scholarly journals A 3-D Finite-Element Minipig Model to Assess Brain Biomechanical Responses to Blast Exposure

2021 ◽  
Vol 9 ◽  
Author(s):  
Aravind Sundaramurthy ◽  
Vivek Bhaskar Kote ◽  
Noah Pearson ◽  
Gregory M. Boiczyk ◽  
Elizabeth M. McNeil ◽  
...  
Keyword(s):  
Brain Tissue ◽  
Material Properties ◽  
Laboratory Experiments ◽  
Scaling Laws ◽  
Brain Injuries ◽  
Blast Waves ◽  
High Fidelity ◽  
Fe Model ◽  
Cerebral Vasculature ◽  
Biomechanical Responses

Despite years of research, it is still unknown whether the interaction of explosion-induced blast waves with the head causes injury to the human brain. One way to fill this gap is to use animal models to establish “scaling laws” that project observed brain injuries in animals to humans. This requires laboratory experiments and high-fidelity mathematical models of the animal head to establish correlates between experimentally observed blast-induced brain injuries and model-predicted biomechanical responses. To this end, we performed laboratory experiments on Göttingen minipigs to develop and validate a three-dimensional (3-D) high-fidelity finite-element (FE) model of the minipig head. First, we performed laboratory experiments on Göttingen minipigs to obtain the geometry of the cerebral vasculature network and to characterize brain-tissue and vasculature material properties in response to high strain rates typical of blast exposures. Next, we used the detailed cerebral vasculature information and species-specific brain tissue and vasculature material properties to develop the 3-D high-fidelity FE model of the minipig head. Then, to validate the model predictions, we performed laboratory shock-tube experiments, where we exposed Göttingen minipigs to a blast overpressure of 210 kPa in a laboratory shock tube and compared brain pressures at two locations. We observed a good agreement between the model-predicted pressures and the experimental measurements, with differences in maximum pressure of less than 6%. Finally, to evaluate the influence of the cerebral vascular network on the biomechanical predictions, we performed simulations where we compared results of FE models with and without the vasculature. As expected, incorporation of the vasculature decreased brain strain but did not affect the predictions of brain pressure. However, we observed that inclusion of the cerebral vasculature in the model changed the strain distribution by as much as 100% in regions near the interface between the vasculature and the brain tissue, suggesting that the vasculature does not merely decrease the strain but causes drastic redistributions. This work will help establish correlates between observed brain injuries and predicted biomechanical responses in minipigs and facilitate the creation of scaling laws to infer potential injuries in the human brain due to exposure to blast waves.

scholarly journals Cerebral Vasculature Influences Blast-Induced Biomechanical Responses of Human Brain Tissue

2021 ◽  
Vol 9 ◽  
Author(s):  
Dhananjay Radhakrishnan Subramaniam ◽  
Ginu Unnikrishnan ◽  
Aravind Sundaramurthy ◽  
Jose E. Rubio ◽  
Vivek Bhaskar Kote ◽  
...  
Keyword(s):  
Human Brain ◽  
Shock Tube ◽  
Brain Tissue ◽  
Human Head ◽  
Cerebral Veins ◽  
Fe Model ◽  
Cerebral Vasculature ◽  
Tissue Properties ◽  
Biomechanical Responses ◽  
The Brain

