Differences in Impact Performance of Bicycle Helmets During Oblique Impacts

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Megan L. Bland ◽  
Craig McNally ◽  
Steven Rowson
Keyword(s):  
Real World ◽  
Head Injuries ◽  
Linear Acceleration ◽  
Design Parameters ◽  
Radius Of Curvature ◽  
Head Impacts ◽  
Impact Performance ◽  
Bicycle Helmets ◽  
Oblique Impacts ◽  
Accident Conditions

Cycling is a leading cause of sport-related head injuries in the U.S. Although bicycle helmets must comply with standards limiting head acceleration in severe impacts, helmets are not evaluated under more common, concussive-level impacts, and limited data are available indicating which helmets offer superior protection. Further, standards evaluate normal impacts, while real-world cyclist head impacts are oblique—involving normal and tangential velocities. The objective of this study was to investigate differences in protective capabilities of ten helmet models under common real-world accident conditions. Oblique impacts were evaluated through drop tests onto an angled anvil at common cyclist head impact velocities and locations. Linear and rotational accelerations were evaluated and related to concussion risk, which was then correlated with design parameters. Significant differences were observed in linear and rotational accelerations between models, producing concussion risks spanning >50% within single impact configurations. Risk differences were more attributable to linear acceleration, as rotational varied less between models. At the temporal location, shell thickness, vent configuration, and radius of curvature were found to influence helmet effective stiffness. This should be optimized to reduce impact kinematics. At the frontal, helmet rim location, liner thickness tapered off for some helmets, likely due to lack of standards testing at this location. This is a frequently impacted location for cyclists, suggesting that the standards testable area should be expanded to include the rim. These results can inform manufacturers, standards bodies, and consumers alike, aiding the development of improved bicycle helmet safety.

The range of bicycle helmet performance at real world impact locations

2021 ◽  
pp. 175433712110577
Author(s):  
Ann R Harlos ◽  
Steven Rowson
Keyword(s):  
Real World ◽  
Test Line ◽  
Linear Acceleration ◽  
The United States ◽  
Consumer Product Safety Commission ◽  
Bicycle Helmets ◽  
Impact Location ◽  
Increased Risk ◽  
Post Hoc ◽  
The Impact

In the United States, all bicycle helmets must comply with the standard created by the Consumer Product Safety Commission (CPSC). In this standard, bike helmets are only required to by tested above an established test line. Unregulated helmet performance below the test line could pose an increased risk of head injury to riders. This study quantified the impact locations of damaged bike helmets from real-world accidents and tested the most commonly impacted locations under CPSC bike helmet testing protocol. Ninety-five real-world impact locations were quantified. The most common impact locations were side-middle (31.6%), rear boss-rim (13.7%), front boss-rim (9.5%), front boss-middle (9.5%), and rear boss-middle (9.5%). The side-middle, rear boss-rim, and front boss (front boss-middle and front boss-rim regions combined) were used for testing. Two of the most commonly impacted regions were below the test line (front boss-rim and rear boss-rim). Twelve purchased helmet models were tested under CPSC protocol at each location for a total of 36 impacts. An ANOVA test showed that impact location had a strong influence on the variance of peak linear acceleration (PLA) ( p = 0.002). A Tukey HSD post hoc test determined that PLA at the side-middle (214.9 ± 20.8 g) and front boss (228.0 ± 39.6 g) locations were significantly higher than the PLA at the rear boss-rim (191.5 ± 24.2 g) location. The highest recorded PLA (318.8 g) was at the front boss-rim region. This was the only test that exceeded the 300 g threshold. This study presented a method for quantifying real-world impact locations of damaged bike helmets. Higher variance in helmet performance was found at the regions on or below the test line than at the region above the test line.

Combat Helmet Design Incorporating Multiple Ballistic Threats, Brain Functional Areas and Injury Considerations

2016 ◽  
Author(s):  
Peter Matic ◽  
Alex E. Moser ◽  
Robert N. Saunders
Keyword(s):  
Head Injury ◽  
Diagnostic Criteria ◽  
Computer Aided Design ◽  
Brain Injuries ◽  
Head Injuries ◽  
Design Parameters ◽  
Head Impacts ◽  
Direct Head ◽  
Back Face ◽  
Helmet Design

Combat helmet protection zone parametric design is presented for small arms and explosive device ballistic threat notional spatial distributions. The analysis is conducted using a computer aided design software application developed to evaluate ballistic threats, helmet design parameters, and a standard set of common brain injuries associated with head impacts. The analysis helps to define the helmet trade space, facilitates prototyping, and supports helmet design optimization. Direct head impacts and helmet impacts, with and without helmet back face contact to the head, are tabulated. Head strikes are assumed to produce critical or fatal penetrating injuries. Helmet back face deflections and impact generated projectile-helmet-head motions are determined. Helmet impact obliquity is accounted for by attenuating back face deflection. Head injury estimates for ten common focal and diffuse head injuries are determined from the back face deflections and the head injury criteria. These, in turn, are related to the abbreviated injury score and associated radiographic dimensional diagnostic criteria and loss of consciousness diagnostic criteria from the trauma literature.

