Energy dissipation characteristics of single curvature metallic shells subjected to ballistic impact

https://doi.org/10.1016/j.euromechsol.2021.104279Get rights and content

Highlights

  • Effect of nose profile of the projectiles on the perforation behavior of single curvature shell targets was observed.

  • Mode of failures observed during the perforation of targets subjected to normal and oblique impact was discussed.

  • Influence of target configuration on the impact performance of monolithic and in-contact layered targets was explored.

  • Strain energy absorbed in the plastic deformation of targets was evaluated and correlated with the failure modes.

Abstract

The impact resistance of single curvature semi-cylindrical shell targets of aluminum 1100-H12 was explored against hard steel cylindrical projectiles. Experimental as well as numerical investigations were carried out to observe the performance of shell targets against ogive, conical, blunt and hemispherical nosed projectiles. Effect of oblique impact was studied on the ballistic performance of the shell targets at 0 (normal), 15 and 30° obliquity. Further, the impact performance of 2 mm thick monolithic and in-contact layered targets of equivalent thickness was evaluated and compared. The projectiles were driven by a pneumatic air gun and the projectile flight path was captured with a high-speed camera. The experimental results obtained in terms of incidence and residual velocities, and deformation profile of the targets, were validated with the numerical analyses conducted in ABAQUS/Explicit solver. Johnson-Cook constitutive strength and damage material model was employed to simulate the deformation and damage evolution in the targets. The ballistic performance of both monolithic and layered targets impacted at oblique incidence, was compared in terms of ballistic limits, failure mechanisms, local and global plastic deformations and plastic strain energy absorbed in radial, circumferential, axial and shear deformation modes. The in-contact layered shell targets exhibited significantly higher impact resistance than the monolithic targets against all projectiles. Target configurations impacted at oblique incidence with conical and ogive nosed projectiles showed increase in global deformation, while, opposite behaviour was observed in case of blunt and hemispherical nosed projectiles. The plastic strain energy absorbed in various deformation modes correlated with the failure patterns observed in the target material during ballistic impact.

Introduction

Metallic plates and shells have various applications in domestic, military, aircraft and aerospace industries. In comparison with simple plate and membrane structural formations, shell structures have always provided efficient load distribution due to their inherent structural mechanism of developing additional in-plane stresses and undergoing minimum large global deformations. Shell formations used in military structures such as; shield, fuselage, boat hulls, tanks, containers, etc. are easily susceptible to ballistic loading and their impact behavior remains to be thoroughly understood. Research studies conducted on shell structures (Ma and Stronge, 1985; Palomby and Stronge, 1988; Zhang and Stronge, 1996, 1998; Colombo and Giglio, 2007; Manes et al., 2013; Gilioli et al., 2015; Fossati et al., 2020), explored the influence of material characteristics, target configurations and failure mechanisms involved in the perforation process during ballistic impact. Both experimental and numerical investigations have been carried out to ascertain the dependency of geometrical and material properties of projectiles and targets on the ballistic resistance of targets (Awerbuch and Bodner, 1977; Goldsmith and Finnegan, 1986; Gupta and Madhu, 1992, 1997; Madhu et al., 2003; Dey et al., 2007; Teng et al., 2007; Zhou and Stronge, 2008; Deng et al., 2012, 2013; Iqbal et al., 2010, 2015). A few researches have also indicated the relation of impact resistance of the targets in terms of energy absorption capacity and plastic work done in local as well as global deformation modes (Iqbal et al., 2016; Gupta et al., 2017, 2018; Mohammad et al., 2017, 2020, 2021). However, influence of oblique impact is yet to be investigated on the inherent failure modes and ballistic resistance capability of thin ductile cylindrical shells, and thus, required to be studied thoroughly.

