Now showing 1 - 10 of 26
  • Publication
    The influence of centric and non-centric impacts to American football helmets on the correlation between commonly metrics in brain injury research
    (International Research Council on the Biomechanics of Injury, 2012) ; ; ;
    Concussion has become recognized as an injury which can be a source of long term neurological damage. This has led to research into which metrics may be more appropriate to define risk of injury. Some researchers support the use of linear acceleration as a metric for concussion, while others suggest the use of linear and rotational acceleration as well as brain deformation metrics. The purpose of this study was to examine the relationships between these metrics using a centric and non‐centric impact protocol. A linear impactor was used to impact a Hybrid III headform fitted with different models of American football helmet using a centric and non‐centric protocol. The dynamic response was then used as input to the FE model for analysis of brain deformations. The results showed that linear acceleration was correlated to rotational acceleration and brain deformation for centric conditions, but under non‐centric conditions it was not. These results indicate that the type of methodology used will influence the relationship between the variables used to assign risk of concussion. These results also support the use of a centric/non‐centric protocol and measurement of rotational acceleration and brain deformation when it comes to the development of helmet technologies.
      364
  • Publication
    The Association among Injury Metrics for Different Events in Ice Hockey Goaltender Impact
    (International Research Council on Biomechanics of Injury (IRCOBI), 2016-09-16) ; ; ;
    Current ice hockey goaltender helmet standards use a drop test and peak linear acceleration to evaluate performance. However, ice hockey goaltenders are exposed to impacts from collisions, falls and pucks which each create unique loading conditions. As a result, the use of peak linear acceleration as a predictor for brain trauma in current ice hockey standards may not be most appropriate. The purpose of this study was to determine how kinematic response measures correlate to maximum principal strain and von Mises stress for different impact events. A NOCSAE headform was fitted with three ice hockey goaltender helmet models and impacted under conditions representing these three different impact events (fall, puck, collision). Peak resultant linear acceleration, rotational acceleration and rotational velocity of the headform were measured. Resulting accelerations were input into the University College Dublin Brain Trauma Model, which calculated maximum principal strain and von Mises stress in the cerebrum. The results demonstrated that the relationship between injury metrics in ice hockey goaltender impacts is dependent on the impact event and velocity. As a result of these changing relationships, the inclusion of finite element analysis in test protocols may provide a more practical representation of brain loading in evaluating the performance of ice hockey goaltender helmets.
      529
  • Publication
    The dynamic response characteristics of traumatic brain injury
    Traumatic brain injury (TBI) is a common injury and is a leading cause of morbidity and mortality throughout the world. Research has been undertaken in order to better understand the characteristics of the injury event and measure the risk of injury to develop more effective environmental, technological, and clinical management strategies. This research used methods that have limited applications to predicting human responses. This limits the current understanding of the mechanisms of TBI in humans. As a result, the purpose of this research was to examine the characteristics of impact and dynamic response that leads to a high risk of incurring a TBI in a human population. Twenty TBI events collected from hospital reports and eyewitness accounts were reconstructed in the laboratory using a combination of computational mechanics models and Hybrid III anthropometric dummy systems. All cases were falls, with an average impact velocity of approximately 4.0 m/s onto hard impact surfaces. The results of the methodology were consistent with current TBI research, describing TBI to occur in the range of 335 to 445 g linear accelerations and 23.7 to 51.2 krad/s2 53 angular accelerations. More significantly, this research demonstrated that lower responses in the antero-posterior direction can cause TBI, with lateral impact responses requiring larger magnitudes for the same types of brain lesions. This suggests an increased likelihood of incurring TBI for impacts to the front or back of the head, a result that has implications affecting current understanding of themechanisms of TBI and associated threshold parameters.
      419
  • Publication
    The influence of impact angle on the dynamic response of a Hybrid III headform and brain tissue deformation
    The objective of this study was to investigate the influence of impact angle on the dynamic response of a Hybrid III headform and brain tissue deformation by impacting the front and side of the headform using four angle conditions (0°, at the impact site and 5, 10 and 15° rightward rotations of the headform from 0°) as well as three additional angle conditions of -5, - 10 and -15° (leftward rotations from 0°) at the side location to examine the effects of the neckform. The acceleration-time curves were used as input into a finite element model of the brain where maximum principal strain was calculated. The study found that an impact angle of 15° significantly influencesthe results when measured using linear and rotational acceleration and maximum principal strain. When developing sophisticated impact protocols and undertaking head injury reconstruction research, it is important to be aware of impact angle.
      452
  • Publication
    The relationship between impact condition and velocity on brain tissue response
    (International Society of Biomechanics, 2011) ; ;
    Injury reconstruction is a well accepted method for investigating the relationship between the event causing brain injury and the resulting trauma to neural tissue. Understanding the effect of the impact characteristics and velocity on the brain deformations is important when interpreting brain stress and strain values obtained from reconstructions. A finite element model (UCDBTM) was used to evaluate brain tissue response under varying impact conditions using an unhelmeted Hybrid III headform. This study was designed to evaluate the relationship between impact conditions and corresponding brain tissue response variables. The results revealed that the dynamic response curve created by different impacting conditions significantly influenced the maximum principal strain and Von Mises stress of brain tissue, providing valuable insight in the limitations of accident reconstruction from descriptive data.
