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Article ; Online: Finite element analysis of a ram brain during impact under wet and dry horn conditions.

Johnson, K L / Trim, M W / Mao, Y / Rhee, H / Williams, L N / Liao, J / Griggs, J / Horstemeyer, M F / Duan, Yuanyuan

Journal of the mechanical behavior of biomedical materials

2021 Volume 119, Page(s) 104400

Abstract: In this study, ram impacts at 5.5 m/s are simulated through finite element analysis in order ...

Abstract	In this study, ram impacts at 5.5 m/s are simulated through finite element analysis in order to study the mechanical response of the brain. A calibrated internal state variable inelastic constitutive model was implemented into the finite element code to capture the brain behavior. Also, constitutive models for the horns were calibrated to experimental data from dry and wet horn keratin at low and high strain rates. By investigating responses in the different keratin material states that occur in nature, the bounds of the ram brain response are quantified. An acceleration as high as 607 g's was observed, which is an order of magnitude higher than predicted brain injury threshold values. In the most extreme case, the maximum tensile pressure and maximum shear strains in the ram brain were 245 kPa and 0.28, respectively. Because the rams do not appear to sustain injury, these impacts could give insight to the threshold limits of mechanical loading that can be applied to the brain. Following this motivation, the brain injury metric values found in this research could serve as true injury metrics for human head impacts.
MeSH term(s)	Acceleration ; Animals ; Biomechanical Phenomena ; Brain ; Brain Injuries ; Finite Element Analysis ; Head ; Humans ; Male ; Sheep ; Stress, Mechanical
Language	English
Publishing date	2021-03-04
Publishing country	Netherlands
Document type	Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	2378381-3
ISSN	1878-0180 ; 1751-6161
ISSN (online)	1878-0180
ISSN	1751-6161
DOI	10.1016/j.jmbbm.2021.104400
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Article ; Online: A Mechanical Brain Damage Framework Used to Model Abnormal Brain Tau Protein Accumulations of National Football League Players.

Horstemeyer, M F / Berthelson, P R / Moore, J / Persons, A K / Dobbins, A / Prabhu, R K

Annals of biomedical engineering

2019 Volume 47, Issue 9, Page(s) 1873–1888

Abstract: A mechanics-based brain damage framework is used to model the abnormal accumulation of hyperphosphorylated p-tau associated with chronic traumatic encephalopathy within the brains of deceased National Football League (NFL) players studied at Boston ... ...

Abstract	A mechanics-based brain damage framework is used to model the abnormal accumulation of hyperphosphorylated p-tau associated with chronic traumatic encephalopathy within the brains of deceased National Football League (NFL) players studied at Boston University and to provide a framework for understanding the damage mechanisms. p-tau damage is formulated as the multiplicative decomposition of three independently evolving damage internal state variables (ISVs): nucleation related to number density, growth related to the average area, and coalescence related to the nearest neighbor distance. The ISVs evolve under different rates for three well known mechanical boundary conditions, which in themselves introduce three different rates making a total of nine scenarios, that we postulate are related to brain damage progression: (1) monotonic overloads, (2) cyclic fatigue which corresponds to repetitive impacts, and (3) creep which is correlated to damage accumulation over time. Different NFL player positions are described to capture the different types of damage progression. Skill position players, such as quarterbacks, are expected to exhibit a greater p-tau protein accumulation during low cycle fatigue (higher amplitude impacts with a lesser number), and linemen who exhibit a greater p-tau protein accumulation during high cycle fatigue (lower amplitude impacts with a greater number of impacts). This mechanics-based damage framework presents a foundation for developing a multiscale model for traumatic brain injury that combines mechanics with biology.
MeSH term(s)	Adult ; Aged ; Brain/metabolism ; Brain Injuries/metabolism ; Football/injuries ; Humans ; Male ; Middle Aged ; Models, Biological ; tau Proteins/metabolism
Chemical Substances	tau Proteins
Language	English
Publishing date	2019-08-01
Publishing country	United States
Document type	Journal Article
ZDB-ID	185984-5
ISSN	1573-9686 ; 0191-5649 ; 0090-6964
ISSN (online)	1573-9686
ISSN	0191-5649 ; 0090-6964
DOI	10.1007/s10439-019-02294-1
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Article ; Online: A mesoscale finite element modeling approach for understanding brain morphology and material heterogeneity effects in chronic traumatic encephalopathy.

