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  • 1.
    Aare, Magnus
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Kleiven, Svein
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Halldin, Peter
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Injury tolerances for oblique impact helmet testing2004In: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 9, no 1, p. 15-23Article in journal (Refereed)
    Abstract [en]

    The most frequently sustained severe injuries in motorcycle crashes are injuries to the head, and many of these are caused by rotational force. Rotational force is most commonly the result of oblique impacts to the head. Good testing methods for evaluating the effects of such impacts are currently lacking. There is also a need for improving our understanding of the effects of oblique impacts on the human head. Helmet standards currently in use today do not measure rotational effects in test dummy heads. However rotational force to the head results in large shear strains arising in the brain, which has been proposed as a cause of traumatic brain injuries like diffuse axonal injuries (DAI). This paper investigates a number of well-defined impacts, simulated using a detailed finite element (FE) model of the human head, an FE model of the Hybrid III dummy head and an FE model of a helmet. The same simulations were performed on both the FE human head model and the FE Hybrid III head model, both fitted with helmets. Simulations on both these heads were performed to describe the relationship between load levels in the FE Hybrid III head model and strains in the brain tissue in the FE human head model. In this study, the change in rotational velocity and the head injury criterion (HIC) value were chosen as appropriate measurements. It was concluded that both rotational and translational effects are important when predicting the strain levels in the human brain.

  • 2.
    Aare, Magnus
    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).
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Proposed global injury thresholds for oblique helmet impacts2003Conference paper (Refereed)
  • 3.
    Alvarez, Victor
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Fahlstedt, Madelen
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Importance of neck muscle tonus in head kinematics during pedestrian accidents2013In: 2013 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury, 2013, p. 747-761Conference paper (Refereed)
    Abstract [en]

    Unprotected pedestrians are an exposed group in the rural traffic and the most vulnerable human body region is the head which is the source of many fatal injuries. This study was performed to gain a better understanding of the influence that the neck muscle tonus has on head kinematics during pedestrian accidents. This was done using a detailed whole body FE model and a detailed FE vehicle model. To determine the influence of the muscle tonus a series of simulations were performed where the vehicle speed, pedestrian posture and muscle tonus were varied. Since the human reaction time for muscle activation is in the order of the collision time, the pedestrian was assumed to be prepared for the oncoming vehicle in order to augment the possible influence of muscle tonus. From the simulations performed, kinematic data such as head rotations, trajectory and velocities were extracted for the whole collision event, as well as velocity and accelerations at head impact. These results show that muscle tonus can influence the head rotation during a vehicle collision and therefore alter the head impact orientation. The level of influence on head rotation was in general lower than when altering the struck leg forward and backward, but in the same order of magnitude for some cases. The influence on head accelerations was higher due to muscle tonus than posture in all cases.

  • 4.
    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. 

  • 5.
    Brolin, Karin
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Halldin, Peter
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Development of a finite element model of the upper cervical spine and a parameter study of ligament characteristics2004In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 29, no 4, p. 376-385Article in journal (Refereed)
    Abstract [en]

    Study Design. Numeric techniques were used to study the upper cervical spine. Objectives. To develop and validate an anatomic detailed finite element model of the ligamentous upper cervical spine and to analyze the effect of material properties of the ligaments on spinal kinematics. Summary of Background Data. Cervical spinal injuries may be prevented with an increased knowledge of spinal behavior and injury mechanisms. The finite element method is tempting to use because stresses and strains in the different tissues can be studied during the course of loading. The authors know of no published results so far of validated finite element models that implement the complex geometry of the upper cervical spine. Methods. The finite element model was developed with anatomic detail from computed tomographic images of the occiput to the C3. The ligaments were modeled with nonlinear spring elements. The model was validated for axial rotation, flexion, extension, lateral bending, and tension for 1.5 Nm, 10 Nm, and 1500 N. A material property sensitivity study was conducted for the ligaments. Results. The model correlated with experimental data for all load cases. Moments of 1.5 Nm produced joint rotations of 3degrees to 23degrees depending on loading direction. The parameter study confirmed that the mechanical properties of the upper cervical ligaments play an important role in spinal kinematics. The capsular ligaments had the largest impact on spinal kinematics (40% change). Conclusions. The anatomic detailed finite element model of the upper cervical spine realistically simulates the complex kinematics of the craniocervical region. An injury that changes the material characteristics of any spinal ligament will influence the structural behavior of the upper cervical spine.

