Impact Energy Attenuation Performance of Cricket Helmets: Standard 2-wire Drop Test vs. Pitching Machine Impact Test

Abstract

Many researches have debated that the current 2-wire drop test method (AS/NZS 4499.1:1997 and AS/NZS 2512.3.2:1997) for cricket helmets does not adequately represent the dynamics of a real ball-helmet impact for fast, elite and express bowlers. This paper presents a new pitching machine test method that was developed to measure the impact performance of cricket helmets. A series of accelerometers were positioned at the centre of gravity (CG) of the test headform to measure the linear accelerations in x-, y- and z-directions due to impact by a cricket ball. The Head Injury Criterion (HIC) was calculated based on the resulting head acceleration (Hres), and impact duration. When compared with the bare headform impacts, the tested helmets were able to reduce the Hres by 25% and 60% for the 2-wire drop test and pitching machine respectively. Similarly, the tested helmets reduced the HIC values by about 82% and 83% for the 2-wire drop test and pitching machine respectively. However, the Hres and HIC values measured using the 2-wire drop tests were significantly higher (p<0.05) than those measured using the pitching machine test. These differences were attributed largely to the differences in the masses of the test apparatus and the resultant impact energy, which was calculated based on the measured impact velocities and impactor mass. The repeatability of results obtained from the pitching machine may, however, be degraded at high velocity impacts due to the test set- up. For the time being, the developed pitching machine test is intended to supplement, but not to replace, the currently accepted cricket helmet standard test method.