Real crash tests against vehicle restraint systems according to the standard EN 1317 are performed with straight barriers. The objective of this study is to investigate the performance of a curved barrier. A validated model of a real tested vehicle restraint system was subjected to a modification. The straight barrier in the original simulation model was modified with different constant curvatures. Virtual crash tests with straight and differently curved barriers were carried out with the same boundary conditions as the real test. The results concerning the behavior of the vehicle and the barrier were compared. The expected consequences of a barrier in a curve are the following: The vehicle is contained by the barrier. The dynamic deflection of the barrier during the crash is lower than the dynamic deflection of the unmodified straight barrier. The acceleration severity increases due to the curvature of the barrier.
Road safety structures are CE (European Commission) marked safety systems which need to be crash tested. Structure performances during the crash tests and the associated rating have a significant marketing impact for the system manufacturer and unfortunately depend on parameters subjected to stochastic variation (raw material mechanical properties, test conditions, vehicle design, …). Numerical simulation has been widely used for several decades to assist in the design of these new road safety devices. Historically, in order to identify a design likely to pass the experimental tests, simulation has mostly been used without taking into account the variability of the modelled system parameters but only its nominal design. However, in too many cases, the great variability of such devices (materials characteristics, ground type, assembly conditions, impact parameters, etc…) leads to unexpected behaviour (and results) and jeopardizes the test validation. In the following sections the full process of one road safety system optimization will be presented starting with the correlation between the numerical model results and the corresponding real crash test results. Then, a design optimization on a reduced model will be performed using an innovative approach based on an advanced use of the DEP MeshWorks morphing capabilities coupled with LS-OPT© and LS-DYNA©. Finally, based on the optimal design found previously, an additional sensitivity study using LS-OPT and LS-DYNA will be conducted to better assess the device robustness and its sensitivity to material characteristics changes. The aim is to enable designers of new systems to better assess the risk of failure when performing the experimental tests required by the standard.
Since 2016 there has been a research project going on which is focused on development of new design of portable road barriers with integrated anti-noise walls. The key feature of the new barrier design is a material selection for anti-noise panels. New panels made of wood and cement-bonded wood-chip material called Velox significantly improve noise absorption properties of the barrier. However, the question is: what are their qualities from mechanical point of view? And will such barrier be able to withstand crash tests required by the highest containment level, H4b according to EN1317 standard? Numerical simulations are being utilized in this research at all levels in order to reduce costs and to predict how particular design modifications influence restraint capabilities of the barrier. As a starting point there were crash test simulations with original barrier design performed and after achieving sufficient correlation between the simulations and the real crash tests, modified systems were designed and tested. Firstly, there were the new panels. From mechanical point of view, Velox is very complex material so an extensive investigation of its mechanical properties had to be performed. This investigation covered small scale tests (quasistatic and dynamic) and large scale dynamic tests as well. Based on the experiments there was an appropriate material model chosen and its parameters determined to faithfully describe behavior of the material. Since crash test simulations with the first Velox wall design identified several weaknesses, certain preventive measures had to be introduced. Besides design changes of the bottom part of the barrier, several kinds of Velox boards back face treatment were proposed in order to enhance resistance and keep overall integrity of the structure after crash load exposure. All these design changes are now being analyzed and further developed based on crash test simulations but also with regard to production processes and mobility of the barrier.
Virtual Testing of Curved Vehicle Restraint Systems