  • 6.
    Brolin, Karin
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Leijonhufvud, I.
    The effect of muscle activation on neck response2005In: Traffic Injury Prevention, ISSN 1538-9588, E-ISSN 1538-957X, Vol. 6, no 1, p. 67-76Article in journal (Refereed)
    Abstract [en]

    Prevention of neck injuries due to complex loading, such as occurs in traffic accidents, requires knowledge of neck injury mechanisms and tolerances. The influence of muscle activation on outcome of the injuries is not clearly understood. Numerical simulations of neck injury accidents can contribute to increase the understanding of injury tolerances. The finite element (FE) method is suitable because it gives data on stress and strain of individual tissues that can be used to predict injuries based on tissue level criteria. The aim of this study was to improve and validate an anatomically detailed FE model of the human cervical spine by implement neck musculature with passive and active material properties. Further, the effect of activation time and force on the stresses and strains in the cervical tissues were studied for dynamic loading due to frontal and lateral impacts. The FE model used includes the seven cervical vertebrae, the spinal ligaments, the facet joints with cartilage, the intervertebral disc, the skull base connected to a rigid head, and a spring element representation of the neck musculature. The passive muscle properties were defined with bilinear force-deformation curves and the active properties were defined using a material model based on the Hill equation. The FE model's responses were compared to volunteer experiments for frontal and lateral impacts of 15 and 7 g. Then, the active muscle properties where varied to study their effect on the motion of the skull, the stress level of the cortical and trabecular bone, and the strain of the ligaments. The FE model had a good correlation to the experimental motion corridors when the muscles activation was implemented. For the frontal impact a suitable peak muscle force was 40 N/cm2 whereas 20 N/cm2 was appropriate for the side impact. The stress levels in the cortical and trabecular bone were influenced by the point forces introduced by the muscle spring elements; therefore a more detailed model of muscle insertion would be preferable. The deformation of each spinal ligament was normalized with an appropriate failure deformation to predict soft tissue injury. For the frontal impact, the muscle activation turned out to mainly protect the upper cervical spine ligaments, while the musculature shielded all the ligaments disregarding spinal level for lateral impacts. It is concluded that the neck musculature does not have the same protective properties during different impacts loadings.

  • 7.
    Brolin, Karin
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hedenstierna, Sofia
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Bass, Cameron
    Center for Applied Biomechanics, University of Virginia, Charlottesville.
    Alem, Nabih
    US Army Aeromedical Research Laboratory, Fort Rucker.
    The importance of muscle tension on the outcome of impacts with a major vertical component2008In: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 13, no 5, p. 487-498Article in journal (Refereed)
    Abstract [en]

    The hypothesis that muscle tension protects the spine from injuries in helicopter scenarios was tested using a finite-element model of the human head and neck. It was compared with cadaver crash sled experiment with good correlation. Then, simulations were performed with a sinusoidal velocity (5-22 G) applied at T1 60° to the horizontal plane. The model with relaxed muscle activation had delayed and decreased peak head rotation compared with passive properties only. Full muscle activation decreased the injury risk for the 13.5-22 G impacts. A sensitivity study of the impact angle showed a very slight variation of the resulting neck flexion, and 1° change affected all ligament injury predictions less than 4%. Finally, simulations with helmets resulted in increased ligament and disc strains with increasing helmet mass and with an anterior or inferior shift of the centre of gravity. It is concluded that the hypothesis seems to hold.

  • 8. 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. 

  • 9.
    Fahlstedt, Madelen
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Baeck, Katrien
    Mechanical Engineering Department, Biomechanics Section, Katholieke Universiteit Leuven, Belgium.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Vander Sloten, Jos
    Mechanical Engineering Department, Biomechanics Section, Katholieke Universiteit Leuven, Belgium.
    Goffin, Jan
    Mechanical Engineering Department, Biomechanics Section, Katholieke Universiteit Leuven, Belgium.
    Depreitere, Bart
    Mechanical Engineering Department, Biomechanics Section, Katholieke Universiteit Leuven, Belgium.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Influence of impact velocity and angle in a detailed reconstruction of a bicycle accident2012In: 2012 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury, 2012, p. 787-799Conference paper (Refereed)
    Abstract [en]

    Bicycle accidents have become the most common cause of serious injury in the traffic during the last couple of years in Sweden. The objective of this study was to investigate the effect of the input variables, initial velocity and head orientation, of a bicycle accident reconstruction on the strain levels in the brain using a detailed FE head model. The accident involved a non-helmeted 68 year old male who sustained a linear skull fracture, contusions, acute subdural hematoma, and small bleeding at the swelling (subarachnoid blood). The orientation of the head just before impact was determined from the swelling appearing in the computer tomography (CT) scans. The head model used in this study was developed at the Royal Institute of Technology in Stockholm. The stress in the cranial bone, first principal strain in the brain tissue and acceleration were determined. The model was able to predict a strain pattern that correlated well with the medical images from the victim. The variation study showed that the tangential velocity had a large effect on the strain levels in the studied case. The strain pattern indicated larger areas of high strain with increased tangential velocity especially at the more superior sections.

