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Importance of the Bicycle Helmet Design and Material for the Outcome in Bicycle Accidents
KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.ORCID iD: 0000-0002-0980-4051
KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.ORCID iD: 0000-0003-0125-0784
2014 (English)In: Proceedings, International Cycling Safety Conference 2014, Chalmers , 2014, 1-14 p.Conference paper (Refereed)
Abstract [en]

In Sweden the most common traffic group that needs to be hospitalized due to injury is cyclists where head injuries are the most common severe injuries. According to current standards, the performance of a helmet is only tested against radial impact which is not commonly seen in real accidents. Some studies about helmet design have been published but those helmets have been tested for only a few loading conditions. Therefore, the purpose of this study was to use finite element models to evaluate the effect of the helmet’s design on the head in some more loading conditions.

A detailed head model was used to evaluate three different helmet designs as well as non-helmet situations. The first helmet (Baseline Helmet) was an ordinary helmet available on the market. The two other helmet designs were a modification of the Baseline helmet with either a lower density of the EPS liner (Helmet 1) or a sliding layer between the scalp and the EPS liner (Helmet 2). Four different impact locations combined with four different impact directions were tested.

The study showed that using a helmet can reduce the peak linear acceleration (85%), peak angular acceleration (87%), peak angular velocity (77%) and peak strain in the brain tissue (77%). The reduction of the strain level was dependent on the loading conditions. Moreover, in thirteen of the sixteen loading conditions Helmet 2 gave lowest peak strain.

The alteration of the helmet design showed that more can be done to improve the protective effect of the helmet. This study highlighted the need of a modification of current helmet standard test which can lead to helmets with even better protective properties as well as some challenges in implementing new test standards.

Place, publisher, year, edition, pages
Chalmers , 2014. 1-14 p.
Keyword [en]
Bicycle, helmet design, head injuries, finite element analysis
National Category
Civil Engineering
URN: urn:nbn:se:kth:diva-158020OAI: diva2:773433
International Cycling Safety Conference, November 18-19, 2014, Gothenburg, Sweden

QC 20150123

Available from: 2014-12-19 Created: 2014-12-19 Last updated: 2015-04-14Bibliographically approved
In thesis
1. Numerical Accident Reconstructions: A Biomechanical Tool to Understand and Prevent Head Injuries
Open this publication in new window or tab >>Numerical Accident Reconstructions: A Biomechanical Tool to Understand and Prevent Head Injuries
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Traumatic brain injuries (TBIs) are a major health and socioeconomic problem throughout the world, with an estimated 10 million deaths and instances of hospitalization annually. Numerical methods such as finite element (FE) methods can be used to study head injuries and optimize the protection, which can lead to a decrease in the number of injuries. The FE head models were initially evaluated for biofidelity by comparing with donated corpses experiments. However, there are some limitations in experiments of corpses, including material degradation after death. One feasible alternative to evaluating head models with living human tissue is to use reconstruction of real accidents. However, the process of accident reconstruction entails some uncertainties since it is not a controlled experiment. Therefore, a deeper understanding of the accident reconstruction process is needed in order to be able to improve the FE human models. Thus, the aim of this thesis was to evaluate and further develop more advanced strategies for accident reconstructions involving head injuries.

A FE head model was used to study head injuries in accidents. Existing bicycle accident data was used, as were hypothetical accident situations for cyclists and pedestrians. A FE bicycle helmet model having different designs was developed to study the protective effect.

An objective method was developed based on the Overlap Index (OI) and Location Index (LI) to facilitate the comparison of FE model responses with injuries visible in medical images. Three bicycle accident reconstructions were performed and the proposed method evaluated. The method showed to have potential to be an objective method to compare FE model response with medical images and could be a step towards improving the evaluation of results from injury reconstructions.

The simulations demonstrated the protective effect of a bicycle helmet. A decrease was seen in the injurious effect on both the brain tissue and the skull. However, the results also showed that the brain tissue strain could be further decreased by modifying the helmet design.

Two different numerical pedestrian models were compared to evaluate whether the more time-efficient rigid body model could be used, instead of a FE pedestrian model, to roughly determine the initial conditions as an accident reconstruction involves some uncertainties. The difference, in terms of the head impact location, rotation and velocity, attributable to the two models was in the same range as differences due to uncertainties in some of the initial parameters, such as vehicle impact velocity.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xvi, 88, XIV p.
TRITA-STH : report, ISSN 1653-3836 ; 2015:4
Head injuries; Accident Reconstruction; Finite element analysis; Injury prevention; Helmet; Cyclist; Pedestrian; Epidemiology
National Category
Other Medical Sciences
Research subject
Applied Medical Technology
urn:nbn:se:kth:diva-164091 (URN)978-91-7595-512-4 (ISBN)
Public defence
2015-05-08, 3-221, Alfred Nobels Allé 10, Huddinge, 09:00 (English)

QC 20150414

Available from: 2015-04-14 Created: 2015-04-13 Last updated: 2015-04-14Bibliographically approved

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