Blunt Criterion Research Articles

Ballistic impact wave and bulge profile propagation characteristics and blunt injury assessment of UHMWPE laminate composite

Amid escalating localized conflicts worldwide, the elucidation of the mechanisms and quantification blunt trauma the emergency services and military personnel confronted becomes imperatively. However, the understanding of bullet-induced bulge formation on the laminate's back face, impact wave propagation, and consequent trauma assessment methods remains incomplete. This study applies 3-dimension digital image correlation (3D-DIC) method to reveals these phenomena by utilizing a lead-core bullet traveling at 334.93 m/s to impact an ultra-high molecular weight polyethylene (UHMWPE) laminate. The results show that the initial transverse propagation velocity of bulge profile is 24.79% smaller than the theoretical calculation, which indicates the reduction caused by cohesive matrix. The transverse wave demonstrates a double exponential attenuation pattern, which could be decomposed into two single exponential attenuation curves. The bulge profile shows hyperbolic pattern, which reveals the stability of the bulge shape and the temporal evolution pattern. Increasing the laminate-body gap leads to a decline in Blunt Criterion (BC) and the Abbreviated Injury Scale (AIS) values reduce from 2 to 0 correspondingly. The numerical model confirms the compression wave velocity as 1447.77 ± 123.10 m/s in the thickness direction and 9542.86 ± 3087.75 m/s in the fiber direction. These findings reveals and quantified the propagation patterns of back bulge and compressive wave, and thus could provide data-driven insights to improve body armor performance and blunt trauma assessment for individual soldiers.

Ballistic impact wave and back bulge propagation mechanism and blunt trauma assessment of ceramic/UHMWPE composite body armor

With increasing local conflicts worldwide, studying the impact response of body armor is crucial for enhancing soldier survival rates. However, there is still insufficient understanding of the back bulge expansion patterns, the impact waves transmission features, and blunt injury assessing method of body armor. To investigate these problems deeply, the three-dimensional digital image correlation method and numerical models were employed to reveal the ballistic response mechanism of ceramic/ultra-high-molecular-weight polyethylene (UHMWPE) composite body armor impacted by 7.62 mm rifle bullet. This study built theoretical function for the bulge expansion, revealed the wave transmission mechanism and fractures in both materials and their interaction. Firstly, the experiment revealed that the back-face bulge transverse expansion velocity exhibits a double exponential decrease. Secondly, the contour of back-face bulges consistently demonstrated excellent hyperbolic characteristics at various moments. Thirdly, the average Viscous Criterion (VC) and Blunt Criterion (BC) values were 5.37 and 0.95, corresponding to Abbreviated Injury Scale (AIS) values of 6 and 4. Fourthly, the simulation revealed that the ceramics transverse and radial cracks seems primarily induced by shear stress xy; ceramics conical cracks occurring at the boundaries of equivalent stress seems primarily induced by stress in x and y directions. Fifthly, numerical results revealed that the velocity of compression waves within the laminate increases over time in the impact direction and consistent with ceramic velocity impacted on the laminate. These findings lead to experimental and theoretical advances in the impact response mechanism of composite body armor and provide index for improving the protective performance.

Energy absorption behavior of aramid/DCPD backing to determining the blunt trauma criterion of a human head in a ballistic helmet

The research involved analyzing a material solution for a 9 mm Full Metal Jacket (FMJ) Parabellum loaded with ballistic impact on a resin laminate strengthened with extra aramid layers. The goal of this research is to determine the impact of material (aramid/DCPD) layer thickness on the energy absorption performance of the laminate for blunt trauma as blunt criterion (BC). For this purpose, aramid fiber laminate with dicyclopentadiene (DCPD) resin matrix was prepared. Laminate samples were tested on the drop test and were subjected to ballistic loads. The ABAQUS/Explicit program and finite element method were used to conduct the study. Individual material systems' optimal solutions were created using numerical analysis, and they were then classified using the mass-efficiency criterion. The numerical results were compared with the experimental using samples prepared according to the modeling methods. Selected results were shown and discussed in the later part of the paper.

Evaluation of the drone-human collision consequences

The operational safety assessment of the unmanned vehicles is crucial for their subsequent practical use. The safety limit criteria used for the operation assessment, especially values closely related to the safety of persons and their vulnerability to collision with these vehicles, represent nowadays a significant limitation. This contribution presents the currently discussed and proposed human safety criteria for the UAS, evaluates the available data from the collision dynamic tests and computer modelling and provides the possibility to compare and evaluate these criteria on a validated set of data. A total of five small UAS, three multi-rotor quadcopters and two fixed-wing aircrafts were used to verify the current methods and serve as a basis for the assessment. The results of the measurements obtained through the crash tests demonstrate the excessive restrictiveness of the currently used kinetic energy threshold values and the limited value of some proposed criterions, e.g. the blunt criterion. On the contrary, they point to the appropriateness of the application of car vulnerability criterions. The UAS mass or kinetic energy tests represent an easily definable threshold value, however, the available data sets and the tests performed showed limitations of its applicability for the deformable and fragile UAS structures. The article aims to verify, based on its own impact tests, the adequacy of the evaluation of the safety criteria of the UAS operation in relation to the development of the current legislation that defines the conditions of use of these machines.

