铝型材挤出速度对模具磨损程度的影响

基于修正的Archard磨损理论，利用数值模拟技术分析挤压成形阶段模具各个测量点的瞬时温度、压力和速度场的分布，研究挤出速度对模具磨损程度的影响。结果表明：随着铝型材挤出速度的增加，模具各个测量点的磨损量都随之增加；由于模具工作带入口的正压力和温度均较其他部位大，使其磨损量也是最大的，故成为模具失效的主要区域；整个挤压过程有5000个阶段，当挤出速度为10m／min时，P15点的总磨损量为1．45mm，计算结果与实际情况基本吻合，为挤压工艺的制定提供了理论依据和参考。     

基于有限元法的空心铝型材挤压过程瞬态分析

采用有限元软件,对一非对称截面列车上侧梁型材挤压分流、焊合直至稳态挤出的整个非稳态过程进行了数值模拟。着重研究了挤压成形过程中变形体的速度、温度、应变速率等物理场量的分布与变化情况,以及模具应力分布情况。针对模拟过程中出现的挤出物前端存在严重变形的问题,对模具的二级焊合室尺寸、阻流块高度以及工作带尺寸作出优化。模具结构优化后模孔出口截面速度均匀性得到明显改善,其速度差从22 mm·s-1减小到7 mm·s-1。通过分析等效应变速率与温度分布的关系,发现坯料温度升高所需的热量主要来源于坯料变形产生的塑性变形能。通过模具应力分析得知模具在各挤压阶段的应力分布情况。     

基于Deform-3D的异型铝型材挤压模具开裂失效分析与参数优化

对某异型铝型材H13钢挤压模具分流桥早期开裂失效的状况,采用Deform-3D软件分析并进行正交优化试验设计。结果表明,当挤压温度为460℃、挤压速度为30 mm·s-1、摩擦因子为0.6和模具预热温度为450℃时,坯料塑性最差、变形抗力及流动阻力最大,模具主应力超过材料许用应力值导致模具开裂失效。优化挤压温度为500℃、挤压速度为10 mm·s-1、摩擦因子为0.4和模具预热温度为470℃时,模具的最大主应力仅为529 MPa,能够最大可能地避免模具早期的开裂失效。     

汽车转向节凹模失效分析与寿命研究

分析了转向节闭式锻造典型失效模具的断口形貌、模具结构及化学成分,同时研究了模具工作应力状态与表层温度分布对其失效形式的影响.结果表明:模具结构及制坯形状设计不合理,造成失稳和引起应力集中是模具早期失效的主要原因;磨削加工对模具的表面质量有很大的影响,模具表面强烈的局部过热而造成表面烧伤、硬度下降和很高的表面拉应力,引发磨削裂纹,从而严重降低摸具的疲劳强度和断裂抗力,造成模具失效.     

H13热作模具钢失效分析及工艺改进

结合实际生产针对H13热作模具钢分流桥根部过早出现开裂的现象进行研究,利用DeForm-3D有限元模拟软件对分流组合模的挤出过程进行数值模拟,研究了模具不同工作带长度对模具的应力场、金属流动均匀性的影响规律。研究发现,当工作带长度为6 mm、焊合室深度为12 mm时,分流桥根部等效应力最小且应力分布较均匀,坯料在下模工作带出口处的流速也较均匀。研究成果为铝型材热挤出成型用H13钢的模具合理设计提供了有效的理论参数。     

管材挤压模具工作带强化的方法

针对挤压模具工作带易断裂失效的特点,提出了模具结构的改进措施.整体模具结构被改为原模具和加固芯轴两个部分,芯轴采用双楔形结构.采用塑性加工、压力加工的方法,并利用热胀冷缩使加固芯轴和模具结合良好并在界面处具有一定的压应力.通过试模证明,改进过的模具工作带断裂情况消失,模具寿命大幅度提高.     

