Experimental investigation of cranial fracture initiation in blunt human head impacts

2019 ◽  
Vol 300 ◽  
pp. 51-62 ◽  
Author(s):  
Mariyam I. Isa ◽  
Todd W. Fenton ◽  
Alexis C. Goots ◽  
Elena O. Watson ◽  
Patrick E. Vaughan ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Human Head ◽  
Fracture Initiation ◽  
Head Impacts

A destructible headform for the assessment of sports impacts

2021 ◽  
pp. 175433712110559
Author(s):  
Ben Stone ◽  
Sean Mitchell ◽  
Yusuke Miyazaki ◽  
Nicholas Peirce ◽  
Andy Harland
Keyword(s):  
Human Subjects ◽  
Permanent Deformation ◽  
Human Head ◽  
Local Deformation ◽  
Resonance Excitation ◽  
Destructive Testing ◽  
Head Impacts ◽  
Resonance Frequencies ◽  
Hybrid Iii ◽  
Athletic Equipment

Commercially available headforms, such as the Hybrid-III and EN 960 headforms, have been used effectively to investigate the mechanics of head impacts. These headforms may result in accelerations that are unrepresentative of a human head in some impact scenarios. This may be important when considering impacts that produce areas of high pressure, since skull deformation and resonance excitation may influence the dynamic response. The National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform may produce a more suitable response during these types of impacts due to the more representative skull component. However, permanent deformation may occur in some unprotected impact scenarios, resulting in the entire headform needing to be replaced. This paper outlines the development of a novel, modular and destructible headform (LU headform) that can be used in potentially destructive testing, where individual components can be replaced. The LU headform was modelled after a UK 50th percentile male. The inertial properties of the LU headform were within 6% of those observed in humans. The skull simulant properties were within the range of values reported for human tissue in two build orientations, but lower in one build orientation. The lowest and highest resonance frequencies observed in the headform model were within 5% of those observed in humans. Drop and projectile tests were conducted in line with previous cadaver tests with the observed accelerations within the range reported for post-mortem human subjects. The LU headform offers a practical means of simulating head dynamics during localised unprotected impacts or in protected impacts where local deformation and/or resonance frequency excitation remains possible.

scholarly journals Developing Brain-Strain-Based Scaling to Inform the Clinical Relevance of Mouse Models of Concussion Induced by Rotation

2021 ◽  
Author(s):  
Xingyu Liu ◽  
Lihong Lu ◽  
Kewei Bian ◽  
Arthur Brown ◽  
Haojie Mao
Keyword(s):  
Brain Injury ◽  
Real World ◽  
Clinical Relevance ◽  
Neuronal Damage ◽  
Animal Experiments ◽  
Human Head ◽  
Axial Rotation ◽  
Head Impacts ◽  
Flexion Extension ◽  
Human And Mouse

Abstract Background Laboratory animal experiments are an invaluable tool for studying mild traumatic brain injury (mTBI)/concussion. Among them, rodent neurotrauma experiments have been most widely used, as transgenic and gene targeting technologies in mice allow us to test the roles of different genes in recovery from brain injury. Furthermore, the clinical relevance of rodent concussion studies can be improved by using these technologies to study concussions in animals that carry the human versions of genes known to play a role in neurological disease. However, delivering concussion injuries to the mice that are relevant to real-world human head impacts is challenging, as the mouse and human heads are dramatically different in shape and size. In the vast majority of mouse concussion experiments, the pathological and behavioral consequences of the injuries are evaluated without considering whether the injury model produces brain stretches (maximum principal strains) of the same magnitude as those experienced by human brains undergoing similar impacts. Methods We conducted a total of 201 computational simulations to understand both human and mouse brain strains that are directly linked to neuronal damage during closed-head concussive impacts. To represent real-world human head impacts we simulated mouse head impacts with durations of 1.5 ms (Type 1 scaling), followed by simulations with durations between 1 and 2 ms (Type 2), and finally, simulations with durations from 0.75 to 4.5 ms (Type 3) to develop scaling between human and mouse, as well as to reveal the predicted effects of small and large changes in impact durations on brain strain. Results Guided by these simulations we calculated that peak rotational velocities in mice could be achieved by scaling human peak rotational velocities with factors of 5.8, 4.6, and 6.8, for flexion/extension, lateral bending, and axial rotation, respectively, to reach equal brain strains between human and mouse. The effects of impact durations on scaling were also calculated and longer-duration mouse head impacts needed larger scaling factors to reach equal strain. Conclusions The scaling method will help us to create brain injury in the mouse with brain strain loading equivalent to those experienced in real-world human head impacts.

