Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Biosystems Engineering

Major Professor

Paul D. Ayers

Committee Members

John B. Wilkerson, Robert S. Freeland, Timothy J. Truster


Agriculture is one of the most dangerous industries in the US. Tractor accidents are the major cause of death in agriculture, producing about one half of the fatal accidents. Tractor overturn is the most common cause of death in tractor accidents. Three projects related to tractor operator safety in rollover accident were defined.

The aim of first project is to develop a Finite Element (FE) model to predict the Roll-Over Protective Structure (ROPS) performance under the standard SAE J2194 (SAE, 2009) static test. The developed model was validated by comparing the model results with experimental test results. The developed model can predict the experimental test results with average errors about 9%.

The rigid ROPS are not appropriate for working in low overhead clearance zones. The foldable ROPS (FROPS) was designed to solve the rigid ROPS problem, but lowering and raising the conventional FROPS is time consuming and strenuous. The actuation forces to raise and lower the FROPS were not well known. In the second project a measurement system was designed to measure the actuation force and the angle of the foldable ROPS. Two measurement setups were developed to examine the effect of speed and friction on the actuation torque. Results showed that both friction and speed had significant effect on actuation torque.

In the third project a model was developed to predict the effect of liquid shift on agricultural machineries CG height calculation. The CG location is one of the determinant factors for finding the stability angle. When the tractor tilting angle is higher than the stability angle the tractor will rollover. The new ISO 16231-2 uses lift axle method to determine the CG height and is subject to inaccuracy related to liquid shift. The model was validated by comparing the results with experimental results of a wagon and a full size tractor. The developed model predicted the measured CG height with less than 5% error. The effect of liquid shift on CG height measurement for a vehicle with 16% liquid is 19.5% and for the tractor with 2% of liquid is 0.35%.

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