The influence of headform/helmet friction on head impact biomechanics in oblique impacts at different tangential velocities

O. Juste-Lorente, M. Maza, M. Piccand, F.J. López-Valdés

Applied Sciences Vol. 11, nº. 23, pp. 11318-1 - 11318-21

Summary:

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. 

Spanish layman's summary:

Este trabajo explora el efecto causado por la interacción existente entre el coeficiente de fricción entre la cabeza y el casco y la velocidad de impacto en cuatro criterios de daño en cabeza. Para que los criterios de daño de origen rotacional sean representativos de las lesiones que pueden ocurrir en colisiones reales es especialmente importante que el valor de la fricción sea alto especialmente cuando la velocidad del impacto del ensayo es baja.

English layman's summary:

This manuscript analyzes the effect of the interaction between the friction in the interior of the helmet and the impact velocity on four head injury criteria. So that rotational related injury criteria can be representative of real-world injuries, it is necessary that friction values are high especially when the impact velocity of the tests is low.

Keywords: motorcycle helmet; oblique impact; tangential velocity; friction

JCR Impact Factor and WoS quartile: 2,838 - Q2 (2021); 2,500 - Q1 (2023)

DOI reference: https://doi.org/10.3390/app112311318

Published on paper: December 2021.

Published on-line: November 2021.

Citation:
O. Juste-Lorente, M. Maza, M. Piccand, F.J. López-Valdés, The influence of headform/helmet friction on head impact biomechanics in oblique impacts at different tangential velocities. Applied Sciences. Vol. 11, nº. 23, pp. 11318-1 - 11318-21, December 2021. [Online: November 2021]