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  • 1.
    Alvarez, Victor
    et al.
    KTH.
    Halldin, Peter
    KTH.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    The Influence of Neck Muscle Tonus and Posture on Brain Tissue Strain in Pedestrian Head Impacts2014In: 58th SAE Stapp Car Crash Conference, STAPP 2014, Vol. 58Article in journal (Refereed)
    Abstract [en]

    Pedestrians are one of the least protected groups in urban traffic and frequently suffer fatal head injuries. An important boundary condition for the head is the cervical spine, and it has previously been demonstrated that neck muscle activation is important for head kinematics during inertial loading. It has also been shown in a recent numerical study that a tensed neck musculature also has some influence on head kinematics during a pedestrian impact situation. The aim of this study was to analyze the influence on head kinematics and injury metrics during the isolated time of head impact by comparing a pedestrian with relaxed neck and a pedestrian with increased tonus. The human body Finite Element model THUMS Version 1.4 was connected to head and neck models developed at KTH and used in pedestrian-to-vehicle impact simulations with a generalized hood, so that the head would impact a surface with an identical impact response in all simulations. In order to isolate the influence of muscle tonus, the model was activated shortly before head impact so the head would have the same initial position prior to impact among different tonus. A symmetric and asymmetric muscle activation scheme that used high level of activation was used in order to create two extremes to investigate. It was found that for the muscle tones used in this study, the influence on the strain in the brain was very minor, in general about 1-14% change. A relatively large increase was observed in a secondary peak in maximum strains in only one of the simulated cases. 

  • 2. Deck, C.
    et al.
    Bourdet, N.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    DeBruyne, G.
    Willinger, R.
    Protection capability of bicycle helmets under oblique impact assessed with two separate brain FE models2017In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2017, p. 190-200Conference paper (Refereed)
    Abstract [en]

    The present study proposes a bicycle helmet evaluation under oblique impact based on a coupled experimental versus numerical test method using two separate brain FE models. For each of the 17 helmet types three oblique impacts have been conducted and the 6D headform acceleration curves have been considered as the initial conditions of the brain injury risk assessment based on the FE simulation. The study gives a new insight into helmet protection capability under oblique loading and shows that adequate protection is offered by most of the helmets when impacts leading to rotation around X and Y are concerned. However when impact leads to rotation around Z axis the protection is critical for nearly all helmets. The study considers two separate brain FE models for the assessment of brain injury risk and thus permits a comparative analysis of brain FE modeling. When impact induces rotation around X and Y axis the computed results are comparable. However when rotation around Z axis are concerned significant differences are observed which demonstrate that further efforts are needed in the domain of model based brain injury criteria harmonization. 

  • 3. Halldin, Peter
    et al.
    Fahlstedt, Madelen
    How sensitive are different headform design parameters in oblique helmeted impacts?2018In: Proceedings of International Research Council on Biomechanics of Injury (IRCOBI) Conference, 2018Conference paper (Refereed)
  • 4.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    The development of next generation test standards for helmets.2013In: The development of next generation test standards for helmets., 2013, Vol. 1, article id HPD-2013-1Conference paper (Refereed)
    Abstract [en]

    Injury statistics show that accidents with a head impact often happen with an angle to the impacting object. An angled impact will result in a rotation of the head if the friction is high enough. It is also known that the head is more sensitive to rotation than pure linear motion of the head. CEN has initiated the work to design a new helmet test oblique or angled impact test method a helmet test method that can measure the rotational energy absorption in a helmet during an angled impact. This paper presents a short summary of possibilities and limitations on how to build a helmet test method that can measure the rotational energy absorption in a helmet during an angled impact.