Head Impact Modeling to Support a Rotational Combat Helmet Drop Test

2021 ◽  
Author(s):  
Ryan Terpsma ◽  
Rika Wright Carlsen ◽  
Ron Szalkowski ◽  
Sushant Malave ◽  
Alice Lux Fawzi ◽  
...  
Keyword(s):  
Human Head ◽  
Mechanical Stimulus ◽  
Scientific Basis ◽  
Test Method ◽  
Drop Test ◽  
Head Impacts ◽  
Digital Twin ◽  
Brain Deformation ◽  
Acceleration Time Histories ◽  
Hybrid Iii

ABSTRACT Introduction The Advanced Combat Helmet (ACH) military specification (mil-spec) provides blunt impact acceleration criteria that must be met before use by the U.S. warfighter. The specification, which requires a helmeted magnesium Department of Transportation (DOT) headform to be dropped onto a steel hemispherical target, results in a translational headform impact response. Relative to translations, rotations of the head generate higher brain tissue strains. Excessive strain has been implicated as a mechanical stimulus leading to traumatic brain injury (TBI). We hypothesized that the linear constrained drop test method of the ACH specification underreports the potential for TBI. Materials and Methods To establish a baseline of translational acceleration time histories, we conducted linear constrained drop tests based on the ACH specification and then performed simulations of the same to verify agreement between experiment and simulation. We then produced a high-fidelity human head digital twin and verified that biological tissue responses matched experimental results. Next, we altered the ACH experimental configuration to use a helmeted Hybrid III headform, a freefall cradle, and an inclined anvil target. This new, modified configuration allowed both a translational and a rotational headform response. We applied this experimental rotation response to the skull of our human digital twin and compared brain deformation relative to the translational baseline. Results The modified configuration produced brain strains that were 4.3 times the brain strains from the linear constrained configuration. Conclusions We provide a scientific basis to motivate revision of the ACH mil-spec to include a rotational component, which would enhance the test’s relevance to TBI arising from severe head impacts.

An Experimental Investigation of Filtercake Reinforced Wellbore Strengthening and Fracture Sealing

2019 ◽  
Author(s):  
Mingzheng Yang ◽  
Yuanhang Chen ◽  
Frederick B. Growcock ◽  
Feifei Zhang
Keyword(s):  
Experimental Investigation ◽  
Critical Role ◽  
Fracture Initiation ◽  
Fluid Loss ◽  
Lost Circulation ◽  
Fracture Sealing ◽  
Sealing Pressure ◽  
Wellbore Strengthening ◽  
Mud Loss ◽  
Lost Circulation Materials

Abstract Drilling-induced lost circulation should be managed before and during fracture initiation rather than after they propagate to form large fractures and losses become uncontrollable. Recent studies indicated the potentially critical role of filtercake in strengthening the wellbore through formation of a pressure-isolating barrier, as well as plugging microfractures during fracture initiation. In this study, an experimental investigation was conducted to understand the role played by filtercake in the presence of lost circulation materials (LCMs). A modified permeability plugging apparatus (PPA) with slotted discs was used to simulate whole mud loss through fractures of known width behind filtercake. Cumulative fluid loss upon achieving a complete seal and the maximum sealing pressure were measured to evaluate the combined effects of filtercake and LCMs in preventing and reducing fluid losses. The effects of some filtercake properties (along with LCM type, concentration and particle size distribution) on filtercake rupture and fracture sealing were investigated. The results indicate that filtercake can accelerate fracture sealing and reduce total mud loss. Efficiently depositing filtercake while drilling can reduce the concentration of LCM that is required to plug and isolate incipient fractures.

scholarly journals Computational Modeling of Skull Bone Structures and Simulation of Skull Fractures Using the YEAHM Head Model