  • 10.
    Fahlstedt, Madelen
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Depreitere, Bart
    Experimental Neurosurgery and Neuroanatomy, KU Leuven, Belgium.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Vander Sloten, Jos
    Biomechanics, KU Leuven, Belgium.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Correlation between Injury Pattern and Finite Element Analysis in Biomechanical Reconstructions of Traumatic Brain Injuries2015In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 48, no 7Article in journal (Refereed)
    Abstract [en]

    At present, Finite Element (FE) analyses are often used as a tool to better understand the mechanisms of head injury. Previously, these models have been compared to cadaver experiments, with the next step under development being accident reconstructions. Thus far, the main focus has been on deriving an injury threshold and little effort has been put into correlating the documented injury location with the response displayed by the FE model. Therefore, the purpose of this study was to introduce a novel image correlation method that compares the response of the FE model with medical images.

    The injuries shown on the medical images were compared to the strain pattern in the FE model and evaluated by two indices; the Overlap Index (OI) and the Location Index (LI). As the name suggests, OI measures the area which indicates both injury in the medical images and high strain values in the FE images. LI evaluates the difference in center of mass in the medical and FE images. A perfect match would give an OI and LI equal to 1.

    This method was applied to three bicycle accident reconstructions. The reconstructions gave an average OI between 0.01 and 0.19 for the three cases and between 0.39 and 0.88 for LI. Performing injury reconstructions are a challenge as the information from the accidents often is uncertain. The suggested method evaluates the response in an objective way which can be used in future injury reconstruction studies.

  • 11.
    Fahlstedt, Madelen
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Comparison of MADYMO and Finite Element Human Body Models in Pedestrian Accidents with the Focus on Head KinematicsManuscript (preprint) (Other academic)
  • 12.
    Fahlstedt, Madelen
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Comparison of multibody and finite element human body models in pedestrian accidents with the focus on head kinematics.2016In: Traffic Injury Prevention, ISSN 1538-9588, E-ISSN 1538-957X, Vol. 17, no 3Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: The objective of this study was to compare and evaluate the difference in head kinematics between the TNO and THUMS models in pedestrian accident situations.

    METHODS: The TNO pedestrian model (version 7.4.2) and the THUMS pedestrian model (version 1.4) were compared in one experiment setup and 14 different accident scenarios where the vehicle velocity, leg posture, pedestrian velocity, and pedestrian's initial orientation were altered. In all simulations, the pedestrian model was impacted by a sedan. The head trajectory, head rotation, and head impact velocity were compared, as was the trend when various different parameters were altered.

    RESULTS: The multibody model had a larger head wrap-around distance for all accident scenarios. The maximum differences of the head's center of gravity between the models in the global x-, y-, and z-directions at impact were 13.9, 5.8, and 5.6 cm, respectively. The maximum difference between the models in head rotation around the head's inferior-superior axis at head impact was 36°. The head impact velocity differed up to 2.4 m/s between the models. The 2 models showed similar trends for the head trajectory when the various parameters were altered.

    CONCLUSIONS: There are differences in kinematics between the THUMS and TNO pedestrian models. However, these model differences are of the same magnitude as those induced by other uncertainties in the accident reconstructions, such as initial leg posture and pedestrian velocity.

  • 13.
    Fahlstedt, Madelen
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Importance of the Bicycle Helmet Design and Material for the Outcome in Bicycle Accidents2014In: Proceedings, International Cycling Safety Conference 2014, Chalmers , 2014, p. 1-14Conference 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.

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  • 14.
    Fahlstedt, Madelen
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    The protective effect of a helmet in three bicycle accidents: A finite element study2016In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 91, p. 135-143Article in journal (Refereed)
    Abstract [en]

    There is some controversy regarding the effectiveness of helmets in preventing head injuries among cyclists. Epidemiological, experimental and computer simulation studies have suggested that helmets do indeed have a protective effect, whereas other studies based on epidemiological data have argued that there is no evidence that the helmet protects the brain. The objective of this study was to evaluate the protective effect of a helmet in single bicycle accident reconstructions using detailed finite element simulations. Strain in the brain tissue, which is associated with brain injuries, was reduced by up to 43% for the accident cases studied when a helmet was included. This resulted in a reduction of the risk of concussion of up to 54%. The stress to the skull bone went from fracture level of 80 MPa down to 13-16 MPa when a helmet was included and the skull fracture risk was reduced by up to 98% based on linear acceleration. Even with a 10% increased riding velocity for the helmeted impacts, to take into account possible increased risk taking, the risk of concussion was still reduced by up to 46% when compared with the unhelmeted impacts with original velocity. The results of this study show that the brain injury risk and risk of skull fracture could have been reduced in these three cases if a helmet had been worn.

