Browsing by Author "Watson, J. W."
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Item Open Access Crashworthiness of foam-filled and reinforced honeycomb crash absorbers in transverse direction(Springer, 2023-11-29) Nicoud, G.; Ghasemnejad, Hessam; Srimanosaowapak, S.; Watson, J. W.Honeycomb crash absorbers have been widely studied as energy absorption devices for use in automotive industries. However, none of these investigations have studied the side impact of empty and foam-filled honeycomb absorbers and adding stiffeners between the different layers of the corrugated sheets which are composing the honeycomb structure to analyse the structure under transverse (L-direction) impacts. In this paper, the foam-filled and reinforced honeycomb crash absorbers are investigated under axial (T) and transverse (L) loading directions. Experimental results for both empty and foam-filled specimens under quasi-static and impact loads were implemented to validate the developed finite element model. Finite element analysis (FEA) was performed to find out the crashworthiness behaviour of the structure under axial and transverse impacts according to road conditions. Finally, a new design of stiffened honeycomb crash absorber was developed and investigated to reduce the level of acceleration experienced by the passengers during the crash event. In this regard, it is concluded that all the requirements related to the energy absorption capabilities and generated deceleration under impact loading can be met by introducing an advanced method to reinforce honeycomb absorbers using stiffeners. It is also proven that the thickness of these stiffeners will not significantly influence the force levels. Due to increase of wall thickness from 1 to 3 mm, the mean crushing force increased from 129 kN to 148 kN. This growth is not sufficient as the goal is to obtain a mean crushing force of 300 kN. Thickening the stiffeners would lead to a loss of efficiency of the structure, as the small increase in mean force would not make up for the gain in mass. Thus, increasing the corrugated sheet’ thickness becomes necessary.Item Open Access Investigation of cyclist and pedestian impacts with motor vehicles using experimentation and simulation(Cranfield University, 2010-02) Watson, J. W.; Irving, Phil E.Physical tests were performed with a bicycle and a dummy in a controlled laboratory environment to reproduce cyclist accidents. The kinematics of 13 sled tests were used to identify the cyclist head impact location, understand the interaction between the cyclist and bicycle and to validate a mathematical model. The finite element software code LS-DYNA was used to simulate 70 cyclist and pedestrian accidents with motor vehicles with four different vehicle shapes which supplemented the physical testing. The study has shown that when cyclists and pedestrians were struck by any of the vehicles their whole body kinematics can be distinguished into two phases, initially a rotation followed by a sliding action. The Sports Utility Vehicle (SUV) vehicle produced more of a rotation action rather than sliding, whereas the other vehicles produced a combination of the two. The current pedestrian legislation does not cover all head impact locations for cyclists and therefore needs to be extended to encompass the windscreen and A-Pillar regions of the vehicles. The wrap around distance (WAD) for all the vehicles, apart from the SUV, should be extended to encompass a larger region. For the SUV the current WAD region is adequate in protecting cyclists and pedestrians and does not need to change. The predicted head impactor angle for cyclists is 40 degrees which is lower than the current legislative value of 65 degrees and the predicted pedestrian head impact angle is higher at a value of 80 degrees for the MPV, SM and LFC. For the SUV the proposed impactor angle increased to 100 degrees for cyclists and pedestrians. This research has demonstrated significant differences in terms of input variables and outcomes between cyclist and pedestrian accidents involving vehicles. It has used mathematical models to obtain injury data from a human mathematical model and physical testing to replicate real world cyclist accident scenarios. Recommendations have been proposed for future legislative testing techniques for cyclists, based on existing pedestrian legislation. These recommendations to alter legislation will improve vehicle design and make future vehicles more cyclist-friendly.Item Open Access Safety requirements for cyclists during impacts to the legs(National Highway Traffic Safety Administration, 2009-06) Hardy, Roger N.; Watson, J. W.; Kayvantash, K.The term vulnerable road user (VRU) is most commonly associated with pedestrians and in particular children and the elderly. In many European countries cyclists make up a significant number of VRU casualties - typically around one third. In the context of the European 6th Framework Integrated Project APROSYS (Advance PROtection SYStems), a study was conducted to examine the safety requirements for cyclists and whether these were addressed by current pedestrian safety assessments of cars. An examination of accident statistics was first conducted to determine the principal accident scenarios for cyclists. Since insufficient cyclist cases were recorded in a detail database of VRU accidents compiled during APROSYS, a programme of virtual testing was then conducted. The objective was to identify the most significant parameters during cyclist impacts with a range of cars sizes and the likely injury consequences. The primary region of investigation was impacts to the legs and knees - the points of first contact. The study indicated that cyclists interacted differently with cars than pedestrians, resulting from the geometric configuration of their legs, the presence of the bicycle and their elevated riding position. The potential for injury was different and the current sub-system impactor tests used by Euro NCAP and for vehicle certification purposes did not address all these differences. It was determined that the relevance of the current pedestrian impact safety assessments of cars for cyclists could be improved by minor changes to the test parameters. However, the study also identified new injury mechanisms that may require further biomechanical investigations. Although this study has considered a wide range of cyclist impact configurations it should not be considered as definitive. Further work including physical testing is needed in order to take forward improved safety test procedures.