Abstract
Understanding the properties of polymer–metal interfacial friction is critical for accurate prototype design and process control in polymer-based advanced manufacturing. The transient polymer–metal interfacial friction characteristics are investigated using united-atom molecular dynamics in this study, which is under the boundary conditions of single sliding friction (SSF) and reciprocating sliding friction (RSF). It reflects the polymer–metal interaction under the conditions of initial compaction and ultrasonic vibration, so that the heat generation mechanism of ultrasonic plasticization microinjection molding (UPMIM) is explored. The contact mechanics, polymer segment rearrangement, and frictional energy transfer features of polymer–metal interface friction are investigated. The results reveal that, in both SSF and RSF modes, the sliding rate has a considerable impact on the dynamic response of the interfacial friction force, where the amplitude has a response time of about 0.6 ns to the friction. The high frequency movement of the polymer segment caused by dynamic interfacial friction may result in the formation of a new coupled interface. Frictional energy transfer is mainly characterized by dihedral and kinetic energy transitions in polymer chains. Our findings also show that the ultrasonic amplitude has a greater impact on polymer–metal interfacial friction heating than the frequency, as much as it does under ultrasonic plasticizing circumstances on the homogeneous polymer–polymer interface. Even if there are differences in thermophysical properties at the heterointerface, transient heating will still cause heat accumulation at the interface with a temperature difference of around 35 K.
Highlights
Polymer–metal interfacial friction has been widely exploited in the advanced molding of plastic materials as a typical functional heterogeneous interface behavior
The interfacial heating rate increases with increasing loading pressure
Polymer–metal interfacial friction characteristics under ultrasonic plasticizing conditions were investigated by united-atom molecular dynamics (UAMD) simulation
Summary
Polymer–metal interfacial friction has been widely exploited in the advanced molding of plastic materials as a typical functional heterogeneous interface behavior. For example, can be successfully conveyed in the plasticizing unit of injection/extrusion molding machines by customizing the interfacial friction between the barrel and the screw [1,2]. Interfacial friction in UPMIM plasticizing units has aroused researchers’ curiosity to understand the quick heat generating mechanism [11–17]. Michaeli et al [15] investigated the heating mechanism during ultrasonic plasticization using theoretical analysis and determined that heat generation was mostly due to polymer damping characteristics and polymer–polymer interfacial friction. Li et al [16] employed finite element modeling to investigate the effect of process factors on the interface heat generation rate, concluding that the effect of ultrasonic amplitude on the transient heat generation of interfacial friction was more significant
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