Bakhtiarydavijani, A / Khalid, G / Murphy, M A / Johnson, K L / Peterson, L E / Jones, M / Horstemeyer, M F / Dobbins, A C / Prabhu, R K

Computer methods in biomechanics and biomedical engineering

2021 Volume 24, Issue 11, Page(s) 1169–1183

Abstract: Chronic Traumatic Encephalopathy (CTE) affects a significant portion of athletes in contact sports but is difficult to quantify using clinical examinations and modeling approaches. We use ... ...

Abstract	Chronic Traumatic Encephalopathy (CTE) affects a significant portion of athletes in contact sports but is difficult to quantify using clinical examinations and modeling approaches. We use an
MeSH term(s)	Brain ; Chronic Traumatic Encephalopathy ; Finite Element Analysis ; Head ; Humans ; Sports
Language	English
Publishing date	2021-02-26
Publishing country	England
Document type	Journal Article
ZDB-ID	2071764-7
ISSN	1476-8259 ; 1025-5842
ISSN (online)	1476-8259
ISSN	1025-5842
DOI	10.1080/10255842.2020.1867851
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Article ; Online: Solute effect on basal and prismatic slip systems of Mg.

Moitra, Amitava / Kim, Seong-Gon / Horstemeyer, M F

Journal of physics. Condensed matter : an Institute of Physics journal

2014 Volume 26, Issue 44, Page(s) 445004

Abstract: In an effort to design novel magnesium (Mg) alloys with high ductility, we present a first principles data based on the Density Functional Theory (DFT). The DFT was employed to calculate the generalized stacking fault energy curves, which can be used in ... ...

Abstract	In an effort to design novel magnesium (Mg) alloys with high ductility, we present a first principles data based on the Density Functional Theory (DFT). The DFT was employed to calculate the generalized stacking fault energy curves, which can be used in the generalized Peierls-Nabarro (PN) model to study the energetics of basal slip and prismatic slip in Mg with and without solutes to calculate continuum scale dislocation core widths, stacking fault widths and Peierls stresses. The generalized stacking fault energy curves for pure Mg agreed well with other DFT calculations. Solute effects on these curves were calculated for nine alloying elements, namely Al, Ca, Ce, Gd, Li, Si, Sn, Zn and Zr, which allowed the strength and ductility to be qualitatively estimated based on the basal dislocation properties. Based on our multiscale methodology, a suggestion has been made to improve Mg formability.
Language	English
Publishing date	2014-11-05
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	1472968-4
ISSN	1361-648X ; 0953-8984
ISSN (online)	1361-648X
ISSN	0953-8984
DOI	10.1088/0953-8984/26/44/445004
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Article ; Online: Microstructure and nanomechanical properties of the exoskeleton of an ironclad beetle (

Lee, Nayeon / Berthelson, Parker R / Nguyen, Vina / Garrett, Me'Lanae / Brinda, AnneMarie K / Moser, Robert D / Horstemeyer, M F / Rhee, Hongjoo / Prabhu, R K

Bioinspiration & biomimetics

2021 Volume 16, Issue 3

Abstract: This study examined natural composite structures within the remarkably strong exoskeleton of the southwestern ironclad beetle ( ...

Abstract	This study examined natural composite structures within the remarkably strong exoskeleton of the southwestern ironclad beetle (
MeSH term(s)	Animals ; Coleoptera ; Elastic Modulus ; Exoskeleton Device ; Hardness
Language	English
Publishing date	2021-03-19
Publishing country	England
Document type	Journal Article ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	2235670-8
ISSN	1748-3190 ; 1748-3182
ISSN (online)	1748-3190
ISSN	1748-3182
DOI	10.1088/1748-3190/abe27b
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Article ; Online: A finite element-guided mathematical surrogate modeling approach for assessing occupant injury trends across variations in simplified vehicular impact conditions.

