Session: IMECE Undergraduate Research and Design Exposition

Paper Number: 121097

121097 - Characterization of the Relationship Between Base Compliance and Cavitation Threshold Under Varying Dynamic Impacts 

Dynamic cavitation in soft materials has gained significance across diverse applications, including Traumatic brain injury (TBI) induction and medical advancements. Researchers have been particularly interested in understanding cavitation within hydrogels like Gelatin, which is widely used to mimic white and grey brain matter, in fields like automotive safety, sports, and military health. Past studies sought to determine the cavitation threshold for various concentrations of Gelatin subjected to accelerative loadings. These findings provided insight into how properties like concentration could be adjusted to simulate responses of target organs. To find this threshold, drop tower impact experiments, equipped with accelerometers and high-speed cameras, were used. Typically, Gelatin filled cuvettes were secured to an additively manufactured structure which was, in turn, attached to a rigid metallic frame/ base (made of aluminum or steel). The key factors that affected cavitation in these studies were the magnitude of applied acceleration and the concentration of Gelatin. Little effort has been focused on mimicking the compliance of actual biological systems like those where cavitation is likely to be an injury mechanism. If the relationship between compliance and cavitation threshold can be understood, the results from experimental devices like drop towers can be easily compared to systems with varying degrees of bio fidelity. Impact experiments are performed on multiple base materials to understand the critical acceleration that causes cavitation in samples of 2.5% gelatin. By correlating this critical acceleration with the stiffness of the base, a function can be proposed that estimates the loading that induces cavitation by knowing the stiffness of, for example, the human head and neck (as experimentally found in systems like the Hybrid III Neck Model). A custom made, drop impact experiment platform have been assembled to quantify this phenomenon. The set up allows different bases including a steel, wooden, and sorbothane foam base. This allows variation in energy transmission in a material. Fastened on these bases is a gazebo like structure made of Nylon PA 12 in which a 2.5% G cuvette can be fixed in the line of impact without being impacted itself. Throughout the experiment, a 2000g 830-M1 uniaxial accelerometer is mounted off the line of impact and used to capture acceleration data (as sampled by LabVIEW at 1 MHz) while a 16000 fps Photron camera is used to observe whether cavitation happens. Preliminary work has been conducted to understand the effect, if any, change of material has on the magnitude of critical acceleration. For the foam, steel, and wood base on the steel tower the respective critical accelerations are 302.575 ± 17.982 g, 640.196 ± 7.305 g, 759.541 ± 22.451 g. Detail on the experiment, interpretation of results and key takeaway from this study will be discussed in the poster. 

Presenting Author: Jacob Navarro The University of Texas at Arlington

Presenting Author Biography: My name is Jacob Navarro and I am a senior, Aerospace Engineering student at the University of Texas at Arlington. My professional goals are to receive my phd in Aerospace and pursue a career within National Research Labs or any other government research agency. My work now (and hopefully in the future) focuses on many things like applying engineering principles to study biofidelic materials like the brain, developing high strain rate experimental devices, and characterizing injury criteria as well as synthesizing protective structures to better protect people like war fighters, automobile drivers, and professional sport players. I grew up as a military kid, and I hope to one day head research programs that are oriented at military health systems. In my personal life, I enjoy outdoor hobbies like fishing, hiking, kayaking, camping, and rock climbing. The most beautiful places I have ever visited would have to include Palo Duro State Park in Texas, the Royal Gorge and Rocky Mountain National Park in Colorado, and Yellowstone National Park in Montana. Two fun facts about me are I did not learn how to tie my shoes properly until college and I have 5 siblings aged 21, 18, 10, 3, and 1.

Authors:

Jacob Navarro The University of Texas at Arlington
Ashfaq Adnan The University of Texas at Arlington