  • 15.
    Fahlstedt, Madelen
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    The Protective Effect of Bicycle HelmetsManuscript (preprint) (Other academic)
  • 16.
    Fahlstedt, Madelen
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    S. Alvarez, Victor
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Influence of the Body and Neck on Head Kinematics and Brain Injury Risk in Bicycle Accident Situations2016In: IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury, International Research Council on the Biomechanics of Injury , 2016, p. 459-478Conference paper (Refereed)
    Abstract [en]

    Previous studies about the influence of the neck on head kinematics and brain injuries have shown different results. Today bicycle helmets are certified with only a headform in radial experiments but could be improved with oblique impacts. Then the question is how the helmet's performance will be affected by the neck and the rest of the body. Therefore, the objective of this study was to use finite element simulations to investigate the influence of the body on head kinematics and injury prediction in single bicycleaccident situations with and without a helmet. The THUMS-KTH model was used to study the difference between head only and full body. In total, a simulation matrix of 120 simulations was compared by altering initial impact posture, head protection, and muscle activation. The results show that the body in impacts against a hard surface can change the amplitudes and curve shapes of the kinematics and brain tissue strain. The study found an average ratio between head only and full body for peak brain tissue strain to be 1.04 (SD 0.11), for peak linear acceleration 1.06 (SD 0.04), for peak angular acceleration 1.08 (SD 0.09) and for peak angular velocity 1.05 (SD 0.13).

  • 17.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Aare, Magnus
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Improved helmet design and test methods to reduce rotational induced brain injuries2003Conference paper (Refereed)
    Abstract [en]

    Accidental impacts to the human head are often a combination of translational and rotational accelerations. The most frequent severe brain injuries from accidents are diffuse axonal injury (DAI) and subdural hematoma that both are reported to arise from rotational violence to the head. Most helmet standards used today do only take the translational accelerations into account. It is therefore suggested that an oblique impact test that measures both translational and rotational accelerations should be a complement to the helmet standards used today. This study investigates the potential to reduce the risk for DAI by improving the helmet design by use of an oblique helmet impact test rig. The method used is a detailed finite element (FE) model of the human head. The FE model is used to measure the maximum principal strain in the brain which is suggested as a measurement for the risk to get DAI. The results clearly show the importance of testing a helmet in oblique impacts. Comparing a pure vertical impact with a 45 degree oblique impact with the same initial impact energy shows that the strain in the central parts of the brain is increased with a factor of 6. It is therefore suggested that a future helmet impact standard should include a rotational component so that the helmet is designed for both radial and tangential forces. Such a test method, an oblique impact test, was used to compare two different helmet designs. One helmet was manufactured with the shell glued to the liner and one helmet was designed with a low friction layer between the shell and the liner (MIPS). It was shown that the strain in the FE model of the human head was reduced be 27% comparing the MIPS helmet to the glued helmet design.

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  • 18.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Aare, Magnus
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Reduced risk for DAI by use of a new safety helmet2003Conference paper (Refereed)
    Abstract [en]

    Accidental impacts to the human head are often a combination of translational and rotational accelerations. The most frequent severe brain injuries from accidents are diffuse axonal injury (DAI) and subdural hematoma that both are reported to arise from rotational violence to the head. Most helmet standards used today do only take the translational accelerations into account. It is therefore suggested that an oblique impact test that measures both translational and rotational accelerations should be a complement to the helmet standards used today. This study investigates the potential to reduce the risk for DAI by improving the helmet design by use of an oblique helmet impact test rig. The method used is a detailed finite element (FE) model of the human head. The FE model is used to measure the maximum principal strain in the brain which is suggested as a measurement for the risk to get DAI. The results clearly show the importance of testing a helmet in oblique impacts. Comparing a pure vertical impact with a 45 degree oblique impact with the same initial impact energy shows that the strain in the central parts of the brain is increased with a factor of 6. It is therefore suggested that a future helmet impact standard should include a rotational component so that the helmet is designed for both radial and tangential forces. Such a test method, an oblique impact test, was used to compare two different helmet designs. One helmet was manufactured with the shell glued to the liner and one helmet was designed with a low friction layer between the shell and the liner (MIPS). It was shown that the strain in the FE model of the human head was reduced be 27% comparing the MIPS helmet to the glued helmet design.

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  • 19.
    Halldin, Peter
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Brolin, Karin
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Hedenstierna, Sofia
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Aare, Magnus
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    von Holst, Hans
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Finite element analysis of the effects of head-supported mass on neck responses: Complete phase one report, United states army european research office of the U.S army2004Report (Refereed)
  • 20.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Brolin, Karin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hedenstierna, Sofia
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Aare, Magnus
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Finite element analysis of the effects of head-supported mass on neck responses: Complete phase two report, United states army european research office of the U.S. army2005Report (Refereed)
  • 21. 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)
  • 22.
    Halldin, Peter
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Gilchrist, A.
    Mills, N. J.
    A new oblique impact test for motorcycle helmets2001In: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 6, no 1, p. 53-64Article in journal (Refereed)
    Abstract [en]

    A new oblique impact test for motorcycle helmets is described, simulating a fall from a motorcycle on to the road surface or the windshield of a car. An instrumented headform falls vertically to impact a horizontally moving rigid rough or deformable surface. Both the impact site on the helmet, and the vertical and horizontal velocities, can be varied, while the headform linear and rotational accelerations are measured. The rig was used to compare a new helmet design with current helmets, which are designed to pass impact tests in which the impact force is perpendicular to the helmet surface. The new design, which has a low friction layer between the shell and the liner, reduced, by up to 50%, the rotational acceleration of the head compared with conventional designs.

