Effect of Temperature and Ram Speed on Isothermal Extrusion for Large-size Tube with Piece-wing

Heat energy change during the extrusion of 7075 aluminium alloy large-size tube with piece-wing in a container was analyzed. Extrusion load vs ram displacement diagrams and exit temperature vs ram displacement diagrams at various speeds were obtained by 3D FEM simulation. Results show that the exit temperature becomes higher as the ram speed and displacement increase. For large-size tube with piece-wing, there is certainly a curve of ram speed decreasing with increasing ram displacement, which enables isothermal extrusion to be achieved. Therefore,an attempt was made to divide the working stroke into five different zones. Each of them has a preset speed that decreases from the ram displacement beginning to the ending. And then, new exit temperature vs ram displacement diagram was obtained by 3D FEM simulation for the five different speeds. It is shown that the variation of exit temperature is very small. Through the above research, a basic method for realizing isothermal extrusion of 7075 large-size tube with piece-wing was obtained, that is, the working stroke was divided into several different zones with a decreasing speed during extrusion, each zonest speed was real-time adjusted on the feedback signal of exit temperature by proportional hydraulic valve through closed-loop control. The engineering experiment verification was carried out on 100 MN aluminium extrusion press with oil-driven double action. The experimental results of the exit temperature agrees with the simulation ones. The achievements of this study may serve as a significant guide to the practice of the relevant processes, particularly for isothermal extrusion. The verified method has been used in the design and manufacture of 125 MN aluminium extrusion press with oil-driven double action.

Experimental investigation and numerical simulation of large-sized aluminum tube extrusion forming

Large-sized aluminum tube has big section effect, aspect ratio and thin thickness, so that the extrusion technology is complex and the large specific pressure is generated in extrusion cavity. The temperature variation and velocity effect is difficult to control. The extrusion forming of large-sized aluminum tube was researched and simulated. Three-dimensional thermo-mechanical coupled finite element model was constructed and appropriate boundary conditions were given out. The results show that large-sized aluminum tube can be formed by isothermal extrusion through controlling the extrusion velocity and founding the relationship between extrusion velocity and extrusion temperature.

Rotating extrusion technique and its effect on quality of aluminum alloy thin-plate weldments

A new technique named rotating extrusion was proposed that uses rotating extrusion action to rectify residual distortion of aluminum alloy thin-plate weldments to improve mechanical properties of welded joints. The basic principle and device of rotating extrusion were introduced. The residual distortion and stresses in rotating extrusion weldments were compared with those in conventional weldments. The differences in microstructure and mechanical properties between conventional welded joints and rotating extrusion welded joints were investigated and analyzed in order to make clear the effect of rotating extrusion on the performance of aluminum alloy weldments. Experimental results show that rotating extrusion can enhance the hardness and tensile strength of aluminum alloy welded joints evidently. This method has also potential effect on extending the life of welded structures.

Reducing residual distortion of thin-plate weldments by rotating extrusion

A new method named rotating extrusion was developed to mitigate residual distortion of thin-plate weldments. The basic principle and characteristic of rotating extrusion as well as an efficient rotating extrusion device were introduced. Systematic trials were conducted to investigate the influence of several technological parameters including the distance between the extrusion tool and welding torch, the pressure acting on weldment, the dimension of the extrusion tool and its rotational speed on distortion control effect. Experimental results show that, as for 2A12T4 aluminum alloy weldment with 2 mm in thickness, 150 mm in width and 350 mm in length, when appropriate technological parameters are adopted, rotating extrusion can reduce its buckling deflection to below 3% of the original value. Implementing rotating extrusion during welding with an extrusion tool more than 100 mm away from the welding torch may achieve better distortion mitigation effect.

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.

Plate方程指数吸引子的存在性

主要研究了在光滑边界?Ω的有界区域上Plate方程指数吸引子的存在性,在前人研究的基础上,在相空间E0上运用Lipschitz连续及离散的挤压性条件,证明了Plate方程指数吸引子的存在性.

