PURPOSE: Oblique impact test can provide important information regarding the level of protection of a helmet. Two factors that influence the results of oblique impact tests on motorcycle helmets are discussed in this work. The first factor is the angle of the anvil on which the helmet impacts. The second one is the friction between the headform and the helmet's interior.
METHODS: To study the first factor, two anvil angles are provided, one 30(º) and the other one 15(º) to the vertical. To analyze the second factor, we consider two types of headform surfaces: the original metal surface of the standard headform, and the same headform covered uniformly with a layer of silicone rubber that is 1 mm thick.
RESULTS: The results show that varying anvil's angle and surface friction can directly affect the linear and rotational acceleration of the headform.
CONCLUSION: Testing helmets for different oblique impact angles can help assess their protection capability. The coefficient of the friction between the helmet's interior and the headform plays an important role in the headform's rotational acceleration during an impact. Using a standard surface friction for headform similar or close to that of the human scalp can ensure that the results of the oblique impact tests are more consistent and realistic.