Oblique impacts of the helmet against the ground are the most frequent scenarios in real-world motorcycle crashes. The combination of two factors that largely affect the results of oblique impact tests are discussed in this work. This study aims to quantify the effect of the friction at the interface between the headform and the interior of a motorcycle helmet at different magnitudes of tangential velocity. The helmeted headform, with low friction and high friction surface of the headform, was dropped against three oblique anvils at different impact velocities resulting in three different magnitudes of the tangential velocity (3.27 m/s, 5.66 m/s, 8.08 m/s) with the same normal component of the impact velocity (5.66 m/s). Three impact directions (front, left-side and right-side) and three repetitions per impact condition were tested resulting in 54 impacts. Tangential velocity variation showed little effect on the linear acceleration results. On the contrary, the rotational results showed that the effect of the headform’s surface depends on the magnitude of the tangential velocity and on the impact direction. These results indicate that a combination of low friction with low tangential velocities may result into underprediction of the rotational headform variables that would not be representative of real-world conditions.

Objectives:The objective of this study was to determine the potential chest injury benefits and influence on occupant kinematics of a belt system with independent control of the shoulder and lap portions.Methods: This article investigates the kinematics and dynamics of human surrogates in 35 km/h impacts with 2 different restraints: a pretensioning (PT), force-limiting (FL) seat belt, a reference belt system, and a concept design with a split buckle consisting (SB) of 2 separate shoulder and lap belt bands. The study combines mathematical simulations with the THOR dummy and THUMS human body model, and mechanical tests with the THOR dummy and 2 postmortem human surrogate (PMHS) tests of similar age (39 and 42 years) and anthropometry (62 kg, 181 cm vs. 60 kg, 171.5 cm). The test setup consisted of a rigid metallic frame representing a standard seating position of a right front passenger. The THOR dummy model predictions were compared to the mechanical THOR dummy test results. The THUMS-predicted number of fractured ribs were compared to the number of fractured ribs in the PMHS. Results: THOR sled tests showed that the SB seat belt system decreased chest deflection significantly without increasing the forward displacement of the head. The THOR model and the THOR physical dummy predicted a 13-and 7-mm reduction in peak chest deflection, respectively. Peak diagonal belt force in the mechanical test with the reference belt was 5,582 N and the predicted force was 4,770 N. The THOR model also predicted lower belt forces with the SB system than observed in the tests (5,606 vs. 6,085 N). THUMS predicted somewhat increased head displacement for the SB system compared to the reference system. Peak diagonal force with the reference belt was 4,000 N and for the SB system it was 5,200 N. The PMHS test with the SB belt resulted in improved kinematics and a smaller number of rib fractures (2 vs. 5 fractures) compared to the reference belt. Conclusion:Concepts for a belt system that can reduce the load on the chest of the occupant in a crash and thereby reduce the number of injured occupants, in particular the elderly, was proposed.

In this study of nearside oblique impact loading, the PMHS exhibited kinematics characterized by reduced torso pitching and increased lateral head excursion as compared to previous frontal impact results. These kinematics resulted in potential cervical and thoracic spinal injuries and in complete, displaced fractures of the lateral and posterior aspects of the rib cage. Though this is a limited number of subjects, it shows the necessity of further understanding of the kinematics of occupants exposed to this loading mode.

Regulation ECE-22.05/06 does not require a helmet penetration test. Penetration testing is controversial since it has been shown that it may cause the helmet to behave in a non-desirable stiff way in real-world crashes. This study aimed to assess the effect of the penetration test in the impact performance of helmets. Twenty full-face motorcycle helmets were penetration tested at multiple locations of the helmet shell. Then, 10 helmets were selected and split into two groups (hard shell and soft shell) depending on the results of the penetration tests. These 10 helmets were then drop tested at front, lateral, and top areas at two different impact speeds (5 m/s and 8.2 m/s) to assess their impact performance against head injuries. The statistical analyses did not show any significant difference between the two groups (hard/soft shell) at 5 m/s. Similar results were observed at 8.2 m/s, except for the top area of the helmet in which the peak linear acceleration was significantly higher for the soft shell group than for the hard shell group (230 ± 12 g vs. 211 ± 11 g; p-value = 0.038). The results of this study suggest that a stiffer shell does not necessarily cause helmets to behave in a stiffer way when striking rigid flat surfaces. These experiments also showed that hard shell helmets can provide better protection at higher impact speeds without damaging helmet performance at lower impact speeds.

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