混合多策略MHSSA智能优化风电拉挤板生产排程

针对带序列相关调整时间和顺序齐套约束的风电拉挤板生产排程问题,构建了最小化设备负荷偏差、交货期偏差和最大化设备利用率的多目标优化模型,改进并设计了基于Pareto寻优和拥挤度计算机制的多目标启发式麻雀搜索算法(multi-objective heuristic sparrow search algorithm, MHSSA)。算法具有“组件-区域”两层编码方式和“倒排-修复-优化”启发式解码算子;采用多规则结合反向学习的改进种群初始化策略,增强了全局搜索能力;利用具有交叉算子和外部存档扰动机制的改进搜索策略,提升了寻优精度和种群多样性。通过数据集测试和实例仿真分析,验证了排程优化模型和智能排程算法的有效性。

热处理对钛铝复合板共挤压界面结合特性的影响

钛铝复合板已经在很多领域得到广泛应用,共挤压技术是制备钛铝复合板的一种重要方法,但界面结合强度是制约其性能发挥的关键因素。本文通过热处理工艺对钛铝复合板进行研究,探讨热处理温度对复合板界面结合特性的影响。

6005A铝合金中厚板在线挤压工艺

进行6005A铝合金中厚板在线和离线挤压工艺试验,根据6005A铝合金内控成分与时间-温度-性能曲线,确认对应的淬火敏感区间,在不同的淬火敏感区间采用不同的淬火方式,进而优化6005A铝合金中厚板在线挤压工艺,使中厚板产品从离线生产转为在线生产,减少了工序,提高了成材率、生产效率,降低了工时,节约了成本。

Effect of Extrusion Combination Types on Microstructure and Mechanical Properties of the AZ31/GW103K Bimetallic Composite Plates

The AZ31/GW103 K bimetallic composite plates were prepared by co-extrusion of different combination types(sandwich extrusion type and double semicircle extrusion type),and effects of different extrusion combination types on the microstructure and mechanical properties of bimetallic composite plates were systematically investigated.The results show that both the AZ31/GW103 K bimetallic composite plates prepared by different extrusion combination types have good metallurgical bonding,and changing the combination type does not affect the thickness of the interfacial transition layer of composite plates.Compared with the monolithic AZ31 and GW103 K extruded plates,co-extrusion can promote the dynamic recrystallization(DRX)of AZ31 and GW103 K components in composite plates,and double semicircular extrusion type has a better promotion effect on the DRX than sandwich extrusion type.In addition,the texture of AZ31 in both monolithic AZ31 and AZ31/GW103 K/AZ31(A/G/A)plates is a typical(0002)basal texture,while that in the AZ31/GW103 K(A/G)composite plate shifts to the tangent direction(TD)of extruded plate.Compared with the monolithic AZ31 extruded plate,both the yield strength and tensile strength of A/G and A/G/A bimetallic composite plates are significantly improved.The strength of A/G/A composite plate is higher than that of A/G composite plate,but its elongation is worse.Meanwhile,co-extrusion reduces the dislocation density of AZ31 and GW 103 K components in composite plates,and different extrusion combination types also affect the dislocation density.

华北板块东部中生代构造变形与盆地格局

华北板块东部印支和燕山期构造演化差异、盆地分布格局变迁及其空间叠合关系是中国东部构造变化的结果。中生代期间 ,郯庐断裂带应对应依兰—舒兰断裂带 ,它们与兰考—聊城—盐山 -台安—大洼 -敦化 -密山断裂带呈共轭关系。两断裂带将华北板块东部分割为多个三角块体 ,三角块体的构造演化与陆内壳下拆沉和壳内挤出逃逸构造有关 ,并控制了华北东部燕山期高原隆升及岩石圈减薄。

薄壁空心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到至关重要的作用,直接影响挤压产品的质量。然而在实际生产中,挤压模具的设计更多依赖设计师的经验,模具设计质量难以保证,需要多次试模和修模。采用基于ALE算法的HyperXtrude软件针对某一复杂薄壁空心型材的挤压过程进行数值模拟,分析模具型腔内材料的流动规律及成形机理;根据初始模具设计的不足,提出在下模开设二级焊合室和增设阻流坎两种优化设计方案,有效地解决了初始模具设计中速度分布不均的问题。在优化方案中,型材截面上的温度分布和应力分布更加均匀,焊缝质量相比初始模具设计有较大改善。利用数值方法可对模具结构进行优化,提出的开设二级焊合室和增设阻流坎的模具设计结构可为同类铝型材挤压模具设计提供指导。

塑料板材挤出口模流道系统的一种设计

根据聚合物加工流变学理论，采用表征值方法，在对衣架式口模缝型截面的流道分配系统进行分析基础上，提出了缝型截面歧管结构的设计计算公式。

用旋转挤压方法控制薄板的焊接变形

提出了旋转挤压控制薄板焊接变形的新方法,它是利用特定形状的挤压头对焊缝及近缝区金属进行旋转挤压,产生拉伸塑性应变,减小甚至抵消残余压缩塑性应变,以此来消除焊接残余变形。该方法处理后的焊道表面平整光滑,减小了应力集中。结果表明,旋转挤压法能将薄壁构件焊接变形降到非常低的水平,选择适当的工艺参数,该方法能将焊接残余变形控制在常规焊接状态的3%以下。旋转挤压控制薄板焊接变形的效果与多个工艺参数有关,只有当各个工艺参数取值适当且匹配良好时,才能取得良好的焊接变形控制效果。