The past studies have investigated the ballistic performance of single curvature tubular shell structures and commented on their residual strength after the impact. Ma and Stronge (1985) studied the impact resistance of empty and filled metallic tubes of different thicknesses against spherical steel projectiles. It was found that the ballistic limit of the tubes was significantly influenced by the density of filling material. Also, increase in wall thickness of tubes changed the failure mode during impact. Palomby and Stronge (1988) investigated damage evolution in thin ductile tubes impacted with blunt projectiles. The failure in the targets was bifurcated into discing and plugging which were further found to be associated with Mode I and Mode II fracture, respectively. Zhang and Stronge (1996) impacted mild steel tubes with blunt nosed missiles and the experimental results so obtained were compared with analytically evaluated ballistic limit of the target. Both shearing and global deformations were observed in the perforation process at normal incidence impact. The study was further extended to observe the influence of oblique impact on the ballistic resistance of the target against blunt, hemispherical and domed projectiles. Targets impacted with blunt nosed projectiles exhibited decrease in ballistic limit velocity with increase in the obliquity, however in other cases the ballistic limit was found to be increased (Zhang and Stronge, 1998). Colombo and Giglio (2007) numerically studied the ballistic resistance of aluminum rotor shaft of a helicopter against 7.62 mm NATO projectile. The shaft was impacted at normal and oblique incidence angle and at different offsets from the longitudinal axis. It was found that for incidence angle less than 45°, the projectiles had perforated the target, whereas at higher incidence angles, ricochet was observed. Manes et al. (2013) observed the impact performance of cylindrical hollow shaft of aluminum against rigid and deformable 7.62 mm diameter projectiles. It was found that the targets experienced more damage when impacted with deformable in comparison with rigid projectiles. Gilioli et al. (2015) studied the ballistic performance of a helicopter rotor shaft of aluminum 6061-T6 with the calibrated Bao-Wierzbicki and Modified Mohr-Coulomb model against 7.62 ball projectiles. A good agreement was observed for both damage shape and residual velocity as obtained from the numerical simulations and live impact. Fossati et al. (2020) presented residual torsional strength of aluminum 6061-T6 helicopter shaft subjected to ballistic impact at oblique incidence angle of 45°. The shaft was impacted with 12.7 mm bullet at the average velocity of 903 ms−1. Further, the reliability of the shaft was tested and fatigue crack propagation was observed after the ballistic impact. Both the experimental steps were also simulated to obtain the stress intensity factors, crack length at different intensity of torsional loads. The results obtained from the numerical and experimental origins showed good correspondence and crack propagation mechanism was accurately predicted from numerical modelling.

The state of the art impact studies conducted on the monolithic and layered target configurations showed significant variation in the ballistic performance of one configuration over another. Madhu et al. (2003) found insignificant difference in the impact performance of monolithic and layered aluminum targets against ogive nosed projectiles. Dey et al. (2007) and Teng et al. (2007) showed that layered targets configuration performed better than monolithic targets when subjected to blunt projectile, whereas impact performance of monolithic targets was observed to be higher for ogive and conical projectiles. Zhou and Stronge (2008) described that layered targets impacted with blunt nosed projectile performed better than monolithic targets, whereas for hemispherical nosed projectiles, the variation in the impact resistance was found insignificant. Iqbal et al. (2015) and Deng et al. (2012, 2013) explored the ballistic response of monolithic, in-contact and separated layered targets against blunt, hemispherical and ogive nosed projectiles and observed that monolithic targets performed better than layered targets. Previous studies conducted on the influence of oblique impact on the behavior of targets showed indistinct results. Awerbuch et al. (1977), Goldsmith and Finnegan (1986), Gupta and Madhu (1992, 1997), Madhu et al. (2003), Zhou and Stronge (2008) and Iqbal et al. (2010) concluded that the impact resistance of the plate targets was increased with impact angle. Further, Mohammad et al. (2017, 2020) and Gupta et al. (2017, 2018) observed that the plate targets showed increased ballistic resistance with obliquity against ogive nosed projectile, but against blunt nosed projectile, the performance of the targets was found to be reduced with increase in incidence angle of the projectile.

