Enhanced wear resistance of tire
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Fracture process of rubber materials by Coarse Grained MD on supercomputer
Coarse-grained molecular dynamics (CGMD) was used to analyze the mechanism to improve the wear resistance of tires[1][2]. The target is the dispersion structure of silica particle aggregates in rubber materials, which was constructed using the Reverse Monte Carlo method based on the results of TEM experiments.
Figure 1 (left) shows the structure of the entire region after deformation. The system size is 350 nm to handle the dispersed structure of silica aggregates, which is large for atomistic molecular dynamics. In addition, the calculation requires more than microseconds to handle the deformation and relaxation of polymers in the rubber state. Therefore, coarse-grained model was used. And the calculation is still a large-scale calculation with 140 million particles, so parallel calculations using VSOP were performed on the K computer [2].
Fig. 1 (left) shows that failure occurs at the interface and voids are also observed in the bulk of the rubber (blue area). In addition, it was able to visualize the failure origin point between silica and rubber (Fig. 1 (right)).
Fig. 1. (Left) Overall structure: Interfacial failure between silica aggregates and rubber are shown. And voids are generated in the rubber bulk region. (Middle) Close-up image of a silica aggregate. Rubber molecules can be seen explicitly. (Right) Close-up image of the interface region between silica particle and rubber. [1][2]
Finally, wear-resistant concept tire was developed as shown in Fig. 2, and this technology won the Tire technology Awards 2017.
Fig. 2: Comparing Kow calculated from σ profiles with experimental data.