scholarly journals Performance analysis of the protective effects of bicycle helmets during impact and crush tests in pediatric skull models

2012 ◽  
Vol 10 (6) ◽  
pp. 490-497 ◽  
Author(s):  
Tobias A. Mattei ◽  
Brandon J. Bond ◽  
Carlos R. Goulart ◽  
Chris A. Sloffer ◽  
Martin J. Morris ◽  
...  
Keyword(s):  
Impact Force ◽  
Compressive Force ◽  
Free Fall ◽  
Protective Effects ◽  
Human Cadaver ◽  
Bicycle Helmet ◽  
Bicycle Helmets ◽  
Drop Tests ◽  
Flat Steel ◽  
Human Skulls

Object Bicycle accidents are a very important cause of clinically important traumatic brain injury (TBI) in children. One factor that has been shown to mitigate the severity of lesions associated with TBI in such scenarios is the proper use of a helmet. The object of this study was to test and evaluate the protection afforded by a children's bicycle helmet to human cadaver skulls with a child's anthropometry in both “impact” and “crushing” situations. Methods The authors tested human skulls with and without bicycle helmets in drop tests in a monorail-guided free-fall impact apparatus from heights of 6 to 48 in onto a flat steel anvil. Unhelmeted skulls were dropped at 6 in, with progressive height increases until failure (fracture). The maximum resultant acceleration rates experienced by helmeted and unhelmeted skulls on impact were recorded by an accelerometer attached to the skulls. In addition, compressive forces were applied to both helmeted and unhelmeted skulls in progressive amounts. The tolerance in each circumstance was recorded and compared between the two groups. Results Helmets conferred up to an 87% reduction in so-called mean maximum resultant acceleration over unhelmeted skulls. In compression testing, helmeted skulls were unable to be crushed in the compression fixture up to 470 pound-force (approximately 230 kgf), whereas both skull and helmet alone failed in testing. Conclusions Children's bicycle helmets provide measurable protection in terms of attenuating the acceleration experienced by a skull on the introduction of an impact force. Moreover, such helmets have the durability to mitigate the effects of a more rare but catastrophic direct compressive force. Therefore, the use of bicycle helmets is an important preventive tool to reduce the incidence of severe associated TBI in children as well as to minimize the morbidity of its neurological consequences.

scholarly journals Numerical Model Study of Prototype Drop Tests on Cube and Cubipod® Concrete Armor Units Using the Combined Finite–Discrete Element Method

2021 ◽  
Vol 9 (5) ◽  
pp. 460
Author(s):  
Giulio Scaravaglione ◽  
John-Paul Latham ◽  
Jiansheng Xiang
Keyword(s):  
Discrete Element Method ◽  
Validation Study ◽  
Free Fall ◽  
Discrete Element ◽  
Drop Test ◽  
Modeling Methodology ◽  
Model Study ◽  
Drop Tests ◽  
Rubble Mound Breakwaters ◽  
Element Method

This paper aims to evaluate the structural strength of unreinforced concrete armor units (CAU), named Cubipod®, used on rubble-mound breakwaters and coastal structures, through a numerical methodology using the combined finite–discrete element method (FDEM). A numerical modeling methodology is developed to reproduce the results of an experimental examination published by Medina et al. (2011) of a free-fall drop test performed on a 15 t conventional Cubic block and a 16 t Cubipod® unit. The field results of the Cube drop tests were used to calibrate the model. The numerically simulated response to the Cubipod® test is then discussed in the context of a validation study. The calibration process and validation study provide insights into the sensitivity of breakage to tensile strength and collision angle, as well as a better understanding of the crushing and cracking damage of this unit under drop test impact conditions.

scholarly journals Impact Force of Free-fall Lifeboats at Water Entry

1994 ◽  
Vol 90 (0) ◽  
pp. 165-173
Author(s):  
Kazuo HITOMI ◽  
Osamu MIYATA
Keyword(s):  
Impact Force ◽  
Free Fall ◽  
Water Entry

scholarly journals Manufacture and Strength Analysis of Ergonomic Bicycle Helmet Made from Polymeric Foam Composite Strengthened by Oil Palm Empty Fruit Bunch Fiber with Free Fall Drop Test Method

2020 ◽  
Vol 64 (1) ◽  
pp. 33-38
Author(s):  
Mahadi Mahadi ◽  
Keyword(s):  
Oil Palm ◽  
Free Fall ◽  
Product Safety ◽  
Drop Test ◽  
Empty Fruit Bunch ◽  
Test Results ◽  
Shell Layer ◽  
Bicycle Helmet ◽  
Polymeric Foam ◽  
Foam Composite

