DSpace Collection: CASR Conference papers

Use of a damped Hertz contact model to represent head impact safety tests

2013-06-14T05:21:32Z

Title: Use of a damped Hertz contact model to represent head impact safety tests Author: Searson, Daniel Jeffrey; Anderson, Robert William Gerard; Hutchinson, Timothy Paul Abstract: Head impacts tests are conducted as part of many types of safety testing, with applications including vehicle crashes, helmets and sports surfaces. A common measure of head injury in these tests is the Head Injury Criterion (HIC), which is calculated from the measured acceleration of a headform during the impact. In this paper, these headform impacts are represented by a Hertz contact model to which a damping term has been added. A power law relationship was found to be appropriate for modelling the effect of headform mass and impact speed on HIC and peak displacement. It was found that the stiffness and damping in the model did not affect the exponents in the power law, but the exponent of displacement in the contact model did have an effect on all of the exponents in the power law. This result may explain why some variation exists in real data. The relationships presented in this paper may be used to predict how the HIC and maximum displacement of the head will vary for a given change in head mass or impact speed. This has applications in test protocol development and for evaluating the safety performance of tested structures under a variety of real world conditions.

Testing in order to measure the protection against impact of people, manufactured items, and agricultural produce: How to consider all severities of shock

2013-06-14T05:11:23Z

Title: Testing in order to measure the protection against impact of people, manufactured items, and agricultural produce: How to consider all severities of shock Author: Hutchinson, Timothy Paul; Anderson, Robert William Gerard; Searson, Daniel Jeffrey Abstract: Instrumented headforms are projected at cars to check that the vehicle is not overly injurious if a pedestrian is struck. We argue that there are at least two different aspects to performance: the impact severity in the test conditions (measured by HIC, the Head Injury Criterion), and the speed at which bottoming out occurs (this refers to the vehicle surface deforming sufficiently that the much more rigid structures underneath are contacted). It is desired to know performance over the wide range of real-life impact conditions, yet the number of tests to be conducted is limited. A procedure is proposed that estimates performance averaged over different speeds (and perhaps also averaged over effective head mass). There are three components: (a) an equation for the dependence of HIC on speed (and perhaps mass), which includes the effect of bottoming out as a sharp rise in severity beyond a certain level of impact energy, (b) an equation for how bad are different levels of HIC (the probability of some specific outcome, such as death or skull fracture, is likely to be used here), and (c) the probability distribution of impact speed (and perhaps mass). Other safety tests (such as impact testing of helmets) are plainly analogous, and similar considerations apply in the packaging and handling of manufactured items and agricultural produce: cushioning should be soft enough not to cause damage itself yet stiff enough to prevent bottoming out.

The potential of autonomous emergency braking systems to mitigate passenger vehicle crashes

2013-04-19T03:30:26Z

Title: The potential of autonomous emergency braking systems to mitigate passenger vehicle crashes Author: Doecke, Samuel David; Anderson, Robert William Gerard; Mackenzie, James Richard Ryder; Ponte, Giulio Abstract: This paper details part of a research program conducted to examine the potential effect of autonomous emergency braking (AEB) systems on common crash types that involve a frontal collision. To accomplish this, simulations were conducted of 103 real world crashes. AEB system models with differing specifications were applied to these simulations to determine the change in impact speed that various AEB interventions could produce. It was found that AEB systems have the potential to reduce the impact speed, and hence the severity, in pedestrian crashes, right turn crashes, head on crashes, rear end crashes and hit fixed object crashes. The greatest potential reductions were for pedestrian crashes, head on crashes and rear end crashes. The variations in system specification demonstrate the advantages of a longer time-to-collision and higher autonomous deceleration. A system that has less potential to generate false alarms than the other systems was considered and demonstrated potential for reducing the impact speed in pedestrian, head on, rear end and hit fixed object crashes.

In-depth analysis of crashes involving younger drivers

2013-04-19T03:30:24Z

Title: In-depth analysis of crashes involving younger drivers Author: Wundersitz, Lisa Narelle Abstract: Young drivers aged 16 to 24 years are over-represented in crashes worldwide. A better understanding of young driver behaviour and the circumstances leading to crash involvement might assist in reducing young driver road trauma. The Centre for Automotive Safety Research (CASR) has conducted three in-depth studies investigating rural and metropolitan crashes in South Australia over the last decade. In-depth investigation of crashes provides detailed information on crashes that otherwise could not be obtained from aggregate police-reported crash data. This paper uses the comprehensive information collected from in-depth crash investigation to examine the causes and contributing factors leading to young driver crashes. Analyses by age group (16-19 years, 20-24 years) and level of experience (P-plates<1 year, P-plates≥1 year) were undertaken to determine whether the incidence of specific driver errors varied over the first few years of driving and could account for the substantial decline in crashes during that time. Detailed information for 256 drivers aged between 16 and 24 years was examined to identify behaviours contributing to young driver crash involvement. Based on the findings from the analysis, measures that might reduce the number of young driver crashes and moderate the injury severity of such crashes are discussed with reference to Safe System principles.