Projectile Penetration and Perforation by Gunnar Wijk

Projectile Penetration and Perforation

byGunnar Wijk

Kobo ebook | January 3, 2015

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This book describes new models for projectile penetration and perforation. The models are based on conservation of mass, momentum, energy and an empirical EOS. There are four chapters
Ch1: Transition from rigid to eroding projectile penetration
Ch2: A new model for rigid projectile perforation of ductile targets
Ch3: Rigid projectile perforation of brittle target material
Ch4: Shaped Charge jets
The EOS for the model in Chapter 1 is simple and non-controversial. For rigid projectiles it states that the hole diameter is equal to the projectile diameter, whereas hole diameters that are produced by eroding projectiles with higher velocities than a certain limit velocity vlim are proportional to these velocities; for lower velocities the hole diameter is constant and given by the hole diameter for the velocity vlim. Projectiles are retarded via a force over the front end that is derived by analogy with the well-known theory for longitudinal impact between rods. This force is independent of the instantaneous projectile velocity for non-hardening target material, but increases with the velocity for hardening target material. For rigid projectiles and for eroding projectiles with lower velocities than vlim there is also friction retardation.
In reality there is always initial increase of the front end retardation force to a limit value Flim at a hole depth that is a few times larger than the hole diameter. If the projectile strength is lower than Flim, then there is rigid penetration to the depth where the strength equals Flim, at which there is sudden change to eroding penetration. Otherwise the projectile continues as rigid, either until it stops or until friction has heated the projectile to the temperature at which the strength has become reduced to equal Flim. In the latter case there is sudden change to eroding penetration, which continues until the projectile is stopped.
The model is shown to agree with experimental results, especially for impact velocities that are well above the limit velocity vlim so that there is no friction involved and so that the projectiles are completely eroded to become a thin coating along the hole wall.
The new model for rigid projectile perforation of ductile targets in Chapter 2 is based on slip line field theory. For the simplest case with a flat-nosed projectile this yields a minimum perforation energy that is four times higher than for punching a hole in a thin target plate. The reason is that punching requires rigid support behind the plate just outside the hole-to-be. For a thick target there is initial penetration as described in Chapter 1 until the distance to the rear target surface is some value h*, the value of which is determined by requiring that the perforation energy and the derivative thereof both are continuous functions of the target thickness h. A similar approach is used for round-, conical- and ogive-nosed projectiles. With blunt (flat- and round-nosed) projectiles a plug is ejected in front of the projectile, whereas sharp (conical- and ogive-nosed) projectiles produce a collar around the exit hole. The model is shown to agree with experimental results for all nose shapes.
The new model for rigid projectile perforation of thin targets of brittle material in Chapter 3 is based on dimensional analysis. For thick targets there is again penetration as described in Chapter 1 to some distance h* from the rear target surface, at which there is connection to the thin model as in Chapter 2. The material ahead of the projectile at the connection point is fractured into large slow-moving fragments from the surface and small fast-moving fragments from the interior. The model is shown to agree with experimental results for the minimum perforation energy. The new model for Shaped Charge jets is the same as for eroding projectiles. A simple model for the generation of SC jets is also proposed.

Title:Projectile Penetration and PerforationFormat:Kobo ebookPublished:January 3, 2015Publisher:Gunnar WijkLanguage:English

The following ISBNs are associated with this title:

ISBN - 10:9163775794

ISBN - 13:9789163775796

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