Human Effects Assessment of 40-mm Nonlethal Impact Munitions

An extensive human effects study was conducted on 40-mm nonlethal impact munitions having two different projectile nose configurations: a compliant sponge nose and a frangible foam nose carrying a powder payload. The study included an initial characterization of the rounds using the blunt criterion (BC). Injury risk assessment was done using two previously validated surrogates; thoracic blunt impact assessment utilized the 3-rib ballistic impact dummy (3RBID), and penetrating trauma assessment utilized a biomechanical surrogate consisting of ordnance gelatin and a specific combination of layers to simulate skin and underlying soft tissue. Production impact munitions were manufactured to produce a range of energy levels on impact by adjusting the propellant charge in the smokeless propulsion system, resulting in different projectile muzzle velocities. Twenty-three impacts were performed on the 3RBID biomechanical surrogate at kinetic energy levels in the range of 148–257 J to generate viscous criterion (VCmax) levels for injury assessment. The production configurations of the sponge and frangible-nose munitions were compared to the acceptable values for blunt trauma (VCmax ≤ 0.8). Thirty-nine impacts were done on a skin penetration surrogate at kinetic energy levels in the range of 170–305 J and the impact energies corresponding to penetrations were identified and compared with the production configurations for these munitions and with the expected energy density values for a 50% risk of penetration for specific areas of the body.

Wear mechanism and life prediction of TiN coated tool in high speed milling of ceramic–PTFE composite

With TiN coated solid carbide, a series of machining experiments were performed to define wear blunt criterion, and the recommended wear blunt criterion is 40 μm. Using orthogonal experiment method, multifactor and multilevel cutting experiments were designed. Based on the measuring results, forms of tool wear are discussed according to grain abrasion, diffusion abrasion, bonding abrasion, and crack and breakage. Tool wear mechanism was analysed in detail by micropattern scan and chemical element analysis. For dependent variable wear extent (VB), regression analysis was performed with independent variables such as cutting speed v, feed rate f, axial depth of cut ap, radial depth of cut ae and cutting length L. Based on the calculated result of VB, a method was proposed to predict tool life. Research results will provide a useful way of processing optimisation and quality improvement for high speed machining of ceramic–polytetrafluoroethylene composites.

Assessment of the TASER XREP Blunt Impact and Penetration Injury Potential Using Cadaveric Testing

TASER International's extended range electronic projectile (XREP) is intended to be fired from a shotgun, impact a threat, and apply remote neuromuscular incapacitation. This study investigated the corresponding potential of blunt impact injury and penetration. Forty-three XREP rounds were deployed onto two male human cadaver torsos at impact velocities between 70.6 and 95.9 m/sec (232 and 315 ft/sec). In 42 of the 43 shots fired, the XREP did not penetrate the abdominal wall, resulting in superficial wounds only. On one shot, the XREP's nose section separated prematurely in flight, resulting in penetration. No bony fractures were observed with any of the shots. The viscous criterion (VC), blunt criterion (BC), and energy density (E/A) were calculated (all nonpenetrating tests, average ± 1 standard deviation: VC: 1.14 ± 0.94 m/sec, BC: 0.77 ± 0.15, E/A: 22.6 ± 4.15 J/cm(2)) and, despite the lack of injuries, were generally found to be greater than published tolerance values.

Comparison of thoracic wall behavior in large animals and human cadavers submitted to an identical ballistic blunt thoracic trauma

BackgroundSeveral models of ballistic blunt thoracic trauma are available, including human cadavers and large animals. Each model has advantages and disadvantages regarding anatomy and physiology, but they have not been compared with identical ballistic aggression. MethodsTo compare thoracic wall behavior in 40-kg pigs and human cadavers, the thorax of 12 human cadavers and 19 anesthetized pigs were impacted with two different projectiles at different speeds. On the thoracic wall, the peak acceleration, peak velocity, maximal compression, viscous criterion, and injury criteria (e.g. abbreviated injury scale and number of rib fractures) were recorded. The correlations between these motion and injury parameters and the blunt criterion were compared between the two groups. The bone mineral density of each subject was also measured. ResultsThe peak acceleration, the peak velocity and the viscous criterion were significantly higher for the pigs. The AIS and the number of rib fractures were significantly higher for human cadavers. The bone mineral density was significantly higher for cadavers, but was, for the two groups, significantly lower than for 30-year-old human. ConclusionThe motion of the pig's thoracic wall is greater than that of the human cadaver, and the severity of the impact is always greater for human cadavers than for pigs. In addition, pig bone is more elastic and less brittle than older human cadaver bone. Due to the bone mineral density, the thoracic wall of human adults should be more rigid and more resistant than the thoracic wall of human cadavers or pigs.

