Explosions in confined spaces lead to complicated patterns of shock wave reflection and interactions which are best investigated by use of experimental tests or numerical simulations. This paper describes the design and outcome of a series of experiments using a test cell to measure the pressures experienced when structures were placed inside to alter the propagation of shock waves, utilising quarter symmetry to reduce the size of the required test cell and charge. An 80 g charge of PE4 (a conventional RDX-based plastic explosive) was placed at half height in one corner of the test cell, which represents the centre of a rectangular enclosure when symmetry is taken into consideration. Steel cylinders and rectangular baffles were placed within the test cell at various locations. Good reproducibility was found between repeated tests in three different arrangements, in terms of both the recorded pressure data and the calculated cumulative impulse. The presence of baffles within the test cell made a small difference to the pressures and cumulative impulse experienced compared to tests with no baffles present; however, the number and spacing of baffles was seen to make minimal difference to the experienced pressures and no noticeable difference to the cumulative impulse history. The paper presents useful experimental data that may be used for three-dimensional code validation.
The open, accessible and crowded nature of urban mass transit networks has attracted previous attacks in London, Madrid and other cities, and it is very difficult to prevent an attacker entering while retaining normal operation of the system. The research presented here contributes to the modelling capability needed to apply a 'passive safety' approach in vehicle design, whereby the impact and consequences of a blast in a mass transit vehicle could be reduced.The multi-material Arbitrary Lagrangian Eulerian (mm-ALE) approach with Fluid Structure Interaction (FSI) is widely reported in the literature, but has been seen as requiring to fine a mesh to be applicable to large scale structures. Reductions in computing cost and improvements in the speed of finite element codes allows large ALE models to be solved, and mm-ALE approach is shown to be effective at predicting the effects of explosions. Also studied is the recently implemented 2D to 3D mapping function available in LS-Dyna, and comparisons are made with the standard 3D approach in terms of computational expense and solution accuracy.
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