Helmet Structure Research Articles

Effect of Structure and Wearing Modes on the Protective Performance of Industrial Safety Helmet.

This study aims to explore the effects of helmet structure designs and wearing modes on the protective performance of safety helmets under the impact of falling objects. Four helmet types (no helmet, V-shaped, dome-shaped, and motorcycle helmets) and five wearing modes (left and right tilt by 5 deg, backward tilt by 15 deg, 0 deg without chin strap, 0 deg with chin strap) were included in this study. The axial impact of a concrete block under various impact velocities was simulated. The results indicate that the energy absorption and shock mitigation effects of the foam cushion are superior to those of the suspension system in traditional industrial safety helmets. The structure of the top of V-shaped helmets is designed to withstand greater impact. Regarding the wearing mode, the helmet strap's deflection angle increases stress in the brain tissue and skull, heightens intracranial pressure, and causes pressure diffusion toward the forehead.

Histological Observation of Helmet Development in the Treehopper Poppea capricornis (Insecta: Hemiptera: Membracidae).

The treehoppers (Hemiptera, Membracidae) are known for possessing a large three-dimensional structure called a helmet. Although some ecological functions of the helmet have already been elucidated, the developmental mechanisms underlying the complex and diverse morphology of the helmet are still largely unknown. The process of helmet formation was first described in Antianthe expansa, which possesses a simple roof-shaped helmet. However, the developmental process in species with more complex helmet morphologies remains largely unexplored. Hence, in this study, we used Poppea capricornis, which possesses a more complex helmet structure than A. expansa, to investigate the helmet development using paraffin sections, micro-CT, and scanning electronic microscopy. Our focus was on the overall helmet developmental process common to both species and formation of structures unique to Poppea and its comparison to Antianthe. As a result, we discovered that miniature structures were also formed in Poppea, similar to Antianthe, during the helmet formation. Common structures that were shared between the two species were discernible at this stage. Additionally, we observed that suprahumeral horns and posterior horns, two morphological traits specific to the Poppea helmet that are apparently similar anatomically, are formed through two distinctly different developmental mechanisms. The suprahumeral horns appeared to be formed by utilizing the nymphal suprahumeral bud as a mold, while we could not detect any nymphal structures potentially used for a mold in the posterior horns formation. Our findings suggest that the helmet formation mechanisms of Antianthe and Poppea employ a common mechanism but form species-specific structures by multiple mechanisms.

Improving Bicycle and Motorcycle Helmet Design to Prevent Traumatic Brain Injury

Traumatic brain injury (TBI) from bicycle and motorcycle-related accidents continues to be a major medical and financial burden in the United States. The complex management and debilitating consequences of TBI demand greater attention to its prevention, of which much relies on helmet use and structure. Conventional helmets today rely on an expanded polystyrene (EPS)-liner, which works to mitigate the linear acceleration experienced by the brain during impact. However, recent evidence suggests that it is not the linear acceleration but the rotational acceleration of the impact that most contribute to TBI development. This has led to the development of novel helmet designs that aim to mitigate rotational kinematics in addition to linear kinematics. The objective of this study was to overview limitations in current helmet design and discuss two of the most well-studied novel prototypes: WaveCels and Multi-Directional Impact Protection Systems (MIPS). Though both ultimately reduce the rotational acceleration of injury, they differ in mechanism and efficacy. Given the importance of helmet structure in the prevention of TBI, we find that more work is needed directly comparing these and other new designs.

Study on two wheeler helmet for reducing head injuries on different 3D-printed materials: A numerical analysis

A helmet is essential for bike riders to protect the head injuries. It has been designed in such a way that it can protect against injuries to the head, so it requires more concern to protect during an accident. Many accidents have been reported, and thousands of life has been lost due to head injuries. Head injuries have happened with the external load, which not gives the natural protection by the head skull. So, this study analyzed the helmet structure and identified the major area of damage to protect the human head. This study may help the helmet industries provide better safety in the major concern area of the helmet. Here, ANSYS software was used to analyze the helmet structure with different boundary conditions, which are fixed bottom and load applied on the top area, fixed bottom and applied load on the top line, left side fixed and applied load on the right side and right side fixed and applied load on the left side of the helmet. In addition, find an optimum material to manufacture the helmet structure with lightweight and better durability during an accident. Here, the material is considered as high impact polystyrene (HIP), thermoplastic elastomer (TPE), polypropylene (PP) for the helmet structure. The simulation has been taken care of for the static condition, such as total deformation and von Mises for the considered boundary conditions. Additionally, a dynamic analysis is to identify the total deformation of the helmet. The comparison result shows that the HIPS material was the most suitable and acceptable material per the BIS standard experimental data.

