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