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Naoki Iikawa and Hiroaki Katsuragi
In relation to the interaction of the earth's surface with machines and organisms and its engineering applications, there has been a recent increase in interest in the penetration resistive force into granular materials at shallow depths. Recent studies have proposed the model in which penetration resistive forces into dry granular materials have a coefficient dependent on the angle of repose and increase in proportion to the penetration volume. In these studies, the model has been validated for various geometries such as cylinders, cones and spheres. However, for cones, the model has only been validated under conditions of a tip angle close to the angle of repose. In this study, the effect of cone tip angle on penetration resistive force is investigated under several conditions with different angles of repose. This study carries out cone penetration simulations using the discrete element method. For the cone geometry, this study prepares five tip angles ranging from sharp to blunt. The results show that the penetration resistive force for cones with blunt tip angles is much higher than that computed by the model proposed in previous studies. To solve the discrepancy between the model and simulation results, this study modifies the penetration volume by assuming that the stagnant zone formed in front of the cone penetrating the granular material behaves as an effective cone. Thereby, the proposed model can calculate penetration resistive forces more accurately for cones with a wider range of tip angles than in the previous model.
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