Abstract
Although numerical simulation accuracy makes progress rapidly, it is in an insufficient phase because of complicated phenomena of the filling process and difficulty of experimental verification in high pressure die casting (HPDC), especially in thin-wall complex die-castings. Therefore, in this paper, a flow visualization experiment is conducted, and the porosity at different locations is predicted under three different fast shot velocities. The differences in flow pattern between the actual filling process and the numerical simulation are compared. It shows that the flow visualization experiment can directly observe the actual and real-time filling process and could be an effective experimental verification method for the accuracy of the flow simulation model in HPDC. Moreover, significant differences start to appear in the flow pattern between the actual experiment and the Anycasting solution after the fragment or atomization formation. Finally, the fast shot velocity would determine the position at which the back flow meets the incoming flow. The junction of two streams of fluid would create more porosity than the other location. There is a transition in flow patterns due to drag crisis under high fast shot velocity around two staggered cylinders, which resulted in the porosity relationship also changing from R1 < R3 < R2 (0.88 m/s) to R1 < R2 < R3 (1.59 and 2.34 m/s).
Highlights
The high pressure die casting (HPDC) process has the characteristics of high speed filling and high pressure solidification, which promotes it to become one of the main manufacturing processes of complicated thin-wall components [1]
The filling process observed under the injection velocity of 2.34 m/s is taken as an example to study the difference in flow pattern between the actual filling process and the numerical simulation results
The significant differences start to appear in the flow pattern between the actual experiment and the Anycasting solution after the break-up and disintegration process takes place
Summary
The high pressure die casting (HPDC) process has the characteristics of high speed filling and high pressure solidification, which promotes it to become one of the main manufacturing processes of complicated thin-wall components [1]. Cao et al [6] used the gas-liquid multiphase flow model to predict the air entrainment phenomenon during the die casting filling process of zinc alloy, and the volume of fluid (VOF) was used to track free surface. The water analogue experiment is the most common method of experimental fluid mechanics to observe the filling process and to validate the numerical predictions [6,7,8,11,12]. These experiments are designed according to dynamic similarity [13,14], water is not the actual melt. The porosity of die-castings is predicted at different locations according to the actual filling process
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