  • 5.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Lanner, Daniel
    MIPS AB.
    Coomber, Richard
    Revision Military Inc., Montreal, Canada.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Evaluation of blunt impact protection in a military helmet designed to offer blunt & ballistic impact protection.2013In: Proceedings of the 1st International Conference on Helmet Performance and Design, 2013, article id HPD-2013-6Conference paper (Refereed)
    Abstract [en]

    This paper describes both a numerical and an experimental approach to measuring the ballistic and blunt impact protection offered by military helmets. The primary purpose of military helmets is to protect users from ballistic impact but modern military helmets protect users from blunt force as well. Altering ballistic shell stiffness, lining the shell with material of different density, even separating the liner from the shell so that they can move independently all affect the transfer of stress to the head and the resulting strain experienced by the brain. The results of this study suggest that there is potential for a helmet that protects the user from both blunt and ballistic impact and can be further improved by implementing an energy absorbing sliding layer, such as the MIPS system, between the shell and the liner to mitigate the effect of oblique impacts.

  • 6.
    Meng, Shiyang
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Cernicchi, Alessandro
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Head impact responses in simulated motorcycle accidents and laboratory reconstructionsManuscript (preprint) (Other academic)
  • 7.
    Meng, Shiyang
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering. MIPS AB, Källtorpsvägen 2, Täby, 183 71, Sweden.
    Cernicchi, Alessandro
    Dainese S.p.A, Via Louvigny 35, 36060, Colceresa (VI), Italy.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering. MIPS AB, Källtorpsvägen 2, Täby, 183 71, Sweden.
    High-speed helmeted head impacts in motorcycling: A computational study2019In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057Article in journal (Refereed)
    Abstract [en]

    The motorcyclist is exposed to the risk of falling and impacting ground head-first at a wide range of travellingspeeds – from a speed limit of less than 50km/h on the urban road to the race circuit where speed can reach well above 200km/h. However, motorcycle helmets today are tested at a single and much lower impact speed, i.e. 30km/h. There is a knowledge gap in understanding the dynamics and head impact responses at high travelling speeds due to the limitation of existing laboratory rigs. This study used a finite element head model coupled with a motorcycle helmet model to simulate head-first falls at travelling speed (or tangential velocity at impact) from 0 to 216km/h. The effect of different falling heights (1.6m and 0.25m) and coefficient of frictions (0.20and 0.45) between the helmet outer shell and ground were also examined. The simulation results were analysed together with the analytical model to better comprehend rolling and/or sliding phenomena that are often observedin helmet oblique impacts. Three types of helmet-to-ground interactions are found when the helmet impacts ground from low to high tangential velocities: (1) helmet rolling without slipping; (2) a combination of sliding and rolling; and (3) continuous sliding. The tangential impulse transmitted to the head-helmet system, peak angular head kinematics and brain strain increase almost linearly with the tangential velocity when the helmet rolls but plateaus when the helmet slides. The critical tangential velocity at which the motion transit from the rolling regime to the sliding regime depends on both the falling height and friction coefficient. Typically, for a fall height of 1.63m and a friction coefficient of 0.45, the rolling/sliding transition occurs at a tangential velocity of 10.8m/s (38.9 km/h). Low sliding resistance in helmet design, i.e. by the means of a lower friction coefficient between the helmet outer shell and ground, has shown a higher reduction of brain tissue strain in the sliding regime than in the rolling regime. This study uncovers the underlying dynamics of rolling and sliding phenomena in high-speed oblique impacts, which largely affect head impact biomechanics. Besides, the study highlights the importance of testing helmets at speeds covering both the rolling and sliding regime since potential designs for improved head protection at high-speed impacts can be more distinguishable in the sliding regime than in the rolling regime.

  • 8.
    Meng, Shiyang
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering. R & D Department, Dainese S.p.A, Via dell’artigianato 35, Molvena, Italy.
    Cernicchi, Alessandro
    R & D Department, Dainese S.p.A, Via dell’artigianato 35, Molvena, Italy.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    The biomechanical differences of shock absorption test methods in the US and European helmet standards2019In: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 24, no 4, p. 399-412Article in journal (Refereed)
    Abstract [en]

    Nowadays crash helmets are tested by dropping a free or unrestrained headform in Europe but a guided or restrained headform in the United States. It remains unclear whether the free fall and the guided fall produce similar impact kinematics that cause head injury. A ?nite element helmet model is developed and compared with experimental tests. The resulting head kinematics from virtual tests are input for a ?nite element head model to compute the brain tissue strain. The guided fall produces higher peak force and linear acceleration than the free fall. Eccentric impact in the free fall test induces angular head motion which directs some of the impact energy into rotational kinetic energy. Consequently, the brain tissue strain in the free fall test is up to 6.3 times more than that in the guided fall. This study recommends a supplemental procedure that records angular head motion in the free fall test.

