Analysis and design of smart mandrels using shape memory polymers

Based on the thermomechanical mechanism of shape memory polymers (SMPs), the three-dimensional thermomechanical constitutive equation that can be used in the ABAQUS finite element simulation was derived. Then this paper compiled UMAT subroutine and simulated the thermomechanical behaviors of SMP smart mandrels. In addition, the properties of shape fixity and shape recovery ratio of SMP were considered in detail. Finally, filament winding experiments were proceeded on bottle-shaped and air duct-shaped mandrels and the simple and efficient demoulding of SMP mandrels were verified. The results showed the feasibility of SMP as the smart mandrels from practical application in the future.     

无心轴托辊管体的旋压成形工艺分析

根据目前带式输送机有心轴托辊存在的问题，设计了一种用旋压工艺制造无心轴托辊的方法，研究了无心轴托辊管体的旋压成形过程，分析了其旋压过程中旋压温度、旋压轨迹、旋压道次、旋压速度和旋压变形力等工艺参数的影响。通过实验，给出了无心轴托辊管体的旋压过程中工艺参数的确定方法和数值。     

Φ159 mm FQM三辊连轧管机组主要设备特点

介绍了攀钢集团成都钢铁有限责任公司Φ159mmFQM三辊连轧管机组的工艺、主要设备组成、特点和基本参数。三辊孔型封闭性好,金属变形更均匀;荒管的壁厚及外径精度显著提高,轧制出的钢管表面更光洁;三辊孔型接触面积小,轧制压力降低,孔型过或欠充满现象大大减少,使轧制薄壁管和难变形钢种的能力提高。封闭良好的孔型可避免或减少管端折叠和飞刺的形成,减少张力减径前的切尾长度甚至可省去张力减径前的切尾工序,提高金属收得率和轧制的稳定性。     

硫化物对冷辗芯辊疲劳裂纹萌生的影响

硫化物夹杂对疲劳裂纹源萌生的影响有正负二重性。本文分析硫化物形状、尺寸、分布和力学性能对高速钢W6Mo5Cr4V2冷辗芯辊疲劳断裂的作用,认为质软硫化物能够减缓硬脆非金属夹杂物对基体产生的嵌镶应力,阻止疲劳裂纹的萌生。     

Ф159mm热轧无缝钢管厂穿孔机顶杆脱出装置的设计

针对某厂Ф159mm热轧无缝钢管生产线投产以来,顶杆脱出装置的夹送链装置频繁出现断裂故障、严重影响正常生产的问题,提出了一种不做过大的改变,把夹送链改为夹送辊的设计方法,简单而有效地达到工作稳定的目的,收到了良好奇的效果。     

Microstructure and Properties of Copper Tube During Three-Roll Planetary Rolling

During three-roll planetary rolling, the microstructure of copper tube with initial columnar grains develops into an equiaxed grain structure due to the large rolling deformation and high rolling temperature. The microstructure of copper tubes significantly influences formability and properties due to the three-roll planetary rolling operation. It is very important to understand the microstructural evolution for such special processing. It was found that dynamic recrystallization occurred at the concentrating deformation zone, followed by rapid grain expansion that gradually stabilized. Corresponding with the transformation of microstructure, the hardness of the tube billet reduced gradually away from the roller’s concentrating deformation zone. The changing of roller velocity is responsible for the extreme evolution of the microstructure in the concentrating deformation zone. Therefore, the properties of copper tubes can be controlled by concentrating the deformation zone. This research can facilitate the application of planetary rolling to the manufacture of tubes for low formability materials.     

卷取机卷筒的静态应力变形分析

笔者应用有限元软件对卷取机卷筒进行静态应力和变形分析,以及卷重与卷筒应力变形的关系,研究影响卷筒使用寿命的主要因素,并对卷筒结构进行了改进.     

水平上调式三辊卷板机卷圆成形控制系统设计

针对目前三辊卷板机由于液压系统驱动导致的定位精度低、卷圆精度不高、运行过程不稳定等问题,在三辊卷圆成形工艺及水平上调式三辊卷板机结构的基础上,建立下辊上升量与卷制半径、板材厚度与材料属性之间的数学模型。利用该数学模型及光栅尺反馈的下辊位置,建立了下辊定位闭环系统,开发了以西门子S7-1200为主控制器的控制系统。试验结果证明:该控制系统实现了对下辊定位的精确控制,通过伺服电机驱动下辊升降提高了卷圆的成形精度及工作效率。     

钢管步进式冷床齿形设计方法及其应用

介绍了Ф159mm连轧管机组步进式冷床的生产工艺及其动作原理,推导出一套适用于该类型冷床齿形设计的公式。利用该公式可从理论上和设计实例上优化冷床齿形设计,并可借助Excel表格进行齿形验算分析,既方便又快捷。     

Effect of vibration extrusion on the structure and properties of high‐density polyethylene pipes

BACKGROUND: The axial strength of a plastic pipe is much higher than its circumferential strength due to the macromolecular orientation during extrusion. In this work, a custom‐made electromagnetic dynamic plasticating extruder was adopted to extrude high‐density polyethylene (HDPE) pipes. A vibration force field was introduced into the whole plasticating and extrusion process by axial vibration of the screw. The aim of superimposing a vibration force field was to change the crystalline structure of HDPE and improve the molecular orientation in the circumferential direction to obtain high‐circumferential‐strength pipes. RESULTS: Through vibration extrusion, the circumferential strength of HDPE pipes increased significantly, and biaxial self‐reinforcement pipes could be obtained. The maximum increase of bursting pressure and tensile yield strength was 34.2 and 5.3%, respectively. According to differential scanning calorimetry and wide‐angle X‐ray diffraction measurements, the HDPE pipes prepared by vibration extrusion had higher crystallinity, higher melting temperature, larger crystal sizes and more perfect crystals. CONCLUSION: Vibration extrusion can effectively enhance the mechanical properties of HDPE pipes, especially the circumferential strength. The improvement of mechanical properties of HDPE pipes obtained by vibration extrusion can be attributed to the higher degree of crystallinity and the improvement of the molecular orientation and of the crystalline morphology. Copyright © 2008 Society of Chemical Industry