Multiple finite-element (FE) models to predict the biomechanical responses in the human brain resulting from the interaction with blast waves have established the importance of including the brain-surface convolutions, the major cerebral veins, and using non-linear brain-tissue properties to improve model accuracy. We hypothesize that inclusion of a more detailed network of cerebral veins and arteries can further enhance the model-predicted biomechanical responses and help identify correlates of blast-induced brain injury. To more comprehensively capture the biomechanical responses of human brain tissues to blast-wave exposure, we coupled a three-dimensional (3-D) detailed-vasculature human-head FE model, previously validated for blunt impact, with a 3-D shock-tube FE model. Using the coupled model, we computed the biomechanical responses of a human head facing an incoming blast wave for blast overpressures (BOPs) equivalent to 68, 83, and 104 kPa. We validated our FE model, which includes the detailed network of cerebral veins and arteries, the gyri and the sulci, and hyper-viscoelastic brain-tissue properties, by comparing the model-predicted intracranial pressure (ICP) values with previously collected data from shock-tube experiments performed on cadaver heads. In addition, to quantify the influence of including a more comprehensive network of brain vessels, we compared the biomechanical responses of our detailed-vasculature model with those of a reduced-vasculature model and a no-vasculature model for the same blast-loading conditions. For the three BOPs, the predicted ICP values matched well with the experimental results in the frontal lobe, with peak-pressure differences of 4–11% and phase-shift differences of 9–13%. As expected, incorporating the detailed cerebral vasculature did not influence the ICP, however, it redistributed the peak brain-tissue strains by as much as 30% and yielded peak strain differences of up to 7%. When compared to existing reduced-vasculature FE models that only include the major cerebral veins, our high-fidelity model redistributed the brain-tissue strains in most of the brain, highlighting the importance of including a detailed cerebral vessel network in human-head FE models to more comprehensively account for the biomechanical responses induced by blast exposure.

The Strain Rates of the Brain and Skull Under Dynamic Loading

2018 ◽  
Author(s):  
Mohammad Hosseini Farid ◽  
Ashkan Eslaminejad ◽  
Mohammadreza Ramzanpour ◽  
Mariusz Ziejewski ◽  
Ghodrat Karami
Keyword(s):  
Material Properties ◽  
Brain Injuries ◽  
Human Head ◽  
Element Model ◽  
Blast Waves ◽  
Cranial Bone ◽  
Strain Rates ◽  
Head Acceleration ◽  
Blunt Impact ◽  
The Brain

Accurate material properties of the brain and skull are needed to examine the biomechanics of head injury during highly dynamic loads such as blunt impact or blast. In this paper, a validated Finite Element Model (FEM) of a human head is used to study the biomechanics of the head in impact and blast leading to traumatic brain injuries (TBI). We simulate the head under various direction and velocity of impacts, as well as helmeted and un-helmeted head under blast waves. It is shown that the strain rates for the brain at impacts and blast scenarios are usually in the range of 36 to 241 s−1. The skull was found to experience a rate in the range of 14 to 182 s−1 under typical impact and blast cases. Results show for impact incidents the strain rates of brain and skull are approximately 1.9 and 0.7 times of the head acceleration. Also, this ratio of strain rate to head acceleration for the brain and skull was found to be 0.86 and 0.43 under blast loadings. These findings provide a good insight into measuring the brain tissue and cranial bone, and selecting material properties in advance for FEM of TBI.

scholarly journals Does Blast Exposure to the Torso Cause a Blood Surge to the Brain?

2020 ◽  
Vol 8 ◽  
Author(s):  
Jose E. Rubio ◽  
Maciej Skotak ◽  
Eren Alay ◽  
Aravind Sundaramurthy ◽  
Dhananjay Radhakrishnan Subramaniam ◽  
...  
Keyword(s):  
Brain Injury ◽  
Carotid Artery ◽  
Brain Tissue ◽  
Shear Stresses ◽  
Fe Model ◽  
Cerebral Vasculature ◽  
Blast Exposure ◽  
Indirect Mechanism ◽  
Wall Shear ◽  
The Brain