Density Variation in the Expanded Polystyrene Foam of Bicycle Helmets and Its Influence on Impact Performance

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Shannon G. Kroeker ◽  
Muammer Ç. Özkul ◽  
Alyssa L. DeMarco ◽  
Stephanie J. Bonin ◽  
Gunter P. Siegmund
Keyword(s):  
Head Injury ◽  
Density Variation ◽  
Expanded Polystyrene ◽  
Polystyrene Foam ◽  
Head Impacts ◽  
Impact Performance ◽  
Expanded Polystyrene Foam ◽  
Bicycle Helmets ◽  
Pilot Work ◽  
The Relationship

Abstract Bicycle helmets attenuate head impacts using expanded polystyrene (EPS) foam liners. The EPS density plays a key role in determining the helmet and head response during an impact. Prior pilot work in our lab showed that EPS density varied by up to 18 kg/m3 within a single helmet, and thus the purpose of this study was to quantify the regional density variations within and between helmets and to establish how these variations influence helmet impact performance. We evaluated 10–12 samples of two traditional and two bicycle motocross (BMX) bicycle helmets with EPS liners. The bulk liner density and density of 16–19 cores extracted from specific locations on each sample were measured. Additional samples of two of these helmet models were then impacted at 3.0, 6.3, and 7.8 m/s to determine the relationship between local EPS density and helmet impact performance. We found that density varied significantly within each sample in all helmet models and also varied significantly between samples in three helmet models. The density variations were not symmetric across the midline in two of the four helmet models. The observed density variations influenced the helmets' impact performance. Our data suggest that variations in peak headform acceleration during impacts to the same location on different samples of the same helmet model can be partially explained by density differences between helmet samples. These density variations and resulting impact performance differences may play a role in a helmet's ability to mitigate head injury.

Impact performance of innovative corrugated polystyrene foam for bicycle helmets

2020 ◽  
pp. 0021955X2096521
Author(s):  
Somen K Bhudolia ◽  
Goram Gohel ◽  
Kah Fai Leong
Keyword(s):  
Energy Absorption ◽  
High Speed ◽  
Head Injuries ◽  
Expanded Polystyrene ◽  
The Novel ◽  
Comparison Study ◽  
Impact Performance ◽  
Bicycle Helmets ◽  
Weight Property ◽  
The Impact

Expanded Polystyrene (EPS) is a common material used to manufacture the inner foam liner of a bicycle helmet due to its outstanding energy absorption characteristics and light-weight property. The current research presents a novel corrugated expanded polystyrene (EPS) foam design concept which is used to enhance the impact dissipation of bicycle helmets from the safety standpoint to reduce head injuries and make them lighter. The baseline comparison study under impact for different foam configurations is compared with a conventional EPS foam sample without corrugation. Corrugated foam designs under current investigation are 12.5–20% lighter and provide up to 10% higher energy absorption. The details of the novel manufacturing concept, CPSC 1203 helmet impact tests, high-speed camera study to understand the differences in the failure mechanisms are deliberated in this paper.

scholarly journals Impact attenuation provided by older adult protective headwear products during simulated fall-related head impacts

2021 ◽  
Vol 8 ◽  
pp. 205566832110503
Author(s):  
Daniel R Martel ◽  
Michelle R Tanel ◽  
Andrew C Laing
Keyword(s):  
Head Injuries ◽  
Linear Acceleration ◽  
Positive Association ◽  
Protective Capacity ◽  
Low Velocity ◽  
Head Impacts ◽  
Frontal Impacts ◽  
Wide Range ◽  
Impact Attenuation ◽  
The Impact

Introduction While protective headwear products (PHP) are designed to protect older adults from fall-related head injuries, there are limited data on their protective capacity. This study’s goal was to assess the impact attenuation provided by commercially available PHP during simulated head impacts. Methods A drop tower and Hybrid III headform measured the decrease in peak linear acceleration ( g atten) provided by 12 PHP for front- and back-of-head impacts at low (clinically relevant: 3.5 m/s) and high (5.7 m/s) impact velocities. Results The range of g atten across PHP was larger at the low velocity (56% and 41% for back and frontal impacts, respectively) vs. high velocity condition (27% and 38% for back and frontal impacts, respectively). A significant interaction between impact location and velocity was observed ( p < .05), with significantly greater g atten for back-of-head compared to front-of-head impacts at the low impact velocity (19% mean difference). While not significant, there was a modest positive association between g atten and product padding thickness for back-of-head impacts ( p = .095; r = 0.349). Conclusion This study demonstrates the wide range in impact attenuation across commercially available PHP, and suggests that existing products provide greater impact attenuation during back-of-head impacts. These data may inform evidence-based decisions for clinicians and consumers and help drive industry innovation.