A Fiber-Optic Sensor-Embedded and Machine Learning Assisted Smart Helmet for Multi-Variable Blunt Force Impact Sensing in Real Time

Early on-site diagnosis of mild traumatic brain injury (mTBI) will provide the best guidance for clinical practice. However, existing methods and sensors cannot provide sufficiently detailed physical information related to the blunt force impact. In the present work, a smart helmet with a single embedded fiber Bragg grating (FBG) sensor is developed, which can monitor complex blunt force impact events in real time under both wired and wireless modes. The transient oscillatory signal "fingerprint" can specifically reflect the impact-caused physical deformation of the local helmet structure. By combination with machine learning algorithms, the unknown transient impact can be recognized quickly and accurately in terms of impact magnitude, direction, and latitude. Optimization of the training dataset was also validated, and the boosted ML models, such as the S-SVM+ and S-IBK+, are able to predict accurately with complex databases. Thus, the ML-FBG smart helmet system developed by this work may become a crucial intervention alternative during a traumatic brain injury event.

FE Analysis of Motorcycle Helmet Performance under Severe Accidents

A helmet is essential protective equipment for the safety of motorcyclists and their passengers. However, motorcycle accidents can cause severe injuries and fatalities, even when wearing helmets, because the strength of motorcycle helmets lacks head protectability in actual impact accidents. Thus, this research investigates the structural performance of commercial motorcycle helmets in Thailand for head injury prevention using finite element analysis via LS-DYNA. The helmet structural model was firstly validated under impact analysis by comparing with the test according to the TIS 369-2557 standard. The finite element results showed that the difference in maximum acceleration was only 4.8%. The protective efficacy of the helmet structure was then studied and analyzed by simulation under various velocities and impact angles according to three cases of accidents. The structural strength was investigated by assessing energy absorption, HIC, and AIS. The worst case was caused when high impact speeds and angles were applied, which showed the highest impact force and HIC. It also enabled a 100% probability of head damage according to AIS 2+, which causes fatality to passengers during impact accidents. The safest conditions in terms of head injury severity occurred when the impact angle was 45 degrees. Finally, at least 75% energy absorption of foam was further recommended for safety design to reduce head injury from motorcycle accidents.

Blast Resistance of an Innovative Helmet Liner composed of an Auxetic Lattice Structure

Helmet liners are employed to prevent or reduce head injuries caused by impact or blast loads. Liners minimize the damage by shock attenuation and absorbing the dynamic energy. In order to improve blast resistance and crashworthiness characteristics of helmet liner under air-blast, in the present study, an innovative structure designed by an arrow-head auxetic lattice structure is suggested to replace the conventional EPS foams usually employed in the liner section. Explicit finite element method is employed to model the innovative helmet structure under blast loading and results are compared with the conventional case based on trend of acceleration, energy absorption, weight, and Head Injury Criteria (HIC) factor. Also, a parametric study is conducted on the effect of lattice structure’s cell size in the protective performance of helmets. Results indicate a great improvement in blast resistance of helmet when the suggested liners are employed so that the HIC number could be decreased by 71% when AH4 configuration is used while the overall energy absorption capacity of helmet is increased about 34% compared to the basic model.

Dissipation of Energy in Sandwich-Structured Equestrian Helmet – Numerical Analysis Under Overload Conditions

Abstract Protection of the head structures is a requirement in many sports where a person is exposed to injuries that threaten life or health. In horse riding accidents occur often, resulting in serious head injuries. The analysis of the available literature shows that the helmets used now protect human head structures in a small percentage. The aim of the research was to analyze the degree of protection of the human head using available helmet structure and a new solution for the Energy absorbing layer in helmet that absorbs Energy from impacts. The research was divided into two stages. During the first one, a simulation was performer under dynamic conditions simulating the rider’s fall and the contact of the head with ground (impact from the side). In the second stage, three structures of the absorbing layers were developed, i.e. honeycomb, auxetic, mixed with three three wall thicknesses (1 mm, 2 mm and 3 mm respectively) and two materials were used: the currently used EPS and the aluminium alloy used in the motorcycle helmet.

