Origami Engineering: Achieving Unidirectional Locomotion with Magnetically Active Elastomers
Jesse Butch, Kelsey Lewis, EIT
January, 2013 -
Contributed to the development of a constitutive analytical model describing the motion of a multi-block sample magnetically active elastomer (MAE) system in a uniform magnetic field. Enhanced skills in programming (Mathematica) and advanced structural mechanics. Reinforced basic electricity and magnetism concepts.
A Biomechanical Study of Locking Screw Performance in Tibia-IM Rod Systems
Jesse Butch, Rohith Gowda, Amanda Mallinder, John Virtue, Kelsey Lewis, EIT
September, 2011 -
Intramedullary (IM) rod fixation is a form of functional bracing that provides mechanical stability to long bones with fracture comminution to promote callus formation. Although tibia-IM rod nailing systems are designed to absorb a fraction of the axial knee-joint load, transcortical locking screw fracture may occur during the osseous formation period. As a consequence, the effectiveness of the tibia-IM rod is compromised, which can lead to malunion or nonunion of the tibia fracture. Since current clinical practice relies on the clinician’s experience and intuition to recommend when patients may safely resume walking after tibia-IM rod fixation, results from this study are intended to provide clinicians with a safety matrix for making recommendations based on analytical and experimental data. The primary objective of this study is to determine the performance of a single distal locking screw in a two transcortical screw IM rod configuration for four grades of Winquist fracture comminution in a medium left tibia on a 70 kg subject during the ten-week callus formation period. Two size cannulated IM rods with proximal bend (11 mm and 8 mm diameter) associated with distal screw diameters 5 mm and 4 mm, respectively were analyzed and compared in this study at four grades of fracture comminution using solid mechanics beam theory. Analytical results suggest that the distal locking screw does not fail due to static loading for both the 4 mm and 5 mm distal screws during the ten week osseous formation period for any fracture grade where the ratio of estimated material strength to von Mises stress on the distal screw is greater than one. Limitations to the analytical model include simplifying the mean maximum axial knee-joint load with axial rather than eccentric load transmission to the tibia-IM rod system; analyzing the tibia as a linearly elastic material; and neglecting temporal bone formation during the ten-week callus formation period.
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