Abstract

As the most produced grain crop world-wide, 5% of corn is lost due to stalk lodging (above-ground structural failure of the stalk near the roots). Current modeling methods lack the ability to manipulate the stalk architecture. In contrast, parameterized models enable advanced analyses such as sensitivity and optimization studies. This thesis advances previous work on a parameterized cross-sectional model of maize stalk morphology and investigates the validity of a parameterized three-dimensional model. The parameterized cross-sectional model is based upon previous work that approximated the cross-section of maize stalks using an ellipse plus principal components. Validation of the cross-sectional model was done by evaluating the structural response in four loading cases: axial tension/compression, bending, transverse compression, and torsion. 2D prismatic extrusions of specimen specific cross-sections were tested under the load conditions and compared against 2D prismatic models of the parametrized cross-sections. Analysis of the 2D prismatic model consisted of a parameter sensitivity analysis to determine influential morphological features, and a load bearing analysis to quantify the proportion of load borne by each material tissue. Validation of the parameterized 3D model was completed by comparing the structural response of the parameterized 3D model against empirical test data. A comparison against CT-based finite element models was also done to quantify the level of predictive discrepancy caused by geometric parameterization. The elliptical 2D prismatic model responded with less than 5% error for axial tension/compression, bending, and transverse compression, suggesting that the ellipse model is sufficient for analyses and 3D parameterization. The 2D prismatic model maintained an error less than 10% under a torsion load. The parameter sensitivity analysis revealed that ellipse parameters are significantly more influential to stalk strength than material or finer geometric details. In the load bearing analysis, the rind bore a median of over 90% of the load in axial tension/compression, bending, and torsion, but less than 10% of the load in transverse compression. The parameterized 3D model validates yielding correlations with empirical test data resulting in R2 values of 0.82 in flexural stiffness, and in critical buckling a value of 0.71. Comparison with CT-based models resulted in very strong correlations with R2 values of 0.81 in flexural stiffness, and for critical buckling a value of 0.87. The parameterized 3D model validates and can be used in future studies.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

Rights

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