Abstract:Although a human eye comprises less than 0.1% of the frontal body surface area, injuries to the eye are found to be disproportionally common in survivors of explosions. This study aimed to introduce a Lagrangian-Eulerian coupling model to predict globe rupture resulting from primary blast effect. A finite element model of a human eye was created using Lagrangian mesh. An explosive and its surrounding air domain were modelled using Eulerian mesh. Coupling the two models allowed simulating the blast wave generat… Show more
“…The air was described by the MAT_NULL constitutive model and EOS_ LINEAR_POLYNOMIAL equation of state. 18 The pressure was expressed as where μ = 1/ V - 1, V is the relative volume, C 0 – C 6 are polynomial equation coefficients, and e 0 is the initial internal energy per unit reference specific volume.…”
Section: Methodsmentioning
confidence: 99%
“…17 Air 1.293E-3 C 0 = C 1 = C 2 = C 3 = C 6 = 0, C 4 = C 5 = 0.4 MPa, e 0 = 0.25 MPa. 18 Steel 7.86 E = 210 GPa, ν = 0.28, σ 0 = 1.08 GPa, E t = 0, C = 40.4 s −1 , p = 5. 19 Muscle 1.20 G 0 = 200 kPa, G ∞ = 195 kPa, K = 2.9 GPa, β = 0.1.…”
Objective
Fragment injury is a type of blast injury that is becoming more and more common in military campaigns and terrorist attacks. Numerical simulation methods investigating the formation of natural fragments and injuries to biological targets are expected to be developed.
Methods
A cylindrical warhead model was established and the formation process of natural fragments was simulated using the approach of tied nodes with failure through the explicit finite element (FE) software of LS-DYNA. The interaction between the detonation product and the warhead shell was simulated using the fluid–structure interaction algorithm. A method to simulate the injury of natural fragments to a biological target was presented by transforming Lagrange elements into smooth particle hydrodynamics (SPH) particles after the natural fragments were successfully formed. A computational model of the human thorax was established to simulate the injury induced by natural fragments by the node-to-surface contact algorithm with erosion.
Results
The discontinuous velocities of the warhead shell at different locations resulted in the formation of natural fragments with different sizes. The velocities of natural fragments increased rapidly at the initial stage and slowly after the warhead shell fractured. The initial velocities of natural fragments at the central part of the warhead shell were the largest, whereas those at both ends of the warhead shell were the smallest. The natural fragments resulted in bullet holes that were of the same shape as that of the fragments but slightly larger in size than the fragments in the human thorax after they penetrated through. Stress waves propagated in the ribs and enhanced the injury to soft tissues; additionally, ballistic pressure waves ahead of the natural fragments were also an injury factor to the soft tissues.
Conclusion
The proposed method is effective in simulating the formation of natural fragments and their injury to biological targets. Moreover, this method will be beneficial for simulating the combined injuries of natural fragments and shock waves to biological targets.
“…The air was described by the MAT_NULL constitutive model and EOS_ LINEAR_POLYNOMIAL equation of state. 18 The pressure was expressed as where μ = 1/ V - 1, V is the relative volume, C 0 – C 6 are polynomial equation coefficients, and e 0 is the initial internal energy per unit reference specific volume.…”
Section: Methodsmentioning
confidence: 99%
“…17 Air 1.293E-3 C 0 = C 1 = C 2 = C 3 = C 6 = 0, C 4 = C 5 = 0.4 MPa, e 0 = 0.25 MPa. 18 Steel 7.86 E = 210 GPa, ν = 0.28, σ 0 = 1.08 GPa, E t = 0, C = 40.4 s −1 , p = 5. 19 Muscle 1.20 G 0 = 200 kPa, G ∞ = 195 kPa, K = 2.9 GPa, β = 0.1.…”
Objective
Fragment injury is a type of blast injury that is becoming more and more common in military campaigns and terrorist attacks. Numerical simulation methods investigating the formation of natural fragments and injuries to biological targets are expected to be developed.
Methods
A cylindrical warhead model was established and the formation process of natural fragments was simulated using the approach of tied nodes with failure through the explicit finite element (FE) software of LS-DYNA. The interaction between the detonation product and the warhead shell was simulated using the fluid–structure interaction algorithm. A method to simulate the injury of natural fragments to a biological target was presented by transforming Lagrange elements into smooth particle hydrodynamics (SPH) particles after the natural fragments were successfully formed. A computational model of the human thorax was established to simulate the injury induced by natural fragments by the node-to-surface contact algorithm with erosion.
