Head Injury Criterion Values Research Articles

Evaluating the Performance of Helmet Linings Incorporating Fluid Channels

Abstract Performance advantages of incorporating fluid channels into a foam made of DERTEXDERTEX Corporation, Southfield, MI, USA. VN600 (vinyl nitrile) are evaluated. This foam has the potential to replace the traditional foam material of helmet liners, like expanded polystyrene (EPS). The experiments involved dropping a certified size E headform vertically onto a flat, solid anvil. Elastically deformable and resilient VN foam outperformed EPS during all impacts. Incorporating a viscous aqueous solution of 30 % by weight glycerin into 3/8 in. (0.95 cm) diameter channels machined through VN foam, reduced the peak headform acceleration by 12 % on first impact compared to VN foam samples without fluid channels. The reduction was 17 % when compared to EPS foam samples. The duration of the first impact increased by 27 % over EPS, significantly lowering the associated head injury criterion values. Repeated impact testing demonstrated an increasing performance advantage of incorporating fluid channels. Samples incorporating 30 % glycerin solution reduced the peak headform acceleration after six impacts by 50 % as compared to EPS.

The effects of impact management materials in ice hockey helmets on head injury criteria

The objective of this study was to compare the capacity of vinyl nitrile and expanded polypropylene, two materials commonly used in ice hockey helmets, to reduce the peak linear acceleration, peak angular acceleration, and head injury criterion values during a direct impact to a hybrid III headform. Six different ice hockey helmets were tested using a pneumatic linear impactor at velocities similar to those in hockey. The results showed that helmets using expanded polypropylene foam liners are significantly better at reducing linear acceleration; however, helmets using vinyl nitrile foam liners are significantly better at reducing angular acceleration. Furthermore, the impact location influenced the performance of the liner.

Head injury criterion

In the design of robotic systems that safely interact with people, it is useful to have validated criteria for measuring injury risks. To this end, some researchers have advocated the use of metrics developed for assessing automotive safety, with the head injury criterion (HIC) receiving particular attention. The aims of this commentary are to clarify the proper use of the HIC, to briefly discuss its relationship to the risk of injury, and to give a closed-form formula for the HIC value produced by a simple mass-spring model of impact. We emphasize that there are many other factors besides HIC to consider before a robot system can be considered safe to interact with humans.

Assessment of Head Injury Risk Associated With Feet-First Free Falls in 12-Month-Old Children Using an Anthropomorphic Test Device

Short distance falls are a common false history provided in cases of child abuse. Falls are also a common occurrence in ambulating young children. The purpose of this study was to determine the risk of head injury in short distance feet-first free falls for a 12-month-old child. Feet-first free falls were simulated using an anthropomorphic test device. Three fall heights and five surfaces were tested to determine whether changing fall environment characteristics leads to differences in head injury risk outcomes. Linear head accelerations were measured and angular head accelerations in the anterior-posterior direction were determined. Head injury criteria values and impact durations were also determined for each fall. The mean peak linear head acceleration across all trials was 52.2g. HIC15 values were all below the injury assessment reference value. The mean peak angular head acceleration across all trials was 4,246 rad/s2. Impact durations ranged from 12.1 milliseconds to 27.8 milliseconds. In general, head accelerations were greater and impact durations were lower for surfaces with lower coefficients of restitution (a measure of resiliency). In falls onto wood and linoleum over concrete, the ground-based fall was associated with greater accelerations than the two higher fall heights. Results show that fall dynamics play an important role in head injury outcome measures. Different fall heights and impact surfaces led to differences in head injury risk, but the risk of severe head injury across all tested scenarios was low for a 12-month-old child in feet-first free falls.

A prospective study of punch biomechanics and cognitive function for amateur boxers

ObjectiveTo evaluate several biomechanical factors of the head during a sparring session and their link to cognitive function.DesignInstrumented Boxing Headgear (IBH) was used for data collection during four 2 min...

Effect of wheelchair headrest use on pediatric head and neck injury risk outcomes during rear impact

Comparative risks or benefits to wheelchair-seated pediatric occupants in motor vehicles associated with wheelchair headrest use during rear impact were evaluated using pediatric head and neck injury outcome measures. A Hybrid III 6-year-old anthropomorphic test device (ATD), seated in identical WC19-compliant pediatric manual wheelchairs, was used to measure head and neck response during a 25 km/h (16 mph), 11 g rear impact. ATD responses were evaluated across two test scenarios: three sled tests conducted without headrests, and three with slightly modified commercial headrests. Head and neck injury outcomes measures included: linear head acceleration, head injury criteria (HIC) values, neck injury criteria ( N ij ) values, and combined rotational head velocity and acceleration. Neck and head injury outcome measures improved by 34–70% in sled tests conducted with headrests compared to tests without headrests. Headrest use reduced N ij values and the likelihood of concussion from values above established injury thresholds to values below injury thresholds. Injury measure outcome reductions suggest lower head and neck injury risks for wheelchair-seated children using wheelchair-mounted headrests as compared to non-headrest users in rear impact. Use of relative comparisons across two test scenarios served to minimize effects of ATD biofidelity limitations.

