PSI - Issue 71

Nikhil Andraskar et al. / Procedia Structural Integrity 71 (2025) 158–163

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4. Results and discussion The fragment-simulating projectile was impacted on an aluminum plate of 6 mm thickness and 50 mm × 50 mm size. Six distinct striking velocities ranging from 100 to 800 m/s were taken into account. This section discusses the ballistic performance of the target plate at the specified impact velocities. The damage to the alumina plate, the change in the fracture conoid zone size at different impact velocities, the remaining velocity of the fragment-simulating projectile, the kinetic energy lost due to the interaction with alumina plate, and the impact force generated on the alumina plate at different impact velocity are presented in this section. Fig. 4 shows the evolution of the fracture conoid zone concerning different impact velocities. Initially, as the projectile makes contact with the ceramic target, a contact force is exerted on the ceramic alumina plate due to the projectile carrying initial kinetic energy. The contact force exerted by FSP on alumina target generates compression stress waves near the point of impact, which propagate radially through the thickness of the plate. These compression stress waves trigger the formation of microcracks at the impact site. As the waves continue to travel through the thickness and reach the free surface, they transform into tensile stress waves, leading to the development of circumferential cracks in the tensile direction of the Al 2 O 3 (99.7%) plate. The initial compressive stress also plays a role in creating cracks in the radial direction within the impact zone. As observed from Fig. 4, the fracture conoid zone increases from the velocity of 200 m/s to 400 m/s, and it is reduced when the impact velocity is further increased above 500 m/s due to lesser time available for the projectile to interact with the alumina plate. Also, as observed from the numerical simulation, the impact force exerted on the alumina plate increases with an increase in impact velocity. Also, a secondary force was observed as the projectile penetrated further inside the target plate. The projectile's velocity was adjusted between 100 m/s and 800 m/s. 800 m/s was considered simply to analyze the magnitude of the fracture conoid zone at higher velocity. Table 1 displays the residual velocity of the projectile at various impact velocities. The energy dissipated can be assessed by comparing the kinetic energy (KE) of the projectile just before it contacts the target and after it has penetrated the target. The reduction in KE represents the energy consumed by the ceramic/metal plate during the perforation process. Florence (1969) indicated that once the impact velocity surpasses the ballistic limit velocity (BLV), the target's energy absorption capacity remains constant. In contrast, Recht and Ipson (1963) noted that beyond the BLV, any increase in impact velocity is inversely related to momentum transfer. Tate (1986), in his mass erosion model for the projectile, stated that the loss of momentum corresponds with an increase in KE absorbed by the ceramic/metal composite plate as the impact velocity exceeds the BLV. Table 1 displays the residual KE of the FSP following complete penetration.

(a) Impact velocity 100 m/s

(b) Impact velocity 200 m/s

(c) Impact velocity 300 m/s