title: Evaluation of brain tissue responses because of the underwash overpressure of helmet and faceshield under blast loading.
abstract: Head protective tools such as helmets and faceshields can induce a localized high pressure region on the skull because of the underwash of the blast waves. Whether this underwash overpressure can affect the brain tissue response is still unknown. Accordingly, a computational approach was taken to confirm the incidence of underwash with regards to blast direction, as well as examine the influence of this effect on the mechanical responses of the brain. The variation of intracranial pressure (ICP) as one of the major injury predictors, as well as the maximum shear stress were mainly addressed in this study. Using a nonlinear finite element (FE) approach, generation and interaction of blast waves with the unprotected, helmeted, and fully protected (helmet and faceshield protected) FE head models were modeled using a multi-material arbitrary Lagrangian-Eulerian (ALE) method and a fluid-structure interaction (FSI) coupling algorithm. The underwash incidence overpressure was found to greatly change with the blast direction. Moreover, while underwash induced ICP (U-ICP) did not exceed the peak ICP of the unprotected head, it was comparable and even more than the peak ICP imposed on the protected heads by the primary shockwaves (Coup-ICP). It was concluded that while both helmet and faceshield protected the head against blast waves, the underwash overpressure affected the brain tissue response and altered the dynamic load experienced by the brain as it led to increased ICP levels at the countercoup site, imparted elevated skull flexure, and induced high negative pressure regions. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Department of Mechanical Engineering, North Dakota State University Fargo, ND, 58108-6050, U.S.A.
authors.forename: Hesam
authors.initials: H
authors.lastname: Sarvghad-Moghaddam
authors.affiliation: Department of Mechanical Engineering, North Dakota State University Fargo, ND, 58108-6050, U.S.A.
authors.forename: Asghar
authors.initials: A
authors.lastname: Rezaei
authors.affiliation: Department of Mechanical Engineering, North Dakota State University Fargo, ND, 58108-6050, U.S.A.
authors.forename: Mariusz
authors.initials: M
authors.lastname: Ziejewski
authors.affiliation: Department of Mechanical Engineering, North Dakota State University Fargo, ND, 58108-6050, U.S.A.
authors.forename: Ghodrat
authors.initials: G
authors.lastname: Karami
mesh_terms: D000465:Algorithms; D001753:Blast Injuries / Q000150:complications* / Q000473:pathology*; D001921:Brain / Q000473:pathology*; D001930:Brain Injuries / Q000209:etiology* / Q000473:pathology*; D003198:Computer Simulation; D005145:Face; D006260:Head Protective Devices; D006801:Humans; D011312:Pressure; D013314:Stress, Mechanical
keywords: blast wave-head interaction; blast-induced traumatic brain injury (bTBI); brain tissue response; head protection; intracranial pressure (ICP); underwash