ALE有限元法在铝型材挤压模具优化设计中的应用

采用了导流板保护结构,短分流桥结构和三级焊合室结构,对一工业用铝合金型材挤压模具进行了设计；运用基于任意拉格朗日-欧拉(ALE)有限元法的专用模块HyperXtrude,模拟了坯料在模具中的稳态挤压过程,并对成形中型材的挤出速度、模具的形变与应力情况进行了分析,验证了其设计方案的合理性.探讨了模具优化方案.通过调整工作带长度和芯部壁厚,实现了对金属流动的控制,获得了合格的型材产品.     

挤压速度对铝型材分流模寿命影响的模拟分析

挤压速度是影响铝型材分流模寿命的主要因素之一。不同挤压速度下,模具所受温度和压力不同,对模具寿命产生直接影响。以矩形管铝型材挤压为例,利用Deform有限元分析软件对挤压过程进行数值模拟,得到不同挤压速度下分流模温度和压力变化情况。结果表明:随挤压速度的增大,分流模各工作部位温度逐渐升高,而所承受压力则先降低后升高。探讨了温度和压力的改变对模具寿命的影响机制,指出挤压速度对模具寿命的影响表现为加速模具各工作部分的塑性变形、磨损和应力集中部位失效,以及加剧挤压模的冷热疲劳现象。     

温差对镁合金压铸模寿命的影响

热交变应力引起的热疲劳失效是镁合金压铸模具失效的主要形式.采用pro/e建立了压铸模具模型,用ABAQUS分析了预热温度与浇注温度之间的温差对其寿命的影响.结果表明:在相同的浇注温度下,随模具预热温度的升高,由热交变应力引起的模具膨胀(或收缩)量会明显减小,即浇注温度和预热温度的差值越小对模具寿命越有利.分析认为,镁合金压铸模具的预热温度应控制在240～280℃之间.     

模具工作带微角度对型材表面挤压纹的影响

主要通过三种不同角度工作带模具挤出型材表面挤压纹的对比试验,探讨了模具工作带微角度变化对工作带粘铝附着层和型材表面挤压纹的影响。建立数学模型,推算出合理的模具工作带微阻碍角,提出了改善挤压纹和提高模具通过量的有效途径。     

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。     

Non-steady FE analysis on porthole dies extrusion of aluminum harmonica-shaped tube

According to the rigid-viscoplasticity finite element method, the porthole die extrusion process of an aluminum harmonica-shaped tube was successfully simulated based on software Deform-3D. The distribution of stress field, effective strain field, velocity field and temperature field during the extrusion process were discussed and the metal flow in welding extrusion was analyzed. The simulation results show that the material flow velocities in the bearing exit are non-uniform with the originally designed die and the forepart of the profile is not neat or even. Aiming at solving this problem, the modification method of die structure was improved. The result shows that the uniform material flow velocities in the die exit and a perfect extruded are obtained by modification bearing length.     

聚合物熔体在L型异型材挤出口模内三维粘弹流动数值模拟~*

利用罚函数有限元法,采用PTT粘弹模型,对聚合物熔体在L型异型材挤出口模内的三维等温流动进行了数值模拟,得出了不同挤出量下的速度和应力分布。结果表明,流速在成型区内并在其入口附近达到其在口模内的最大值;剪切应力在成型区内并在其入口附近明显持续上升,达到其在口模内的最大值后迅速回落;第一法向应力差在过渡区内并在其出口附近达到其在口模内的最大值,此后在过渡区和成型区的结合面两端近距离内急剧下降,因此成型区和过渡区接合处是熔体流动不稳定的发源地;口模内最大剪切应力和最大第一法向应力差均随挤出量的增加而近似呈线性上升,而不会急剧增加。     

振动场作用下聚合物熔体在L型挤出口模内的流动分析

利用ANSYS软件对受口模入口处周期性振动的压力驱动的非牛顿幂律聚合物熔体在“L”形异型材挤出口模内的流动过程进行了三维等温数值模拟,以曲线图、等值线图和等值面图的形式展示了不同条件下的反映流动全貌的速度场、压力场和应力场。结果表明:由于振动场的引入,熔体速度、压力、应力均产生振动,其频率和入口压力的振动频率相同,但振幅从口模入口至出口逐渐衰减,直至消失;压力从口模入口至出口近似线性递减,但在入口附近有一个急剧下降而后又短暂上升的过程,这是因振动的引入而产生的特殊现象。     