Biology ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 267 ◽  
Author(s):  
Alcino Barbosa ◽  
Fábio A. O. Fernandes ◽  
Ricardo J. Alves de Sousa ◽  
Mariusz Ptak ◽  
Johannes Wilhelm
Keyword(s):  
Computational Models ◽  
Soft Tissues ◽  
Constitutive Models ◽  
Human Head ◽  
Head Model ◽  
Head Impacts ◽  
Skull Model ◽  
Linear Behavior ◽  
Local Material ◽  
Direct Head

The human head is a complex multi-layered structure of hard and soft tissues, governed by complex materials laws and interactions. Computational models of the human head have been developed over the years, reaching high levels of detail, complexity, and precision. However, most of the attention has been devoted to the brain and other intracranial structures. The skull, despite playing a major role in direct head impacts, is often overlooked and simplified. In this work, a new skull model is developed for the authors’ head model, the YEAHM, based on the original outer geometry, but segmenting it with sutures, diploë, and cortical bone, having variable thickness across different head sections and based on medical craniometric data. These structures are modeled with constitutive models that consider the non-linear behavior of skull bones and also the nature of their failure. Several validations are performed, comparing the simulation results with experimental results available in the literature at several levels: (i) local material validation; (ii) blunt trauma from direct impact against stationary skull; (iii) three impacts at different velocities simulating falls; (iv) blunt ballistic temporoparietal head impacts. Accelerations, impact forces, and fracture patterns are used to validate the skull model.

Experimental investigation of the structural aspect of fracture initiation in specimens of hard alloys of WC-20% Co loaded in unixial compression

1977 ◽  
Vol 9 (7) ◽  
pp. 874-877
Author(s):  
G. G. Travushkin ◽  
K. S. Chernyavskii ◽  
V. A. Fal'kovskii ◽  
N. F. Koval'skaya
Keyword(s):  
Experimental Investigation ◽  
Fracture Initiation ◽  
Structural Aspect ◽  
Hard Alloys

The Presence of the Temporal Horn Exacerbates the Vulnerability of Hippocampus during Head Impacts

2021 ◽  
Author(s):  
Zhou Zhou ◽  
Xiaogai Li ◽  
August Domel ◽  
Emily Dennis ◽  
Marios Georgiadis ◽  
...  
Keyword(s):  
Collegiate Athletes ◽  
Human Head ◽  
Hippocampal Volume ◽  
Arbitrary Lagrangian Eulerian ◽  
Predisposing Factor ◽  
Head Impacts ◽  
Strain And Strain Rate ◽  
Temporal Horn ◽  
Cornu Ammonis ◽  
Coupling Approach

Hippocampal injury is common in traumatic brain injury (TBI) patients, but the underlying pathogenesis remains elusive. In this study, we hypothesize that the presence of the adjacent fluid-containing temporal horn exacerbates the biomechanical vulnerability of the hippocampus. Two finite element models of the human head were used to investigate this hypothesis, one with and one without the temporal horn, and both including a detailed hippocampal subfield delineation. A fluid-structure interaction coupling approach was used to simulate the brain-ventricle interface, in which the intraventricular cerebrospinal fluid was represented by an arbitrary Lagrangian-Eulerian multi-material formation to account for its fluid behavior. By comparing the response of these two models under identical loadings, the model that included the temporal horn predicted increased magnitudes of strain and strain rate in the hippocampus with respect to its counterpart without the temporal horn. This specifically affected cornu ammonis (CA) 1 (CA1), CA2/3, hippocampal tail, subiculum, and the adjacent amygdala and ventral diencephalon. These computational results suggest the presence of the temporal horn is a predisposing factor for the prevalence of hippocampal injury, advancing the understanding of hippocampal injury during head impacts. A corresponding analysis in an imaging cohort of collegiate athletes found that temporal horn size negatively correlates with hippocampal volume in the same subfields, suggesting a possible real-world correlation whereby a larger temporal horn may be associated with decreased hippocampal volume. Our biomechanical and neuroimaging effort collectively highlight the mechanobiological and anatomical interdependency between the hippocampus and temporal horn.

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