Babak N. Safa

Babak Naghizadeh Safa- Mechanical Engineering

PhD Candidate
Mechanical Engineering
126 Spencer Laboratory
safa(at)udel.edu

 Linkedin @BabakNSafa

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Education

  • Ph.D. in Mechanical Engineering, 2014-2019
    University of Delaware, Newark, DE
  • B.Sc. in Mechanical Engineering, 2010-2014
    Sharif University of Technology, Tehran, Iran

Tendon’s Inelastic Mechanics

Overuse is a common disease in tendon that is due to excessive mechanical loading, which causes structural damage. Damage is one of the major inelastic behaviors of tendon that also include viscoelastic, and plastic deformation behaviors. Yet, there is little known about the mechanism of inelasticity in tendon at different length scales. My studies establish mechanisms of inelasticity and failure in tendon, a clinical problem of overuse and rupture, using state-of-art mechanical testing and constitutive modeling techniques, as well as structural imaging at different length scales.

3D reconstruction of rat tail tendon fascicle’s collagen-I fibrils from SBF-SEM imaging (adapted from Safa et al. 2019)

 

Journal Publications

  1. Babak N. Safa, John M. Peloquin, Jessica R. Natriello, Jeffrey L. Caplan, Dawn M. Elliott. “Helical Fibrillar Microstructure of Tendon using Serial Block-Face Scanning Electron Microscopy and a Mechanical Model for Interfibrillar Load Transfer,” Journal of Royal Society Interface (2019) (https://doi.org/10.1098/rsif.2019.0547)
  2. Babak N. Safa, Andrea H. Lee, Michael H. Santare, Dawn M. Elliott. “Evaluating Plastic Deformation and Damage as Potential Mechanisms for Tendon Inelasticity using a Reactive Modeling Framework,” Journal of Biomechanical Engineering (2019) (https://doi.org/10.1115/1.4043520)
  3. Babak N. Safa, Michael H. Santare, Dawn M. Elliott. “A Reactive Inelasticity Theoretical Framework for modeling Viscoelasticity, Plastic Deformation, and Damage in Soft Tissue,” Journal of Biomechanical Engineering 141(2) (2018) (https://doi.org/10.1115/1.4041575)
  4. Babak N. Safa, Kyle D. Meadows, Spencer E. Szczesny, Dawn M. Elliott. “Exposure to Buffer Solution Alters Tendon Hydration and Mechanics,” Journal of Biomechanics 61 (2017) 18-25  (https://doi.org/10.1016/j.jbiomech.2017.06.045)

Conference Proceedings

  1. Babak N. Safa, John M. Peloquin, Jessica R. Natriello, Jeffrey L. Caplan, Dawn M. Elliott. “Helical Grouping is a Potential Mechanism of Interfibrillar Load Transfer: A FE study based on Serial Block-face SEM of Tendon” 16th International Symposium Computer Methods in Biomechanics and Biomedical Engineering (CMBBE), New York, NY, USA, Aug 2019 (podium presentation)
  2. Babak N. Safa, Ellen T. Bloom, Andrea H. Lee, Michael H. Santare, Dawn M. Elliott. “Assessment of Tendon Hydraulic Permeability using Osmotic Loading and Biphasic Finite Element modeling” SB3C, Seven Springs, PA, USA, June 2019 (podium presentation)
  3. Babak N. Safa, John M. Peloquin, Jessica R. Natriello, Jeffrey L. Caplan, Dawn M. Elliott.“3D Microstructure of Tendon Reveals Helically Wrapped Fibrils with the Potential to Mediate Mechanical Load Transfer by Friction” SB3C, Seven Springs, PA, USA, June 2019 (podium presentation)
  4. Babak N. Safa, Michael H. Santare, Dawn M. Elliott. “Theory and Application of Reactive Inelasticity Framework for Modeling Tendon Viscoelasticity, Plastic Deformation, and Damage” World Congress on Computational Mechanics (WCCM), 2018 New York, NY, USA, July 2018 (podium presentation)
  5. Babak N. Safa, Jessica H. Natriello, Dawn M. Elliott. “Tendon Fibril Structure Has Complex Wrapping, Branching, and Cell Interactions as Observed in Three-Dimensional  serial Block-Face SEM,” Orthopaedic Research Society Conference (ORS), New Orleans, LA, USA, March 2018 (poster presentation)
  6. Dawn M. Elliott, Andrea H. Lee, Babak N. Safa. “Microscale structure, mechanics, and damage of tendon”, Cellular and Molecular Bioengineering Conference (CMBE), Key Largo, FL, USA, January 2018.
  7. Babak N. Safa, Michael H. Santare, Dawn M. Elliott. “Modeling Tendon Viscoelasticity, Plasticity, and Damage Using Reactive Inelasticity” Summer Biomechanics, Bioengineering, Biotransport Conference (SB3C), 2017 Tucson, AZ, USA, June 2017 (PhD student paper competition 3rd place)
  8. Babak N. Safa, Kyle D. Meadows, Spencer E. Szczesny, Dawn M. Elliott. “Long-term Exposure to Buffer Solution Alters Tendon Structure and Mechanics-Implications for Fatigue Studies.” Summer Biomechanics, Bioengineering, Biotransport Conference (SB3C), 2016 National Harbor, MD, USA, June 2016 (M.Sc. level poster competition 3rd place)
  9. Babak N. Safa, Andrea H. Lee, Michael H. Santare, Dawn M. Elliott. “A Reactive Viscoelastic Continuum Damage Model for Tendon.” Summer Biomechanics, Bioengineering, Biotransport Conference (SB3C), 2016 National Harbor, MD, USA, June 2016 (podium presentation)

Research Highlights

Tissue Inelasticity

“Consecutive step deformations and multiple generations: ((a)–(c)) number fraction of multiple generations initiated at four consecutive step deformations at t=50; 15; 30; 45 with a first-order rate equation, and ((d)–(f)) their corresponding reference deformation gradients. ((a), (d) Formative bonds ((b), (e)) permanent bonds ((c), (f)) sliding bonds. For the number fraction graphs, the sum of all of the generations is shown with a horizontal green dashed line. The deformation stretch is shown with a red dashed line on reference configuration graphs.” (Safa et al. 2018a)

“Cyclic loading and damage (a) an increasing cyclic loading protocol applied for non-
damaged (b) formative, (c) permanent, and (d) sliding bonds. When damage is added to the response for (e) formative, (f) permanent, and (g) sliding bonds, all the bond types show a softening behavior. The evolution of sliding and damage thresholds is also shown in (a) in response to loading and unloading phases.” (Safa et al. 2018a)

3D Electron Microscopy

Helical structure are seen in the axial view of the fibrils that are evident in the figures (A) with and  B) without the cell nuclei. The helical fibril groups have both left (marked with +⭯) and right-handed (marked with −⭮) twist. (C) Shows three examples of the groups of
twisting fibrils (adapted from Safa et al. 2019)