Blast effect on the lower extremities and its mitigation: A computational study (original) (raw)
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Evaluation of Lower Limb Injury against AP Mine Blast:Numerical and Experimental Trials
EC Orthopaedics, 2020
In this study, the effectiveness of blast deflectors used in protective footwear against AP mines was investigated. The tip-angle of a V-shaped deflector and the overall shape (symmetrical, unsymmetrical) were chosen as the design parameters to be examined, whereas parameters such as deflector material and wall thickness were kept constant. Both explicit dynamic finite element analysis (LS-Dyna) and blasts tests were performed to evaluate the effectiveness of these design parameters. The analysis results were also verified with the blast tests. A visual (qualitative) comparison between the analysis results and blast tests show a good agreement on the final deformed geometry of the deflector, which suggests the simulation was able to capture the energy absorption mechanism of the deflector. The analysis results show that the peak force transmitted to the leg decreases tremendously with the addition a blast deflectors. When compared to the case with no deflectors, an unsymmetrical and symmetrical deflector reduced the peak force by a factor of 24 and 36, respectively.
Reduction of Acceleration Induced Injuries from Mine Blasts under Infantry Vehicles Authors
Anti tank (AT) mines and improvised explosive devices (IED) pose a serious threat to the occupants of infantry vehicles. The use of an energy absorbing seat in conjunction with vehicle armor plating greatly improves occupant survivability during such an explosion. The dynamic axial crushing of aluminum tubes constitutes the principal energy absorption mechanism to reduce the blast pulse transmitted to the occupant in this investigation. The injury mechanisms of both vehicle-occupant contact interfaces are simulated viz. vehicle seat upon the occupant's torso and vehicle floor upon the occupant's feet. Data such as hip and knee moment, femoral force, and foot acceleration is collected from the numerical dummy which simulates the occupant's response. This data is then compared to injury threshold values from various references to assess survivability.
Biomedical Engineering. Detroit, Wayne State …, 2005
The aim of this study was to assess the ability of lower limb surrogates to predict injury due to floor/foot plate impact in military vehicles during anti-vehicular land mine explosions. Testing was conducted using two loading conditions simulated to represent those conditions created in the field. The lower condition was represented by a 24-kg mass impactor with a velocity of 4.7 m/s. The higher loading condition was represented by a 37-kg mass impactor with a velocity of 8.3 m/s. Two biomechanical surrogates were evaluated using the loading conditions: 50th percentile Hybrid III foot/ankle and Test Device for Human Occupant Restraint THOR-Lx. Comparisons of the force-time response were made to established corridors. Results show a better correlation to the corridors with the THOR-Lx; however, future improvements to the THOR-Lx are recommended.
Frontiers in Bioengineering and Biotechnology, 2021
Improvised explosive devices (IEDs) used in the battlefield cause damage to vehicles and their occupants. The injury burden to the casualties is significant. The biofidelity and practicality of current methods for assessing current protection to reduce the injury severity is limited. In this study, a finite-element (FE) model of the leg was developed and validated in relevant blast-loading conditions, and then used to quantify the level of protection offered by a combat boot. An FE model of the leg of a 35 years old male cadaver was developed. The cadaveric leg was tested physically in a seated posture using a traumatic injury simulator and the results used to calibrate the FE model. The calibrated model predicted hindfoot forces that were in good correlation (using the CORrelation and Analysis or CORA tool) with data from force sensors; the average correlation and analysis rating (according to ISO18571) was 0.842. The boundary conditions of the FE model were then changed to replica...
Frontiers in Bioengineering and Biotechnology, 2021
Attacks with improvised explosive device (IED) constituted the main threat to, for example, Polish soldiers in Iraq and Afghanistan. Improving safety during transport in an armored vehicle has become an important issue. The main purpose of the presented research is to investigate the mechanism of lower leg injuries during explosion under an armored vehicle. Using a numerical anatomic model of the lower leg, the analysis of the leg position was carried out. In all presented positions, the stress limit of 160 (MPa) was reached, which indicates bone damage. There is a difference in stress distribution in anatomic elements pointing to different injury mechanisms.