The interaction of explosion-induced blast waves with the torso is suspected to contribute to brain injury. In this indirect mechanism, the wave-torso interaction is assumed to generate a blood surge, which ultimately reaches and damages the brain. However, this hypothesis has not been comprehensively and systematically investigated, and the potential role, if any, of the indirect mechanism in causing brain injury remains unclear. In this interdisciplinary study, we performed experiments and developed mathematical models to address this knowledge gap. First, we conducted blast-wave exposures of Sprague-Dawley rats in a shock tube at incident overpressures of 70 and 130 kPa, where we measured carotid-artery and brain pressures while limiting exposure to the torso. Then, we developed three-dimensional (3-D) fluid-structure interaction (FSI) models of the neck and cerebral vasculature and, using the measured carotid-artery pressures, performed simulations to predict mass flow rates and wall shear stresses in the cerebral vasculature. Finally, we developed a 3-D finite element (FE) model of the brain and used the FSI-computed vasculature pressures to drive the FE model to quantify the blast-exposure effects in the brain tissue. The measurements from the torso-only exposure experiments revealed marginal increases in the peak carotid-artery overpressures (from 13.1 to 28.9 kPa). Yet, relative to the blast-free, normotensive condition, the FSI simulations for the blast exposures predicted increases in the peak mass flow rate of up to 255% at the base of the brain and increases in the wall shear stress of up to 289% on the cerebral vasculature. In contrast, our simulations suggest that the effect of the indirect mechanism on the brain-tissue-strain response is negligible (<1%). In summary, our analyses show that the indirect mechanism causes a sudden and abundant stream of blood to rapidly propagate from the torso through the neck to the cerebral vasculature. This blood surge causes a considerable increase in the wall shear stresses in the brain vasculature network, which may lead to functional and structural effects on the cerebral veins and arteries, ultimately leading to vascular pathology. In contrast, our findings do not support the notion of strain-induced brain-tissue damage due to the indirect mechanism.

scholarly journals Ballistic impact of single particles into gelatin : experiments and modeling with application to transdermal pharmaceutical delivery

2021 ◽  
Author(s):  
Rachel Ann Guha
Keyword(s):  
Material Properties ◽  
High Speed ◽  
Scaling Laws ◽  
Impact Behavior ◽  
Powder Injection ◽  
Fe Model ◽  
Calibration System ◽  
Human Dermis ◽  
Steel Balls ◽  
Impact Experiments

The high speed penetration of particles into the human dermis is of interest for targeted drug delivery by transdermal powder injection. However, performing well-controlled single impact experiments with micron scale particles on dermal tissues is difficult. Therefore, the suitability of the use of a dimensionally scaled up 'model' system utilizing steel balls impacting a gelatin to simulate the perforation of micron sized gold particles into human skin was investigated. A finite element (FE) model of a 'calibration' system consisting of a 2 μm gold sphere impacting the human dermis at 651 m/s was used to extract the combinations of possible epidermal material properties which allowed an FE predicted penetration able to match measured data from an existing study in the literature. Novel scaling laws were developed to link the 'model' and 'calibration' systems, and impact experiments were performed on gelatins of various formulations to determine the formulation that produced a penetration which, when scaled, matched that of the calibration system. The resulting material properties of the gelatin were appropriately scaled and used to choose the best combination of skin material properties. In this manner, a quasi static elastic modulus of 2.25 MPa was found for skin, in good agreement with reported values from the literature. Further experiments were performed with steel, polymethyl-methacrylate, titanium, and tungsten carbide balls impacting the gelatin, in order to determine the effects of particle size and density on penetration depth. FE simulations of both the model and calibration systems confirmed the scaling relationships and impact behavior found in these experiments. Both the FE model and the steel-gelatin experiments were able to predict the penetration trends found by other investigators in the examination of typical particles used for vaccine delivery. It can therefore be concluded that scaled up systems utilizing ballistic gelatins can be used to investigate the performance of transdermal powder injection technology.

scholarly journals Ballistic Impact of Single Particles into Gelatin : Experiments and Modeling with Application to Transdermal Pharmaceutical Delivery

2021 ◽  
Author(s):  
Rachel Ann Guha
Keyword(s):  
Material Properties ◽  
High Speed ◽  
Scaling Laws ◽  
Impact Behavior ◽  
Powder Injection ◽  
Fe Model ◽  
Calibration System ◽  
Human Dermis ◽  
Steel Balls ◽  
Impact Experiments

