Digital Commons Network^™

Lower Extremity Biomechanics In Individuals With And Without Previous Hamstring Injury, Jessica A. Mutchler

Human Movement Studies & Special Education Theses & Dissertations

Primary risk factors for hamstrings strains such as fatigue, previous injury and strength deficits have been identified in the research, yet re-injury rates remain high among the physically active. Sub-acute analysis of the hip, knee and ankle biomechanics following a hamstrings strain have been largely overlooked and may provide additional insight into re-injury risks. It was the aim of this dissertation to explore long-term adaptations in walking and running tasks following a hamstrings strain, and to develop a hip endurance test that could be used in future studies.

Project one used a cross-sectional study with test-retest design to develop and …

Implementation Of Analytical Fatigue Models Into Opensim To Predict The Effects Of Fatigue On Anterior Cruciate Ligament Loading, Michael A. Samann

Mechanical & Aerospace Engineering Theses & Dissertations

The anterior cruciate ligament (ACL) provides stability to the knee joint while performing activities such as a side step cut. Neuromuscular fatigue, a reduction in muscle force producing capabilities, alters lower extremity mechanics while performing a side step cut and may increase the risk of ACL injury, particularly in females. Musculoskeletal modeling allows for the measurement of muscle forces, which are difficult to measure in-vivo. Therefore, musculoskeletal modeling, may improve our understanding of the effects of neuromuscular fatigue on muscle force production and loading of the ACL. Therefore, the purpose of this study was to develop a musculoskeletal model which …

Fatigue's Influence On Workload, Situation Awareness, And Performance In A Military Simulation Of Combat, Carlotta M. Boone

Psychology Theses & Dissertations

Military operations routinely require military personnel to consistently perform their duties over several hours or days. Tasks that require prolonged work can lead to mental fatigue and decreased performance. The transactional model proposes that individuals cope with changes in the environment and maintain performance. This ability to cope is determined by factors of the environment and the individual's personality. One environmental factor that can influence coping is extended task performance. This study examined the effect of extended task performance and its interaction with task difficulty. Participants interacted with the military simulation game Command and Conquer: Generals™ for three hours. They …

Nonlinear Response And Fatigue Estimation Of Aerospace Curved Surface Panels To Acoustic And Thermal Loads, Adam Przekop

Mechanical & Aerospace Engineering Theses & Dissertations

This work presents a finite element modal formulation for large amplitude free vibration of arbitrary laminated composite shallow shells. The system equations of motion are formulated first in the physical structural-node degrees of freedom (DOF). Then, the system is transformed into general Duffing-type modal equations with modal amplitudes of coupled linear bending-inplane modes. The linear bending-inplane coupling is due to the shell curvature as well as unsymmetric lamination stacking. Multiple modes, inplane inertia, and the first-order transverse shear deformation for composites are considered in the formulation. A triangular shallow shell finite element is developed from an extension of the triangular …

Nonlinear Response And Fatigue Estimation Of Surface Panels To White And Non-White Gaussian Random Excitations, Jean-Michel Dhainaut

Mechanical & Aerospace Engineering Theses & Dissertations

In stochastic structural dynamics, the majority of analyses have dealt with linear structures under stationary, Gaussian, and band-limited white noise excitations. Although these simplifying assumptions may be justified, in many processes experimental data have shown quite frequently the non-stationary and non-Gaussian characteristics of the loads. An efficient finite element modal formulation has recently been developed to extend the analysis to nonlinear structural responses. Laminated plate theory and von Karman large displacement relations are used to derive the nonlinear equations of motion for an arbitrarily laminated composite panel subjected to combined acoustic and thermal loads. The nonlinear equations of motion in …

Finite Element Frequency Domain Solution Of Nonlinear Panel Flutter With Temperature Effects And Fatigue Life Analysis, David Yongxiang Xue

Mechanical & Aerospace Engineering Theses & Dissertations

A frequency domain solution method for nonlinear panel flutter with thermal effects using a consistent finite element formulation has been developed. The von Karman nonlinear strain-displacement relation is used to account for large deflections, the quasi-steady first-order piston theory is employed for aerodynamic loading and the quasi-steady thermal stress theory is applied for the thermal stresses with a given change of the temperature distribution, ΔΤ (x, y, z). The equation of motion under a combined thermal-aerodynamic loading can be mathematically separated into two equations and then solved in sequence: (1) thermal-aerodynamic postbuckling and (2) limit-cycle oscillation. The Newton-Raphson iteration technique …

Three-Dimensional Elastic-Plastic Finite Element Analysis Of Fatique Crack Growth And Closure, Rahmatollah G. Chermahini

Mechanical & Aerospace Engineering Theses & Dissertations

The purpose of this study was to develop a three-dimensional, elastic-plastic, finite element analysis to investigate crack extension and closure under cyclic loading. The initial study concentrated on the behavior of a straight through crack in a finite-thickness plate subjected to tensile loading (middle-crack tension specimen). The finite element model was composed of 8-noded (linear-strain) isoparametric elements. In the analysis, the material was assumed to be elastic-perfectly plastic. Zienkiewicz's "initial-stress" method, von Mises' yield criterion, and Drucker's normality condition, under small-strain assumptions, were used to account for plasticity. The three-dimensional analysis is capable of extending the crack and changing boundary …