Protection against Impact with the Ground Using Wearable Airbags

Incidental falls from heights, falls on the same level caused by slipping or tripping, and falls from wheelchair overturns are commonplace phenomena, associated with serious injuries from impact with the ground. A wearable airbag device is a countermeasure applicable to all these types of incidents. Three types of wearable airbag systems were developed and evaluated: for protection against falls from heights (Type-1), against wheelchair overturns (Type-2), and against falls on the same level (Type-3). The systems consist of an airbag, sensor, inflator, and jacket. The sensor detects the fall and the airbag inflates to protect the user. Fall tests using dummies with/without the airbags demonstrated the effectiveness of these devices. In the experiments with system Type-1, for fall heights of less than 2m, the airbags reduced the impact acceleration, and the Head Injury Criterion (HIC) values were under 1,000, the auto-crash test requirement. However, there are limits to the amount of protection afforded: in Type-1, the airbag can protect only the back of the head.; in Types-2 and 3, the fall height of the center of gravity is lower than 2m, and there is some margin of extra protective resource, which can be used to extend the protected area.

The localized low-velocity impact response of aluminium honeycombs and sandwich panels for occupant head protection: experimental characterization and analytical modelling

This paper describes an investigation into the localized impact response of aluminium honeycombs and sandwich panels from the perspective of their use in occupant head protection applications. A programme of quasi-static and dynamic low-velocity impact testing using a hemispheric ‘head form’ impactor is described. From this, design data is presented in terms of acceleration histories and head injury criterion values. Furthermore, a simple analytical model is described for predicting acceleration histories for preliminary design purposes.

Space needed by a decelerating head to keep an imposed HIC at a given impact velocity

Among the technical limitations imposed by standards to head protection system manufacturers, a given Head Injury Criterion (HIC) value must be met by the recorded acceleration of a dummy head thrown with a specified impact velocity. The goal of the present theoretical study is to determine the minimum space needed by the decelerating head to stop and not to exceed the HIC value. To this end, theoretical generic sinusoidal and rectangular shaped acceleration curves have been used. Rectangular shaped accelerations were found to lead to best results, that is, less space needed. As an example, a minimum needed space of 5.9 cm was deduced for the 2003/102/EC pedestrian standard and 3.3 cm for the ECE R02 motorcyclist standard.

Protective Performance of Plate-Cell Rubber Tiles against Childhood Head Injury on Playground Surfaces - A Finite Element Analysis

Rubber tiles are commonly used in playgrounds as protective surfacing to reduce the incidence of head injuries in children caused by falling from equipment. This study developed a rubber tile model consisting of a surface layer of solid and a base layer of plate-cell and used it to investigate head injury protective performance. An explicit finite element method based on the experimental data was used to simulate head impact on the rubber tile. The peak acceleration and head injury criterion (HIC) were employed to assess the shock-absorbing capability of the tile. The results showed that compared to the peak acceleration, use of the HIC index provided a more conservative assessment of the shock absorption ability, and ultimately the protection against head injuries. This study supports the feasibility of using rubber tile with plate-cell construction to improve shock-absorbing capability. The plate-cell structure provided an excellent cushioning effect via a lower axial shear stiffness of the surface layer and lower transverse shearing stiffness of the core. The core's dimensions were an important parameter in determining the shearing stiffness. The analysis suggested that the cushioning effect would significantly reduce the peak force on the head from a fall and delay the occurrence of the peak value during impact, resulting in a marked reduction in the peak acceleration and HIC values of the head. Two plate-cell constructions with honeycomb and box-like cores were proposed and validated in this study. The better protective ability of the honeycomb core was attributed to its lower transverse shearing stiffness.

