Current requirements and regulations governing motorcycle helmets around the world are based on test results of purely radial impacts, which are statistically rare in real accidents. This study presents a new impact rig for subjecting test helmets to oblique impacts, which therefore is able to test impacts of increased statistical relevance to real motorcycle accidents. A number of different head-helmet interfaces have been investigated. A test rig was constructed to produce oblique impacts to helmets simulating those occurring in real motorcycle accidents. A Hybrid III dummy head was fitted with accelerometers to measure the accelerations arising during impact testing. The equipment used for data collection was validated in both translational and rotational acceleration. In order to better resemble the human head, an artificial scalp was fitted to the hybrid dummy. The same test rig was used to investigate the performance of a number of different helmets. Impact velocities ranging from 7.3 to 9.9 m/s were tested using a number of different impact angles and impact areas. This study shows that the new test rig can be used to provide useful data at speeds of up to 50 km/h and with impact angles varying from purely tangential to purely radial. The rotational accelerations observed differ greatly depending on both helmet and scalp designs. For example, a helmet with a sliding outer shell placed on an experimental head fitted with an artificial scalp (made to resemble the human scalp) reduces rotational accelerations of the head by up to 56%, compared with those of an experimental head fitted with a fixed scalp and conventional helmet. The degree of slippage between the skull and the scalp, and between the scalp and the helmet, leads to considerable variation in the results. This innovative test rig appears to provide an accurate method for measuring accelerations in an oblique impact to a helmet. In order to obtain a good level of repeatability in oblique impact testing, it is crucial that the helmet be fixed to the head in the exact same way in each individual test. Both the position and the angle of impact must be reproduced identically in each test. The test rig used here has shown that this type of rig can be used to compare different helmet designs, and it therefore is able to contribute to achieving safer helmets. (Author/publisher).
Samenvatting