Experimental Methodology Using Digital Image Correlation to Assess Ballistic Helmet Blunt Trauma

As modern helmets have become quite capable of defeating the penetration capabilities of ballistic threats, Soldiers may experience head injuries due to blunt trauma caused by helmet back face deformation (BFD). Possible resulting injuries include skull fracture, hematoma, concussion, contusion, diffuse axonal injury, etc. Some of these injuries have been associated with traumatic brain injury. In order to assess potential injury mechanisms prior to fielding new helmets, we have developed a means to experimentally replicate and measure helmet BFD that can be correlated to injury criteria. In this study, helmet performance test methodology is developed using a digital image correlation (DIC) technique. DIC provides the capability to measure dynamic displacements, thereby providing the ability to calculate deformation, velocity, and acceleration rates. We have shown that digital image correlation is an experimentation technique that accurately captures BFD area and rate of deformation for impacts against combat helmets. We used the DIC data to calculate a new metric; the available energy that could potentially impact a Soldier’s head. Our study shows that DIC data upholds the hypothesis that helmet BFD mechanically loads the skull similar to a direct impact from a less-than-lethal projectile or blunt object impact. The available energy obtained from DIC measurements was used to calculate the blunt criterion (BC) for helmet standoff distances of 12.7 mm (0.5 in) and 19.1 mm (0.75 in), which in turn can provide a prediction of the probability of abbreviated injury scale (AIS) levels and, in particular, skull fracture. DIC can be used to provide dynamic helmet performance data that will allow increased understanding of BFD and quantitative assessment and validation of helmet performance results. Knowledge of the conditions leading to head trauma obtained through DIC experimentation should enable the selection of new energy-absorbing materials for helmets; thus, allowing new helmet design candidate performances to be objectively evaluated. Test data and characterization of helmet response could then be used to achieve improved warfighter survivability.

When backyard fun turns to trauma: risk assessment of blunt ballistic impact trauma due to potato cannons

Although potato cannons are an area of great interest among internet users, they are almost completely unknown in the medical community. These simple ballistic devices are made from plastic plumbing pipes and are powered with propellant gas from aerosol cans. By combustion of the gas-oxygen mixture, a high pressure is produced which propels the potato chunks through the barrel. It is the aim of this study to investigate the hazardous potential of these shooting devices. Test shots were performed using three illegally manufactured potato cannons that were confiscated by police authorities. Velocity, impulse, kinetic energy, and energy density were calculated. The risk of head and chest injuries was investigated by using Sturdivan's Blunt Criterion (BC), an energy based five parametric trauma model assessing the vulnerability to blunt weapons, projectile impacts, and behind-body-armor exposures. The probability of lethality due to blunt impact trauma to the chest was assessed using Sturdivan's lethality model. For potential head impacts, all test shots far exceeded the critical BC (head) value which corresponds to a 50% risk of skull fracture. The risk of injury with regard to chest impacts was similar. All but two test shots far exceeded the critical BC (chest) value corresponding to a 50% risk of sustaining a thoracic skeletal injury of Abbreviated Injury Scale 2 or 3. The probability of a lethal injury due to blunt chest impact was as high as 20%. To conclude, this work demonstrates that potato cannons should be considered dangerous weapons rather than as toys used by adventurous adolescents.

Blunt Criterion trauma model for head and chest injury risk assessment of cal. 380 R and cal. 22 long blank cartridge actuated gundog retrieval devices

Blunt ballistic impact trauma is a current research topic due to the widespread use of kinetic energy munitions in law enforcement. In the civilian setting, an automatic dummy launcher has recently been identified as source of blunt impact trauma. However, there is no data on the injury risk of conventional dummy launchers. It is the aim of this investigation to predict potential impact injury to the human head and chest on the basis of the Blunt Criterion which is an energy based blunt trauma model to assess vulnerability to blunt weapons, projectile impacts, and behind-armor-exposures. Based on experimentally investigated kinetic parameters, the injury risk of two commercially available gundog retrieval devices (Waidwerk Telebock, Germany; Turner Richards, United Kingdom) was assessed using the Blunt Criterion trauma model for blunt ballistic impact trauma to the head and chest. Assessing chest impact, the Blunt Criterion values for both shooting devices were higher than the critical Blunt Criterion value of 0.37, which represents a 50% risk of sustaining a thoracic skeletal injury of AIS 2 (moderate injury) or AIS 3 (serious injury). The maximum Blunt Criterion value (1.106) was higher than the Blunt Criterion value corresponding to AIS 4 (severe injury). With regard to the impact injury risk to the head, both devices surpass by far the critical Blunt Criterion value of 1.61, which represents a 50% risk of skull fracture. Highest Blunt Criterion values were measured for the Turner Richards Launcher (2.884) corresponding to a risk of skull fracture of higher than 80%. Even though the classification as non-guns by legal authorities might implicate harmlessness, the Blunt Criterion trauma model illustrates the hazardous potential of these shooting devices. The Blunt Criterion trauma model links the laboratory findings to the impact injury patterns of the head and chest that might be expected.