scholarly journals The Influence of Headform/Helmet Friction on Head Impact Biomechanics in Oblique Impacts at Different Tangential Velocities

2021 ◽  
Vol 11 (23) ◽  
pp. 11318
Author(s):  
Óscar Juste-Lorente ◽  
Mario Maza ◽  
Mathieu Piccand ◽  
Francisco J. López-Valdés
Keyword(s):  
Real World ◽  
Normal Component ◽  
Tangential Velocity ◽  
Linear Acceleration ◽  
Velocity Variation ◽  
Low Friction ◽  
Motorcycle Helmet ◽  
Impact Biomechanics ◽  
Oblique Impacts ◽  
The Impact

Oblique impacts of the helmet against the ground are the most frequent scenarios in real-world motorcycle crashes. The combination of two factors that largely affect the results of oblique impact tests are discussed in this work. This study aims to quantify the effect of the friction at the interface between the headform and the interior of a motorcycle helmet at different magnitudes of tangential velocity. The helmeted headform, with low friction and high friction surface of the headform, was dropped against three oblique anvils at different impact velocities resulting in three different magnitudes of the tangential velocity (3.27 m/s, 5.66 m/s, 8.08 m/s) with the same normal component of the impact velocity (5.66 m/s). Three impact directions (front, left-side and right-side) and three repetitions per impact condition were tested resulting in 54 impacts. Tangential velocity variation showed little effect on the linear acceleration results. On the contrary, the rotational results showed that the effect of the headform’s surface depends on the magnitude of the tangential velocity and on the impact direction. These results indicate that a combination of low friction with low tangential velocities may result into underprediction of the rotational headform variables that would not be representative of real-world conditions.

scholarly journals Ranking and Rating Bicycle Helmet Safety Performance in Oblique Impacts Using Eight Different Brain Injury Models

2021 ◽  
Author(s):  
Madelen Fahlstedt ◽  
Fady Abayazid ◽  
Matthew B. Panzer ◽  
Antonia Trotta ◽  
Wei Zhao ◽  
...  
Keyword(s):  
Brain Injury ◽  
Head Injuries ◽  
Safety Performance ◽  
Test Standards ◽  
Bicycle Helmets ◽  
Injury Criteria ◽  
Relative Safety ◽  
Oblique Impacts ◽  
Brain Models ◽  
Injury Models

AbstractBicycle helmets are shown to offer protection against head injuries. Rating methods and test standards are used to evaluate different helmet designs and safety performance. Both strain-based injury criteria obtained from finite element brain injury models and metrics derived from global kinematic responses can be used to evaluate helmet safety performance. Little is known about how different injury models or injury metrics would rank and rate different helmets. The objective of this study was to determine how eight brain models and eight metrics based on global kinematics rank and rate a large number of bicycle helmets (n=17) subjected to oblique impacts. The results showed that the ranking and rating are influenced by the choice of model and metric. Kendall’s tau varied between 0.50 and 0.95 when the ranking was based on maximum principal strain from brain models. One specific helmet was rated as 2-star when using one brain model but as 4-star by another model. This could cause confusion for consumers rather than inform them of the relative safety performance of a helmet. Therefore, we suggest that the biomechanics community should create a norm or recommendation for future ranking and rating methods.

Combat helmet liner design for blunt impact absorption using multi-output Gaussian process surrogates

2020 ◽  
pp. 095440622096076 ◽  
Author(s):  
George J Barlow ◽  
Christopher Page ◽  
Patrick Drane ◽  
Scott E Stapleton ◽  
Benjamin Fasel ◽  
...  
Keyword(s):  
Gaussian Process ◽  
Impact Velocity ◽  
Linear Acceleration ◽  
Design Parameters ◽  
Test Results ◽  
Design Metrics ◽  
Impact Performance ◽  
Blunt Impact ◽  
Testing Standards ◽  
First Time

A finite element based computational model simulating the standard drop tower test for military helmets was created and used in conjunction with a multi-output Gaussian process surrogate to seek different designs of helmets for improved blunt impact performance. Experimental drop test results were used for the validation of the model’s ability to simulate impact. The influence of foam stiffness, impact velocity, strap tension, as well as pad placement and size on parameters on the peak linear acceleration (PLA) of the headform was investigated for the first time through a surrogate model trained by strategically choosing simulation points. Impact velocity was found to have the greatest effect. The strap tension and foam pad stiffness ranges examined within this sampling plan were found to have less of an effect on the performance of the helmet than the pad size and shape parameters examined. The surrogate modeling approach was used to quantify the influence of design parameters and can lead to not only improved helmet designs but also new data-driven design metrics and testing standards to accelerate the development of TBI-mitigating helmets.