This article contains a study report on the manufacturing of bicycle helmet models that use polymeric foam composite materials strengthened by oil palm empty fruit bunch (OPEFB). The test results of mechanical polymeric foam obtain tensile stress (σt) 1.17 MPa, compressive stress (σc) 0.51 MPa, bending stress (σb) 3.94 MPa, modulus of elasticity (E) 37.97 MPa, density ( ρ) 193 (kg / m3). The testing results of thermal conductivity (k) with ASTM C177-04 standard obtain 0.096 W/mK. Aerodynamic simulation is carried out on 5 bicycle helmet models with different variations of air ventilation formations and obtained the M4A model that best met the ergonomic criteria. The simulation results of the M4A helmet model are max 65.668 Pa of air pressure (Pu), 26,8 0C of inner wall temperature (Ti), 11.0724 m/s of air velocity (vi) and 0.89 of drag coefficient (CD). Bicycle helmet manufacturing is carried out by hand lay up method for shell layer and casting mold for liner by using GFRP polymer composite molds. Both layers are made by sandwich method with the composition of the shell layer is 100 grams resin, 15 grams glass fiber and 5 grams catalyst. The composition of the liner layer is 275 grams (50%) of unsaturated Polyester 157 BQTN-EX resin, 27.5 grams (5%) of OPEFB fiber, 247 grams (45%) of Blowing Agent Polyurethane and 27.5 grams (5%) of Methyl Ketone Perokside catalyst (MEKPO). The toughness of the helmet is tested by using a free fall drop test with the standard of Consumer Product Safety Commission (CPSC) with the height of impact 1.5 meters. The free fall drop test results are max 2.02 MPa of the impact stress of the M4A bicycle helmet model (σi) and max 283.77 joules of energy impact (Ei) which is close to the Consumer Product Safety Commission’s (CPSC) standard value of 110 joules.

Analysis of Parameters Affecting Impact Force Attenuation during Landing in Human Vertical Free Fall

1982 ◽  
Vol 11 (3) ◽  
pp. 141-147 ◽  
Author(s):  
J Mizrahi ◽  
Z Susak
Keyword(s):  
Early Phase ◽  
Impact Force ◽  
Body Position ◽  
Free Fall ◽  
Muscle Action ◽  
Impact Forces ◽  
Ground Roll ◽  
Vertical Landing

The characteristics of impact forces on the legs during vertical landing of human vertical free fall in different falling conditions were studied to reveal the parameters which take part in the attenuation of these impact forces. The following parameters were investigated: body position during landing, range of flexion of the joints of the legs at impact, usage of ground-roll immediately after impact and softness of the ground. The results indicate that joint movements and muscle action play a major role in reducing peak forces during landing. This emphasizes the importance of adequate training to improve the pre-programmed non-reflex muscle action, necessary in the early phase of impact.

Local All-Age Bicycle Helmet Ordinances in the United States: A Review and Analysis

2019 ◽  
Vol 47 (2) ◽  
pp. 283-291 ◽  
Author(s):  
Molly Merrill-Francis ◽  
Jon S. Vernick ◽  
Keshia M. Pollack Porter
Keyword(s):  
United States ◽  
Head Injury ◽  
The United States ◽  
Washington Dc ◽  
Bicycle Helmet ◽  
Bicycle Helmets ◽  
Helmet Laws

Bicycle helmets protect against head injury. Mandatory helmet laws likely increase their use. Although 21 states and Washington, DC have mandatory helmet laws for youth (variously defined) bicyclists, no U.S. state has a mandatory helmet law that applies to all ages; however, some localities have all-age helmet laws for bicyclists. This study abstracted local helmet laws applicable to all-ages to examine their elements.

A comparative study on the behaviour of free-fall lifeboat launching from a skid and from a hook

2000 ◽  
Vol 214 (2) ◽  
pp. 359-370 ◽  
Author(s):  
M Reaz H Khondoker ◽  
M Arai
Keyword(s):  
Numerical Simulation ◽  
Dynamic Response ◽  
Comparative Study ◽  
Impact Force ◽  
Free Fall ◽  
Water Entry ◽  
Hydrodynamic Forces ◽  
Response Criteria ◽  
Risk Of Injury ◽  
Tremendous Impact

There are two commonly used launching methods of free-fall lifeboats: from a skid and from a hook. A free-fall lifeboat, whether it is released from a skid or from a hook, experiences tremendous impact when it enters the water. This impact force, together with other hydrostatic and hydrodynamic forces and moments, affects the motions and accelerations of the boat considerably. In this paper, a comparative study on the behaviours of the skid and hook launching of free-fall lifeboats has been presented. Numerical simulation for different launching methods has been used as a tool to obtain trajectories of the lifeboat for different launching conditions. Also polar diagrams of accelerations are drawn using the data computed for the same conditions. Dynamic response criteria have been used in order to evaluate the risk of injury to the occupants during water entry of the lifeboat.

