Kevin Troyer Ph.D. Final Exam & Defense
Kevin L. Troyer Ph.D. Final Exam and Defense 2:30 P.M., Monday, May 14th, 2012 Lory Student Center Room 208 Advisor: Christian Puttlitz Committee: Susan James, Lakshmi Dasi, Paul Heyliger "Viscoelastic Characterization and Modeling of Musculoskeletal Soft Tissues."
Abstract Over the last decade there has been a dramatic rise in musculoskeletal soft tissue injuries in the general, athletic, and military populations. The etiology of this increase has been largely ascribed to dynamic loading events, including strenuous physical overuse and trauma. Additionally, instability arising from soft tissue pathology or trauma can induce and/or accelerate joint degeneration. Degenerative sequelae, such as post-traumatic osteoarthritis, can cause significant debility and an associated reduction in one’s quality of life. Development of successful treatment modalities for joint instability and soft tissue compromise is highly dependent upon a thorough understanding of the affected tissue’s mechanical (viscoelastic) behavior. However, current soft tissue viscoelastic characterization paradigms predominantly utilize quasi-linear viscoelastic (QLV) formulae despite substantial empirical evidence which has conclusively demonstrated that these tissues violate its fundamental assumption of elastic and viscous behavior separability. Furthermore, development of more applicable nonlinear viscoelastic formulations has been hindered by the inability of currently-available constitutive models and characterization methodologies to include relaxation manifested during dynamic loading events. As a result, implementation of nonlinear viscoelastic formulae in soft tissue computational models has not been widespread. To surmount these shortcomings, this work develops a novel, nonlinear viscoelastic constitutive formulation and a corresponding experimental characterization technique which can be included in current state-of-the-art computational algorithms. Specifically, the aims of this dissertation were: (1) Develop and validate a nonlinear viscoelastic characterization technique for musculoskeletal soft tissues that incorporates relaxation manifested during loading; (2) Characterize the nonlinear viscoelastic behavior of various types of ligamentous tissues and tendon; (3) Integrate a fully nonlinear viscoelastic constitutive formulation into a finite element algorithm. Aims 1 and 2 were accomplished via development and application of a novel comprehensive viscoelastic characterization (CVC) technique and constitutive formulation to describe the nonlinear viscoelastic behavior of various human cervical spine ligaments (anterior and posterior longitudinal ligament and ligamentum flavum) and ovine Achilles tendon. Additionally, improvements in the predictive accuracy of the CVC fitted coefficients over previously accepted viscoelastic characterization techniques were quantified. Furthermore, a computationally tractable fully nonlinear viscoelastic formulation was developed and validated against an analytical solution (Aim 3). Implementation of the important nonlinear viscoelastic behavior into computational models will greatly accelerate our ability to understand the functional role of soft connective tissues in whole joint mechanics and facilitate future treatment options.
Event Contact: Zulema Sierra can be reached at (970) 491-6036
Sponsored by Mechanical Engineering
|Calendar Name:||All University Events Calendar|
|Event Category:||Dissertation & Thesis Defenses|
|Start Time:||02:30 PM|
|End Time:||06:00 PM|
|Event Begins On:||Monday, May 14, 2012|
|Event Ends On:||Monday, May 14, 2012|
|Submitter's Name:||Zulema Sierra|