Estimating Dynamic Properties for Biological Materials Design, Development, and Calibration of a Desktop Miniaturized Pulse-shaping Kolsky Bar

Open Access
Author:
Sodha, Kush B
Area of Honors:
Mechanical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Reuben H Kraft, Thesis Supervisor
  • Zoubeida Ounaies, Honors Advisor
Keywords:
  • soft materials
  • kolsky bar
  • brain tissue
  • miniaturize
  • design
  • development
  • calibration
  • dynamic properties
  • material properties
Abstract:
Modeling and simulations are used to better understand the brains response to external loading. Modeling requires supplying the mathematical description of the tissue behavior, or constitutive model, as well as its material properties. We seek to examine the performance of existing methods and develop new methods in order to characterize the mechanical properties of the tissue us ed in models of the brain. Recently, there have been concerns regarding the validity of using the Kolsky bar to acquire mechanical properties of soft, biological materials at high strain rates. This effort further explores the validity of the Kolsky bar for soft materials. Currently, Kolsky bars are too large and geared towards testing traditional engineering materials such as metals or ceramics. Using the known mechanics of the Kolsky bar in engineering materials, we aim to miniaturize the model to eliminate some of the inertial effects and employ pulse shaping to further address the compressible nature of the specimens. Even with these alterations, additional testing including shear mechanisms to develop a shear modulus and changing specimen geometry remain possible options to fully optimize the response of soft materials. In order to explore the validity of the Kolsky bar, we employ solid and computational modeling to evaluate different materials tested in miniaturized Kolsky bar apparatus. Our approach started by developing a miniaturized compression model in Solidworks. We then developed and refined a finite element mesh using Ansys ICEM-CFD. With a high-quality mesh, we employed LS-DYNA to conduct the dynamic simulations of the experiment. The material properties assigned start with aluminum cylindrical specimens, but are then transitioned to a softer material. Understanding the weaknesses with the soft specimens prompted the use of pulse shaping. This analysis can prove the validity of using Kolsky bars with modifications on soft, biological materials. Combining these mechanical properties with existing models for the human body can expand the current understanding of the brains response to high-strain rate loading and aid in prevention, treatment, and rehabilitation of TBIs.