Rod Projectiles Research Articles

Applying Tate's model for the interaction of long rod projectiles with ceramic targets

The penetration of ceramic tiles by long rod penetrators is discussed in terms of the modified hydrodynamic theory of A. Tate which was developed for thick metallic targets. The resistance of the tile to penetration is determined with the threshold velocity for the penetration of a very large ceramic block. According to Tate's theory, the threshold impact velocity for a given projectile (with a well defined strength) depends only on the tile's resistance to penetration. We show here that using three different projectiles (copper, steel and tungsten) resulted in the same value for this parameter for thick alumina tiles. This fact strongly enhances the idea of applying Tate's theory to ceramics. A different set of experiments, with relatively thin tiles bonded to thick steel plates, was performed determining penetration depths of the long rods into the steel backing. These were compared with predictions based on Tate's model using the values for the penetration resistance, which were determined by thick tile experiments. The good agreement can be considered as a further confirmation of our main thesis. Resistance of penetration parameters ( R t) were determined for other ceramics (silicon carbide, titanium diboride, etc.) by measuring the penetration depths of the long rod projectile into the thick backing and using Tate's model with R t as a parameter.

Engineering modelling of some aspects of segmented rod penetration

Some of the possible advantages and disadvantages of segmented rod projectiles are discussed. Simple engineering models for the minimum separation of segments to avoid clashing and the maximum separation to optimize after-flow effects are proposed. The theory is compared with some experimental results of Orphal and Franzen.

Hypervelocity impact of rod projectiles with L/D from 1 to 32

Beside a short remark on the “hydrodynamic theory of rod projectiles”, the paper deals with the terminal ballistic behaviour of cylindrical projectiles against semi-infinite targets. Experimental data of EMI, completed by results of some other authors, are presented. Crater parameters like depth, diameter and volume and their dependence on projectile velocity (up to 5000 m/s), projectile and target material properties, as well as L/D-ratios (1–32), will be discussed. Mainly the projectile materials steel and tungsten sinter-alloys are considered. Target materials are mild steel and high strength steel, an Al-alloy and a tungsten sinter-alloy. The results show that the influence of material density on the crater dimensions is considerably greater than the influence of strength. The L/D ratio determines the velocity dependence of crater depth, diameter and volume. At high velocities in the hydrodynamic regime, the crater depth of short cylinders (L/D ∼ 1) is approximately proportional to v p 2/3 (V p=projectile velocity). With increasing L/D-ratio, the slope of the penetration curves decreases and converges for rods (L/D ≫ 1) versus a saturation, i. e. becomes nearly independent on v p. A consequence of this saturation is the existence of a so-called “tangent velocity”, above which an optimal increase of efficiency is only realized by increasing the projectile mass and not the velocity. Furthermore, ballistic limits of real targets like single plates and symmetric double plates meteorite bumper shield) are taken into account. The expected better performance of “segmented rods” is also discussed.

The Normal Impact of square Section long rods on ‘Rigid’ and ‘Soft’ Targets

Studies of long rod impact are almost invariably associated with rods of circular cross-section, but in this paper experiments are described in which square cross-section long rods were made to impinge normally on nominally rigid target plates as well as on ‘soft’ targets of comparable strength. Plasticine has been used as the model material to simulate metallic projectiles and targets. The various modes of deformation and flow associated with square section rod projectiles have been identified and compared with those observed earlier by Johnson et al. (5)¶ in a study using long rods of circular cross-section.

High velocity oblique impact and ricochet mainly of long rod projectiles: An overview

A review of the literature on high velocity oblique impact and the ricochet of projectiles of various shapes is given, with emphasis on long rod projectiles. Aspects of cratering and penetration in oblique impact are highlighted and the mechanics of ricochet off solid, fluid and granular media are also discussed.

Mechanics of high speed impact at normal incidence between plasticine long rods and plates

A brief literature review of long rod impact is given. Experimental results and observations on the penetration and perforation of plasticine targets of finite thickness (25 and 50 mm) impinged upon normally by long rods of plasticine of various length-to-diameter ratios (2–12) are presented and discussed. An account of the range of modes of deformation as it pertains to long rods and targets of identical materials is given, i.e. mushrooming of the projectile leading-end, partial penetration and embedment of the projectile in the target, gross target penetration by the projectile, and penetration followed by perforation. The difference in penetration behaviour as between long and short rods is discussed. Plasticine has been used for both the target and projectile materials in order to simulate hypervelocity impact conditions for deformable long rod projectiles on deformable target plates. This permits the use of equipment based on an industrial stud driver which is substantially cheaper than the equipment (e.g. a light gas gun) required to achieve the range of speeds necessary for hypervelocity conditions with real ballistics-related metals and alloys. Projectile-target interactions and damage observed in the present tests compare well with those reported in similar investigations using metallic projectiles and targets. The attraction of performing ballistics experiments with plasticine models outweighs such inherent limitations as the inability to model the extreme conditions of temperature and strain-hardening in real materials, because testing is cheap and easily performed in a laboratory.

Bending of Long Steel and Aluminium Rods during end Impact with a Rigid Target

Bless and Barber (1) ‖ have shown that rod projectiles can be affected by the propagation of bending deformation along their lengths when they strike rigid targets at sub-ordnance velocities. Experiments are described in which a range of different modes of deformation are identified for both normally and obliquely incident steel and aluminium rods of length to diameter ratio 24 : 1. The results are discussed from the point of view of classical dynamic structural plasticity.

A simple estimate of the minimum target obliquity required for the ricochet of a high speed long rod projectile

A simple model for the minimum obliquity required to induce ricochet of a high speed long rod projectile from a thick target plate is suggested.

A simple hydrodynamic model for the strain field produced in a target by the penetration of a high speed long rod projectile

A simple hydrodynamic model is used to estimate the strain field around the cavity created by a rod penetrating a thick plate and to find the distortion of the rear surface of the plate. An interesting feature of the theory is that both the strain field and the rear surface distortion tend to an asymptotic form after sufficiently deep penetration.

Penetration mechanics of yawed rods

The penetration of rod projectiles is a function of impact yaw. Armor steel targets were struck at 0° obliquity by long steel rods at ~2.15 km/s and various angles of yaw. Crater dimensions varied systematically with yaw angle. Trenching behavior was observed for yaw angles exceeding about 30°. Analysis indicates that the rods collapsed into the targets with no significant rotation, and that penetration chiefly depends on the parameters D and D sin θ (where D is rod diameter and θ is yaw angle).

Analysis of High-Velocity Projectile Penetration Mechanics

The process of cratering in materials is described in terms of four phases: transient, primary, secondary, and recovery. Rod projectiles were used in an experimental study of the relative importance of each phase and its influence on final crater dimensions. Aluminum and steel rods with aspect ratios of 1/6 to 25 were impacted into metallic and nonmetallic target materials at impact velocities of 0.3 to 6.7 km/sec. During the primary penetration phase, rod deformation was found to be comparable to that observed for shaped-charge liner collapse, and measured rod penetration rates showed good agreement with rates calculated on the basis of incompressible fluid flow considerations. Empirically developed equations are presented for predicting crater penetration and volume in metal targets.