Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed April 26, 2007). PDF text: vii, 158 p. : ill. UMI publication number: AAT 3221294. Includes bibliographical references. Also available in microfilm and microfiche formats.

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Digitized by Kansas Correctional Industries

A prediction model based upon Mohr-Coulomb soil mechanics theory has been developed to predict the interaction between the soil and agricultural discs of different geometries and operating angles to both vertical and tilted discs. The model is based on two forms of soil failure. The magnitude of each form of failure is depen- dent upon a passive reaction on the concave side of the disc and a vertical bearing reaction on the convex side of the disc. The predicted results are in close agreement with the results of the experimental studies. Disc geometry is one of the most important factors to be considered in evaluating the soil reaction acting upon a disc tool. A theoretical analysis of the disc geometry was therefore carried out. The analysis of the disc geometry makes it possible to determine the factors required for the predicted forces acting on a disc tool. The experimental studies were conducted in a sandy loam soil at a moisture content in the friable range, under controlled soil bin conditions. The work was carried out at full-scale with 3 dimensional force measuring apparatus developed primarily for this investigation. The discs studied had a range of disc angles between 150 and 600 and a range of tilt angles between 0 and 35. The depth of cut ranged from 80 mm to 140 mm and at speeds between 0.75 m/s and 1.5 m/s. The disturbance area of the soil caused by the rotating soil cutting disc is calculated to define the disturbed area for any combination of disc angle, disc diameter, gang spacing and depth of work in order to accurately calculate specific resistance. Disturbance and soil inversion were investigated using transparent discs and soil tracers, with a variety disc and tilt angles in order to quantify inversion and mixing.

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Thesis (M.S.)--Oregon State University, 1983. / Typescript (photocopy). Includes bibliographical references (leaves 41-44). Also available on the World Wide Web.

Emphasis on soil conservation in recent times has been brought about by the degradation of soils due to intensive tillage operations. A relatively new tillage philosophy, coined conservation tillage, has opened up a new realm of tillage equipment design. The Rotary Tine Aerator (RTA) is new tillage tool that is starting to see commercial applications within the agriculture industry.<p> Being a new tillage tool, very little information has been gathered about the RTA and especially the variables that affect tool loading. For the purpose of improving the design of the soil engaging components of the RTA, an experiment was carried out investigating the effect various settings have on tool loading. A factorial experiment was set up with three factors and two levels. The variables examined were depth, velocity of the tool carriage and tine, and the tine gang angle, with soil density and moisture content maintained constant.<p> Draft and vertical forces on the frame were seen to increase with depth. Side loading on the bearing mounts was seen to be primarily affected by the angle of the tine gang, increasing as the gang angle increased. Tool shape was seen to affect the side loading of the bearing mounts causing the force to change directions when the tool was working and 20 cm depth and the tine gang was set a 0º. Forward velocity was not seen to be a significant factor affecting forces on the frame.<p> The loading in the X, Y and Z direction on the tine increased as depth increased from 10cm to 20 cm. A decrease in force on the tine in the X, Y and Z direction was seen with increasing tine velocity. It is suggested that an overlap in soil failure zones could be the cause of this relationship. Opening the gang angle from 0º to 10º increased the force in the Z direction and decreased the force in the X direction. Tool shape was also seen to affect the direction of the load on the tine in the Z direction when the tine was tilling at a depth 20cm with a tine gang of 0º.<p> From the information gathered in this experiment, statistical models were developed for the loading on the tine and frame. The all possible regressors approach was used to formulate the statistical models. As each regressor was added, the new equations fit was assessed using the coefficient of determination (R2 ) and the sum of squared error (SSE). If there was a discrepancy as to whether an added regressor significantly contributed to the fit of the equation, a hypothesis test using the F-statistic was used to justify the regressors addition or removal. The models were then compared against the original data.<p> The models developed for the tine loading showed sufficient accuracy. The models for side loading of the bearing mounts and draft loading of the tool frame contained only one significant regressor. The lowest coefficient of correlation was R=0.63 for the model of side loading of the bearing mount. The statistical model for the vertical loading correlated well with the test data with a coefficient of correlation of R=0.95.

Emphasis on soil conservation in recent times has been brought about by the degradation of soils due to intensive tillage operations. A relatively new tillage philosophy, coined conservation tillage, has opened up a new realm of tillage equipment design. The Rotary Tine Aerator (RTA) is new tillage tool that is starting to see commercial applications within the agriculture industry.<p> Being a new tillage tool, very little information has been gathered about the RTA and especially the variables that affect tool loading. For the purpose of improving the design of the soil engaging components of the RTA, an experiment was carried out investigating the effect various settings have on tool loading. A factorial experiment was set up with three factors and two levels. The variables examined were depth, velocity of the tool carriage and tine, and the tine gang angle, with soil density and moisture content maintained constant.<p> Draft and vertical forces on the frame were seen to increase with depth. Side loading on the bearing mounts was seen to be primarily affected by the angle of the tine gang, increasing as the gang angle increased. Tool shape was seen to affect the side loading of the bearing mounts causing the force to change directions when the tool was working and 20 cm depth and the tine gang was set a 0º. Forward velocity was not seen to be a significant factor affecting forces on the frame.<p> The loading in the X, Y and Z direction on the tine increased as depth increased from 10cm to 20 cm. A decrease in force on the tine in the X, Y and Z direction was seen with increasing tine velocity. It is suggested that an overlap in soil failure zones could be the cause of this relationship. Opening the gang angle from 0º to 10º increased the force in the Z direction and decreased the force in the X direction. Tool shape was also seen to affect the direction of the load on the tine in the Z direction when the tine was tilling at a depth 20cm with a tine gang of 0º.<p> From the information gathered in this experiment, statistical models were developed for the loading on the tine and frame. The all possible regressors approach was used to formulate the statistical models. As each regressor was added, the new equations fit was assessed using the coefficient of determination (R2 ) and the sum of squared error (SSE). If there was a discrepancy as to whether an added regressor significantly contributed to the fit of the equation, a hypothesis test using the F-statistic was used to justify the regressors addition or removal. The models were then compared against the original data.<p> The models developed for the tine loading showed sufficient accuracy. The models for side loading of the bearing mounts and draft loading of the tool frame contained only one significant regressor. The lowest coefficient of correlation was R=0.63 for the model of side loading of the bearing mount. The statistical model for the vertical loading correlated well with the test data with a coefficient of correlation of R=0.95.