  • 9.
    Meng, Shiyang
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering. Helmet division, Dainese S.p.A., Italy..
    Fahlstedt, Madelen
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    The effect of impact velocity angle on helmeted head impact severity: A rationale for motorcycle helmet impact test design2018In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2018, p. 454-469Conference paper (Refereed)
    Abstract [en]

    The impact velocity angle determined by the normal and tangential velocity has been shown to be an important description of head impact conditions but can vary in real-world accidents. The objective of this paper was to investigate the effect of impact velocity angle on helmeted head impact severity indicated by the brain tissue strain. The human body model coupled with a validated motorcycle helmet model was propelled at a constant resultant velocity but varying angle relative to a rigid surface. Different body angles, impact directions and helmet designs have also been incorporated in the simulation matrix (n=300). The results show an influence of impact velocity angle on brain tissue strain response. By aggregating all simulation cases into different impact velocity angle groups, i.e., 15, 30, 45, 60 and 75 degrees, a 30- or 45-degree angle group give the highest median and inter-quartile range of the peak brain tissue strain. Comparisons of strain pattern and its peak value between individual cases give consistent results. The brain tissue strain is less sensitive to the body angle than to the velocity angle. The study suggests that UN/ECE 22.05 can be improved by increasing the current 'oblique' angle, i.e. 15 degrees inclined to vertical axis, to a level that can produce sufficient normal velocity component and hence angular head motion. This study also underline the importance of understanding post-impact head kinematics, and the need for further evaluation of human body models.

  • 10.
    Panzer, Matthew B.
    et al.
    Univ Virginia, Ctr Appl Biomech, Charlottesville, VA USA..
    Giudice, J. Sebastian
    Univ Virginia, Ctr Appl Biomech, Charlottesville, VA USA..
    Caudillo, Adrian
    Univ Virginia, Ctr Appl Biomech, Charlottesville, VA USA..
    Mukherjee, Sayak
    Univ Virginia, Ctr Appl Biomech, Charlottesville, VA USA..
    Kong, Kevin
    Univ Virginia, Ctr Appl Biomech, Charlottesville, VA USA..
    Cronin, Duane S.
    Univ Waterloo, Waterloo, ON, Canada..
    Barker, Jeffrey
    Univ Waterloo, Waterloo, ON, Canada..
    Gierczycka, Donata
    Univ Waterloo, Waterloo, ON, Canada..
    Bustamante, Michael
    Univ Waterloo, Waterloo, ON, Canada..
    Bruneau, David
    Univ Waterloo, Waterloo, ON, Canada..
    Corrales, Miguel
    Univ Waterloo, Waterloo, ON, Canada..
    Halldin, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Fahlstedt, Madelen
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Arnesen, Marcus
    Jungstedt, Erik
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Gayzik, F. Scott
    Wake Forest Univ, Bowman Gray Sch Med, Winston Salem, NC USA..
    Stitzel, Joel D.
    Wake Forest Univ, Bowman Gray Sch Med, Winston Salem, NC USA..
    Decker, William
    Wake Forest Univ, Bowman Gray Sch Med, Winston Salem, NC USA..
    Baker, Alex M.
    Wake Forest Univ, Bowman Gray Sch Med, Winston Salem, NC USA..
    Ye, Xin
    Wake Forest Univ, Bowman Gray Sch Med, Winston Salem, NC USA..
    Brown, Philip
    Wake Forest Univ, Bowman Gray Sch Med, Winston Salem, NC USA..
    NUMERICAL CROWDSOURCING OF NFL FOOTBALL HELMETS2018In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042, Vol. 35, no 16, p. A148-A148Article in journal (Other academic)
1 - 10 of 10
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