Acoustic methods for regionalizing an impact force acting on a structure

It is often desired to know the location and magnitude of a force acting on a structure. Unfortunately, it is not always possible to install a sensor at the force location, particularly when that location is unknown. A structure subjected to an impact has many different vibrational modes that are excited to different levels based on the excitation location. These vibrations decay with time depending on their different rates of modal damping and the associated acoustic radiation characteristics. In this work, acoustic signatures for a number of structure impact locations were measured, normalized relative to the force magnitude, and processed to examine the ability to correlate the acoustic signal to the force impact location. Various processing techniques, such as the Short Time Fourier Transform, were considered. A primary interest focused on the ability of single-number metrics to aid in identifying the force location. For the experiments, a football helmet structure was used and multiple impact locatio...

Manufacture and impact analysis of bmx helmet made from polymeric foam composite strengthened by oil palm empty fruit bunch fiber

Helmets are protective head gears wear by bicycle riders for protection against injury in case of the accident. Helmet standards require helmets to be tested with a simple drop test onto an anvil. The purpose of research is to know toughness of bicycle helmet made from polymeric foam composite strengthened by oil palm empty fruit bunch fiber. This research contains report result manufacture and impacts analysis of bicycle helmet made from polymeric foam composite materials strengthened by oil palm empty fruit bunch fiber (EFB). The geometric helmet structure consists of shell and liner; both layers have sandwich structure. The shell uses matrix unsaturated Polyester BQTN-157EX material, chopped strand mat 300 glass fiber reinforce and methyl ethyl ketone peroxide (MEKPO) catalyst with the weight composition of 100 gr, 15 gr, and 5 gr. The liner uses matrix unsaturated Polyester BQTN-157 EX material, EFB fiber reinforces, Polyurethane blowing agent, and MEKPO catalyst with the composition of 275 gr (50%), 27.5 gr (5%), 247 gr (45%), and 27.5 gr (5%). Layers of the helmet made by using hand lay-up method and gravity casting method. Mechanical properties of polymeric foam were the tensile strength (ơt) 1.17 Mpa, compressive strength (ơc) 0.51 MPa, bending strength (ơb) 3.94 MPa, elasticity modulus (E) 37.97 Mpa, density (ρ) 193 (kg/m3). M4A model helmet is the most ergonomic with the thickness 10 mm and the amount of air channel 11. Free fall impact test was done in 9 samples with the thickness of 10 mm with the height of 1.5 m. The result of the impact test was impacted force (Fi) 241.55 N, Impulse (I) 6.28 Ns, impact Strength (ơi) 2.02 Mpa and impact Energy (Ei) 283.77 Joule. The properties of bicycle helmet model BMX-M4A type was 264 mm length, 184 mm width, 154 mm height, 10 mm thick, 580 mm head circle, 331 g mass and 11 wind channels.

The impact response of traditional and BMX-style bicycle helmets at different impact severities

Bicycle helmets reduce the frequency and severity of severe to fatal head and brain injuries in bicycle crashes. Our goal here was to measure the impact attenuation performance of common bicycle helmets over a range of impact speeds. We performed 127 drop tests using 13 different bicycle helmet models (6 traditional style helmets and 7 BMX-style helmets) at impact speeds ranging from 1 to 10m/s onto a flat anvil. Helmets were struck on their left front and/or right front areas, a common impact location that was at or just below the test line of most bicycle helmet standards. All but one of the 10 certified helmet models remained below the 300g level at an impact speed of 6m/s, whereas none of the 3 uncertified helmets met this criterion. We found that the helmets with expanded polystyrene liners performed similarly and universally well. The single certified helmet with a polyurethane liner performed below the level expected by the Consumer Product Safety Commission (CPSC) standard at our impact location and the helmet structure failed during one of two supplemental tests of this helmet above the test line. Overall, we found that increased liner thickness generally reduced peak headform acceleration, particularly at higher impact speeds.

