Water-projectile-assisted injection molding (W-PAIM) is a novel molding process for plastic pipes with complicated shape. It utilizes high-pressure water as a power to push a solid projectile to penetrate through the melt to form a hollow space. In order to investigate the penetration behavior of the projectile during the water injection stage of W-PAIM process, numerical simulation of the water injection stage of a W-PAIM pipe with straight and curved segments was carried out. A turbulent flow for the driving water was considered in the motion equation, and the dynamic mesh technology was used to deal with the moving solid projectile. The simulation results, including RWT and the flow fields, were compared with those of water-assisted injection molding (WAIM) pipe with the same outer dimensions. It was found that the residual wall thickness (RWT) of the W-PAIM pipe is much thinner than that of the WAIM pipe. The projectile has a crucial influence on the RWT. The pressure fields of W-PAIM and WAIM are very similar in both straight and curved segments. The velocity field and strain rate field near the penetration front in W-PAIM are quite different from those in WAIM due to the drag flow caused by the projectile penetration.

中文翻译：

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水弹辅助注射成型工艺注水阶段弹丸穿透行为的数值模拟

水弹辅助注射成型（W-PAIM）是一种用于复杂形状塑料管材的新型成型工艺。它以高压水为动力，推动实心弹丸穿透熔体，形成中空空间。为研究W-PAIM工艺注水阶段弹丸的穿透行为，对W-PAIM直管段和弯管段注水阶段进行了数值模拟。运动方程考虑了驱动水的湍流，采用动态网格技术处理运动的固体弹丸。将包括 RWT 和流场在内的模拟结果与具有相同外部尺寸的水辅助注射成型 (WAIM) 管的模拟结果进行了比较。发现W-PAIM管的残余壁厚(RWT)比WAIM管薄得多。弹丸对 RWT 有至关重要的影响。W-PAIM 和 WAIM 的压力场在直线段和曲线段都非常相似。由于弹丸穿透引起的阻力流，W-PAIM 中穿透前沿附近的速度场和应变率场与 WAIM 中的有很大不同。