押出ブロー成形法におけるパリソン形成過程の数値解析
Numerical Analysis of Parison Formation Process in Extrusion Blow Molding
谷藤眞一郎・滝本淳一・小山清人
Tanifuji, Shin-ichiro / Takimoto, Jun-ichi / Koyama, Kiyohito
In the present study, a mathematical model employing the K-BKZ integral type viscoelastic constitutive equation was developed for a numerical analysis of the parison formation process in extrusion blow molding. The parison shape is controlled by the two competing influences of swell and draw-down. This mathematical model was made on the assumptions that swell and draw-down contributions could be separately considered and simply added in order to avoid elaborate computations. The swell phenomena was estimated by a steady state viscoelastic flow analysis using a streamline finite element method. On the other hand, the draw-down was modeled in terms of the uniaxial extension that could be analyzed by an unsteady numerical technique. To evaluate the capability of the present model, firstly, steady sate annular die swell simulations were carried out using the flow characteristics of high density polyethylene (HDPE) resin. By a modification of the model prediction for the elongational viscosity at high stretching rates beyond the experimental range, the calculated swell ratio was in reasonable agreement with the experimental data. Secondly, unsteady numerical simulations were performed for the extrusion experiment with HDPE and polycarbonate (PC) under conditions of severe draw-down. In the HDPE extrusion simulation, there was good qualitative agreement between numerical results and the experimental data for time-dependent effects on the parison shape. The good model fitting of the elongational viscosity for the PC extrusion simulation yielded a good prediction of the parison length as a function of the extrusion time.
Key words: Numerical analysis / Parison formation / K-BKZ viscoelastic model / Swell / Draw-down Numerical analysis / Parison formation / K-BKZ viscoelastic model / Swell / Draw-down