Finite Element Analysis of Brain Damage due to Impact Force with a Three Dimensional Head Model

Brain damage by the impact force was evaluated by the numerical analysis with a three dimensional Finite Element (FE) model. The FE model was constructed from the MRI data of a subject, and visco-elastic behavior for constitutive equation was applied to the brain tissue. From the FE simulation, brain damage and deformation of the frontal head impacted by a steel impactor were analyzed. The variations of head acceleration and Intra-Cranial Pressure (ICP) during the impact were analyzed in order to evaluate Traumatic Brain Injury (TBI). In addition, relative displacement between the skull and the brain due to head impact was investigated. And, pathological severity was evaluated according to Head Injury Criterion (HIC) from the FE simulation. The analytic results of brain damage showed a good agreement with those of the cadaver test performed by Nahum et al. (1977) and other medical reports. And then, the variation of the HIC value was evaluated according to various impact conditions. This study would provide useful data and methodology in the field of biomechanics for analyzing the brain damage by head impact.

Analysis of traumatic brain injury using

In this study, head injury by impact force was evaluated by numerical analysis with 3-dimensional finite element (FE) model. Brain deformation by frontal head impact was analyzed to evaluate traumatic brain injury (TBI). The variations of head acceleration and intra-cranial pressure (ICP) during the impact were analyzed. Relative displacement between the skull and the brain due to head impact was investigated from this simulation. In addition, pathological severity was evaluated according to head injury criterion (HIC) from simulation with FE model. The analytic result of brain damage was accorded with that of the cadaver test performed by Nahum et al. (1977) and many medical reports. The main emphasis of this study is that our FE model was valid to simulate the traumatic brain injury by head impact and the variation of the HIC value was evaluated according to various impact conditions using the FE model.

Influence of wet surfaces and fall height on pediatric injury risk in feet-first freefalls as predicted using a test dummy

Introduction: Falls are a major cause of morbidity and mortality in children, but are also reported falsely in child abuse. Therefore, it is of interest to understand those factors which may lead to a higher likelihood of injury in a feet-first freefall. Methods: We used laboratory freefall experiments and a 3-year-old Hybrid III anthropomorphic test dummy (ATD) to assess head and femur injury risk. Wet and dry linoleum impact surfaces were used from three fall heights: 22, 35 and 47 in. Results: For a given fall height, dry surfaces were associated with higher head injury criteria (HIC) values than wet surfaces. Changes in fall height 22–47 in. did not significantly affect HIC values for falls onto either surface. Generally, compressive and bending femur loading increased significantly for wet as compared to dry linoleum. Conclusions: In simulated feet first freefall experiments up to 47 in. using a 3-year-old test dummy, a low risk of contact type head injury and femur fracture was found. However, both fall height and surface conditions influenced femur loading and head injury measures. Future efforts should explore the risk of head injury associated with angular acceleration in freefalls.

EXPERIMENTAL EVALUATION OF THE IMPACTABSORPTION PROPERTIES OF RUBBER TILES FOR THE PLAYGROUND

Rubber tiles are popular in playgrounds as protective surfacing to reduce the incidence of head injuries caused by children falling from equipment. However, Taiwan has not yet established a test code for assessment of the shock-absorption properties of such surfacing. For this study, an experimental model was established to evaluate the behavior of various rubber tiles. A hemispherical headform was dropped from a set height to strike the center of the specimen tile. The peak acceleration and Head Injury Criterion (HIC) were measured to assess the impact absorption of and critical height for a given rubber tile. The results show that utilization of the HIC index provides a more conservative assessment of the shock absorption and, ultimately, protection from head injuries than peak acceleration. The maximum critical heights of the rubber tiles used in this study for tile thicknesses of 45, 60 and 80 mm were 1.6, 2.0 and 2.2 m, respectively. Two-part rubber tiles with a base structure consisting of a box-like core offer superior protection from head injuries relative to analogous cylindrical, square pillar and solid structures. The maximum differences in peakacceleration and HIC values comparing the box-like core and solid structures at a thickness of 45 mm were 21% and 44%, respectively. The results of this study suggest a minimum of rubber thickness of 60 mm, based on probable maximum fall heights of more than 1.6 m. Moreover, incorporation of an appropriate cushioning structure in the base of the rubber tile could further improve protection.

Comparative performance of playground surfacing materials including conditions of extreme non-compliance

Objective: A recent case series study found that only 4.7% of 402 playgrounds in which arm fractures occurred in Victorian schools complied with the recommended 20 cm depth of tanbark....

Impact energy attentuation of protective football headgear against a yielding surface

There is no standard test to assess the ability of soft headgear to prevent the likelihood of head injuries in the Australian football codes. Therefore the impact energy attenuation of protective football headgear was assessed using a yielding artificial headform and impact surface to characterise the impact scenario. Seven soft football headgear of varying mass, materials and thickness were dropped from a height to generate impact energy of 56 J. The headgear were tested for a number of different impact locations. Accelerometers within the headform monitored the impact mechanics. A Head Injury Criterion (HIC) of 1000 was selected as the injury threshold. Reliability data, collected one week apart, revealed that the results were highly reproducible. Although several of the headgear generated HIC values about 1000 for the various impact locations, only one of the headgear, that with the greatest thickness (15 mm) generated a HIC score below 1000 for impacts to the side and front of the headgear. There was a significant correlation between headgear thickness and HIC scores. It was concluded that all but one of the commercially available soft football headgear tested provided inadequate impact energy attenuation due to the limited amount of padding. It is postulated that the padding material of the headgear would need to be at least 15 mm thick to offer adequate protection.