The high speed penetration of particles into the human dermis is of interest for targeted drug delivery by transdermal powder injection. However, performing well-controlled single impact experiments with micron scale particles on dermal tissues is difficult. Therefore, the suitability of the use of a dimensionally scaled up 'model' system utilizing steel balls impacting a gelatin to simulate the perforation of micron sized gold particles into human skin was investigated. A finite element (FE) model of a 'calibration' system consisting of a 2 μm gold sphere impacting the human dermis at 651 m/s was used to extract the combinations of possible epidermal material properties which allowed an FE predicted penetration able to match measured data from an existing study in the literature. Novel scaling laws were developed to link the 'model' and 'calibration' systems, and impact experiments were performed on gelatins of various formulations to determine the formulation that produced a penetration which, when scaled, matched that of the calibration system. The resulting material properties of the gelatin were appropriately scaled and used to choose the best combination of skin material properties. In this manner, a quasi static elastic modulus of 2.25 MPa was found for skin, in good agreement with reported values from the literature. Further experiments were performed with steel, polymethyl-methacrylate, titanium, and tungsten carbide balls impacting the gelatin, in order to determine the effects of particle size and density on penetration depth. FE simulations of both the model and calibration systems confirmed the scaling relationships and impact behavior found in these experiments. Both the FE model and the steel-gelatin experiments were able to predict the penetration trends found by other investigators in the examination of typical particles used for vaccine delivery. It can therefore be concluded that scaled up systems utilizing ballistic gelatins can be used to investigate the performance of transdermal powder injection technology.

scholarly journals Ballistic impact of single particles into gelatin : experiments and modeling with application to transdermal pharmaceutical delivery

2021 ◽  
Author(s):  
Rachel Ann Guha
Keyword(s):  
Material Properties ◽  
High Speed ◽  
Scaling Laws ◽  
Impact Behavior ◽  
Powder Injection ◽  
Fe Model ◽  
Calibration System ◽  
Human Dermis ◽  
Steel Balls ◽  
Impact Experiments

The high speed penetration of particles into the human dermis is of interest for targeted drug delivery by transdermal powder injection. However, performing well-controlled single impact experiments with micron scale particles on dermal tissues is difficult. Therefore, the suitability of the use of a dimensionally scaled up 'model' system utilizing steel balls impacting a gelatin to simulate the perforation of micron sized gold particles into human skin was investigated. A finite element (FE) model of a 'calibration' system consisting of a 2 μm gold sphere impacting the human dermis at 651 m/s was used to extract the combinations of possible epidermal material properties which allowed an FE predicted penetration able to match measured data from an existing study in the literature. Novel scaling laws were developed to link the 'model' and 'calibration' systems, and impact experiments were performed on gelatins of various formulations to determine the formulation that produced a penetration which, when scaled, matched that of the calibration system. The resulting material properties of the gelatin were appropriately scaled and used to choose the best combination of skin material properties. In this manner, a quasi static elastic modulus of 2.25 MPa was found for skin, in good agreement with reported values from the literature. Further experiments were performed with steel, polymethyl-methacrylate, titanium, and tungsten carbide balls impacting the gelatin, in order to determine the effects of particle size and density on penetration depth. FE simulations of both the model and calibration systems confirmed the scaling relationships and impact behavior found in these experiments. Both the FE model and the steel-gelatin experiments were able to predict the penetration trends found by other investigators in the examination of typical particles used for vaccine delivery. It can therefore be concluded that scaled up systems utilizing ballistic gelatins can be used to investigate the performance of transdermal powder injection technology.

scholarly journals Ballistic Impact of Single Particles into Gelatin : Experiments and Modeling with Application to Transdermal Pharmaceutical Delivery

