Robert Kunc

Minimum mesh design criteria for blast wave development and structural response - MMALE method

The Multi Material Arbitrary Lagrange Euler (MMALE) method is widely used method for numerical investigation of structural response under blast loading. However the method is very demanding for use at the other hand. In this paper are presented the results of the detailed numerical investigation in order to simplify some decisions contributing to the accuracy and efficiency of this model. The influence of mesh properties (particularly mesh size, its biasing and distance of the boundary (DoB) conditions from the deforming structure) on blast wave loading parameters and structural response is investigated in detail and based on the results minimum mesh design criteria is proposed. The results obtained are presented as a function of the scaled distance and additionally related to the radius of the charge. Validation studies were also done successfully.

Parametric analysis study of blast loaded armour V-plates

Continuous improvement in the hull floor of light armoured vehicles in terms of landmine response and crew safety is required among other things, in order to meet higher demands in the market and to obtain a product safety certificate. Previous research studies have shown that V-shaped hull floors of light armoured vehicles have a better response to blast loading in terms of saving the lives of vehicle crews or reducing the number of injuries. For this reason, parametric and design optimization analyses of V-shaped hull floors play an important role in achieving an optimal, safe and cost-effective light armoured vehicle design. However, this kind of structural optimization is complex, involving a multidisciplinary fluid–structure interaction processes, as well as large structural deformations. This article presents the results of the metamodel-based parametric analysis of blast loaded armour V-plates. The contribution of most important variable parameters such as plate angle, plate thickness, explosive mass and stand-off distance to blast loading and blast response parameters was examined using a combined smooth particle hydrodynamic – finite element numerical model. The results showed that the plate angle has the greatest impact on all response parameters of the metamodel, followed by the stand-off distance and plate thickness.

Comparative study of European tunnel emergency-stop-area-wall protection measures

Due to the increasing number of traffic accidents involving the collisions of vehicles with the emergency-stop-area head walls in tunnels, a comparative numerical analysis in accordance with the EN 1317 standard has been performed in order to assess the quality of the available protective safety barriers. Based on the simulation results, the values of the relevant injury criteria - the acceleration severity index (ASI), the theoretical head impact velocity (THIV) and the post-impact head deceleration (PHD) - were computed for several collision scenarios involving two different passenger vehicles colliding with two different safety barriers in various ways. The results show that due to the geometrical restrictions in the tunnels emergency stop area none of the barriers can provide total protection for the occupants of the vehicle in the event of a collision. The installation of a steel-sheet-tube crash cushion was, however, found to provide the best possible protection within the given limitations. The results of the analysis were the basis for selecting a safety-barrier design for existing tunnel installations and for the proposed changes in regulations governing the geometry of the tunnels emergency stop area.

The Importance of Friction Coefficient between Vehicle Tyres and Concrete Safety Barrier to Vehicle Rollover - FE Analysis Study

The most important mechanical factors in an impact scenario of a vehicle into a concrete safety barrier are vehicle speed, the impact angle, the static stability factor of the vehicle as well as the concrete safety barrier design and conditions. Concrete safety barriers (CSB) are primarily designed to minimize vehicle damage by allowing the vehicle to be lifted when riding up on the lower slope and then redirected back on to the road. In some cases, though, the vehicle-CSB contact might end up with a rollover often with fatal consequences. To reduce the rollover risk, different concrete barrier shapes were designed in the past while omitting the importance of the friction coefficient between the tyre and barrier. Therefore, the aim of this paper is to research and emphasize the importance of the friction coefficient between the vehicle tyres and the CSB in rollover accidents. For that purpose, a series of Finite Element analyses were performed using different values of the friction coefficient between the vehicle tyres and the CSB. Experimental measurements of the coefficient of friction between the rubber and CSB blocks of different surface were additionally performed in dry and wet conditions in order to examine the real onsite friction characteristics. The results show that the coefficient of friction can have a crucial impact in vehicle rollover scenarios and should therefore be kept as low as possible by the concrete safety barriers manufacturers and maintainers.

Blast Resistant Trash Receptacles With Blast Loading Redirection – Comparative Analyses

Many terrorist attacks in the last decade around the world have exposed the vulnerability of citizens in public places. Public trash receptacles can be easily abused as well-covered places in which Improvised Explosive Devices (IED) can be simply left and then remotely activated. Therefore, blast resistance and possibility of blast loads redirection are very important characteristics of trash receptacles placed in crowded public areas. This paper presents the results of three different trash receptacles: non-blast resistant, blast resistant and blast resistant trash receptacle with blast load redirection. The results have shown that a considerable effect can be achieved by using blast resistant receptacles, thus reducing the possibility of deaths and injuries. A thickness optimization study was additionally performed, based on the size and geometry of the opening by using a finite element model. Based on the results of the study, some valuable recommendations for design of trash receptacles are also given.