消防盔结构设计及主要零部件材料与加工工艺的选择

消防盔通过结构的优化设计，可以达到在重物撞击和钝器穿刺的情况下保护消防员头颅不受到伤害的目的；可以通过消防盔主要零部件材料的选择，达到防止消防员头颅不被烧伤的目的；还可以通过主要零部件成型加工方法选取，达到防止消防员在硬物撞击和钝器穿刺下的人身安全的目的。通过本文的论述充分说明了只有在全面地考虑消防盔结构优化设计、主要零部件材料正确选取和成型工艺的应用，才能完全确保消防盔的安保性能，而只是片面地考虑消防盔单方面因素，是不能保证其安保性能的。 Fire helmet with optimized structure design can protect firefighters from hurt even in the case of the helmet being stroked by heavy objects or punctured by blunt; fire helmet can prevent fire-fighters being burned by selecting material of main components; fire helmet can protect firefighters from hunt by heavy strike and blunt puncture through selecting main components processing and forming. This article will illustrate that the security performance of the fire helmet can only be fully ensured when fire helmet structure optimization and correct selection of components material and molding applications being considered comprehensively. In other word, security performance of the fire helmet can not be guaranteed if only one or few factors be considered./span>

A Photogrammetric Technique for Acquiring Accurate Head Surfaces of Newborn Infants for Optical Tomography Under Clinical Conditions

AbstractOptical tomography (OT) generates 3D images that can be used to monitor blood volume and oxygenation in the brains of newborn infants safely and non‐invasively at the bedside. OT image reconstruction requires that source optical fibres and detector bundles (optodes) are brought into optical contact with the head and that the scalp surface geometry and optode positions for each individual infant are accurately known. The photogrammetric challenge is to create affordable tools that can be employed on newborn, and often severely ill, infants in an intensive care environment with a minimum level of intrusion. The paper describes the application and development of a system capable of mapping each individual infant head surface in the clinic and coordinating optode positions and orientations during optical tomography scans. The system developed includes a combination of stereo and multi‐photo photogrammetry with a pair of digital SLR cameras and a laser dot projector. A bundle adjustment of the sequential stereo‐image pairs is used to generate accurate head meshes that are combined with a photogrammetric network of images from a single camera to bring optodes mounted on a deformable helmet structure into a common coordinate system. This data can then be used in the 3D reconstruction of blood flow in the infant head.

Trajectory Designing and Realizing for the Variable Structure Motorcycle Helmet

A new type of variable structure motorcycle helmet is proposed in this paper, in which that the helmet’s chin-guard can be transformed between the full-helmet status and the half-helmet status as needed. The helmet creatively adopts double movement nails and double track grooves to constraint the chin-guard movement according to the predetermined trajectory, and thus smoothly accomplishing the chin-guard’s lifting, climbing, passing zenith, falling and closing in the helmet shell. The paper introduces the chin-guard’s trajectory planning principles, realizing methods and designing steps, and then gives a design case for the constraint slot tracks in detail. The results show that the new type helmet can reliably realize helmet structure conversion between full-helmet and half-helmet and fully meets the design requirements.

Radiant heat transfer of bicycle helmets and visors

Twenty-six bicycle helmets and their associated visors were characterized for radiant heat transfer using a thermal manikin headform in a climate chamber to assess their ability to protect the wearer from heating by the sun. A single configuration for applied radiant flow of 9.3 W was used to assess the roles of the forward and upper vents and the visor. The helmets shielded 50–75% of the radiant heating without a visor and 65–85% with one. Twenty-three visors were shown to result in a relevant reduction of radiant heating of the face (>0.5 W), with 15 reaching approximately 1 W. Heating of the visor and/or helmet and subsequent heating of the air flowing into the helmet was nevertheless found to be a relevant effect in many cases, suggesting that simple measures like reflective upper surfaces could noticeably improve the radiant heat rejection without changing the helmet structure. The forward vents in the helmets that allow the transmission of radiant heat are often important for forced convection, so that minimizing radiant heating geneally reduces the maximization of forced convective heat loss for current helmets.

