TECHNICAL ARTICLE the bubble dynamic model proposed by Prof Taki from Kanazawa and the batch ’ s experimental data [ 1 ], the bubbles will surpass the energy barrier to nucleate and grow as the pressure releases . If the pressure on the bubbles increases , the bubbles will gradually shrink until they dissolve back into the melt ( that is , it is back to the initial state of the mixture of melt and gas ). If the pressure is released again at this time , the bubbles will nucleate and grow at the same location . The experimental results also have a very close trend with the bubble dynamic model , verifying the process of bubble shrinkage caused by the pressure imposed ( Figure 3 ).
In the past , when the Han and Yoo model was used to simulate the thinpart geometry , the process of bubble shrinkage could not be accurately predicted . Therefore , the number of bubbles that disappeared due to the increasing pressure was underestimated . Now , in the latest Moldex3D 2021 version , the option of the Modified Han and Yoo model has been added ( Figure 4 ). Compared with the original Han and Yoo model , the modified one can predict the shrinking bubbles more accurately ( Figure 5 ). Similarly , if we apply this modified model in the core-back process , the required packing time for all the bubbles to dissolve back to the melt will be obtained .
The foaming process is very diverse and complicated and is widely applied in various fields . Therefore , it is particularly important to control the changes during the whole process . If we can accurately predict the bubble size through the microscopic model , it will be helpful for further prediction of many macroscopic properties such as heat transfer , mechanical strength , sound absorption , and low dielectric constant . As a result , the product design and production efficiency will be significantly enhanced . z
Figure 4 The Modified Han and Yoo model option has been added in Moldex3D 2021 .
Figure 5 The comparison of the original and Modified Han and Yoo models
Reference [ 1 ] K . Taki et al ., “ 3D Numerical simulation and experimental observation of bubble growth and collapse in Nitrogen-gas saturated molten polymer for the core-back foam injection molding ”, ANTEC ® 2021 – SPE .
5 October 2021 Packaging South Asia
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