  • 23.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hedenstierna, Sofia
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Brolin, Karin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Finite element analysis of the effects of head-supported mass on neck responses: Complete phase three report, united states army european research office of the U.S.army2006Report (Refereed)
    Abstract [en]

    The objectives for the whole project were to: I. determine the relationships between head supported mass and the risk of neck injuries. The results should be used in a Graphical user interface. In this phase three report has also the Graphical User Interface (GUI) been evaluated and the question about the how the muscle activation affect the injury risk. II. to develop and implement a 3D numerical muscle model. Results: I. The KTH neck model has successfully been used to generate results for the GUI. Results from all simulations have been reported and sent to Titan Corporation that is contracted by USAARL to program the GUI. The GUI that uses an interpolation method to calculate the neck injury risk for a general helmet with a user defined HSM configuration shows to give realistic interpolated values compared to the FE model of the neck. II. The 3D muscle model for the cervical spine includes 22 pairs of muscles. The solid muscle model showed to stabilize the vertebral column better than the spring muscle model. The model is still under evaluation and need further validation to be used in the HSM evaluation project.

  • 24.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Jakobsson, Lotta
    Chalmers tekniska högskola School of Mechanical Engineering. Institutionen för tillämpad mekanik. .
    Brolin, Karin
    Chalmers tekniska högskola School of Mechanical Engineering. Institutionen för tillämpad mekanik. .
    Palmertz, Camilla
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Investigations of Conditions that Affect Neck Compression-Flexion Injuries Using Numerical Techniques2000In: Stapp Car Crash Journal, ISSN 1532-8546Article in journal (Refereed)
  • 25.
    Halldin, Peter
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Improved helmet design and test methods to reduce rotational induced brain injuries2009Conference paper (Other (popular science, discussion, etc.))
  • 26.
    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.

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  • 27.
    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.

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  • 28.
    Halldin, Peter
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    von Holst, Hans
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Eriksson, Ingvar
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    An experimental head restraint concept for primary prevention of head and neck injuries in frontal collisions.1998In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 30, no 4, p. 535-43Article in journal (Refereed)
    Abstract [en]

    The Experimental Head Restraint Concept (EHRC), a 'safety belt' for the head, is designed to reduce forces to the head and neck, in frontal car crashes. The EHRC was evaluated experimentally in frontal collision for a crash severity of 11 m/s, and numerically in frontal collision for a crash severity of 11 and 15 m/s. Experimental data obtained from a frontal barrier test (11 m/s) showed a 67% reduction of the HIC value from 411 (without EHRC) to 136 (with EHRC). The same level of reduction was also obtained for the higher speed in the numerical simulation. The moment in the neck was shown in experimental configuration to increase a few percent using the EHRC, but as presented in a numerical analysis, the moment was reduced by stiffening the EHRC. The EHRC clearly has a potential role in the search for primary prevention of neurotrauma injuries in frontal related car crashes. However, there is a strong need for more advanced injury criteria for the neck in order to optimize such complex safety systems.

  • 29.
    Hedenstierna, Sofia
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    How does a three-dimensional continuum muscle model affect the kinematics and muscle strains of a finite element neck model compared to a discrete muscle model in rear-end, frontal, and lateral impacts2008In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 33, no 8, p. E236-E245Article in journal (Refereed)
    Abstract [en]

    STUDY DESIGN. A finite element (FE) model of the human neck with incorporated continuum or discrete muscles was used to simulate experimental impacts in rear, frontal, and lateral directions. OBJECTIVE. The aim of this study was to determine how a continuum muscle model influences the impact behavior of a FE human neck model compared with a discrete muscle model. SUMMARY OF BACKGROUND DATA. Most FE neck models used for impact analysis today include a spring element musculature and are limited to discrete geometries and nodal output results. A solid-element muscle model was thought to improve the behavior of the model by adding properties such as tissue inertia and compressive stiffness and by improving the geometry. It would also predict the strain distribution within the continuum elements. METHODS. A passive continuum muscle model with nonlinear viscoelastic materials was incorporated into the KTH neck model together with active spring muscles and used in impact simulations. The resulting head and vertebral kinematics was compared with the results from a discrete muscle model as well as volunteer corridors. The muscle strain prediction was compared between the 2 muscle models. RESULTS. The head and vertebral kinematics were within the volunteer corridors for both models when activated. The continuum model behaved more stiffly than the discrete model and needed less active force to fit the experimental results. The largest difference was seen in the rear impact. The strain predicted by the continuum model was lower than for the discrete model. CONCLUSION. The continuum muscle model stiffened the response of the KTH neck model compared with a discrete model, and the strain prediction in the muscles was improved.