NCAP Test Improvements with Pretensioners and Load Limiters

New Car Assessment Program (NCAP) test scores, measured by the United States Department of Transportation's (USDOT) National Highway Traffic Safety Administration (NHTSA), were analyzed in order to assess the benefits of equipping safety belt systems with pretensioners and load limiters. Safety belt pretensioners retract the safety belt almost instantly in a crash to remove excess slack. They tie the occupant to the vehicle's deceleration early during the crash, reducing the peak load experienced by the occupant. Load limiters and other energy management systems allow safety belts to yield in a crash, preventing the shoulder belt from directing too much energy on the chest of the occupant. In NCAP tests, vehicles are crashed into a fixed barrier at 35 mph. During the test, instruments measure the accelerations of the head and chest, as well as the force on the legs of anthropomorphic dummies secured in the vehicle by safety belts. NCAP data from model year 1998 through 2001 cars and light trucks were examined. The combination of pretensioners and load limiters is estimated to reduce Head Injury Criterion (HIC) by 232, chest acceleration by an average of 6.6 g's, and chest deflection (displacement) by 10.6 mm, for drivers and right front passengers. The unit used to measure chest acceleration (g) is defined as a unit of force equal to the force exerted by gravity. All of these reductions are statistically significant. When looked at individually, pretensioners are more effective in reducing HIC scores for both drivers and right front passengers, as well as chest acceleration and chest deflection scores for drivers. Load limiters show greater reductions in chest acceleration and chest deflection scores for right front passengers. By contrast, in make-models for which neither load limiters nor pretensioners have been added, there is little change during 1998 to 2001 in HIC, chest acceleration, or chest deflection values in NCAP tests.

Injury tolerances for oblique impact helmet testing

The most frequently sustained severe injuries in motorcycle crashes are injuries to the head, and many of these are caused by rotational force. Rotational force is most commonly the result of oblique impacts to the head. Good testing methods for evaluating the effects of such impacts are currently lacking. There is also a need for improving our understanding of the effects of oblique impacts on the human head. Helmet standards currently in use today do not measure rotational effects in test dummy heads. However rotational force to the head results in large shear strains arising in the brain, which has been proposed as a cause of traumatic brain injuries like diffuse axonal injuries (DAI). This paper investigates a number of well-defined impacts, simulated using a detailed finite element (FE) model of the human head, an FE model of the Hybrid III dummy head and an FE model of a helmet. The same simulations were performed on both the FE human head model and the FE Hybrid III head model, both fitted with helmets. Simulations on both these heads were performed to describe the relationship between load levels in the FE Hybrid III head model and strains in the brain tissue in the FE human head model. In this study, the change in rotational velocity and the head injury criterion (HIC) value were chosen as appropriate measurements. It was concluded that both rotational and translational effects are important when predicting the strain levels in the human brain.

マルチボディモデルを用いたヘルメットの衝撃応答シミュレーション(J14-1 衝撃と傷害,J14 ヒューマン・ダイナミクス)

This paper describes the simulations of impact responses of a helmet by using a multi-body model and a head form. HIC (Head Injury Criterion) values obtained by the simulation are -significantly higher than the results by using a head form only. It is concluded that the existence of the body connected with the head cannot be ignored in order to evaluate the head injury level caused by a falling impact with surface.

Finite element analysis of the effect of motorcycle helmet materials against impact velocity

A motorcycle helmet is the best protective headgear for the prevention of head injuries caused by direct cranial impact. A finite element model based on realistic geometric features of a motorcycle helmet is established, and explicit finite element LS‐DYNA code is employed to simulate dynamic responses at different impact velocities. Peak acceleration and Head Injury Criterion values derived from the headform are used to assess the protective performance of the helmet. We have concluded that the dynamic responses of the helmet dramatically vary with impact velocity, as well as the mechanical properties of the outer shell and energy‐absorbing liner. At low velocities, e.g., less than 8.3 m/s, the shell stiffness and liner density should be relatively low to diminish head‐contact force. At high velocity, e.g., 11.1 m/s, a stiffer shell and denser liner offer superior protection against head injuries.