Design and Analysis of Bicycle Helmet with Impaxx Foam Liner

2013 ◽  
Vol 706-708 ◽  
pp. 1778-1781
Author(s):  
Tso Liang Teng ◽  
Cho Chung Liang ◽  
Chien Jong Shih ◽  
Van Hai Nguyen
Keyword(s):  
Heat Dissipation ◽  
Low Cost ◽  
Experimental Tests ◽  
Absorption Test ◽  
Bicycle Helmet ◽  
Shock Absorption ◽  
Liner Material ◽  
Bicycle Helmets ◽  
And Performance ◽  
Energy Absorbing

Currently, expended polystyrene (EPS) are widely used as liner material in bicycle helmet. Due to its characteristics is excellent performance, lightweight, low cost of manufacturing. However, EPS has some disadvantage as difficulty to optimize energy absorbing in different areas of head and inferior effect of heat dissipation and a brittle characteristic. This study focuses on to find a replacement material for EPS foam to improve liner of bicycle helmet. Impaxx energy absorbing (EA) foams present strong potential in overcoming such problems of EPS foam. To make certain that all bicycle helmets reach efficiency, the helmets are required to pass shock absorption test of EN1078 standard. This study performs finite element analyses of helmet impact tests using LS-DYNA software. Simulation results indicate Impaxx foams are suitable for shock absorption test according to the EN1078 standard. Therefore these results encouraged the authors to extend the manufacturing work to cover the creating helmet design and performance experimental tests.

scholarly journals An Overview of the Effectiveness of Bicycle Helmet Designs in Impact Testing

2021 ◽  
Vol 9 ◽  
Author(s):  
Javid Abderezaei ◽  
Fargol Rezayaraghi ◽  
Brigit Kain ◽  
Andrea Menichetti ◽  
Mehmet Kurt
Keyword(s):  
Angular Momentum ◽  
Brain Injury ◽  
Impact Velocity ◽  
New Technologies ◽  
Expanded Polystyrene ◽  
Impact Testing ◽  
Superior Performance ◽  
Bicycle Helmet ◽  
Bicycle Helmets ◽  
The Impact

Cycling accidents are the leading cause of sports-related head injuries in the US. Conventional bicycle helmets typically consist of polycarbonate shell over Expanded Polystyrene (EPS) foam and are tested with drop tests to evaluate a helmet’s ability to reduce head kinematics. Within the last decade, novel helmet technologies have been proposed to mitigate brain injuries during bicycle accidents, which necessitates the evaluation of their effectiveness in impact testing as compared to conventional helmets. In this paper, we reviewed the literature to collect and analyze the kinematic data of drop test experiments carried out on helmets with different technologies. In order to provide a fair comparison across different types of tests, we clustered the datasets with respect to their normal impact velocities, impact angular momentum, and the type of neck apparatus. When we analyzed the data based on impact velocity and angular momentum clusters, we found that the bicycle helmets that used rotation damping based technology, namely MIPS, had significantly lower peak rotational acceleration (PRA) and Generalized Acceleration Model for Brain Injury Threshold (GAMBIT) as compared to the conventional EPS liner helmets (p < 0.01). SPIN helmets had a superior performance in PRA compared to conventional helmets (p < 0.05) in the impact angular momentum clustered group, but not in the impact-velocity clustered comparisons. We also analyzed other recently developed helmets that primarily use collapsible structures in their liners, such as WaveCel and Koroyd. In both of the impact velocity and angular momentum groups, helmets based on the WaveCel technology had significantly lower peak linear acceleration (PLA), PRA, and GAMBIT at low impact velocities as compared to the conventional helmets, respectively (p < 0.05). The protective gear with the airbag technology, namely Hövding, also performed significantly better compared to the conventional helmets in the analyzed kinematic-based injury metrics (p < 0.001), possibly due to its advantage in helmet size and stiffness. We also observed that the differences in the kinematic datasets strongly depend on the type of neck apparatus. Our findings highlight the importance and benefits of developing new technologies and impact testing standards for bicycle helmet designs for better prevention of traumatic brain injury (TBI).

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