PSI - Issue 14

4

D R Makwana et al. / Procedia Structural Integrity 14 (2019) 44–52 D R Makwana, Dr D G Thakur, K Senthilkuma / Structu al Integrity P ocedia 0 (2018) 000–000

47

Fig. 3. Process of blast interaction with vehicle

Mahajan & Murlidharan (2017) had highlighted the effects caused by blast, where mainly propagation of blast wave, deformation of hull and displacement of the vehicle were highlighted which is shown in Fig. 3. Edyta had further expanded the process of deformation with respect to time. When the shock wave collides with the plate that is at 90º to the wave direction, the point of impact will experience the maximum reflected pressure. When the reflecting surface is parallel to the blast wave, the minimum reflected pressure or incident pressure will be experienced. The magnitude of the peak reflected pressure is dependent on angle of incidence, peak incident pressure, which is a function of the net explosive weight and distance from the detonation. As shown in Fig. 4, the response of the mine blast is calculated for 1000 ms, where the primary phases like initiation, interaction with structure and causing deflection to the hull bottom takes place within 10ms. Subsequently, the highest floor deformation is followed by lifting or tilting of the vehicle. The effects of the blast wave are categorised as per NATO.

Fig. 4. Time Sequence of Events during an AV Mine Detonation

5.1. Local effects As shown in Fig. 4, as the mine blast under a vehicle occurs, a shock wave is formed by the explosion. This shock wave hits the hull of the vehicle within approximately 0.5ms and is subsequently reflected causing an very high peak pressure resulting in a local acceleration of the hull. Within 5ms after the detonation, the hull deformation takes place both elastically as well as plastically. The deformation depends on the shape of hull, plate thickness, material and additional stiffeners provided for design. The shock wave travels with speeds up to 5500 m/s through the vehicle super structure and causes strong accelerations in the vehicle. All parts mounted on or just above the V-plate or bottom plate can be hit and get accelerated in an upward direction. 5.2. Global effects Due to the reflecting blast wave under the vehicle, a pressure force gets developed, which expands on the complete hull of a vehicle. The total impulse load of this pressure force is a measure of the initial vertical velocity causing a jump of the whole vehicle. The jump height depends on the vehicle weight and for asymmetric loading, it