Berthelson, P R / Ghassemi, P / Wood, J W / Stubblefield, G G / Al-Graitti, A J / Jones, M D / Horstemeyer, M F / Chowdhury, S / Prabhu, R K

Medical & biological engineering & computing

2021 Volume 59, Issue 5, Page(s) 1065–1079

Abstract: A finite element (FE)-guided mathematical surrogate modeling methodology is presented for evaluating relative injury trends across varied vehicular impact conditions. The prevalence of crash-induced injuries necessitates the quantification of the human ... ...

Abstract	A finite element (FE)-guided mathematical surrogate modeling methodology is presented for evaluating relative injury trends across varied vehicular impact conditions. The prevalence of crash-induced injuries necessitates the quantification of the human body's response to impacts. FE modeling is often used for crash analyses but requires time and computational cost. However, surrogate modeling can predict injury trends between the FE data, requiring fewer FE simulations to evaluate the complete testing range. To determine the viability of this methodology for injury assessment, crash-induced occupant head injury criterion (HIC
MeSH term(s)	Accidents, Traffic ; Biomechanical Phenomena ; Craniocerebral Trauma/epidemiology ; Finite Element Analysis ; Head ; Humans
Language	English
Publishing date	2021-04-21
Publishing country	United States
Document type	Journal Article
ZDB-ID	282327-5
ISSN	1741-0444 ; 0025-696X ; 0140-0118
ISSN (online)	1741-0444
ISSN	0025-696X ; 0140-0118
DOI	10.1007/s11517-021-02349-3
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Article ; Online: Modified Drop Tower Impact Tests for American Football Helmets.

Rush, G Alston / Prabhu, R / Rush, Gus A / Williams, Lakiesha N / Horstemeyer, M F

Journal of visualized experiments : JoVE

2017 , Issue 120

Abstract: A modified National Operating Committee on Standards for Athletic Equipment (NOCSAE) test method for American football helmet drop impact test standards is presented that would provide better assessment of a helmet's on-field impact performance by ... ...

Abstract	A modified National Operating Committee on Standards for Athletic Equipment (NOCSAE) test method for American football helmet drop impact test standards is presented that would provide better assessment of a helmet's on-field impact performance by including a faceguard on the helmet. In this study, a merger of faceguard and helmet test standards is proposed. The need for a more robust systematic approach to football helmet testing procedures is emphasized by comparing representative results of the Head Injury Criterion (HIC), Severity Index (SI), and peak acceleration values for different helmets at different helmet locations under modified NOCSAE standard drop tower tests. Essentially, these comparative drop test results revealed that the faceguard adds a stiffening kinematic constraint to the shell that lessens total energy absorption. The current NOCSAE standard test methods can be improved to represent on-field helmet hits by attaching the faceguards to helmets and by including two new helmet impact locations (Front Top and Front Top Boss). The reported football helmet test method gives a more accurate representation of a helmet's performance and its ability to mitigate on-field impacts while promoting safer football helmets.
MeSH term(s)	Biomechanical Phenomena ; Craniocerebral Trauma/prevention & control ; Football ; Head Protective Devices/standards ; Humans ; Sports Equipment/standards ; United States
Language	English
Publishing date	2017-02-19
Publishing country	United States
Document type	Journal Article ; Video-Audio Media
ISSN	1940-087X
ISSN (online)	1940-087X
DOI	10.3791/53929
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Article ; Online: Structure, property, and function of sheepshead (Archosargus probatocephalus) teeth.

Deang, J F / Persons, A K / Oppedal, A L / Rhee, H / Moser, R D / Horstemeyer, M F

Archives of oral biology

2018 Volume 89, Page(s) 1–8

Abstract: Objectives: This paper studies A. probatocephalus teeth and investigates the mechanical properties and chemical composition of the enameloid and dentin.: Design: Nanoindentation tests with a max load of 1000 μN and X-ray Energy Dispersive ... ...

