The effects of time of sugar beet root storage on the parameters determined by impact testing were studied. The 9 mm diameter and 20 mm high cylindrical samples were cut crosswise and lengthwise along the root axis. The impact velocity was 1 m s-1 and the change in the response force over time was observed at both ends of the sample. The measurements were made directly after harvesting and after 24, 48, 96 and 120 h of storage at room temperature. Failure stress and strain, impact energy, absorbed energy, Young's modulus and shock wave speed were determined in the sample tissue from the change in the response force at both ends of the sample. A drop of 40% in the average values of the energy required to damage the samples was observed during 120 h of storage. A similar dependence was found for the energy absorbed by the sample as evidenced by the greater susceptibility of the roots to impact loads. The experiment confirms the importance of critical stress criterion for cylindrical samples of sugar beet. The velocities of shock wave propagation obtained from the samples during impact were in the range of 220-384 m s-1 and were not correlated with the other experimental parameters. K e y w o r d s: sugar beet root, impact energy, absorbed energy, storage time
This paper presents an algorithm for rectilinear-arc trajectory planning whose path is composed of two rectilinear segments connected with a loop-shaped arc. The algorithm can be used in solutions with high speed cornering applications. During the realization of the given trajectory, the end-effector passed through the corner twice and the time difference is, simultaneously, the time of loop tracking. On the rectilinear segments, end-effector acceleration was described by a 7 th degree polynomial, whereas the velocity while moving through a loop was a constant value. The results of the trajectory planning are presented as courses of displacements, speeds and accelerations of the end-effector and displacements, speeds and accelerations in kinematic pairs of the three manipulators.
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