分流组合模挤压铝合金口琴管的数值模拟

采用刚粘塑性有限元法,在DEFORM-3D有限元商业软件上成功实现了铝合金口琴管分流组合模挤压过程的三维数值模拟,获得了分流组合模挤压过程中材料的流动规律,挤压力、应力场、应变场和温度场的分布,以及模具出口处金属流速的分布情况。通过数值模拟发现,型材出口流速不均匀,造成端面不齐,对此,提出了模具修改方案,通过调节模具工作带的长度,实现了型材挤压出口流速均匀的目的,从而保障了型材的产品质量。模拟结果为模具的优化设计及工艺参数的选取提供了理论参考。     

CPU散热片挤压过程的数值模拟及模具优化

采用刚粘塑性有限元法,利用Deform-3D有限元软件实现了铝合金CPU散热片导流模挤压过程的数值模拟。获得了挤压过程中材料的流动规律、挤压力、模具应力以及模具出口处流速的分布。通过数值模拟发现,型材出口流速很不均匀,远离型材中心的散热片齿部流速过慢。通过对导流模结构的调节,使得型材出口流速基本均匀,模具应力降低,提高了模具的使用寿命。模拟结果为导流模优化设计提供了依据。     

铝材长方形空心管挤压过程数值模拟与模具结构优化设计

对AA1100铝材长方形空心管的挤压过程使用数值分析软件SuperForge进行数值模拟。在挤压生产中,金属流出工作带时的流速均匀性是得到高质量型材的关键。在挤压生产中通常采用几种方法修改模具,消除流速不均,例如修改分流孔的大小、形状和位置分布,修改工作带长度和焊合室形状尺寸等。本文通过数值模拟发现在长方形空心管挤压的初始模具设计中型材截面流速不均匀,造成端面不平。对此,提出了三种模具修改方案,并分别对其进行了数值模拟,经过分析比较确定了最佳模具设计方案,由此方案可以生产出合格的挤压件。     

Optimal extrusion die design to achieve flow balance

The design of a plane strain two-hole extrusion die is presented. This design example can be considered as a test case to judge the usefulness of the present method in the design of extrusion dies for uniform exit flow. Bearings for this die are to be designed so that the material exits both holes with parallel balanced flow. The finite-element method combined with techniques of mathematical programming is adopted. Derivatives of the objective function used during the optimization phase are efficiently computed using analytical sensitivity analysis and an optimal bearing length is reached after few iterations of the optimization procedure. Available experimental data for a two-out extrusion die with bearings have been used to validate the numerical results.     

FEM simulation of aluminum extrusion process in porthole die with pockets

In order to investigate the effects of pockets in the porthole die on the metal flow, temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in the lower die. Two different multi-hole porthole dies with and without pockets in lower die were designed. And the extrusion process was simulated based on the commercial software DEFORM-3D. The simulation results show that the pockets could be used to effectively adjust the metal flow and especially benefit to the metal flow under the legs. In addition, the maximum temperature at the die bearing and the peak extrusion load decrease, which indicates the possibility of increasing the extrusion speed and productivity.     

铝型材出口速度分布的数值模拟

铝型材挤压过程中的出口速度,是模具优化设计的重要参数之一,型材出口速度不均的原因之一是模具设计不当。为了获得高质量的挤压制品,对模具出口区域速度分布的研究是必须的。本文采用DEFORM3D对铝型材进行了3D模拟,获得了在模具制造之间铝型材的出口速度。数值模拟的结果得到了实验的验证,这对优化模具过程是非常重要的。     

基于有限体积法的异形空心型材挤压模具设计

采用有限体积法,对异形空心铝合金型材挤压过程进行数值模拟,得到了挤压过程中材料流动速度场、应力场、应变场、温度场和挤压力的分布规律。以数值模拟结果为依据,针对模具设计存在的问题提出了解决方案,并通过分析得到了模具的最佳设计方案。结果表明：对于薄壁、结构复杂的异型空心型材,挤压模具设计的关键是合理地分配金属流量和平衡金属的流动速度。     

Mathematical model of determination of die bearing length in design of aluminum profile extrusion die

Based on the finite element simulation of profile extrusion process, the effect of local extrusion ratio, die bearing area and the distance between extrusion cylindrical center and local die orfice center on mental flow velocity was investigated. The laws of deformed metal flow on profile extrusion process were obtained. The smaller the local extrusion ratio, the faster the metal flow velocity； the smaller the area of die bearing, the faster the metal flow velocity； the smaller the distance of position of local die orifice(the closer the distance of position of local die orifice from extrusion cylindrical axis), the faster the metal flow velocity. The effect of main parameters of die structure on metal flow velocity was integrated and the mathematical model of determination of die bearing length in design of aluminum profile extrusion die was proposed. The calculated results with proposed model were well compared withthe experimental results. The proposed model can be applied to determine die bearing length in design of aluminum profile extrusion die.     

