Topic: Mechanical & Industrial Engineering
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An Engineering Penetration/Perforation Model of Hemispherical Nosed Rigid Cylindrical Rods into Strain-hardening Targets
A four-stage model of the penetration/perforation by hemispherical-nosed rigid cylindrical rods into targets whose materials exhibit strain-hardening effects. During each stage of the penetration process, a kinematically admissible velocity field involving one or more unknown parameters is assumed. These parameters are determined by minimizing the rate of plastic dissipation. From this velocity field, the incremental deformations of the target, the penetration depth, the resisting force acting on the penetrator and hence its deceleration are evaluated. We propose a criterion for the formation and ejection of the cylindrical plug in the target and use it to study problems involving the perforation of the target. Computed results for the exit speed of the penetrator and, when the targets are not perforated, of the penetration depth are found to match well with the corresponding test values.
One way to analyze an impact problem is to seek a solution of the dynamic equations expressing the balance of mass, linear momentum and internal energy subject to suitable initial and boundary conditions.
However, this technique, while furnishing details of the deformation fields in the penetrator and the target, is computationally very expensive. When one is interested in gross effects such as the penetration depth, exit speed of the rod impacting at normal incidence a metallic plate and the time history of the speed of the rod, then one can use an approximate method to obtain reliable solutions with considerably less computational resources.
Develop shortly after initial impact and is characterized by continuously growing plastic zones surrounding the projectile. We presume that the deforming target region can be divided approximately into two distinct regions; region I which is undergoing severe plastic deformations and the material particles are moving both in the radial and Fig. 1. A schematic sketch of the penetrator position and deforming target region during stage I of the penetration process.
Source: www.esm.vt.edu
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