# Fracture Prediction in Weldox 700E Steel Subjected to High Velocity Impact Using LS-DYNA
## 1 Introduction  
Impact refers to the brief collision between two objects, a phenomenon that is a significant area of study in engineering and technology. Impact phenomena are relevant across various applications, including terrestrial transportation, aerospace, and aquatic environments. Analyzing impact involves understanding contact interfaces, non-linear deformation, fractures, and fragmentation that occur over short time scales [1]. In recent years, steel plates are increasingly being used in both defense and civil sectors to protect against ballistic threats. Understanding the fracture behaviour of the material under high-velocity impact is crucial for designing components for effective functioning under such protective applications. For simplification, most of the impact studies focus on a bullet as the projectile and a flat plate as the target. Numerous researchers have explored impact-related problems through experimental, numerical, and analytical approaches. [PERSON] et al. [2] conducted experimental and numerical studies on the impact of blunt-shaped projectiles on 8 mm thick Weldox 460E steel plates, with velocities ranging from 137 to 298 m/s using LS-DYNA. They found that strain rate, stress, and temperature are critical factors for predicting fracture in the target material. [PERSON] et al. [3] further investigated the fracture behaviour of 12 mm thick Weldox steel plates impacted by blunt, hemispherical, and conical projectiles at velocities of 181.5-399.6 m/s for blunt projectiles, 278.9-452 m/s for hemispherical, and 206.9-405.7 m/s for conical shapes. They found that the ballistic limit of the blunt-shaped projectile was lower than hemispherical and conical projectiles, with less deformation observed in the plate with the blunt projectile. [PERSON] et al. [4] also conducted experimental, analytical, and numerical studies on the perforation behaviour of 6-30 mm thick steel target plates impacted by blunt-shaped projectiles at velocities ranging from 150 to 525 m/s. They showed that perforation time remained nearly constant for plates thicker than 8 mm, and deformation increased with higher impact velocity and plate thickness. [PERSON] et al. [5] studied the perforation strength of three structural steels, viz. Weldox 460E, Weldox 700E, and Weldox 900E, impacted by projectiles with blunt, conical, and ogival nose shapes. The plate thickness was 12 mm, and the velocity range was 150-350 m/s. [PERSON] et al. [6; 7] and [PERSON] et al. [8] explored the perforation resistance of five steel plate variants, 6 mm and 12 mm thick, against 7.62 mm ball-type and 7.62 mm AP-type projectiles at a velocity of 830 m/s. They concluded that, within certain limits, the perforation resistance increased linearly for both types of projectiles. [PERSON] et al. [9] investigated the ballistic limit of 12-16 mm thick mild steel plates impacted by 7.62 mm AP-type projectiles at varying obliquity angles. The study covered impact velocities of 445 to 818 m/s for the 12 mm thick plate and 531 to 819.7 m/s for the 16 mm thick plate. They found the critical ricochet angles for the 12 mm and 16 mm plates to be 58\({}^{\circ}\) and 59\({}^{\circ}\), respectively, with ballistic limits of 447.5 m/s for the 12 mm plate and 533 m/s for the 16 mm plate. [PERSON] et al. [10] investigated the effect of projectile nose shape and impact velocity on fracture behaviour in the target plate. They found that hemispherical-shaped projectiles have the highest ballistic limit. The blunt-nose projectile requires less energy for plug formation. [PERSON] et al. [11] investigated the ballistic resistance of high-strength steel using 7.62 APM2 projectiles under various configurations. They found that the ballistic resistance of the plates improved after heat treatment. [PERSON] and [PERSON] [12] examined the development of ductile fracture in high-strength steels, where fracture occurs due to stress states transitioning from shear to plane-strain tension.