An assessment of blast modelling techniques for injury biomechanics research
International Journal for Numerical Methods in Biomedical Engineering, 2019
Blast-induced Traumatic Brain Injury (TBI) has been affecting combatants and civilians. The blast pressure wave is thought to have a significant contribution to blast related TBI. Due to the limitations and difficulties of conducting blast tests on surrogates, computational modelling has been used as a key method for exploring this field. However, the blast wave modelling methods reported in current literature have drawbacks. They either cannot generate the desirable blast pressure wave history, or they are unable to accurately simulate the blast wave/structure interaction. In addition, boundary conditions, which can have significant effects on model predictions, have not been described adequately. Here, we critically assess the commonly used methods for simulating blast wave propagation in air (open-field blast) and its interaction with the human body. We investigate the predicted blast wave time history, blast wave transmission and the effects of various boundary conditions in 3 dimensional (3D) models of blast prediction. We propose a suitable meshing topology, which enables accurate prediction of blast wave propagation and interaction with the human head and significantly decreases the computational cost in 3D simulations. Finally, we predict strain and strain rate in the human brain during blast wave exposure and show the influence of the blast wave modelling methods on the brain response. The findings presented here can serve as guidelines for accurately modelling blast wave generation and interaction with the human body for injury biomechanics studies and design of prevention systems. Blast injuries have been common in recent military conflicts, caused by blast waves (primary blast injury), bullet/shrapnel impacts (secondary blast injury), the human body impacting with objects/ground (tertiary blast injury) and burn/toxic gas, etc (quaternary blast injury) [1]. These loadings are usually generated by Improvised Explosive Devices (IEDs), and many soldiers and civilians have been affected by such attacks in conflict zones. Among injuries to different parts of the human body, blast-induced TBI has attracted increasing medical and scientific attention due to the large percentage of affected combat troops. The data shows that there is a growing trend in blastinduced TBI in modern conflicts [2]. In the recent Iraq and Afghanistan conflicts, 22% of US injured soldiers suffered injuries in the head or neck, compared with 17.3% in Operation Desert Storm and 12-14% in Vietnam War. Between 2001 and 2014, about 230,000 soldiers were identified as suffering from TBI, which is nearly 20% of all deployed service members in Iraq and Afghanistan [3, 4]. The primary blast wave is suspected to contribute to blast-induced TBI [5]. Computational modelling has been widely used for studying the biomechanics of blast-induced TBI [6-11], given the limitations and difficulties of blast experiments on human surrogates or animals [12]. Computational modelling can provide high spatial and temporal resolutions, which provide new opportunities for understanding the mechanical response of different organs and tissues subjected to blast waves. The majority of previous studies have used the blast generation and Fluid-Structure Interaction (FSI) capabilities of the nonlinear hydro-code LS-DYNA to simulate blast wave interaction with human or animal biomechanical models of injury [6-9, 13, 14]. These approaches can be put into three categories: the Multi-Material Arbitrary Eulerian-Lagrangian method (MM-ALE), the combined Load Blast Enhanced and ALE method (LBE-ALE) and the combined Prescribed Inflow and ALE method (PIF-ALE). These methods are briefly described below. All three methods use the ALE formulation, which is a combination of the Lagrangian and Eulerian methods. The ALE formulation takes advantage of both methods by solving the problem in two steps: the Lagrangian motion, which moves the mesh with the material, and the Eulerian convection, which restores the mesh shape by allowing the material to flow through elements. Detailed fundamentals and theories of ALE method are well introduced elsewhere [15, 16]. This combination of Eulerian and Lagrangian methods enables modelling the fluid/structure interaction, without mesh distortion problems [17, 18]. This makes the ALE method suitable for simulating the interaction of the incident and reflected blast waves with the human body.
Journal of Biomechanics, 2016
Under-vehicle explosions often result in injury of occupants' lower extremities. The majority of these injuries are associated with poor outcomes. The protective ability of vehicles against explosions is assessed with Anthropometric Test Devices (ATDs) such as the MIL-Lx, which is designed to behave in a similar way to the human lower extremity when subjected to axial loading. It incorporates tibia load cells, the response of which can provide an indication of the risk of injury to the lower extremity through the use of injury risk curves developed from cadaveric experiments. In this study an axisymmetric finite element model of the MIL-Lx with a combat boot was developed and validated. Model geometry was obtained from measurements taken using digital callipers and rulers from the MIL-Lx, and using CT images for the combat boot. Appropriate experimental methods were used to obtain material properties. These included dynamic, uniaxial compression tests, quasi-static stress-relaxation tests and 3 point bending tests. The model was validated by comparing force-time response measured at the tibia load cells and the amount of compliant element compression obtained experimentally and computationally using two blast-injury experimental rigs. Good correlations between the numerical and experimental results were obtained with both. This model can now be used as a virtual test-bed of mitigation designs and in surrogate device development.
Biomechanical evaluations of injury risk for blast loading
Journal of biomechanical engineering, 2017
Ocular trauma is one of the most common types of combat injuries resulting from the exposure of military personnel with improvised explosive devices. The injury mechanism associated with the primary blast wave are poorly understood. We employed a three-dimensional computational model, which included the main internal ocular structures of the eye, spatially varying thickness of the cornea-scleral shell, and nonlinear tissue properties, to calculate the intraocular pressure and stress state of the eye-wall and internal ocular structure caused by blast. The intraocular pressure and stress magnitudes were applied to estimate the injury risk using existing models for blunt impact and blast loading. The simulation results demonstrated that blast loading can induce significant stresses in the different components of the eyes that correlate with observed primary blast injuries in animal studies. Different injury models produced widely different injury risk predictions, which highlights the ...