Date of Award

Spring 2015

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical Engineering

First Advisor

Eric Nauman

Committee Chair

Eric Nauman

Committee Member 1

Charles Krousgrill

Committee Member 2

Darryl Dickerson

Committee Member 3

Lynetta Freeman


Localized ischemia, impaired interstitial fluid flow, and sustained mechanical loading of cells have all been hypothesized as mechanisms of pressure ulcer (PrU) etiology. Time-varying loading has experimentally been shown to increase fluid flow in human skin in vivo. Towards the design of prophylactic protocols and treatment modalities for PrU management there is a need for an analytical model to investigate the local fluid flow characteristics of skin tissue under time-varying loading. In this study, a triphasic mixture theory model with constituents of extracellular matrix, interstitial fluid, and blood was calibrated and validated and used to investigate stress and fluid velocity under quasi-static and time-varying loading conditions, respectively. Four input strain profiles were considered, including uniform, geometric circular segment, Gaussian, and Hertz-type strain profiles. Calibrated bulk and shear modulus (κ;=227.7kPa, µ=1.04kPa) were on the same order of magnitude as literature. Fluid velocities were investigated for apparent strain amplitudes of 100-700μϵ and frequencies of 10-80Hz. At the lowest amplitude and frequency, interstitial fluid velocities were on the same order of magnitude as literature values, 1 micrometers/s and 1 mm/s, respectively. Interstitial fluid and blood velocity both experienced significant increases with increasing amplitude and frequency. The study demonstrated the ability to analytically predict quasi-static stress profiles as well as predict fluid velocity increases in cyclically loaded soft tissues by employing quasi-static mechanics and mixture theory models. Consequently, this study builds a strong foundation for use in the development of vibrational support surfaces for use in prophylactic protocols and adjunctive treatment modalities for PrU management