To properly assess sports helmet performance, it is important to select impact conditions that yield high peak linear or angular accelerations. This was done by measuring the kinematic response of a Hybrid III headform when impacted with a modified Wayne State University linear impactor with special consideration for impact locations and angles. The 20 impact conditions (five locations and four angles) were then compared to published thresholds to identify the conditions, which were linked to an increased risk of head injury. These conditions were the following: 1A (linear 121.3g; angular 3.84 krad s -2 ), 2A (linear 102.1g; angular 9.28 krad s -2 ), 2C (linear 94.4g; angular 8.67 krad s -2 ), 3A (linear 132.8g; angular 9.38 krad s -2 ), 4A (linear 92.8g; angular 11.49 krad s -2 ), 4D (linear 113.3g; angular 12.86 krad s -2 ), 5A (linear 116.9g; angular 9.01 krad s -2 ) and 5D (linear 87.5g; angular 8.81 krad s -2 ). The results presented in this study were specific to the test rig used as well as the tested conditions; however, it is believed that a test protocol using the above impact conditions could identify the ability of sports helmets to reduce risk of head injuries.
In brain injury research, linear and angular resultant acceleration data have been considered important mechanisms contributing to various levels of brain injury. The development of biofidelic headforms with similar dimensions and weight to that of a real human head has allowed for researchers to repeatedly collect data related to the effects of different impacts on the human head. Currently, there are different types of headforms available for impact testing, each with varying degrees of biofidelity and repeatability. Two commonly used headforms were tested: the Hybrid III and the Hodgson-WSU (NOCSAE). The two headforms were outfitted with nine single-axis accelerometers positioned orthogonally following a 3-2-2-2 array. Both headforms show good linearity and correlate well throughout the different velocities and are, therefore, reliable tools. Significant differences are observed in peak linear and peak angular accelerations between Hybrid III and Hodgson-WSU headforms. The shapes of the loading curves are visually different and thus may have significant impact on the output from FE modelling of the brain response.
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