title: Dynamic material characterization of the human heel pad based on in vivo experimental tests and numerical analysis.
abstract: A numerical-experimental, proof-of-concept approach is described to characterize the mechanical material behavior of the human heel pad under impact conditions similar to a heel strike while running. A 3D finite-element model of the right foot of a healthy female subject was generated using magnetic resonance imaging. Based on quasi-static experimental testing of the subject's heel pad, force-displacement data was obtained. Using this experimental data as well as a numerical optimization algorithm, an inverse finite-element analysis and the 3D model, heel pad hyperelastic (long-term) material parameters were determined. Applying the same methodology, based on the dynamic experimental data from the impact test and obtained long-term parameters, linear viscoelastic parameters were established with a Prony series. Model validation was performed employing quasi-static and dynamic force-displacement data. Coefficients of determination when comparing model to experimental data during quasi-static and dynamic (initial velocity: 1480mm/s) procedure were R(2) = 0.999 and R(2) = 0.990, respectively. Knowledge of these heel pad material parameters enables realistic numerical analysis to evaluate internal stress and strain in the heel pad during different quasi-static or dynamic load conditions.
authors.affiliation: Institute for Materials Science, Frankfurt University of Applied Sciences, Frankfurt am Main, Germany; Department of Diagnostic and Interventional Radiology, Hospital of the Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Kardeh
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hospital of the Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
authors.forename: T J
authors.initials: TJ
authors.lastname: Vogl
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hospital of the Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Huebner
authors.affiliation: Department of Vascular and Endovascular Surgery, Hospital of the Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Nelson
authors.affiliation: Orthopedic University Hospital Friedrichsheim GmbH, Frankfurt am Main, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Stief
authors.affiliation: Institute for Materials Science, Frankfurt University of Applied Sciences, Frankfurt am Main, Germany. Electronic address: silber@fb2.fh-frankfurt.de.
authors.forename: G
authors.initials: G
authors.lastname: Silber
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004548:Elasticity; D005260:Female; D020342:Finite Element Analysis; D006365:Heel / Q000000981:diagnostic imaging; D006801:Humans; D008279:Magnetic Resonance Imaging; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D055595:Mechanical Phenomena
keywords: Finite element analysis; Heel pad; Impact test; In vivo material parameter