  • 30.
    Hedenstierna, Sofia
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Brolin, Karin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Evaluation of a combination of continuum and truss finite elements in a model of passive and active muscle tissue2008In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 11, no 6, p. 627-639Article in journal (Refereed)
    Abstract [en]

    The numerical method of finite elements (FE) is a powerful tool for analysing stresses and strains in the human body. One area of increasing interest is the skeletal musculature. This study evaluated modelling of skeletal muscle tissue using a combination of passive non-linear, viscoelastic solid elements and active Hill-type truss elements, the super-positioned muscle finite element (SMFE). The performance of the combined materials and elements was evaluated for eccentric motions by simulating a tensile experiment from a published study on a stimulated rabbit muscle including three different strain rates. It was also evaluated for isometric and concentric contractions. The resulting stress-strain curves had the same overall pattern as the experiments, with the main limitation being sensitivity to the active force-length relation. It was concluded that the SMFE could model active and passive muscle tissue at constant rate elongations for strains below failure, as well as isometric and concentric contractions.

  • 31.
    Hedenstierna, Sofia
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Brolin, Karin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Development and evaluation of a continuum neck muscle model2006In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 39, no Supplement 1, p. 150-Article in journal (Refereed)
  • 32.
    Hedenstierna, Sofia
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Siegmund, Gunter
    MEA Forensic Engineers and Scientists Ltd., Richmond, BC, Canada.
    Neck Muscle Load Distribution in Lateral, Frontal, and Rear-end Impacts: A Three-Dimensional Finite Element Analysis2009In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 34, no 24, p. 2626-2633Article in journal (Refereed)
    Abstract [en]

    Study Design. A finite element (FE) model of the human neck was used to study the distribution of neck muscle loads during multidirectional impacts. The computed load distributions were compared to experimental electromyography (EMG) recordings.

    Objective. To quantify passive muscle loads in nonactive cervical muscles during impacts of varying direction and energy, using a three-dimensional (3D) continuum FE muscle model.

    Summary of Background Data. Experimental and numerical studies have confirmed the importance of muscles in the impact response of the neck. Although EMG has been used to measure the relative activity levels in neck muscles during impact tests, this technique has not been able to measure all neck muscles and cannot directly quantify the force distribution between the muscles. A numerical model can give additional insight into muscle loading during impact.

    Methods. An FE model with solid element musculature was used to simulate frontal, lateral, and rear-end vehicle impacts at 4 peak accelerations. The peak cross-sectional forces, internal energies, and effective strains were calculated for each muscle and impact configuration. The computed load distribution was compared with experimental EMG data.

    Results. The load distribution in the cervical muscles varied with load direction. Peak sectional forces, internal energies, and strains increased in most muscles with increasing impact acceleration. The dominant muscles identified by the model for each direction were splenius capitis, levator scapulae, and sternocleidomastoid in lateral impacts, splenius capitis, and trapezoid in frontal impacts, and sternocleidomastoid, rectus capitis posterior minor, and hyoids in rear-end impacts. This corresponded with the most active muscles identified by EMG recordings, although within these muscles the distribution of forces and EMG levels were not the same.

    Conclusion. The passive muscle forces, strains, and energies computed using a continuum FE model of the cervical musculature distinguished between impact directions and peak accelerations, and on the basis of prior studies, isolated the most important muscles for each direction.

  • 33. Hedman, L.
    et al.
    Fahlstedt, Madelen
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Schlickum, M.
    Möller, H.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Felländer-Tsai, L.
    Training diagnosis and treatment of cervical spine trauma using a new educational program for visualization through imaging and simulation (VIS): A first evaluation by medical students2012In: Stud. Health Technol. Informatics, 2012, p. 171-174Conference paper (Refereed)
    Abstract [en]

    In this pilot study we investigated how medical students evaluated a VIS practice session. Immediately after training 43 students answered a questionnaire on the training session. They evaluated VIS as a good interactive scenario based educational tool.

