PSI - Issue 68

Hande Vural et al. / Procedia Structural Integrity 68 (2025) 573–580 Vural et al. / Procedia Structural Integrity 00 (2024) 000–000

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ture are generally preferred in ballistic impact studies. The Johnson-Cook (JC, Johnson and Cook (1985)) model is a widely used model in this type of simulation in Rezasefat et al. (2019); Vural et al. (2023). Recently, the modified Mohr-Coulomb (MMC, Bai and Wierzbicki (2010)) model, which accounts for stress triaxiality and the Lode param eter, has been increasingly favored (Vural et al. (2022); Go¨c¸men et al. (2022)), especially in cases where the ”shear plugging” e ff ect of blunt projectiles is dominant. Besides these models, the Cockcroft-Latham (CL, Cockcroft (1968)) damage criterion, which is simpler to calibrate due to its single damage parameter, is also commonly used in ballistic impact and metal forming studies (see e.g. Holmen et al. (2016); Erdogan et al. (2023)). The advantage of single parameter models is that they can be calibrated using a single tensile or compression test, providing a cost-e ff ective alternative. Numerous experimental and numerical analyses have been conducted in the literature on the ballistic limits of monolithic and multi-layered targets. These studies have examined high-strength steels such as Armox 500T and Weldox 700E, as well as medium-strength aluminum series, particularly the 2xxx and 7xxx series. In Paman et al. (2020); Senthil and Iqbal (2021) conducted on Armox 500T, only ogival projectiles and the Johnson-Cook damage model are employed, revealing that multi-layered structures incorporating di ff erent materials o ff er superior ballistic resistance. Similarly, aluminum series have utilized the Johnson-Cook damage model for damage prediction in Iqbal et al. (2012); Xiao et al. (2022), while the CL damage model has predominantly been applied to Weldox 700E (see e.g. Palta et al. (2018); Flores-Johnson et al. (2011)). The ballistic performance of these structures is closely related to parameters such as projectile nose shape, layer sequence, thickness, and material properties. Ballistic resistance of targets varies with configuration, making it challenging to reach general conclusions, as each study presents specific results based on the material and projectile combination. This study aims to investigate the ballistic resistance of monolithic and multi-layered targets of Armox 500T using various damage models through numerical methods. Single-parameter damage models (Ayada (Ayada, 1987), Ayada-m (Ma et al., 2015), Ko-Huh (KH, Ko et al. (2007)), Brozzo (Brozzo et al., 1972), Le-Roy (LR, Le Roy et al. (1981)), McClintock (MC, McClintock (1968)), Oh (Oh et al., 1979), Rice-Trace (RC, Rice and Tracey (1969)), CL, and Freudenthal (Freudenthal, 1950)) are calibrated to assess their potential for predicting ballistic limit velocity and failure modes. All damage models are implemented into the Abaqus environment through a user-defined subroutine (USDFLD / VUSDFLD). Plasticity and JC damage model parameters are taken from Go¨c¸men et al. (2023). Six di ff erent layer configurations are performed to ballistic impact simulations using hemispherical, blunt, and ogival projectiles at various velocities. The results of numerical simulations are compared with the experimental data from Iqbal et al. (2016) to evaluate the predictive capabilities of the damage models, and the trend predictions of the six di ff erent configurations are also compared with the results in Deng et al. (2012, 2013). 2. Material and Methods In this section, the finite element (FE) modeling of the tensile tests used for material characterization, the employed plasticity and damage models, and the calibration process of these models are discussed. In this study, Armox 500T steel, widely used in armored vehicles and military equipment requiring ballistic pro tection, is selected as the target material. The geometry and experimental results of the tensile test are taken from Poplawski et al. (2020). The displacement-controlled implicit FE tensile simulations of the smooth round bar speci men, shown in Figure 1a, are carried out to calibrate the plasticity and damage models. Due to the symmetry, a 1 / 8 model is used to reduce computational cost. The mesh distribution is denser in the gauge length, while the element size is determined as 0.05 mm at the edge in the tensile direction to ensure controlled element elongation and 0.1 mm on the other edges. Eight-node linear brick elements with reduced integration (C3D8R) are utilized, while the parts held by the test machine during the experiment are modeled as rigid bodies (the gray part in Figure 1a). 2.1. Finite Element Modelling of Tensile Test

2.2. Plasticity and Damage Models

In the plasticity modeling of Armox 500T, strain hardening is modeled with isotropic hardening using the J 2 plasticity framework. The plasticity of the material is defined by the Voce hardening rule, which multiples a term