Modification of Filtered Air Intake Flowrate to Improve Control Room Habitability

2018 ◽  
Author(s):  
Xinjian Liu ◽  
Weipeng Shu ◽  
Mengxi Wang
Keyword(s):  
Extended Period ◽  
Leakage Rate ◽  
Design Parameters ◽  
Source Terms ◽  
Control Room ◽  
Limit Operator ◽  
Radioactive Aerosols ◽  
Loss Of Coolant Accident ◽  
Operator Dose ◽  
Accident Conditions

Control room habitability (CRH) shall be maintained to provide adequate protection for control room operators, such that they can remain in the control room envelope (CRE) safely for an extended period and thus control the nuclear facility during normal and accident conditions. A critical objective of CRH systems is to limit operator doses and/or exposure to toxic gases. The CRH systems does this by the combination of the intake of filtered air, isolation of outside air, recirculation systems and etc. Among the parameters determining radioactivity in a control room (in proportion to radiation doses of operators), intake flowrate of filtered air is an important one. For different types of accident source terms, the evolution of operator doses in a control room versus intake flowrate were analyzed in this paper. It turns out that the increase of intake flowrate results in larger operator doses when inert radioactive gases are the dominant radioactive substances. On the contrary, increasing intake flowrate does good to lower the irradiation level of control room operators when radioactive aerosols dominate the source terms. The rationality behind this fact was interpreted in detail in this paper, with special attention paid to the unfiltered in-leakage rate. It can be inferred that an optimal intake flowrate probably exists leading to the minimum operator dose under an actual accident condition. This paper then performed a calculation analysis based on design parameters and source terms of design basis accident of LOCA (a large break loss of coolant accident) accident. The evolution of operator dose was found to be a U-curve versus increasing intake flowrate, which proved the existence of the abovementioned optimal intake flowrate of filtered air for CRH systems. Furthermore, the sensitivity analysis of intake flowrate was carried out to study the effects of unfiltered in-leakage rate and filtered recirculation. This study indicates that intake flowrate of filtered air can significantly influence the CRH. For different accidents, the intake flowrate should be properly modified rather than set as a fixed value. To optimize the radiological habitability of control rooms, the effects of unfiltered in-leakage must be taken into consideration. Besides, filtered recirculation is an effective way to control radiation exposure caused by iodine and radioactive aerosols.

Optimization of Radiation Shielding Concrete for Radiotherapy Treatment Room at Bangabandhu Sheikh Mujib Medical University

2016 ◽  
Vol 705 ◽  
pp. 338-344
Author(s):  
Debojit Sarker ◽  
Arnab Biswas ◽  
Md. Mizanur Rahman ◽  
Muhammad Mohsin Mehedi
Keyword(s):  
Side Wall ◽  
Linear Acceleration ◽  
Radiation Shielding ◽  
Design Parameters ◽  
Slab Thickness ◽  
Optimized Design ◽  
The Public ◽  
Dose Limits ◽  
Medical University ◽  
Shield Design

The objective of this study is to recommend optimized shield design from the shielding viewpoint for installation of the Cyclotron,Cyberknife and Linear Acceleration (LINAC) facility at Bangabandhu Sheikh Mujib Medical University (BSMMU) in Dhaka, Bangladesh. The shield design for Cyclotron, Cyberknife and LINAC has been performed considering ICRP-103 (2007) recommendations for occupational and public dose limits. The optimized design parameters for Radiation Shielding Concrete (RSC) with hardened density of 2.35 gm/cm3 are: 254 cm thickness of RSC as primary barrier for LINAC on both side of the source, 198 cm and 178 cm thickness of RSC on parking side and earthen side wall for Cyclotron, a maze wall of thickness 198 cm and 122 cmRSC for Cyclotron and LINAC, 168 cm and 152 cm thickness of RSC from opposite to the maze wall, slab thickness 152 cm excluding a false ceiling of thickness 122 cm with RSC having a functional story height of 503 cm for LINAC, 122 cm and 259 cm slab thickness of RSC for Cyberknife and Cyclotron. The use of RSC in the shield design of wall and roof shows that it limits radiation exposure of staff, patients, visitors and the public to acceptable level, thus optimizing radiation protection.

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