The previous researches indicate that the entrance effect and the shear effect are the main reasons for die swell of polymer in the steady field.

• 高聚物熔体流动的入口效应和在口模中的剪切作用是导致稳态场中挤出物胀大的主要原因,而振动力场能有效地减小高聚物的挤出胀大比。