Results
The discontinuous velocities of the warhead shell at different locations resulted in the formation of natural fragments with different sizes. The velocities of natural fragments increased rapidly at the initial stage and slowly after the warhead shell fractured. The initial velocities of natural fragments at the central part of the warhead shell were the largest, whereas those at both ends of the warhead shell were the smallest. The natural fragments resulted in bullet holes that were of the same shape as that of the fragments but slightly larger in size than the fragments in the human thorax after they penetrated through. Stress waves propagated in the ribs and enhanced the injury to soft tissues; additionally, ballistic pressure waves ahead of the natural fragments were also an injury factor to the soft tissues.
Conclusion
The proposed method is effective in simulating the formation of natural fragments and their injury to biological targets. Moreover, this method will be beneficial for simulating the combined injuries of natural fragments and shock waves to biological targets.
“…Linear elastic material properties were used for lens, retina, choroid, tendon, ciliary body, socket-bone as recommended in the literature. For the aqueous, shock EOS material was employed with the coefficient taken from Liu et al 20 Cornea was the exposed component which was directly subjected to the airbag impact. It undergoes large deformations and can be simulated by hyperelastic material properties (Ogden formulation was employed here Liu et al, 20 Table 1 since it was highly strain rate dependent in small duration impacts.…”
Section: Methodsmentioning
confidence: 99%
“…For the aqueous, shock EOS material was employed with the coefficient taken from Liu et al 20 Cornea was the exposed component which was directly subjected to the airbag impact. It undergoes large deformations and can be simulated by hyperelastic material properties (Ogden formulation was employed here Liu et al, 20 Table 1 since it was highly strain rate dependent in small duration impacts. Properties of the sclera and vitreous body were given as the test data acquired from the in vitro tests of this study.…”
Airbags are safety devices in vehicles effectively suppressing passengers' injuries during accidents. Although there are still many cases of eye injuries reported due to eye-airbag impacts in recent years. Biomechanical approaches are now feasible and can considerably help experts to investigate the issue without ethical concerns. The eye-airbag impact-induced stresses/strains in various components of the eye were found to investigate the risk of injury in different conditions (impact velocity and airbag pressure). Three-dimensional geometry of the eyeball, fat and bony socket as well as the airbag were developed and meshed to develop a finite element model. Nonlinear material properties of the vitreous body and sclera were found through the in vitro tests on ovine samples and for the other components were taken from the literature. The eye collided the airbag due to the velocity field in the dynamic explicit step in Abaqus. Results of compression tests showed a nonlinear curve for vitreous body with average ultimate stress of 22 (18-25) kPa. Tensile behavior of sclera was viscoelastic nonlinear with ultimate stresses changing from 2.51 (2.3-2.7) to 4.3 (4-4.6) MPa when loading strain rate increased from 10 to 600 mm/min. Sclera, ciliary body, cornea and lens were the eye components with highest stresses (maximum stress reached up to 9.3 MPa). Cornea, retina and choroid experienced the highest strains with the maximum up to 14.1%. According to the previously reported injury criteria for cornea, it was at high risk of injury considering both stress and strains. Reduced pressure of the airbag was beneficial decreased stress of all components. Comprehensive investigations in this area can disclose biomechanical behavior of the eye during eye-airbag impact. Effective guidelines can be drawn for airbag design for instance the airbag pressure which reduces risk of eye injury.
This paper presents a novel principle for intraocular pressure (IOP)-sensing (monitoring) based on a pressure-sensitive soft composite in which a dual optical signal is produced in response to impulsive pressure input. For the initial assessment of the new IOP sensing principle, a human eye is modeled as the spherically shaped shell structure filled with the pressurized fluid, including cornea, sclera, lens and zonular fiber, and a fluid–structure interaction (FSI) analysis was performed to determine the correlation between the internal pressure and deformation (i.e., strain) rate of the spherical shell structure filled with fluid by formulating the finite element model. The FSI analysis results for human eye model are experimentally validated using a proof-of-conceptual experimental model consisting of a pressurized spherical shell structure filled with fluid and a simple air-puff actuation system. In this study, a mechanoluminescent ZnS:Cu- polydimethylsiloxane (PDMS)-based soft composite is fabricated and used to generate the dual optical signal because mechanically driven ZnS:Cu/PDMS soft composite can emit strong luminescence, suitable for soft sensor applications. Similar to the corneal behavior of the human eye, inward and outward deformations occur on the soft composite attached to the spherical shell structure in response to air puffing, resulting in a dual optical signal in the mechnoluminescence (ML) soft composite.
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