PSI - Issue 14

D R Makwana et al. / Procedia Structural Integrity 14 (2019) 44–52 D R Makwana, Dr D G Thakur, K Senthilkumar/ Structural Integrity Procedia 00 (2018) 000–000

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The ways to mitigate and reduce the primary blast effects is mainly by increasing stand-off, secondary effects can be reduced by using heavy armour and tertiary effects can be reduced by providing protection to the occupants. The main security measure of any Army vehicle is their armour protection. Nomenclature t A arrival time of blast wave P so peak value of overpressure Po ambient pressure t d phase of duration σ y yield stress µ poisson's ratio

2. Types of Mines The mines can be categorised as; 2.1. Anti-Personnel(AP) mines  Blast mines  Fragmenting mines

2.2. Anti-Tank (AT) mines  Blast mines  Shaped charge mines

The AT-mines are mainly to restrict the movement main battle tanks of the enemy. The first generation mines use a pressure fuse activated by loads of more than 200 kg from the vehicle’s wheels or tracks. The large amount of explosive causes extreme blast loads resulting in mobility kill to the vehicle. The second generation of AT mines uses tilt rods or magnetic/seismic influence fuses so that they can also detonate under the bottom of the vehicle. These fuses are also used in combination with the shaped charge mines. All AT mines are designed to detonate under the vehicle. The third generation of AT mines are the off-route or the top-attack mines with sophisticated fuses. In the event of blast the driving mechanism is the generation of very high pressure shock wave and its propagation on the structure. 3. General Air Blast Loading Theory A typical blast pressure profile is depicted in Fig. 1. The blast effect associated with the detonation of high explosive is in the form of a high-speed shock wave with very high overpressure being released from the explosive. This overpressure decays very rapidly with distance due to expansion of the pressure into the surrounding air. At the arrival time t A , following the explosion, pressure at that position suddenly increases to a peak value of overpressure, P so , over the ambient pressure, P o . Throughout the pressure-time profile, two main phases can be observed; portion above ambient is called positive phase of duration t d , while that below ambient is called negative phase of duration, t d a lower intensity than the positive duration. A lower amplitude, longer duration shock pulse is observed due to increase in stand-off distance and subsequently the duration of the positive phase. The physical properties of the explosion affects the air blast wave characteristics. The pressure then decays to ambient level at time t d , then decays further to an under pressure P so - (creating a partial vacuum) before eventually returning to ambient conditions at time t d + t d . The quantity P so is usually referred to as the peak side-on overpressure, incident peak overpressure or merely peak overpressure.