Pedro Hurtado de Mendoza Borges

Demanda tractiva en función de la resistencia mecánica del suelo a la penetración

In this study, empirical models were developed to determine the tensile force demanded by disc plows, harrows and planters fertilizers, as function of soil mechanical resistance to penetration. The mean of the referred resistance was determined until 25, 35 and 15 cm depths, according to the regulations for the disc plow, springs harrow and fertilizer seeder. The adjustment was verified based on the coefficient of determination, dispersion graphics, residual analysis and t test (Student). It was confirm the normality of the residuals and to establish intervals of confidence with 95% of probability. The estimated and experimentally obtained values did not differ significantly. It was concluded that the associated exponential functions presented appropriate precision and reliability to predict the traction force being considered the soil mechanical resistance to penetration and that the models can be a useful tool for planning and management of mechanized farming operations in soils with texture similar to those of this research.

Análise dos ciclos de tensões em colhedoras de forragens

The study of stress in forage harvester is necessary, because the operation conditions are very different and rigorous. A calibrated datalogger system was used to measure the stress as function of time for a forage harvester. Mathematical models were developed to obtain the periodical variation of this stress by considering the influence of support wheel and the angular velocity of cutterheads. The agreement of these models was verified by the determination coefficient (R2). The periodical variation of stress as function of time for both experimental and theoretical values was graphically represented by using of the software EXCEL. It was observed that the minimal amplitude stress and the maximal periods of cycle corresponded to the treatments employed, which utilized the support wheel. The statistical analysis showed that the angular velocity of cutterheads presented significant difference, according to the Tukey Test for 5%. Based on the obtained results was concluded that, the stress cycle can be represented by senoidal functions with an adequate agreement, and that the operation time of harvesters can be increased by using a support wheel.