2021 ◽  
Author(s):  
Rachel Ann Guha
Keyword(s):  
Material Properties ◽  
High Speed ◽  
Scaling Laws ◽  
Impact Behavior ◽  
Powder Injection ◽  
Fe Model ◽  
Calibration System ◽  
Human Dermis ◽  
Steel Balls ◽  
Impact Experiments

The high speed penetration of particles into the human dermis is of interest for targeted drug delivery by transdermal powder injection. However, performing well-controlled single impact experiments with micron scale particles on dermal tissues is difficult. Therefore, the suitability of the use of a dimensionally scaled up 'model' system utilizing steel balls impacting a gelatin to simulate the perforation of micron sized gold particles into human skin was investigated. A finite element (FE) model of a 'calibration' system consisting of a 2 μm gold sphere impacting the human dermis at 651 m/s was used to extract the combinations of possible epidermal material properties which allowed an FE predicted penetration able to match measured data from an existing study in the literature. Novel scaling laws were developed to link the 'model' and 'calibration' systems, and impact experiments were performed on gelatins of various formulations to determine the formulation that produced a penetration which, when scaled, matched that of the calibration system. The resulting material properties of the gelatin were appropriately scaled and used to choose the best combination of skin material properties. In this manner, a quasi static elastic modulus of 2.25 MPa was found for skin, in good agreement with reported values from the literature. Further experiments were performed with steel, polymethyl-methacrylate, titanium, and tungsten carbide balls impacting the gelatin, in order to determine the effects of particle size and density on penetration depth. FE simulations of both the model and calibration systems confirmed the scaling relationships and impact behavior found in these experiments. Both the FE model and the steel-gelatin experiments were able to predict the penetration trends found by other investigators in the examination of typical particles used for vaccine delivery. It can therefore be concluded that scaled up systems utilizing ballistic gelatins can be used to investigate the performance of transdermal powder injection technology.

A two-stage design optimization framework for multifield origami-inspired structures

2021 ◽  
pp. 1045389X2110116
Author(s):  
Wei Zhang ◽  
Saad Ahmed ◽  
Jonathan Hong ◽  
Zoubeida Ounaies ◽  
Mary Frecker
Keyword(s):  
Case Studies ◽  
Computing Time ◽  
Computational Cost ◽  
High Fidelity ◽  
Fe Model ◽  
Two Stage ◽  
Baseline Design ◽  
Optimization Framework ◽  
Highly Nonlinear ◽  
Stage 1

Different types of active materials have been used to actuate origami-inspired self-folding structures. To model the highly nonlinear deformation and material responses, as well as the coupled field equations and boundary conditions of such structures, high-fidelity models such as finite element (FE) models are needed but usually computationally expensive, which makes optimization intractable. In this paper, a computationally efficient two-stage optimization framework is developed as a systematic method for the multi-objective designs of such multifield self-folding structures where the deformations are concentrated in crease-like areas, active and passive materials are assumed to behave linearly, and low- and high-fidelity models of the structures can be developed. In Stage 1, low-fidelity models are used to determine the topology of the structure. At the end of Stage 1, a distance measure [Formula: see text] is applied as the metric to determine the best design, which then serves as the baseline design in Stage 2. In Stage 2, designs are further optimized from the baseline design with greatly reduced computing time compared to a full FEA-based topology optimization. The design framework is first described in a general formulation. To demonstrate its efficacy, this framework is implemented in two case studies, namely, a three-finger soft gripper actuated using a PVDF-based terpolymer, and a 3D multifield example actuated using both the terpolymer and a magneto-active elastomer, where the key steps are elaborated in detail, including the variable filter, metrics to select the best design, determination of design domains, and material conversion methods from low- to high-fidelity models. In this paper, analytical models and rigid body dynamic models are developed as the low-fidelity models for the terpolymer- and MAE-based actuations, respectively, and the FE model of the MAE-based actuation is generalized from previous work. Additional generalizable techniques to further reduce the computational cost are elaborated. As a result, designs with better overall performance than the baseline design were achieved at the end of Stage 2 with computing times of 15 days for the gripper and 9 days for the multifield example, which would rather be over 3 and 2 months for full FEA-based optimizations, respectively. Tradeoffs between the competing design objectives were achieved. In both case studies, the efficacy and computational efficiency of the two-stage optimization framework are successfully demonstrated.