  • 34.
    Lanner, Daniel
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Iraeus, Johan
    Epsilon, Göteborg, Sweden.
    Holmqvist, Kristian
    SAFER, Chalmers University of Technology, Göteborg, Sweden.
    Mroz, Krystoffer
    Autoliv Research, Vårgårda, Sweden.
    Pipkorn, Bengt
    Autoliv Research, Vårgårda, Sweden.
    Jakobsson, Lotta
    Volvo Car Corporation, Göteborg, Sweden.
    Backlund, Maria
    Volvo Car Corporation, Göteborg, Sweden.
    Bolte, John H.
    The Ohio State University, Ohio, USA.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Evaluation of finite element human body models in lateral padded pendulum impacts to the shoulder2010In: International Journal of Crashworthiness, ISSN 1358-8265, E-ISSN 1754-2111, Vol. 15, no 2, p. 125-142Article in journal (Refereed)
    Abstract [en]

    Lateral impacts are of great concern for occupant safety. In order to design side protective systems, it is of importance that the timing of the body and the head should be well predicted. Today, experimental and numerical Anthropometric Test Devices (ATDs) are used as human substitutes to predict the human kinematics. As a complement to the ATDs, numerical Human Body Models (HBMs) are used as research tools. The objective of this study is to compare the loading and kinematics of the shoulder complex in three different HBMs with published biological experiments. This study also compares the models with each other and with two numerical ATDs. The results indicate that no HBM can be used for detailed prediction of the kinematics of the human shoulder complex. However, in the presented statistical analysis, all HBMs show a better overall correlation to experiments compared to the numerical ATDs.

  • 35.
    Lanner, Daniel
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Investigation of the importance of the neck in oblique helmet testingManuscript (preprint) (Other academic)
  • 36.
    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)
  • 37.
    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.

  • 38.
    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
    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 study2020In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 134, article id 105297Article in journal (Refereed)
    Abstract [en]

    The motorcyclist is exposed to the risk of falling and impacting ground head-first at a wide range of travelling speeds - from a speed limit of less than 50 km/h on the urban road to the race circuit where speed can reach well above 200 km/h. However, motorcycle helmets today are tested at a single and much lower impact speed, i.e. 30 km/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 216 km/h. The effect of different falling heights (1.6 m and 0.25 m) and coefficient of frictions (0.20 and 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 observed in 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 1.63 m and a friction coefficient of 0.45, the rolling/sliding transition occurs at a tangential velocity of 10.8 m/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.

  • 39.
    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.

  • 40.
    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.

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    fulltext
  • 41.
    Nordberg, Axel
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Evaluation of fiber reinforced adhesive fixation of vertebral fractures; an experimental and numerical studyManuscript (preprint) (Other academic)
  • 42.
    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)
  • 43. Pipkorn, B.
    et al.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Jakobsson, L.
    Iraeus, J.
    Backlund, M.
    Mroz, K.
    Lanner, Daniel
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Holmqvist, K.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Mathematical human body models in side impacts- A validation study with particular emphasis on the torso and shoulder and their influence on head and neck motion2008In: Int. Res. Counc. Biomech. Inj. - Int. IRCOBI Conf. Biomech. Inj., Proc., 2008, p. 99-114Conference paper (Refereed)
    Abstract [en]

    The ability of three mathematical human body models to predict previously published human responses in two different side impact loading configurations was evaluated using an objective rating method. In particular the kinematics of the shoulder, T1 and head were evaluated. The human body models evaluated were THUMS, HUMOS 2 and the GM model. The impact loading configurations used were pendulum impact tests and sled tests. In the pendulum configurations, the closest correlation to the published responses was shown by THUMS followed by the GM model. In the sled configuration, closest correlation to the published responses was shown by HUMOS 2 followed by THUMS. According to the objective rating method the published responses in the pendulum configuration were predicted by all human body models. The published responses in the sled configuration were predicted by HUMOS 2 and THUMS.

  • 44.
    Pipkorn, Bengt
    et al.
    Chalmers tekniska högskola School of Mechanical Engineering. Institutionen för tillämpad mekanik. .
    Halldin, Peter
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Jakobsson, Lotta
    Chalmers tekniska högskola School of Mechanical Engineering. Institutionen för tillämpad mekanik. .
    Iraeus, Johan
    Backlund, ria
    Mroz, Krystoffer
    Holmqvist, Kristian
    Chalmers tekniska högskola School of Mechanical Engineering. Institutionen för tillämpad mekanik. .
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Mathematical Occupant Models in Side Impacts: A Validation Study with Particular Emphasis on the Torso and Shoulder and their Influence on Head and Neck Motion2008In: International IRCOBI Conference on the Biomechanics of Impact, 2008, p. 99-111Conference paper (Refereed)
    Abstract [en]

    The ability of three mathematical human body models to predict previously published human responses in two different side impact loading configurations was evaluated using an objective rating method. In particular the kinematics of the shoulder, T1 and head were evaluated. The human body models evaluated were THUMS, HUMOS 2 and the GM model. The impact loading configurations used were pendulum impact tests and sled tests. In the pendulum configurations, the closest correlation to the published responses was shown by THUMS followed by the GM model. In the sled configuration, closest correlation to the published responses was shown by HUMOS 2 followed by THUMS. According to the objective rating method the published responses in the pendulum configuration were predicted by all human body models. The published responses in the sled configuration were predicted by HUMOS 2 and THUMS.

