Safety performance testing of climbing helmet-mounted cameras.

BACKGROUND: No research establishing the effects of climbing helmet-mounted cameras on head injury biomechanics. OBJECTIVE: Establish the potential effects of climbing helmet-mounted cameras on the injury risks associated with falling object strikes and falls onto flat and angled surfaces. METHODS: Three experimental studies were developed via the adaptation of European helmet testing standards and regulations. Study 1 performed falling striker tests to the helmet, Study 2 performed linear headform drop tests onto a flat anvil and Study 3 performed oblique headform drop tests onto an anvil angled 15° from vertical. Three helmet categories (hard-shell, foam and hybrid) were impacted at three locations (vertex, front and side), using five camera mounting combinations and three control helmets. Data was collected for the forces, linear accelerations, rotational velocities and rotational accelerations experienced by the headform. RESULTS: All helmet and camera combinations investigated by this project complied with current legislative performance criteria, while no combination exceeded published injury thresholds. No increase in head injury risk was observed for the forces transferred to the head during falling object strikes or with the linear accelerations experienced during falls onto flat and angled surfaces. Finally, although greater rotational head velocities and accelerations were observed with falls onto flat and angled surfaces, no injury threshold was exceeded by any investigated helmet and camera combination. CONCLUSIONS: All helmet and camera combinations investigated by this project complied with current legislative performance criteria, while no combination exceeded published injury thresholds. Further research may be required to establish the effects of additional impact mechanism, helmet or camera mounting configurations.

Evaluation of near-side oblique frontal impacts using THOR with SD3 shoulder.

OBJECTIVE: Within the EC Seventh Framework project THORAX, the Mod-Kit THOR was upgraded with a new thorax and shoulder. The aim of this study was to investigate whether the THOR ATD met a set of prerequisites to a greater extent than Hybrid III and by that measure whether the dummy could serve as a potential tool for future evaluation of serious head and chest injuries in near-side oblique frontal impacts. METHOD: A small-overlap/oblique sled system was used to reflect occupant forces observed in oblique frontal crashes. The head and thoracic response from THOR was evaluated for 3 combinations: belt only with no deformation of the driver's side door (configuration A), belt only in combination with a predeformed door (configuration B), and prepretensioning belt and driver airbag (PPT+DAB) in combination with a predeformed door (configuration C). To evaluate head injury risk, the head injury criterion (HIC) and brain injury criteria (BrIC) were used. For evaluation of the thoracic injury risk, 3 injury criteria proposed by the THORAX project were evaluated: Dmax, DcTHOR, and strain (dummy rib fractures). RESULTS: Unlike Hybrid III, the THOR with SD3 shoulder interacted with the side structure in a near-side oblique frontal impact. HIC values for the 3 test configurations corresponded to a 90% (A) and 100% (B and C) risk of Abbreviated Injury Scale (AIS) 2+ head injury, and BrIC values resulted in a 100% risk of AIS 2+ head injury in configurations A and B. In C the risk was reduced to 75%. The AIS 2+ thoracic injury risks based on Dmax were similar (14-18%) for all tests. Based on DcTHOR, AIS 2+ injury risk increased from 29 to 53% as the predeformed door side was introduced (A to B), and the risk increased, to 64%, as a PPT+DAB was added (C). Considering the AIS 2+ injury risk based on strain, tests in A resulted in an average of 3 dummy rib fractures (17%). Introducing the predeformed door (B) increased the average of dummy fractures to 5 (39%), but in C the average number of dummy rib fractures decreased to 4 (28%). CONCLUSIONS: THOR with an SD3 shoulder should be the preferred ATD rather than the Hybrid III for evaluating head and thorax injuries in oblique frontal impacts. Thoracic interaction with the predeformed door was not well captured by the 3D IR-Traccs; hence, use of deflection as an injury predictor in oblique loading is insufficient for evaluating injury risk in this load case. However, injury risk evaluation may be performed using the strain measurements, which characterize loading from seat belt and airbag as well as the lateral contribution of the structural impact in the loading condition used in this study.

The repeatability and reproducibility of the BioRID IIg in a repeatable laboratory seat based on a production car seat.