FE analysis of extrusion defect and optimization of metal flow in porthole die for complex hollow aluminium profile

To solve the defects of bottom concave appearing in the extrusion experiments of complex hollow aluminium profiles, a 3D finite element model for simulating steady-state porthole die extrusion process was established based on HyperXtrude software using Arbitrary Lagrangian–Eulerian (ALE) algorithm. The velocity distribution on the cross-section of the extrudate at the die exit and pressure distribution at different heights in the welding chamber were quantitatively analyzed. To obtain an uniformity of metal flow velocity at the die exit, the porthole die structure was optimized by adding baffle plates. After optimization, maximum displacement in the Y direction at the bottom of profile decreases from 1.1 to 0.15 mm, and the concave defects are remarkably improved. The research method provides an effective guidance for improving extrusion defects and optimizing the metal flow of complex hollow aluminium profiles during porthole die extrusion.     

铝型材挤压模工作带的计算机辅助设计

本文提出了一个铝型材挤压模工作带的数学模型，该模型不仅反映了模孔形状对金属流动的影响，而且考虑了模孔位置的影响，根据该模型作者在ＣＡＤＤＳ５上开发了铝型材挤压模工作带的计算机辅助设计系统。实践表明，该系统设计的挤压模工作带能较好地平衡金属流出模孔的速度，减轻型材的歪扭，弯曲，波浪，裂纹等缺陷。     

铝合金空心型材挤压截面内凹变形有限元分析及模具结构优化设计

截面变形是复杂空心型材挤压过程中经常遇到的难题,实际生产中需通过反复试模、修模才能得到合格的产品。针对6063铝合金空心型材截面内凹问题,采用数值模拟方法获得了挤压过程中不同方向上的金属流速及模具焊合室内不同高度的压力分布,分析与讨论了产生缺陷的原因,并优化了模具结构。模拟仿真结果表明,添加阻流块后挤压过程中型材不同位置和不同方向上的流动速度更加均匀,挤出型材向内凹的现象得到改善。实测结果显示,采用改进后的模具结构,挤压型材最大内凹量减小为0.15 mm,可以满足实际应用要求。     

铝合金挤压材“麻面”缺陷产生机制的研究

“麻面”是影响铝合金挤压材表面质量的主要缺陷之一。研究了铝合金挤压材,特别是铝型材在挤压过程中出现的“麻面”缺陷产生的机制、规律及影响因素。结果表明,“麻面”缺陷的产生与合金的本性、挤压工艺参数、模子工作带的表面状况、工作带的形状,特别是模孔出口直径及工作带出口方向的圆角大有关。提出了预防或消除这一缺陷的主要措施。     

A general methodology for bearing design in non-symmetric T-shaped sections in extrusion process

In this study, a general methodology has been developed to design the proper bearing in order to eliminate the curvature of the final product in extrusion process. Three smooth curved (advanced-surface) dies with non-symmetric T-shaped sections and different off-centricities have been studied. For each die, the proper bearing has been designed and physical and numerical modeling have been performed to validate the design. The design procedure is as follows: A formulation, based on Bezier curves, has been used to determine the exit velocity profile. Since the result of Bezier method is different from the actual velocity profile, the Chitkara corrective function has been modified and applied to improve the velocity field. A deviation function has been developed to measure the curvature of the final product in terms of the exit velocity field. Considering the obtained velocity field, the friction effects, and the geometry of the dies, the proper bearing for each die has been designed. Finally, numerical and physical modeling have been performed on the die-bearing combination. According to the results, the curvature of the final product was eliminated to a great extent.     