  • 45.
    Robinson, Yohan
    et al.
    Uppsala University Hospital, Uppsala, Sweden.
    Lison Almkvist, Viktor
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Olerud, Claes
    Uppsala University Hospital, Uppsala, Sweden.
    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.
    Finite Element Analysis of Long Posterior Transpedicular Instrumentation for Cervicothoracic Fractures Related to Ankylosing Spondylitis2018In: Global Spine Journal, ISSN 2192-5682, E-ISSN 2192-5690Article in journal (Refereed)
  • 46.
    S. Alvarez, Victor
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Fahlstedt, Madelen
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Pipkorn, Bengt
    Autoliv Research.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Influence of Body and Head Angular Velocity on Brain Injury Prediction in Pedestrian AccidentsManuscript (preprint) (Other academic)
    Abstract [en]

    Pedestrian protection has historically not been prioritized in the vehicle safety development, but represents a large portion of the severe and deadly injuries in vehicle accidents. One of the most common severely injured body parts is the head and the focus of many researchers and safety system developers. The Finite Element (FE) method is an increasingly popular approach to better understand the injury biomechanics, but due to the large system needed to be solved in pedestrian simulations a common approach is to reduce the problem to a head only impact. In EuroNCAP rating an isolated head form is impacted towards different regions of the vehicle with only linear velocity components. The aim of this study is to determine the effect of removing the neck and body, as well as rotational velocity components on the brain injury prediction. A pedestrian full body human FE model was impacted against a generalized buck model to simulate pedestrian accidents involving windscreen impacts, at three velocities (30, 40 and 50 or 45 km/h), two pedestrian velocities (0 and 5 km/h) and two standard walking gaits. The head position was extracted from the pedestrian full body simulations at 1 ms before head impact. The isolated head was impacted with the vehicle model using either all velocity components from the full body simulations, or only the linear components. The results show that the body and neck can affect the brain injury prediction in windscreen impacts, reducing the strains by up to 49%. It was also shown that removing the rotational impact velocities, in general, further increased the strain, with up to 138%. However, several cases showed a reduction in brain strains for the head only simulations by up to 40%, and in other cases only very small difference down to 1% were seen, indicating a high sensitivity to impact conditions and highlighting the difficulty in generalizing the effect. It is however generally seen that the body is limiting the severity in impacts close to the windscreen center, and amplifying the severity of those close to the lower frame. It could also be seen that removing the angular velocity, in most cases, further increased the difference between the full body and head only simulations.

  • 47.
    Strömbäck Alvarez, Victor
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Influence of Neck Muscle Tone on Brain Tissue Strain during Pedestrian Impacts2014In: 11th World Congress on Computational Mechanics (WCCM XI), 5th European Conference on Computational Mechanics (ECCM V), July 20 - 25, 2014, Barcelona, Spain, 2014Conference paper (Refereed)
    Abstract [en]

    Unprotected pedestrians are an exposed group in rural traffic were the most vulnerable humanbody region is the head and the source of many fatal injuries. Brain tissue strain has been shown to correlate well with brain injuries in a detailed FE model [1]. This study was performed to gain a better understanding of the influence that the neck muscle tone has on brain tissue strain during pedestrian head impacts. The study was carried out using a detailed whole body FE model with a detailed neck [2], [3] and brain model [4]. To determine the influence of the muscle tone, a series of simulations were performed where the vehicle speed,pedestrian posture and muscle tone were varied. A generalized hood was also used to get the same impact surface in the different simulations and isolate the influence on strain due changed head kinematics. The influence of increased muscle stiffness was also isolated by adding the increased stiffnes momentaraly before head impact. Hence, the head kinematics did not have time to change and a change in strain was asumed to only be due to the changed neck stiffness. It has previously been shown that the neck muscle tone has a relatively small influence on head kinematics compared to posture, and hence head impact orientation [5]. The influence on brain tissue strain levels was however highly sensitive to impact point on a detailed vehicle due to the complex impact surface. When impacting a generalized surface the diffrences in strain between all simulations were significantly reduced and the influence due to muscle tone was in the same level as due to posture. The isolated influence of increased neck stiffness due to muscle tone was lower than the influence due to slightly changed head impact orientation. The increased neck stiffnes was therefore considered relatively unsignificant when considering brain injuries due to first impact on a vehicle structure in pedestrain accidents.

  • 48.
    Strömbäck Alvarez, Victor
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Halldin, Peter
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    The Influence of Neck Muscle Tonus and Posture on Brain Tissue Strain in Pedestrian Head Impacts2014In: Stapp Car Crash Journal, ISSN 1532-8546, Vol. 58, p. ​63-101Article 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.

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