Case Studies

Polymer/Solid Interface Friction

Friction between amorphous polyethylene (PE) and a graphite wall have been calculated using full atomistic molecular dynamics.

Figure 1 shows the model overview. The J-OCTA system modeler was used to create the interface model. Carbon is drawn in white and hydrogen is drawn in blue. The X-axis and Y-axis represent the periodic boundary. The Z-axis represents the reflective boundary at the relaxation calculation time. Then after relaxation, the atoms at the top of the PE layer were solidified which created no boundary conditions. Temperature was set to 100 K, making the PE form a glass state.

For the graphite wall, the entire wall was moved at a constant speed toward the interface along the X-axis. The migration speed was set to 2.5 m/sec.


Figure 1 Interface Model of PE and Graphite Wall

Figure 2 shows the stress, which moving horizontally along the interface placed on the surface atoms of the graphite wall. A positive stress is set in the opposite direction of the moving wall. Average values are expressed with the dotted line.

Thus, the friction coefficient in microscale can be calculated from the above calculations using the stress placed on the wall both horizontally and vertically.


Figure 2 Changes in Horizontal Pressure Over Time of the Interface on the Wall Surface


Reference
[1] A. P. Awasthi, D. C. Langoudas and D. C. Hammerand, Modeling Simul. Mater. Sci. Eng. 17 (2009) 015002





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