Abstract	Objectives: This paper studies A. probatocephalus teeth and investigates the mechanical properties and chemical composition of the enameloid and dentin. Design: Nanoindentation tests with a max load of 1000 μN and X-ray Energy Dispersive Spectroscopy (EDS) were performed along the diameter of the polished sample. Microstructural analysis of the dentin tubules was performed from SEM images. Results: From nanoindentation testing, the dentin of the sheepshead teeth has a nanoindentation hardness of 0.89 ± 0.21 (mean ± S.D.) GPa and a reduced Young's modulus of 23.29 ± 5.30 GPa. The enameloid of A. probatocephalus has a hardness of 4.36 ± 0.44 GPa and a mean reduced Young's modulus of 98.14 ± 6.91 GPa. Additionally, nanoindentation tests showed that the enameloid's hardness and modulus increased closer to the surface of the tooth. X-ray Energy Dispersive Spectroscopy (EDS) data further suggests that the gradient may be a result of the wt% fluoride within the enameloid, where an increase in fluoride results in an increase in reduced Young's modulus and hardness. Conclusion: The microstructural characterization of the number density and area of the dentin tubules were used to address the porosity effect in the dentin to achieve the experimentally validated microhardness. The mechanical properties of the sheepshead teeth were also compared with previous nanoindentation tests from other aquatic species. The sheepshead teeth exhibit a greater reduced Young's modulus and hardness compared to shark and piranha teeth.
MeSH term(s)	Animals ; Biomechanical Phenomena ; Dental Enamel/chemistry ; Dental Enamel/diagnostic imaging ; Dental Enamel/drug effects ; Dental Stress Analysis ; Dentin/chemistry ; Dentin/diagnostic imaging ; Dentin/drug effects ; Dentin/ultrastructure ; Elastic Modulus ; Fishes/anatomy & histology ; Fluorides/pharmacology ; Hardness ; Stress, Mechanical ; Tooth/chemistry ; Tooth/diagnostic imaging ; Tooth/drug effects ; Tooth/ultrastructure
Chemical Substances	Fluorides (Q80VPU408O)
Language	English
Publishing date	2018-02-02
Publishing country	England
Document type	Journal Article
ZDB-ID	80227-x
ISSN	1879-1506 ; 0003-9969
ISSN (online)	1879-1506
ISSN	0003-9969
DOI	10.1016/j.archoralbio.2018.01.013
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Article ; Online: Moisture, anisotropy, stress state, and strain rate effects on bighorn sheep horn keratin mechanical properties.

Johnson, K L / Trim, M W / Francis, D K / Whittington, W R / Miller, J A / Bennett, C E / Horstemeyer, M F

Acta biomaterialia

2017 Volume 48, Page(s) 300–308

Abstract: This paper investigates the effects of moisture, anisotropy, stress state, and strain rate on the mechanical properties of the bighorn sheep (Ovis Canadensis) horn keratin. The horns consist of fibrous keratin tubules extending along the length of the ... ...

Abstract	This paper investigates the effects of moisture, anisotropy, stress state, and strain rate on the mechanical properties of the bighorn sheep (Ovis Canadensis) horn keratin. The horns consist of fibrous keratin tubules extending along the length of the horn and are contained within an amorphous keratin matrix. Samples were tested in the rehydrated (35wt% water) and ambient dry (10wt% water) conditions along the longitudinal and radial directions under tension and compression. Increased moisture content was found to increase ductility and decrease strength, as well as alter the stress state dependent nature of the material. The horn keratin demonstrates a significant strain rate dependence in both tension and compression, and also showed increased energy absorption in the hydrated condition at high strain rates when compared to quasi-static data, with increases of 114% in tension and 192% in compression. Compressive failure occurred by lamellar buckling in the longitudinal orientation followed by shear delamination. Tensile failure in the longitudinal orientation occurred by lamellar delamination combined with tubule pullout and fracture. The structure-property relationships quantified here for bighorn sheep horn keratin can be used to help validate finite element simulations of ram's impacting each other as well as being useful for other analysis regarding horn keratin on other animals. Statement of significance: The horn of the bighorn sheep is an anisotropic composite composed of keratin that is highly sensitive to moisture content. Keratin is also found in many other animals in the form of hooves, claws, beaks, and feathers. Only one previous study contains high rate experimental data, which was performed in the dry condition and only in compression. Considering the bighorn sheep horns' protective role in high speed impacts along with the moisture and strain rate sensitivity, more high strain rate data is needed to fully characterize and model the material. This study provides high strain rate results demonstrating the effects of moisture, anisotropy, and stress state. As a result, the comprehensive data allows modeling efforts to be greatly improved.
MeSH term(s)	Animals ; Anisotropy ; Biomechanical Phenomena ; Compressive Strength ; Horns/chemistry ; Horns/ultrastructure ; Humidity ; Image Processing, Computer-Assisted ; Keratins/chemistry ; Sheep, Bighorn ; Statistics as Topic ; Stress, Mechanical ; Tensile Strength
Chemical Substances	Keratins (68238-35-7)
Language	English
Publishing date	2017-01-15
Publishing country	England
Document type	Journal Article
ZDB-ID	2173841-5
ISSN	1878-7568 ; 1742-7061
ISSN (online)	1878-7568
ISSN	1742-7061
DOI	10.1016/j.actbio.2016.10.033
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Article ; Online: An interatomic potential for saturated hydrocarbons based on the modified embedded-atom method.

