the optimum combination of process parameters for uniform flow velocity distribution was obtained, with the billet diameter of 170?mm, ram speed of 2.2?mm/s, die temperature of 465°C, billet preheated temperature of 480°C, and container temperature of 425°C. Compared with the initial process parameters, the velocity relative difference in the cross-section of extrudate was decreased from 2.81% to 1.39%. In the same way, the optimum process parameters for minimum required extrusion force were gained, with the billet diameter of 165?mm, ram speed of 0.4?mm/s, die temperature of 475°C, billet preheated temperature of 495°C, and container temperature of 445°C. A 24.7% decrease of required extrusion force with optimum process parameters was realized. Through the optimization analysis in this study, the extrusion performance has been greatly improved. Finally, the numerical results were validated by practical experiments, and the comparison showed that the optimization strategy developed in this work could provide the effective guidance for practical production.     

悬臂铝合金型材伪分流挤压模具结构设计及其强度分析

铝型材挤压工艺和模具设计不仅需要保障挤出型材质量,还要保障模具强度和寿命,但对于大而长的悬臂铝合金型材,常规平模或导流模结构设计往往导致模具悬臂部位损坏,即使将模具相应部位加厚,也很难达到提高模具强度的要求。以某大悬臂铝型材为例,研究伪分流模具结构设计方法及长悬臂梁分解技术,对比分析常规模具设计与伪分流模具设计对型材挤压速度分布、温度分布、材料粒子运动轨迹等的影响规律,研究不同结构的模具强度。研究表明,采用伪分流模具不仅能够大幅度降低模具应力,而且通过材料流动优化可获得良好的材料流动规律和型材质量。总结给出伪分流结构的设计原则。     

基于特征矩阵和神经网络的铝型材整体壁板外形识别

针对铝型材整体壁板的外形特征和设计要求，提取出9种典型壁板并构建出对应的壁板特征矩阵和目标矩阵。采用神经网络分别对带与不带噪声的整体壁板特征识别进行了研究、训练和测试，测试结果显示，采用矩阵构造的神经网络对壁板特征识别继承了神经网络的优点，可扩充性好，解决了整体壁板挤压模具CAD专家系统关于特征识别的前处理瓶颈问题。     

挤压模具型腔的等磨损优化设计

针对目前国内挤压模具寿命过低的情况,将有限元分析、神经网络和遗传算法结合起来应用到挤压模具型腔优化设计中。采用B样条函数插值描述凹模型腔轮廓形状,用有限元数值模拟获得型腔表面节点的应力场、速度场和温度场,基于修正Archard磨损模型计算型腔磨损深度,以此作为样本训练BP神经网络,建立模具型腔控制点与磨损深度之间的映射关系,再结合遗传算法以等磨损为目标,优化模具型腔轮廓形状。优化结果与序列二次规划法一致,可以降低模具磨损,提高模具寿命,结果与实际情况吻合,表明了这种设计方法是可行的。     

铝型材挤压成型数值模拟及优化设计

应用有限元法,通过对AA6063铝合金方管挤出过程进行数值模拟,优化了分流组合模的工作带,以模孔出口处型材挤出速度的流速均方差为目标,使模孔出口处型材挤出速度均匀;同时通过对影响型材焊合品质的3个重要工艺参数:挤压速度、模具预热温度和坯料预热温度进行正交试验,以焊合面上的压力大小作为评定型材焊合品质好坏的标准,获得了AA6063铝型材挤压的最佳工艺参数组合。