      143
  • Publication
    Effect of impact surface in equestrian falls
    (International Society of Biomechanics in Sports (ISBS), 2016-07-22) ; ; ; ;
    This study examines the effect of impact surface on head kinematic response and maximum principal strain (MPS) for equestrian falls. A helmeted Hybrid III headform was dropped unrestrained onto three impact surfaces of different stiffness (steel, turf and sand) and three locations. Peak resultant linear acceleration, rotational acceleration and duration of the impact events were measured. A finite element brain model was used to calculate MPS. The results revealed that drops onto steel produced higher peak linear acceleration, rotational acceleration and MPS but lower impact durations than drops to turf and sand. However, despite lower MPS values, turf and sand impacts compared to steel impacts still represented a risk of concussion. This suggests that certification standards for equestrian helmets do not properly account for the loading conditions experienced in equestrian accidents.
      213
  • Publication
    Estimating the influence of neckform compliance on brain tissue strain during a Helmeted impact
    (Society of Automotive Engineers, 2010-11) ; ;
    The aim of this study was to determine if a change in neckform compliance could influence maximum principal strain in the brain white and grey matter, the brain stem and the cerebellum. This was done by impacting a Hybrid III headform with a 16.6 kg impactor arm at 5 m/s. Three different Hybrid III neckforms were used: 1) one 50th percentile male neckform - standard neckform; 2) one 50th percentile male neckform plus 30 per cent compliance - soft neckform; 3) one 50th percentile male neckform minus 30 per cent compliance - stiff neckform. The kinematic data obtained was then used to drive a finite element model developed by University College Dublin. The results showed that a decrease in neckform compliance had a significant effect on maximal principal strain in the cerebellum, where the stiff neck (0.050 ± 0.004) generated higher maximum principal strains than the standard neck (0.036 ± 0.003) and the soft neck (0.037 ± 0.001). There were no significant differences between the stiff (0.122 ± 0.013), standard (0.114 ± 0.020) and soft neck (0.119 ± 0.019) in the white matter; the stiff (0.168 ± 0.011), standard (0.176 ± 0.011) and soft neck (0.176 ± 0.007) in the grey matter; or the stiff (0.080 ± 0.003), standard (0.081 ± 0.006) and soft neck (0.085 ± 0.009) in the brain stem. The results were not linked to brain injury due to the absence of a commonly accepted threshold.
      417
  • Publication
    For ASTM F-08: Protective Capacity of Ice Hockey Player Helmets against Puck Impacts
    Many studies have assessed the ability of hockey helmets to protect against falls and collisions, yet none have addressed the injury risk associated with puck impacts. Thus, the purpose of this study was to document the capacity of a typical vinyl nitrile ice hockey helmet to reduce head accelerations and brain deformation caused by a puck impact. A bare and a helmeted Hybrid III male 50th percentile headform was struck with a puck three times to the forehead at 17, 23, 29, 35, and 41 m/s using a pneumatic puck launcher. Linear and rotational accelerations were captured using accelerometers fitted in the headform and used as input in the University College Dublin Brain Trauma Model to obtain brain deformation. The helmet reduced peak resultant linear acceleration, peak resultant rotational acceleration, and maximum principal strain, but a comparison with published brain injury risk curves shows that it did not reduce the concussion risk below 50 % for impacts at or above 23 m/s. Thus, a vinyl nitrile ice hockey helmet can protect players from direct puck impacts in amateur and youth leagues but may not be adequate in competitive elite leagues, where the puck can be shot at velocities well above 23 m/s. Furthermore, competitive adult male ice hockey players struck to the helmet by a puck may need to consider changing their helmet, as it was shown that direct impacts at or above 35 m/s decreased the helmet’s ability to reduce head peak linear acceleration in subsequent impacts.
    Scopus© Citations 8  444
  • Publication
    Determining the relationship between linear and rotational acceleration and MPS for different magnitudes of classified brain injury risk in ice hockey
    (International Research Council on the Biomechanics of Injury (IRCOBI), 2015-09-11) ; ; ;
    Helmets have successfully decreased the incidence of traumatic brain injuries (TBI) in ice hockey, yet the incidence of concussions has essentially remained unchanged. Current ice hockey helmet certification standards use peak linear acceleration as the principal measuring helmet performance, however peak linear acceleration may not be an appropriate variable to evaluate risk at all magnitudes of brain injury. The purpose of this study is to determine the relationship between linear acceleration, rotational acceleration and maximum principal strain (MPS) for different magnitudes of classified brain injury risk in ice hockey. A helmeted and unhelmeted Hybrid III headform were impacted to the side of the head at two sites and at three velocities under conditions representing three common mechanisms of injury. Resulting linear and rotational accelerations were used as input for the University College Dublin Brain Trauma Model (UCDBTM), to calculate MPS in the brain. The resulting MPS magnitudes were used to separate the data into three groups: low risk; concussion; and TBI. The results demonstrate that the relationship between injury metrics in ice hockey impacts is dependent on the magnitude of classified injury risk and the mechanism of injury.
      386
  • Publication
    Protective capacity of an ice hockey goaltender helmet for three events associated with concussion
    The purpose of this study was to assess the protective capacity of an ice hockey goaltender helmet for three concussive impact events. A helmeted and unhelmeted headform was used to test three common impact events in ice hockey (fall, puck impacts and shoulder collisions). Peak linear acceleration, rotational acceleration and rotational velocity as well as maximum principal strain and von Mises stress were measured for each impact condition. The results demonstrated the tested ice hockey goaltender helmet was well designed to manage fall and puck impacts but does not consistently protect against shoulder collisions and an opportunity may exist to improve helmet designs to better protect goaltenders from shoulder collisions.
    Scopus© Citations 16  582