In this study, an experimental investigation regarding the influence of three independent variables including tillage\ndepth (10, 15, 20 cm), angle of attack (60, 75, 90 degrees) and forward speed (0.5, 1, 1.35, 1.7 m/s) on draft force of a thin\nblade is presented. Chisel plow in this research was constructed in two furrows with a blade width of 3 cm and a maximum\ndepth of 25 cm (the distance between two blades was 1 m). Some changes were made in the chassis of the chisel plow in\norder to obtain different attack angle of the blade. The experimental work was then complemented with a new theoretical\nmodel for predicting the blade force using dimensional analysis method. The final expression for estimating the pull\nresistance is as a function of several soil engineering properties (soil bulk density, soil adhesion and cohesion coefficients),\nblade parameters (blade width and blade rake angle) and operational conditions (tillage depth and forward speed). Finally\nconstants of the model were computed based on obtained experimental data. The proposed model properly estimated the draft\nforce of a thin blade. Results obtained in this study indicate the stronger influence of tillage depth on the pulling force of a\nthin soil-working blade compared to the penetration angle and forward velocity. The average error for the vertical blade with\ndepth of 20, 15 and 10 cm were obtained equal to 4.5%, 4% and 1.5%, respectively.
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