导流室设计对薄壁铝型材挤压出口速度的影响

采用基于ALE算法的HyperXtrude软件,模拟薄壁铝合金型材挤压模具导流室各种设计的金属流动情况,分析了各设计参数对金属流速的影响规律,并统计挤出型材断面上挤出方向的流速均方差S.D.作为衡量流速均匀程度的指标。分析结果表明,在设计断面不对称、壁厚不等型材模具时,有时需将型材的质心相对于模具的中心做一定距离的调整。型材断面上各处的壁厚差异和局部质心偏离都对流速有影响,但壁厚差异对于流速均匀程度的影响更大。在模具的型腔内添加阻流块结构,流速均匀程度可大为改善。调节阻流块的宽度、高度、形状、位置等参数,能够完全消除流速不均匀,但如果尺寸调整超过最佳点,流速均匀程度将迅速恶化。根据最优模拟结果对应的设计生产模具,并进行挤压实验,所得型材的尺寸质检合格,模具达到"零试模"要求。     

Effect of deformation speed on the microstructure and mechanical properties of AA6063 during continuous extrusion process

Experiments and numerical simulations were conducted to analyze the continuous extrusion of AA6063 aluminum alloy under extrusion wheel angular velocities of 0.52, 0.78, 1.04 and 1.3 rad/s. Simulation results indicate that variations in extrusion wheel velocity directly affect material deformation and significantly influence the maximum extrusion temperature. This work also reveals that deformation and temperature have opposing effects on the microstructure of the resulting product. A greater wheel velocity causes a higher strain rate and extrusion temperature. Increasing the wheel velocity, at an initially low speed, causes a large increase in strain rate. This results in a decrease in grain size. In contrast, at high wheel velocities, further increases to wheel velocity have much less effect on the strain rate, leading to an increase in grain size as the increased extrusion temperature dominates the mechanics of grain growth. Tensile test results demonstrate that the tensile strength of the resulting aluminum extrusions mainly depends on the exit temperature, which is decided by the deformation speed. Tensile strength and hardness slightly increase with increased deformation speed. Extremely high extrusion temperature results in brittle failure and low mechanical properties of the resulting product when the extrusion speed reaches 1.3 rad/s. This paper suggests that an optimum extrusion wheel velocity, which will generate products with good mechanical properties, exists.     

An innovative extrusion die layout design approach for single-hole dies

To avoid distortion of complex extrudate profiles, it is essential that the exit velocity of the metal is uniform. The most important design parameter that controls the exit velocity is bearing length. However, this factor is not sufficient to achieve optimal design settings. This paper proposes an innovative layout design approach using a geometry based bearing length design methodology to minimise variations in exit velocity. This paper focuses on single hole extrusion dies and develops an optimisation algorithm suitable for any die profile. Since the optimised die design produces less bearing length difference, more uniform exit velocity and higher design quality would be achieved using the proposed approach.     

Effect of extrusion wheel angular velocity on continuous extrusion forming process of copper concave bus bar

The continuous extrusion forming process for producing large section copper concave bus bar under different extrusion wheel angular velocities was studied by three-dimensional finite element technology based on software DEFORM-3D. The rigid-viscoplastic constitutive equation was employed in the model. The numerical simulation results show that the deformation body flow velocity in the die orifice increases gradually with the increase of the extrusion wheel angular velocity. But slippage between the rod and extrusion wheel occurs when the extrusion wheel angular velocity is high. The effective stress near the die orifice enhances gradually with increasing extrusion wheel angular velocity. High stress is concentrated in adjacent regions of the flash gap. The effective strain gradient is greater near the abutment than that near the die orifice. The effective strain of the product increases gradually with increasing extrusion wheel angular velocity. In the deformation process, the deformation body temperature increases remarkably due to friction and deformation. So the cooling is necessary in the region of the die and tools.     

Die land optimization of section extrusion by finite element method

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