Development and verification of data analysis strategies for characterizing military helmet-head performance
Abstract
Soldiers sometimes experience traumatic brain injury and helmet research is being conducted to reduce these injuries. Most research is centered on crash worthiness or ballistic impact. The objective of this work is to develop a method to characterize the dynamic response of helmets to broadband loading for helmets of various materials and designs while the helmet is coupled to a head-neck system. The experimental setup consists of a Denton Hybrid III 50th percentile crash test head and neck attached to an optical isolation table to simulate the human torso. The method utilizes standard modal impact tests with sensors on the helmet, neck, table, and head to measure the dynamic helmet-head coupling. The data acquired from the sensors is used to calculate the frequency response functions of the head and helmet. There are two different methods of analysis: (1) different responses of the surrogate head are compared and (2) the response of the surrogate head is compared with the response of the helmet. The transmissibility function is calculated using the frequency response function, in order to compare the response of the surrogate head to the helmet. In addition, aggregate methods such as the complex mode indicator function, aggregate mean transmissibility, impact location average transmissibility, and analysis of variance are extracted from the impact test results. Three helmets, which are provided by the Army Research Laboratory, are tested. The tests reveal that helmets affect the effective mass and moment of inertia of the surrogate head. However, one helmet (ARL3) in particular affects the effective mass the least. Frequency response and complex mode indicator function results indicate that helmet ARL3 absorbs more energy from a blunt impact than the other two helmets, resulting in less transfer of energy to the head. Transmissibility function analysis is conducted to confirm this finding that helmet ARL3 attenuates the transmitted force relative to the other two helmets. ANOVA analysis of ILAT indicates that helmet ARL3 is statistically different from the other two helmets; whereas the other two helmets are statistically the same. Tests verify that the test fixture and methodology is sensitive to changes in system parameters. In particular, measurements that are made using this test fixture are sensitive to chinstrap tension (padding pre-load), impact magnitude, impact type, and helmet padding.
Degree
M.S.M.E.
Advisors
Adams, Purdue University.
Subject Area
Biomedical engineering|Mechanical engineering|Military studies
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