随焊旋转挤压控制薄板焊件应力变形新方法

提出随焊旋转挤压(Welding with trailing rotating extrusion,WTRE)控制薄板焊件残余应力和变形新方法,其工作原理为:通过一工作端为圆柱状的挤压头跟随电弧对焊缝区金属进行旋转挤压,延展焊后变短的焊缝及近缝区金属,降低该部位的纵向残余拉应力水平从而达到减小焊接变形的目的。该方法设备简单,容易实现自动化,工作时噪声小。试验结果表明:WTRE法可以显著降低薄板焊件的残余应力和变形,在合适的工艺参数下,能够将2mm厚2A12T4铝合金焊件的残余变形降低到常规焊件变形量的4%以下。

挤扩支盘桩的试验研究

挤扩支盘桩是近年开发出来并已投入使用的一种新桩型 ,在我国河南、河北、山东等地应用较多 ,并取得了很好的经济效益。本文介绍了挤扩支盘桩的成桩方法和工作原理 ,通过对试验桩桩周土的开挖取样做室内土工试验 ,得出挤扩分支盘挤压应力对桩周土挤密效应所引起的土干密度的变化规律 。

对中国大陆构造格架的讨论

大陆动力学的理论与研究开启了人们一个新的思路:在确认中国大陆构造格架、划分构造单元时,除了前寒武纪基底、南华—印支期生物地层格架以外,不能不考虑中-新生代以来重大的陆内变形事件所产生的陆内变形(大型走滑断裂、推覆构造、挤出构造)对印支与前印支期所形成大陆构造格架大幅度的改造,因此对前印支期构造单元的性质需要通过构造复位来重新认识。通过构造复位认为:阿拉善、中祁连—柴达木、北羌塘等微陆块和塔里木板块是一个整体的克拉通——西域板块,不存在整体的昆(仑)—祁(连)—秦(岭)海洋板块,早古生代满加尔—北祁连坳拉槽-小洋盆和晚古生代东昆仑—阿尼玛卿—金沙江裂陷洋盆可能是由古特提斯洋脊楔入所引起的,类似于现今的红海—亚丁湾。本文拟从阿拉善、北羌塘地块的构造归属、西域板块的确认;中国境内北亚构造域的构造划分和晚侏罗—早白垩世陆内变形、中亚挤出构造;中朝与扬子—华南板块划分和南北黄海、朝鲜半岛的构造归属等方面,来讨论有关中国及邻区大陆构造格架的一些争议问题。

挤扩支盘桩在非饱和土体中的挤密效应探讨

介绍了挤扩支盘桩的成桩方法和工作原理 ,通过对试验桩桩周土的开挖取样做室内土工试验 ,得出挤扩分支盘挤压应力对桩周土的挤密效应所引起的土干密度在水平和竖直方向的变化规律 ,发现最大干密度可提高 2 0 %以上 ,并提出了挤密效应综合影响系数的概念 ,建议设计时可适当考虑支盘底部土体承载力的提高 。

塑料板材和吹塑型坯挤出口模设计的一种改进(Ⅱ)考虑歧管斜率的影响

基于第 (Ⅰ )部分表征值方法在大尺寸比挤出口模设计计算的成功应用 ,本文考虑歧管斜率的影响 ,根据在扇形狭缝区内熔体等压线平行于模唇的流动模式 ,对缝型截面歧管系统的设计计算公式进行修正 ,克服了由于忽略歧管斜率影响而产生的流动不均匀性 ,通过与试验数据对比证明了歧管系统设计计算公式的正确性。并对第(Ⅰ )部分和本部分的两种流动模式的等效性从理论上给予了证明。

挤压力对过共晶高铬铸铁半固态挤压件内部质量的影响

采用倾斜板式流变挤压成形工艺制备过共晶高铬铸铁半固态挤压件,重点研究了挤压力对半固态挤压件内部质量的影响。结果表明,挤压力较小时,挤压件内部易形成较大的缩孔、缩松,其初生M7C3型碳化物不易长大,平均横截面直径较小;挤压力较大时,挤压件内部形成缩孔、缩松的几率大大减小,但其初生M7C3型碳化物易于长大,平均横截面直径较大,对挤压件的性能影响较大。挤压力为20MPa左右可制备出性能较优异、内部质量较好的半固态挤压件。