Numerical simulation and experimental study on gas⁃assisted extrusion process of U⁃shaped parts

doi:10.19491/j.issn.1001-9278.2022.07.013

Abstract

Abstract:

A die–gas–melt three?phase heat transfer model was established by introducing gas?assisted extrusion into the extrusion process of U?shaped parts. The simulation results indicated that the melt flow velocity was uniform in the same section of the die. The melt temperature field was seldom affected by the outside environment. The melt temperature range varied with the die wall temperature during the conventional extrusion process. The U?shaped parts were prepared through both conventional extrusion and gas?assisted extrusion. In the conventional extrusion， the PP melt could be stretched smoothly under certain technological conditions. However， the melt was affected by gravity in the gas?assisted extrusion molding process. After the extrusion process was balanced， the sample surface was transparent and smooth， and the droop from the die was reduced significantly. The PP composite with 10 wt% glass fiber showed significant extrusion swell in the traditional extrusion process. The fibers were not homogenously distributed on the side wall and bottom of the U?shaped part. The delamination was serious at the corner of the U?shaped part. In the gas?assisted extrusion process， the extrusion swell and the inhomogeneous distribution of fibers on the side wall and the bottom surface were improved， and the fiber delamination at the corner of the U?shaped part were also partially alleviated. The thickness of the U?shaped part became thinner the PP composites with 20 wt% glass fiber. The fiber distribution in the sample was more homogenous， and there was no significant fiber delamination at the corner. However， there was a remarkable fiber emergence on the sample surface， with serious opening deformation on U?shaped parts.

Key words: extrusion forming, fiber orientation, U?shape, gas?assisted extrusion, numerical simulation

CLC Number:

TQ320.66

HUANG Xuemei, LIU Hesheng, HUANG Xingyuan, YU Zhong, JIANG Shiyu. Numerical simulation and experimental study on gas⁃assisted extrusion process of U⁃shaped parts[J]. China Plastics, 2022, 36(7): 93-103.

Figures/Tables 23

Fig.1. Schematic diagram of the gas?assisted extrusion （GAE） forming system

材料

Ⅰ区

温度/

℃

Ⅱ区

温度/

℃

Ⅲ区

温度/

℃

口模

温度/

℃

牵引转速/

r∙min^-1

Tab.1. Experimental materials and temperature parameters

Fig.2. Mesh of melt and die of conventional extrusion

Fig.3. Mesh of melt， gas layer and die of gas?assisted extrusion

Fig.4. Melt velocity of conventional and gas?assisted extrusion

Fig.5. The origin of the coordinates on the melt， the positions of lines L1，L2 and the points

Fig.6. Velocity curve on L 1 line at the exit of conventional extrusion and gas?assisted extrusion

Fig.7. Temperature of die and melt for conventional extrusion at different die temperature

Fig.8. Temperature of die， air cushion layer and melt for gas?assisted extrusion at different temperature

Fig.9. Temperature profile on L2 line for conventional extrusion and gas?assisted extrusion

Fig.10. Temperature curves on L2 line for gas?assisted extrusion at different temperature of die and melt

Fig.11. Shear rate diagram of outlet melt during extrusion

Fig.12. Shear rate diagram on L1 for conventional extrusion and gas?assisted extrusion

Fig.13. Extrusion section

Fig.14. Conventional extrusion

Fig.15. Extrusion at high temperature

Fig.16. Gas?assisted extrusion

Fig.17. PP/10 % glass fiber prepared by conventional extrusion

Fig.18. Sectional view of PP/10 % glass fiber by conventional extrusion

Fig.19. PP/10 % glass fiber by gas?assisted extrusion

Fig.20. Fiber orientation phenomenon in PP/10 % glass fiber extruded parts

Fig.21. PP/20 % glass fiber by gas?assisted extrusion

Fig.22. Fiber orientation phenomenon in PP/20 % glass fiber extruded parts

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