Targeting the Cerebrovascular System: Next-Generation Biomarkers and Treatment for Mild Traumatic Brain Injury

2021 ◽  
pp. 107385842110122
Author(s):  
Tamara L. Baker ◽  
Denes V. Agoston ◽  
Rhys D. Brady ◽  
Brendan Major ◽  
Stuart J. McDonald ◽  
...  
Keyword(s):  
Brain Function ◽  
Brain Injuries ◽  
Neurological Dysfunction ◽  
Clinical Approach ◽  
Cerebral Vasculature ◽  
Review Of The Literature ◽  
Cerebrovascular Injury ◽  
Medical Issues ◽  
And Function ◽  
Cerebrovascular System

The diagnosis, prognosis, and treatment of mild traumatic brain injuries (mTBIs), such as concussions, are significant unmet medical issues. The kinetic forces that occur in mTBI adversely affect the cerebral vasculature, making cerebrovascular injury (CVI) a pathophysiological hallmark of mTBI. Given the importance of a healthy cerebrovascular system in overall brain function, CVI is likely to contribute to neurological dysfunction after mTBI. As such, CVI and related pathomechanisms may provide objective biomarkers and therapeutic targets to improve the clinical management and outcomes of mTBI. Despite this potential, until recently, few studies have focused on the cerebral vasculature in this context. This article will begin by providing a brief overview of the cerebrovascular system followed by a review of the literature regarding how mTBI can affect the integrity and function of the cerebrovascular system, and how this may ultimately contribute to neurological dysfunction and neurodegenerative conditions. We then discuss promising avenues of research related to mTBI biomarkers and interventions that target CVI, and conclude that a clinical approach that takes CVI into account could result in substantial improvements in the care and outcomes of patients with mTBI.

Probabilistic Oblique Impact Analysis of Functionally Graded Plates – A Multivariate Adaptive Regression Splines Approach

2021 ◽  
Author(s):  
P. K. Karsh ◽  
Bindi Thakkar ◽  
R. R. Kumar ◽  
Vaishali ◽  
Sudip Dey
Keyword(s):  
Material Properties ◽  
Mass Density ◽  
Plate Thickness ◽  
Functionally Graded ◽  
Multivariate Adaptive Regression Splines ◽  
Low Velocity Impact ◽  
Fe Model ◽  
Low Velocity ◽  
Velocity Impact ◽  
Mars Model

Purpose: To investigate the probabilistic low-velocity impact of functionally graded (FG) plate using the MARS model, considering uncertain system parameters. Design/methodology/application: The distribution of various material properties throughout FG plate thickness is calculated using power law. For finite element (FE) formulation, isoparametric elements with eight nodes are considered, each component has five degrees of freedom. The combined effect of variability in material properties such as elastic modulus, modulus of rigidity, Poisson’s ratio, and mass density are considered. The surrogate model is validated with the FE model represented by the scatter plot and the probability density function (PDF) plot based on Monte Carlo simulation (MCS). Findings: The outcome of the degree of stochasticity, impact angle, impactor’s velocity, impactor’s mass density, and point of impact on the maximum value of contact force (CFmax ), plate deformation (PDmax), and impactor deformation (IDmax ) are determined. A convergence study is also performed to determine the optimal number of the constructed MARS model’s sample size. Originality/value: The results illustrate the significant effects of uncertain input parameters on FGM plates’ low-velocity impact responses by employing a surrogate-based MARS model.

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