The small unmanned aircraft blunt criterion based injury potential estimation

Operational restrictions are imposed upon small unmanned aircraft systems weighing up to 15 kg, denying them access to the airspace over populated areas because of, for one reason, the dearth of reliable data defining the complex risks associated. Injury biomechanics resulting from blunt ballistic impact is used for small unmanned aircraft system injury potential assessment. Small unmanned aircraft injury potential correlates to the impact kinetic energy and characteristic diameter of its part that contacts the body. The injury severity of small unmanned aircraft can be less than serious in impacts at minimal airspeed that contact the body with their sufficiently blunt part; however, they are capable of inflicting lethal injury, even when impacting at minimal airspeed, if they impact the body with their sharper part. Consequently, for injury minimization the small unmanned aircraft basic operational and physical design criteria are described regarding impact velocity and attitude upon impact, along with the shape of the airframe part that contacts the body.

Tolerance of the skull to blunt ballistic temporo-parietal impact

Less-lethal ballistic projectiles are used by police personnel to temporarily incapacitate suspects. While the frequency of these impacts to the head is low, they account for more serious injuries than impacts to any other body region. As a result, there is an urgent need to assess the tolerance of the head to such impacts. The focus of this study was to investigate the tolerance of the temporo-parietal skull to blunt ballistic impact and establish injury criteria for risk assessment. Seven unembalmed isolated cadaver heads were subjected to fourteen impacts. Specimens were instrumented with a nine-accelerometer array as well as strain gages surrounding the impact site. Impacts were performed with a 38 mm instrumented projectile at velocities ranging from 18 to 37 m/s. CT images and autopsies were performed to document resulting fractures. Peak fracture force for the seven resulting fractures was 5633±2095 N. Peak deformation for fracture-producing impacts was 7.8±3.2 mm. The blunt criterion (BC), peak force and principal strain were determined to be the best predictors of depressed comminuted fractures. Temporo-parietal tolerance levels were consistent with previous studies. An initial force tolerance level of 2346 N is established for the temporo-parietal region for blunt ballistic impact with a 38 mm diameter impactor.

Design and Injury Assessment Criteria for Blunt Ballistic Impacts

Less-lethal technologies are used in situations where lethal force is not warranted; however, a variety of injuries have been reported. Design and injury criteria are needed to assess the safety of these munitions. Injury data from ballistic impacts of cadavers were analyzed to validate design and injury criteria. Logistic regression analysis determined the predictive ability of the blunt criterion (BC) for munition design and the viscous criterion (VC) for injury risk assessment. Differences in risk for men and women were determined. For a 50% risk of Abbreviated Injury Scale 2 or 3 thoracic injury, BC = 0.37 (chi = 17.71, p = 0.001) and VCmax = 0.8 m/s (chi = 11.28, p = 0.001). The 5th percentile female subject has a 36% lower tolerance to ballistic energy than the 50the percentile male subject. The BC can be used in the development of kinetic energy munitions and the VC for testing impact injury risk. These criteria provide much needed tools for the development and progression of less-lethal munitions.

Analysis of injury criteria to assess chest and abdominal injury risks in blunt and ballistic impacts.

The Viscous Criterion (VC) is an experimental measure developed by the automotive industry to assess injury risks for high-speed impacts. The Blunt Criterion (BC) is a prospective measure developed by the Department of Defense to predict injury from blunt projectiles. The range of applicability of BC was extended and compared with VC for its ability to assess injury risk using published cadaver and animal data. Department of Defense projectiles were 0.05 to 0.43 kg mass at velocities up to 86 m/s. VC data were generated from impacts with 1.75 to 23.4 kg at 3.6 to 10.2 m/s. Chest and abdominal injuries ranged from Abbreviated Injury Scale scores of 1 to 6. Both criteria correlated very well with the experimental data, demonstrating correlation coefficients of R = 0.84 to 0.96. The correlation between VC and BC was R = 0.99. Logistic probability curves were derived to predict blunt impact injuries of Abbreviated Injury Scale scores of 1 to 6 for the chest and abdomen. BC and VC are virtually identical in their ability to assess blunt and ballistic impact injury risks. They are different measures of impact energy absorbed by the body. One is predictive using input parameters, and the other measures the impact response of the body.