The relative error of between the simulation and the experimental results, ��, is defined as��=|qE?qSqE|��100,(16)where selleck chem qE and qS mean a position result of experiments and simulations, respectively. In the impact experiments of the link, qE is considered as the position of the end T in the vertical direction, zT. Table 2 shows the difference rate of the experiments and the simulation.Table 2Relative error between the experimental and the simulation results of the free link.The stopping time into the granular matter is decreasing when the initial velocity is increasing as most simulation results represented. The characteristics of the stopping time and the penetrating depth do not change.The vertical velocity vTz becomes zero faster when the initial vertical impact velocity increases.
The increasing of the initial velocity causes the stopping time into the granular medium to decrease. The faster the end of the link impacts the surface of the granular medium, the sooner it will come to a stop. This is an interesting phenomenon involving how rapidly a body vertically strikes the granular medium slowing down upon contact. The results can be explained by the reaction of the granular medium on the free link that can be decomposed into the sum of velocity-dependent force and depth-dependent force [26].4. ConclusionsThe experimental and the simulation results for the oblique impact of a free link impacting with a granular medium are analyzed.
The resistance forces acting during the penetration of the free link into the granular matter is modeled as the sum of the static force represented by a depth-dependent friction force as well as the dynamic frictional force which is a velocity-dependent drag force. The penetrating depth of the impacting end of the free link increases with the increase of the initial impact velocity. The stopping time of the impacting end in vertical direction decreases as the initial impacting velocity increases. The faster the end of the link impacts the surface of the granular medium, the sooner it will come to a stop.This research provides a new strategy in the theory of general impacting bodies with granular materials. This study is very useful in the design of impacting systems such as walking machines, variable geometry wheeled and tracked vehicles, active cord mechanisms, and robot manipulators.
The results obtained are significant in the areas of mining, military transport, planetary exploration, construction work on land and under water, and study of locomotion.Conflict of InterestsThe authors declare that there is no conflict of interests regarding the publication of this paper.
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