Numerical study on the effect of gas layer width on the gas-assisted extrusion forming of plastic pipes

To study the effect of the gas layer width on the gas-assisted extrusion forming of plastic pipes, we established 2D models of gas-assisted extrusion forming of plastic pipes based on two phase fluid model. In the geometric models, four different widths of gas layers were used. Under the same boundary conditions and material parameters, the numerical results about the effect of gas layer width on the extrusion forming of plastic pipes were obtained by the finite element software Polyflow. In the numerical simulations, the non-isothermal effect and gas compression effect were also considered. Numerical results show that the gas layer width has great impact for the gas-assisted extrusion forming of plastic pipes, the flow velocities of melt at X and Y direction, first normal stress difference increase with the gas width. It is demonstrated that the flow behaviours and stresses of melt can be greatly influenced by the gas layer. Therefore, in practice, the reasonable controlling of the gas layer width is one of most important factors of impacting the stability and quality of gas-assisted extrusion forming of plastic pipes. (paper)