Narrow Results

As the projectile moves through the gun tube, the gun tube is subjected to a traveling load consisting of the weight of the projectile and a transverse force, probably much greater than the weight, due to the mass of the projectile being constrained to follow a curved path, defined by the shape of the gun tube. This is not simply the curvature of the barrel due to gravity, but the instantaneous value resulting from all the causes of vibration. The gun tube profile and properties of sabot may affects on strength on the penetrator traveling in the gun tube. In addition to these, the aspect ratio of penetrator is also the principal factor for the strength of penetrator. Combined influences of the forward sabot diameter and aspect ratio of penetrator on the strength of penetrator was analyzed using three dimensional dynamic finite element analysis method in the study.

To analyze the influence of penetration resistance for different steel plate configurations, different steel plates impacted by various projectiles were studied using the LS-DYNA code. The calculation results obtained using the LS-DYNA code and prior experimental results reported in the literature agree well with the damaged image of projectiles penetrating steel plates and the initial residual velocity curve of the projectile. The Q235 steel constitutive model is modified based on the Johnson–Cook model. It can be concluded that the LS-DYNA code analysis is reliable when compared with the experimental results. We then used the LS-DYNA code to conduct an extensive study into the penetration resistance of monolithic, contact-type double-layered and gap-type double-layered targets with the same surface density, impacted by different projectiles. The failure mode of the steel plate, initial residual velocity, ballistic limit velocity, energy absorption and plastic deformation of the monolithic and double-layered plates were studied. The results in this paper can provide guidance for the design and application of structural protection using steel plates.

An experimental study of oblique water entry of projectiles with different noses has been conducted using high-speed photography technology. The images of the initial water entry impact, cavity evolution, and the closure and shedding of vortices of cavity are presented in the paper. The results reveal that for high-speed oblique water entry (the initial impact velocity $>$50 m/s), the cavity attached to the projectile is symmetrical and free from the influence of gravity. The shedding of the water–vapor–air mixture in the tail of the cavity produces vortices which disappear in the rear of the projectile trajectory. Particular attention is given to the velocity attenuation of the projectile after water entry. The results show that there is a transition point at the time corresponding to the surface seal of the cavity during the velocity attenuation after oblique water entry, and the rates of velocity attenuation are different before and after this transition point. Additionally, the chronophotography of the cavity evolution shows that the time when the surface seal of the cavity occurs decreases with the increase of the initial impact velocity of the projectile.

Water entry experiments of projectiles with different nose shapes were performed under different entry angles and velocities using high-speed photography technology. The cavity flow characteristics of the near water surface, including splash jet, splash crown, surface seal of cavity, pull away, deep seal of cavity and cavity collapses, were systematically investigated using a high-speed camera. The emphasis of the study is paid on the effect of nose shape, water entry angle and velocity on the evolution of the air entraining cavity. The experimental results demonstrate that the nose shape of projectile has a significant influence on the jet flow, the cavity diameter and trajectory stability in the case of certain other conditions. On the other hand, the splash scale, cavity diameter increase gradually with the increasing of the water entry velocity, as well as the cavitation closed in advance. Furthermore, the water entry angle of the projectile plays an important role in the cavity evolution and the close type.

A failure model based on the three-dimensional strains in a composite layer with improved progressive damage modeling has been implemented to predict the deformation behavior of composite armors subjected to ballistic impact. The present model comprises mainly of two parts. First, quadratic strain based failure criteria are presented to predict the initiation of failure modes. Second, the post damage softening behavior and degradation of the material stiffness is measured by damage evolution law. The model has been implemented within ABAQUS/Explicit as a user defined subroutine VUMAT. The validity of the model has been carried out by performing computational analysis of different composite armor materials such as Kevlar 29 and Kevlar 129 impacting with cylindrical-hemispherical nosed and 120° conical projectiles. It transpires that the predictions from the present model are in good agreement with the experimental and numerical observations available in the literature in terms of back face signature (BFS) for both the targets and projectiles. Further, the model has been implemented to study the effect of projectile geometry on the velocity time histories of the projectile, residual velocity and ballistic limit velocity. BFS values showed good agreement for conical projectile while for hemispherical projectile it is slightly low. The combination of Kevlar 129 armor and hemispherical projectile shows higher ballistic limit compared to that of the other combinations.

In this study, the numerical simulation using AUTODYN-3D program was investigated for trajectory prediction for inclined impacts of projectiles. The penetration and perforation of polycarbonate(PC) plate by 7.62 mm projectile was investigated numerically. The characteristic structure of the projectile's trajectory in the PC plates was studied. Two combined failure criteria were used in the target plate, and the target plate was modeled with the properties of polycarbonate for simulating the ricochet phenomenon. The numerical analyses were used to study the effect of the angle of inclination on the trajectory and kinetic energy of the projectile. The dynamic deformation behaviors tests of PC were compared with numerical simulation results which can be used for predictive purpose. Ricochet phenomenon for angles of inclination of 0° ≤ θ ≤ 20° in the analysis. The projectile perforated the plate for θ > 30°, thus defined a failure envelope for numerical configuration. The numerical analyses was used to study the effect under the projectile impact velocity on the depth of penetration(DOP).

The use of computers as a learning tool has been a time-tested method, which can attract the interest and motivation of students to solve any complicated system easily. Scilab is an open-source computational software package that provides various tools to simulate and solve problems in classical mechanics.

In this paper, two types of classical mechanics problems are solved. Under kinematics section, we solve the Projectile motion considering air resistance and particle falling under the action of gravity, with resistive force dependence on different exponents of velocity. Similarly, under the waves superposition section, we solve the two sinusoidal waves superimposed to give a Lissajous pattern and superposition of two or more waves using Scilab software for a better understanding of the classical problems by visualization of graphs, as Scilab has 2D and 3D plotting facilities.