Heat transfer variations of bicycle helmets

Bicycle helmets exhibit complex structures so as to combine impact protection with ventilation. A quantitative experimental measure of the state of the art and variations therein is a first step towards establishing principles of bicycle helmet ventilation. A thermal headform mounted in a climate-regulated wind tunnel was used to study the ventilation efficiency of 24 bicycle helmets at two wind speeds. Flow visualization in a water tunnel with a second headform demonstrated the flow patterns involved. The influence of design details such as channel length and vent placement was studied, as well as the impact of hair. Differences in heat transfer among the helmets of up to 30% (scalp) and 10% (face) were observed, with the nude headform showing the highest values. On occasion, a negative role of some vents for forced convection was demonstrated. A weak correlation was found between the projected vent cross-section and heat transfer variations when changing the head tilt angle. A simple analytical model is introduced that facilitates the understanding of forced convection phenomena. A weak correlation between exposed scalp area and heat transfer was deduced. Adding a wig reduces the heat transfer by approximately a factor of 8 in the scalp region and up to one-third for the rest of the head for a selection of the best ventilated helmets. The results suggest that there is significant optimization potential within the basic helmet structure represented in modern bicycle helmets.

Cross‐Field Currents: An Energy Source for Coronal Mass Ejections?

Eruptive solar events like flares and coronal mass ejections are thought to involve the release of energy stored in magnetic fields. In a mass ejection, the coronal magnetic field opens to interplanetary space and some 1016 g of material are propelled outward along the open field lines at a speed of typically 350 km s-1. A considerable body of research shows that the energy in force-free magnetic fields, in which electric currents flow parallel to the field, may be sufficient to open the coronal magnetic field but not additionally to accelerate the ejected material nor to lift it against solar gravity. Thus a purely magnetic explanation for coronal mass ejections must involve cross-field currents—that is, currents with components perpendicular to the magnetic field direction. This paper explores the energetics of a family of simple solutions for an axisymmetric corona in magnetostatic equilibrium including cross-field currents. We extend previous treatments to show that it is possible to build up magnetic energy in excess of that in the presumed fully open state that follows a mass ejection, even if the latter still contains horizontal pressure gradients. We show further that energies in excess of the energy of a fully open state without horizontal pressure gradients are attainable over a wider range of parameters than previously reported. However, our results are tempered by our demonstration that excess mass associated with pressure gradients that balance the magnetic forces of cross-field currents always results in negative total energy. This is because the excess mass is great enough that its negative gravitational energy exceeds in magnitude the sum of the magnetic and thermal energies that also arise from the presence of excess mass. We suggest that nonlinear solutions, involving more realistic density distributions that model the helmet structure and cavity of coronal streamers, may overcome this problem of negative excess energy.

Reformation of a coronal helmet streamer by magnetic reconnection after a coronal mass ejection

A bright feature observed on Jan. 24–26, 1992 with the soft X‐ray telescope on the YOHKOH spacecraft and with the coronameter at the Mauna Loa Solar Observatory assumed the appearance of a coronal helmet streamer as it slowly expanded. Mauna Loa observations from Jan. 22–24 indicate that a prominence eruption and coronal mass ejection occurred before this feature was seen. We interpret the Jan. 24–26 observations as evidence for “reformation” of a magnetically closed helmet structure as a consequence of magnetic reconnection that proceeded along a vertical magnetic neutral sheet formed by the mass ejection.

The H? development of an intense limb flare and associated flaring arches

The Hα analysis of the development of the strong impulsive and faint gradual phase of the June 26, 1983 flare indicates the following: (1) The flare originated from two microprominences on the southeast border of NOAA 4227. Several similar events are summarized in Table II. (2) The main flare structure was a flare cone, which consisted of a bright surge-like stream, elevated above two flare ribbons (located in the cone's base). The flare cone had a height of about 40 × 103 km and lasted 4 min in Hα. The upper part of the cone was terminated by a very fine loop, which was bent to the west, where later a chromospheric brightening occurred at the footpoint of a flaring arch. A 300 keV burst and radio spikes were observed during the maximum flare phase. (3) The flaring arch system, with its apex at a height of about 48 × 103 km, formed the skeleton for the coronal helmet structure (Figure 7(c)). The velocity of the plasma moving along the flaring arch was between 3500 km s−1} and 6900 km s−1} during the first brightening (14:07 UT).

Coronal temperature measurements near a helmet structure base at the 1973 solar eclipse

Observations of coronal Fe XIV emission lines from the NE quadrant during the 1973 solar eclipse are reported. Temperatures are deduced from a pure thermal broadening model, and, in the region near an observed white-light enhancement, an alternative interpretation of halfwidth as being in part due to turbulent velocities is suggested.