Now showing 1 - 10 of 26
  • 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.
      223
  • 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.
      425
  • 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.
      461
  • 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.
      399
  • 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.
      430
  • 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.
      535
  • 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.
      148
  • Publication
    Examination of the relationship between peak linear and angular accelerations to brain deformation metrics in hockey helmet impacts
    (Informa UK (Taylor & Francis), 2013-05) ; ; ;
    Ice hockey is a contact sport which has a high incidence of brain injury. The current methods of evaluating protective devices use peak resultant linear acceleration as their pass/fail criteria, which are not fully representative of brain injuries as a whole. The purpose of this study was to examine how the linear and angular acceleration loading curves from a helmeted impact influence currently used brain deformation injury metrics. A helmeted Hybrid III headform was impacted in five centric and non-centric impact sites to elicit linear and angular acceleration responses. These responses were examined through the use of a brain model. The results indicated that when the helmet is examined using peak resultant linear acceleration alone, they are similar and protective, but when a 3D brain deformation response is used to examine the helmets, there are risks of brain injury with lower linear accelerations which would pass standard certifications for safety.
      804Scopus© Citations 58
  • Publication
    The Influence of Impactor Mass on the Dynamic Response of the Hybrid III Headform and Brain Tissue Deformation
    When determining head injury risks through event reconstruction, it is important to understand how individual impact characteristics influence the dynamic response of the head and its internal structures. The effect of impactor mass has not yet been analyzed in the literature. The purpose of this study was to determine the effects of impactor mass on the dynamic impact response and brain tissue deformation. A 50th-percentile Hybrid III adult male head form was impacted using a simple pendulum system. Impacts to a centric and a non-centric impact location were performed with six varied impactor masses at a velocity of 4.0 m/s. The peak linear and peak angular accelerations were measured. A finite element model (University College Dublin Brain Trauma Model) was used to determine brain deformation, namely, peak maximum principal strain and peak von Mises stress. Impactor mass produced significant differences for peak linear acceleration for centric (F5,24 = 217.55, p = 0.0005) and non-centric (F5,24 = 161.98, p = 0.0005) impact locations, and for peak angular acceleration for centric (F5,24 = 52.51, p = 0.0005) and non-centric (F5,24 = 4.18, p = 0.007) impact locations. A change in impactor mass also had a significant effect on the peak maximum principal strain for centric (F5,24 = 11.04, p = 0.0005) and non-centric (F5,24 = 5.87, p = 0.001) impact locations, and for peak von Mises stress for centric (F5,24 = 24.01, p = 0.0005) and non-centric (F5,24 = 4.62, p = 0.004) impact locations. These results confirm that the impactor mass of an impact should be considered when determining risks and prevention of head and brain injury.
      1048Scopus© Citations 15
  • Publication
    The effect of acceleration signal processing for head impact numeric simulations
    Brain injury research in sport employs a variety of physical models equipped with accelerometers. These acceleration signals are commonly processed using filters. The purpose of this research was to determine the effect of applying filters with different cutoff frequencies to the acceleration signals used as input for finite element modelling of the brain. Signals were generated from reconstructions of concussion events from American football and ice hockey in the laboratory using a Hybrid III headform. The resulting acceleration signals were used as input for the University College Dublin Brain Trauma Model after being processed with filters. The results indicated that using a filter with a cutoff of 300 Hz or higher had little effect on the resulting strain measures. In some cases there was some effect of the filters on the peak linear (8¿30g) and rotational measures (1000¿4000 rad/s2), but little effect on the finite element strain result (approximately 2¿6 %). The short duration and high magnitude accelerations, such as the puck impact, were most affected by the cutoff frequency of different filters.
      1773Scopus© Citations 22