In previous experimental and numerical investigations, the impact response of metallic tubular shells has been investigated. Influence of oblique impact and residual load carrying capacity after the ballistic impact have been determined stating the dependency of target rupture and resistance on geometrical and material properties of projectiles and targets. A few research studies were conducted on single curvature shells, however, the damage morphology against projectiles with different nose profiles is yet to be explored. Previous studies also stated that the ballistic behavior is significantly influenced with the effect of target configuration and obliquity. Moreover, strain energy absorption in different failure mechanisms developed in single curvature shells during the impact process is not available in the literature. Thus, in present study, the performance of single curvature semi-cylindrical shell targets of aluminum 1100-H12 was studied against ballistic impact of cylindrical steel projectiles. Experimental as well as numerical studies were carried out to observe the performance of shell targets against conical, ogive, blunt and hemispherical nosed projectiles. The effect of oblique impact was studied on the ballistic performance of the shell targets at 0 (normal), 15 and 30° obliquity. Further, the impact resistance of 2 mm thick monolithic and in-contact layered targets (2 × 1 mm) was evaluated and compared. The projectiles were driven by a pneumatic air gun and the projectile flight path was captured with a high-speed camera. All experimental results obtained in terms of incidence and residual velocities, and deformation profile of the targets, were validated with the numerical analyses conducted in ABAQUS/Explicit solver. The shell targets were considered as deformable body, whereas, the projectiles were modelled as rigid body. Johnson-Cook constitutive strength and damage material model was used to simulate the deformation and damage evolution in the targets. The ballistic performance of both target configurations impacted at oblique incidence, was discussed in terms of ballistic limits, failure mechanisms, local and global plastic deformations and plastic strain energy absorbed in radial, circumferential, axial and shear deformation modes.

Section snippets

Experimental study

The ballistic experiments were conducted to determine the influence of nose profile of projectiles, oblique impact and target configuration on the ballistic resistance of the semi-cylindrical shell targets. Both monolithic and layered shell targets were impacted at 0 (normal), 15 and 30° obliquity with conical, ogive, blunt and hemispherical nosed projectiles. The projectiles were acquired from EN-24 steel bar of 19 mm diameter and were later lathed into desired shapes. The length and mass of

Numerical modelling and analysis

The numerical analyses of all ballistic experiments were carried out using finite element method in ABAQUS/Explicit solver. All target configurations and projectiles were modelled in three-dimensional space. The assembly of the part instances was done ABAQUS/CAE module and appropriate loading and boundary conditions were applied. During the experiments, very insignificant deformation in the projectiles was observed thus, they were assumed as rigid body to save computational cost (Fig. 3).

Results and discussion

The present study explores experimental and numerical investigations on the ballistic resistance of thin metallic aluminum 1100-H12 semi-cylindrical shells at normal as well as oblique impact. The shell targets were impacted with four different nosed shape cylindrical projectiles, viz. conical, ogive, blunt and hemispherical at 0 (normal impact), 15 and 30° obliquity. Effect of target configurations, viz. 2 mm thick monolithic and in-contact layered targets, on their impact performance was

Conclusion

The ballistic results obtained from the experiments were validated with the finite element analysis and a close agreement between the results was observed. Due to increase in the contact area, monolithic shell targets subjected to conical and ogive nosed projectiles at oblique incidence, exhibited 14.08 and 13.46% increase in the ballistic performance in comparison with the targets impacted at normal impact. On the other hand, same targets impacted with blunt and hemispherical nosed

Author statement

Zaid Mohammad; Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Validation; Visualization; Roles/Writing – original draft; Writing – review & editing, Pramod Kumar Gupta; Conceptualization; Data curation; Formal analysis; Resources; Software; Investigation; Methodology; Validation; Supervision; Visualization; Writing – review & editing, Abdul Baqi; Supervision; Writing – review & editing, Mohd. Ashraf Iqbal; Conceptualization; Data curation; Formal analysis;

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (32)

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