| To study the protection performance of assembled explosion-proof wall against fragments penetration and the impact of fragments penetration on the wave absorption performance of the explosion-proof wall,the influence of angle and velocity of high-speed fragments on the penetration depth law of explosion-proof wall filled with sandy soil was investigated by theoretical analysis,physical experiment and numerical simulation.The dynamic process of high-speed fragments penetration into the composite filling medium was conducted by the first stage light gas gun and AUTODYN software respectively.The penetration depth law of high-speed fragments and the energy dissipation law of the composite filling material were obtained.The initial penetration velocity of the high-speed fragments and the distribution law of penetration of the explosion-proof wall were obtained through the live fire test at the target range,and the distribution law of shock wave behind the explosion-proof wall was obtained.AUTODYN software is adopted to simulate the process of shock wave and high-speed fragments impacting the explosion-proof wall,and the shock wave absorption law of the wall after fragments impacting the explosion-proof wall is obtained.The main conclusions are as follows:(1)When the high-speed fragments with 0° and the initial velocity of 200 ~ 2100 m/s penetrate into explosion-proof wall filled with sandy soil,the penetration depth increases sharply with the increase of the initial velocity,then decreases slightly and then increases again.The inflection point velocities are 800 m/s and 1500 m/s respectively:(1)When the fragment velocity is less than 800 m/s,the penetration depth increases sharply with the increase of the initial fragment velocity(the fragment deformation is small,and the friction resistance changes little with the increase of the velocity).(2)When the speed is 800 ~ 1500 m/s,the penetration depth of fragments fluctuates slightly with the increase of the speed(the deformation of fragments is large,and the friction resistance changes greatly with the increase of the speed).(3)When the velocity is 1500 ~ 2100 m/s,the penetration depth increases again with the increase of the velocity(the fragment deformation is basically fixed,and the friction resistance changes little with the increase of the velocity).(2)In the condition that high-speed fragments penetrate explosion-proof wall filled with sandy soil with a certain speed and different initial angles(0 ~ 80°),when the fragment velocity is less than 800 m/s,the incidence angle has a great influence on the penetration depth.With the increase of the incidence angle of fragments,the penetration depth of fragments first decreases and then increases,and the inflection point angle is 45°;When the velocity is greater than 800m/s,the incidence angle has little effect on the penetration depth.When the incident angle of fragment is the same,the penetration depth of fragment increases gradually with the increase of initial velocity.(3)When the high speed fragments penetrate explosion-proof wall filled with composite filling medium at an incident angle of 0°,the penetration depth increases sharply with the increase of the velocity when the thickness of aluminum foam sandwich plate is constant and the initial velocity varies from 200 m/s to 800 m/s;When the initial velocity varies from 800 m/s to 2100m/s,the fragment penetration depth fluctuates slightly with the increase of the initial velocity and gradually tends to a fixed value range.(4)The penetration depth variation trend of aluminum foam sandwich plate with thickness of0 ~ 36 mm is the same as that of without aluminum foam sandwich plate;When the thickness of sandwich plate is 48 mm,the penetration depth of fragment increases sharply before the velocity is 800 m/s,and slightly oscillates when the velocity is greater than 800 m/s.The penetration depth of fragments can be significantly reduced by adding aluminum foam sandwich plate,which is mainly related to the initial energy absorbed by high-speed fragments.The energy absorbed per unit area density of filling medium is negatively correlated with the penetration depth of fragments.When the initial velocity is constant,the more energy absorbed per unit area density,the smaller the penetration depth of fragments.(5)The distribution law of impact and fragment at the rear of the explosion-proof wall under the combined action of shock wave and high-speed fragment was obtained through the live firing experiment at the firing range: When the detonation distance is 2.04 m ~ 3.98 m,the maximum overpressure behind the wall appears at about 1.3 ~ 2.5 times the height of the explosion-proof wall,and all of them have a trend of first rising and then falling.The average number of fragments distributed in each unit of the explosion-proof wall is about 4 pieces,5pieces,3 pieces and 2 pieces,respectively.When the detonation distance is 2.04 m and 3.18 m,fragments are mostly concentrated in the right unit opposite the source,and when the detonation distance is 2.57 m and 3.98 m,fragments are mostly concentrated in the middle unit.The initial velocity range of high-speed fragments is about 1700 ~ 2100 m/s.The fragments of penetration depth over 60 cm accounted for about 5.5%,and those over 40 cm accounted for about 11% and 4.8%,respectively.(6)AUTODYN software is used to reproduce the distribution of fragments after explosion of the projectile: the mass of fragments is mostly concentrated within 100 g.The distribution law of shock wave after the fragment penetrates the wall is obtained: in the same position behind the explosion-proof wall,compared with the explosion-proof wall with impact hole,the reduction rate of shock wave of the explosion-proof wall without impact hole can reach about90%.The peak overpressure of the shock wave behind the wall is about one order of magnitude larger than that without the impact hole.The peak overpressure of the shock wave behind the wall decreases rapidly with the increase of the distance from the blast source.The theoretical reference is provided for the rational design of explosion-proof wall,which is significant to reduce the damage of shock wave and fragments of projectile,reduce equipment losses and casualties,and effectively increase the safety of protected targets. |
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