铝型材挤出速度对模具工作带的影响

铝型材挤出速度对模具工作带的失效有着重要影响。本文利用数值模拟实验,分析了不同出口速度下的模具应力、模具温度和模具工作带尺寸的变化规律。实验表明,随着挤出速度的提高,模具内应力增大,模具温升相对变慢。由于模具工作带附近的应力和温度均较其它部位大,从而使得模具工作带成为挤出模具失效的主要区域。     

一种轴承内外套圈毛坯复合温挤压成形工艺及模具

为了解决目前轴承套圈生产中普遍存在的材料利用率低、生产工序繁多、产品质量低等问题,提出一种轴承内外套圈毛坯的复合温挤压成形工艺和模具。该工艺采用一步复合温挤压成形出含有内外套圈毛坯的挤压件,然后利用两套冲裁模具将挤压件进行分离,得到所需尺寸的内外套圈毛坯。通过有限元模拟复合温挤压过程,结果表明采用上下压料卸料装置并施加合适的压紧力能获得到尺寸精度高、产品质量好的工件。     

铝型材挤压模工作带优化

基于MATLAB平台，将BP神经网络、遗传算法和数值模拟技术应用于铝型材挤压模具参数优化设计。采用三层BP神经网络建立型材挤压模具的数学模型，由正交实验法安排模拟实验组合，采用有限元软件进行挤压过程的数值模拟，并以具有不同工作带尺寸的挤压模具中金属流出模口平面上的Z向质点流速均方差作为模型目标值，将模拟结果作为神经网络的输人样本对训练网络并建立网络知识源，通过遗传算法求得模型的全局优化解；最后通过有限元数值模拟技术验证并比较优化所得工作带与经验法确定的工作带对金属流动均匀性的影响。数值模拟结果表明，本研究对挤压模具工作带的优化是有效的。     

Numerical Simulation and Experimental Study on Porthole Die Extrusion Process of LZ91 Mg-Li AlloyEI北大核心CSCD

Porthole die extrusion is the dominant process to produce hollow profiles due to its high productivity and capacity in producing complex profiles. In this study, the finite element simulation model of porthole die extrusion of LZ91 Mg-Li alloy was established. The effects of extrusion ratio on strain, temperature and flow velocity were studied, and the welding quality was quantitatively evaluated by means of J criterion. The experiments of porthole die extrusion were carried out by varying extrusion ratios. The microstructures of as-cast, homogenized and extruded LZ91 Mg-Li alloy were examined. The results show that the materials near the bridge surface and at the bottom of the bridge have large deformation, while the materials inside the portholes have small deformation. Moreover, with the increase of extrusion ratio, the effective strain of material is increased. Due to the heat generated by plastic deformation and the heat dissipation caused by profile cooling, the temperature of the material on the top of bridge is increased, while that of the material near the die exit becomes lower. The welding quality in the central area of weld seam is lower than that in the edge area of weld seam. With the increase of extrusion ratio, the welding quality is improved. More nucleation is generated in welding zone due to its large strain, resulting in the formation of fine grains. However, the dynamic recrystallization is not complete in the matrix zone, and some coarse grains still remain. Moreover, the material temperature becomes higher with high extrusion ratio, and the phenomenon of grain growth is observed.     

铝质齿轮挤压模设计与数值模拟

对铝质齿轮进行挤压模设计,建立有限元分析模型,获得挤压金属的稳态流动情况,分析速度分布、应力分布和出口位移分布;针对数值模拟结果,对模具提出修改意见,通过修改上模块工作带和下模增加阻流圈的方案,最终加工出来的模具可以生产出合格的产品。     

A deformation model for tube extrusion

Plastic forming processes, the origins of which go back to ancient times, have become more popular in the last five decades, amongst other material-shaping processes. As the needs of the modern world and competition between the processes increase, knowledge of the deformation pattern of the material during a process is being recognized as primary information in the related field. Today, this kind of information is made use of in all areas associated with the process, from the planning of the plant to the ensuring of the quality of the final product.

In this study a deformation model for axisymmetric tube extrusion is proposed, in which the flow lines in the deformation zone are chosen as straight lines passing through a fixed point on the axis of symmetry and the exit surface of the deformation zone which is the plane at the die exit perpendicular to the axis of symmetry. A kinematically admissible velocity field is obtained from this deformation model and the parameter contained in the model is found by introducing this velocity field into the Upper-Bound Theorem. Since there is not a model for tube extrusion in the literature it was not possible to carry out a comparative study, which is why only the results obtained in the study are given, along with the indication of some further research directions.