Mobile machine design through dynamic load simulation on their drive units

Introduction. The mobile machine design is impossible without considering the vibration parameters of their units. This requires the development of specialized dynamic models that take into account the probabilistic nature of these parameters. The root cause for the occurrence of vibration effects is the profile irregularity of the mobile machine path, and the variability of physicomechanical characteristics of the soil. Problems that consider these features are solved linearly with sufficient accuracy; but in multidimensional dynamical systems, such an approach is unacceptable due to the presence of a large number of interrelationships. The work objective is to conduct a comparative analysis of the efficiency of existing calculation methods of statistical characteristics of uncorrelated external actions as applied to a mobile machine presented as a multidimensional dynamic system with actions having different correlations.

Materials and Methods. External actions in the multidimensional dynamical systems are considered in a matrix form. When calculating statistical characteristics, intercouplings in the spectral density matrices are taken into account. The elements of the main and secondary diagonals are determined; the correlations between the effects are taken into account. These features significantly complicate the calculations. So, to get matrices of uncorrelated actions, the matrix of external actions is reduced to a diagonal form.

Results. A numerical comparison of spectral densities and intensity of the mobile machine oscillations under variation of speeds and nature of the soil fertility microprofile was carried out using various methods of calculation. Certain characteristics of spectral densities and oscillations of mobile machines of agroindustrial complex enabled to develop recommendations on the practical application of the presented dependences for designing this machinery.

Discussion and Conclusions. The results of solving the matrix of spectral densities of external actions by various methods are presented on the diagram of spectral oscillation velocities. The analysis of characteristic curves has shown that the identical results, regardless of the calculation method, are obtained only for machines with weak functional relations under the uncorrelated external action of the soil fertility. For some cases, the resonance machine speeds are set. The effect of irregularities of the soil fertility on the oscillation intensity of the machine units and the dispersion of loads on the units is shown in the graphical representation.

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