Nouranian, S / Tschopp, M A / Gwaltney, S R / Baskes, M I / Horstemeyer, M F

Physical chemistry chemical physics : PCCP

2014 Volume 16, Issue 13, Page(s) 6233–6249

Abstract: In this work, we developed an interatomic potential for saturated hydrocarbons using the modified embedded-atom method (MEAM), a reactive semi-empirical many-body potential based on density functional theory and pair potentials. We parameterized the ... ...

Abstract	In this work, we developed an interatomic potential for saturated hydrocarbons using the modified embedded-atom method (MEAM), a reactive semi-empirical many-body potential based on density functional theory and pair potentials. We parameterized the potential by fitting to a large experimental and first-principles (FP) database consisting of (1) bond distances, bond angles, and atomization energies at 0 K of a homologous series of alkanes and their select isomers from methane to n-octane, (2) the potential energy curves of H2, CH, and C2 diatomics, (3) the potential energy curves of hydrogen, methane, ethane, and propane dimers, i.e., (H2)2, (CH4)2, (C2H6)2, and (C3H8)2, respectively, and (4) pressure-volume-temperature (PVT) data of a dense high-pressure methane system with the density of 0.5534 g cc(-1). We compared the atomization energies and geometries of a range of linear alkanes, cycloalkanes, and free radicals calculated from the MEAM potential to those calculated by other commonly used reactive potentials for hydrocarbons, i.e., second-generation reactive empirical bond order (REBO) and reactive force field (ReaxFF). MEAM reproduced the experimental and/or FP data with accuracy comparable to or better than REBO or ReaxFF. The experimental PVT data for a relatively large series of methane, ethane, propane, and butane systems with different densities were predicted reasonably well by the MEAM potential. Although the MEAM formalism has been applied to atomic systems with predominantly metallic bonding in the past, the current work demonstrates the promising extension of the MEAM potential to covalently bonded molecular systems, specifically saturated hydrocarbons and saturated hydrocarbon-based polymers. The MEAM potential has already been parameterized for a large number of metallic unary, binary, ternary, carbide, nitride, and hydride systems, and extending it to saturated hydrocarbons provides a reliable and transferable potential for atomistic/molecular studies of complex material phenomena involving hydrocarbon-metal or polymer-metal interfaces, polymer-metal nanocomposites, fracture and failure in hydrocarbon-based polymers, etc. The latter is especially true since MEAM is a reactive potential that allows for dynamic bond formation and bond breaking during simulation. Our results show that MEAM predicts the energetics of two major chemical reactions for saturated hydrocarbons, i.e., breaking a C-C and a C-H bond, reasonably well. However, the current parameterization does not accurately reproduce the energetics and structures of unsaturated hydrocarbons and, therefore, should not be applied to such systems.
Language	English
Publishing date	2014-04-07
Publishing country	England
Document type	Journal Article
ZDB-ID	1476244-4
ISSN	1463-9084 ; 1463-9076
ISSN (online)	1463-9084
ISSN	1463-9076
DOI	10.1039/c4cp00027g
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