Date of Award

2016

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Gopal Jayaraman

Committee Member 1

V.C. Rao Komaravolu

Committee Member 2

Ibrahim Miskioglu

Committee Member 3

Allan Struthers

Abstract

How many times have you seen a person slip and fall down and had a good laugh about it? How many times we slip and fall down on the floor and got up and walked away thinking everything is normal? Probably we might wonder “Are drops which occur at a small height dangerous?” Yes, they can be. Brain injuries are main reason for the fatality in youth [1], and low level falls are one of the most neglected and understated injuries.

The main objective of this study is to study the response of the brain for low level falls from a drop height of 2-5 feet. Earlier studies have related the brain kinematics to injuries, while fewer data is available regarding the relation of brain kinetics to a Traumatic Brain Injury (TBI). The main purpose of this work is to study the effect of an impact due to free fall on the head. The Linear acceleration of the head is measured using an uniaxial accelerometers and Siglab unit by performing drop tests as per NOCSAE standards in Frontal, 45º to Frontal, Lateral and Posterior regions from a height of 2 feet, 3 feet, 4 feet and 5 feet. The corresponding pressure on head called Head Impact Contact Pressure (HICP), has been measured using Fujifilm Prescale and validated by the HICP values calculated from the linear head accelerations. The corresponding Impact pressure curves has been used as an input for finite element (FE) analysis in Radioss module from Hypermesh, using a 3-D FE model of a 50th percentile human male from the National Library of Medicine (NLM) Visible Human Project (VHP), to study the response of brain during these impacts. Various entities like resultant pressure on the brain, Normal and Shear stresses on the brain, Maximum principal stresses and von Mises Stresses were extracted from the FE analysis. These values are used in conjunction with the Kang and Ward’s [24] criteria and Anna’s [25] criteria for Traumatic Brain Injury (TBI) to determine the tolerance values of drop height, linear head acceleration, Maximum Principal Stresses and von Mises stresses for a chance of risk of TBI. It is been observed that a TBI can be caused either by linear acceleration component or angular acceleration component or both. Hence, a new formula has been proposed to determine the chance of TBI due to impact in particular region.

It is been observed that the lateral region of the brain is more susceptible to injury followed by the Posterior region, a mere drop height of 2.52 feet produces a HICP of 1.21 MPa, an acceleration of 138.67 G, a von Mises stresses of 30.1 KPa and a maximum Principal stress of 0.154 MPa. These values are the tolerance limits for TBI in lateral region and a value higher than those might cause a TBI although any external damage is not observed on the head.

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