OBJECTIVE: The United Nations Economic Commission for Europe Informal Group on GTR No. 7 Phase 2 are working to define a build level for the BioRID II rear impact (whiplash) crash test dummy that ensures repeatable and reproducible performance in a test procedure that has been proposed for future legislation. This includes the specification of dummy hardware, as well as the development of comprehensive certification procedures for the dummy. This study evaluated whether the dummy build level and certification procedures deliver the desired level of repeatability and reproducibility. METHODS: A custom-designed laboratory seat was made using the seat base, back, and head restraint from a production car seat to ensure a representative interface with the dummy. The seat back was reinforced for use in multiple tests and the recliner mechanism was replaced by an external spring-damper mechanism. A total of 65 tests were performed with 6 BioRID IIg dummies using the draft GTR No.7 sled pulse and seating procedure. All dummies were subject to the build, maintenance, and certification procedures defined by the Informal Group. RESULTS: The test condition was highly repeatable, with a very repeatable pulse, a well-controlled seat back response, and minimal observed degradation of seat foams. The results showed qualitatively reasonable repeatability and reproducibility for the upper torso and head accelerations, as well as for T1 Fx and upper neck Fx . However, reproducibility was not acceptable for T1 and upper neck Fz or for T1 and upper neck My . The Informal Group has not selected injury or seat assessment criteria for use with BioRID II, so it is not known whether these channels would be used in the regulation. However, the ramping-up behavior of the dummy showed poor reproducibility, which would be expected to affect the reproducibility of dummy measurements in general. Pelvis and spine characteristics were found to significantly influence the dummy measurements for which poor reproducibility was observed. It was also observed that the primary neck response in these tests was flexion, not extension. This correlates well with recent findings from Japan and the United States showing a correlation between neck flexion and injury in accident replication simulations and postmortem human subjects (PMHS) studies, respectively. CONCLUSIONS: The present certification tests may not adequately control front cervical spine bumper characteristics, which are important for neck flexion response. The certification sled test also does not include the pelvis and so cannot be used to control pelvis response and does not substantially load the lumbar bumpers and so does not control these parts of the dummy. The stiffness of all spine bumpers and of the pelvis flesh should be much more tightly controlled. It is recommended that a method for certifying the front cervical bumpers should be developed. Recommendations are also made for tighter tolerance on the input parameters for the existing certification tests.

Injury risk curves for the WorldSID 50th male dummy.

The development of the WorldSID 50th percentile male dummy was initiated in 1997 by the International Organisation for Standardisation (ISO/TC22/SC12/WG5) with the objective of developing a more biofidelic side impact dummy and supporting the adoption of a harmonised dummy into regulations. The dummy is currently under evaluation at the Working Party on Passive Safety (GRSP) in order to be included in the pole side impact global technical regulation (GTR). Injury risk curves dedicated to this dummy and built on behalf of ISO/TC22/SC12/WG6 were proposed in order to assess the occupant safety performance (Petitjean et al. 2009). At that time, there was no recommendation yet on the injury criteria and no consensus on the most accurate statistical method to be used. Since 2009, ISO/TC22/SC12/WG6 reached a consensus on the definition of guidelines to build injury risk curves, including the use of the survival analysis, the distribution assessment and quality checks. These guidelines were applied to the WorldSID 50th results published in 2009 in order to be able to provide a final set of injury risk curves recommended by ISO/TC22/SC12/WG6. The paper presents the different steps of the guidelines as well as the recommended injury risk curves dedicated to the WorldSID 50th for lateral shoulder load, thoracic rib deflection, abdomen rib deflection and pubic force.

The effect of strain rate on the mechanical properties of human cortical bone.

Bone mechanical properties are typically evaluated at relatively low strain rates. However, the strain rate related to traumatic failure is likely to be orders of magnitude higher and this higher strain rate is likely to affect the mechanical properties. Previous work reporting on the effect of strain rate on the mechanical properties of bone predominantly used nonhuman bone. In the work reported here, the effect of strain rate on the tensile and compressive properties of human bone was investigated. Human femoral cortical bone was tested longitudinally at strain rates ranging between 0.14-29.1 s(-1) in compression and 0.08-17 s(-1) in tension. Young's modulus generally increased, across this strain rate range, for both tension and compression. Strength and strain (at maximum load) increased slightly in compression and decreased (for strain rates beyond 1 s(-1)) in tension. Stress and strain at yield decreased (for strain rates beyond 1 s(-1)) for both tension and compression. In general, there seemed to be a relatively simple linear relationship between yield properties and strain rate, but the relationships between postyield properties and strain rate were more complicated and indicated that strain rate has a stronger effect on postyield deformation than on initiation of yielding. The behavior seen in compression is broadly in agreement with past literature, while the behavior observed in tension may be explained by a ductile to brittle transition of bone at moderate to high strain rates.