EP0527218B1 - Armour-piercing fragmentation projectile - Google Patents

Abstract

An armour-piercing fragmentation ammunition projectile is disclosed, and comprises a body (1) made of a dense material, a head (2) also made of a dense material, and means for fragmenting the body on impact. It is characterized in that the said means comprise a blind hole (9) delimited by the body and occupied by a mass (10) of compression material subjecting the said body to a fragmentation pre-stress. Application to sub-calibre projectiles.

Description

The present invention relates to the technical field of projectiles used for the destruction, at a distance, of any target, more generally of an armored nature.

The present invention relates to projectiles of the piercing type.

US-A-1,709,414, the description of which is taken from the preamble of independent claim 1, describes a projectile for a hunting weapon comprising a hard metal casing enclosing a soft metal head, an intermediate part or hammer. made of hard metal and a rear part made of lead. It is not a piercing projectile acting against armored targets.

The destruction of a target at long distance and, more particularly, of an armored target, requires a high accuracy of fire, as well as a high terminal efficiency.

The high shooting accuracy can be obtained by using projectiles, for example of the under-calibrated and perforating type, developing, by their construction, a high impact energy, while offering a remarkable shooting precision during the trajectory exterior ballistics.

Terminal destruction efficiency can be obtained by using an explosive projectile, that is to say internally containing a charge causing the explosion of the projectile at the time of impact.

It may be envisaged to use the combination of these two characteristics to constitute a shell or a projectile capable of meeting the objective of precise destruction capacity, at long distance, of an armored target.

However, the production of a projectile combining these two characteristics is certainly a relatively high cost price and involves handling, during manufacturing, an explosive charge which should be strictly controlled to avoid nuisance explosions.

The presence of such a charge poses, moreover, the same problems for the storage, handling, placement of projectiles in or on the installations responsible for firing them.

The object of the invention is to meet the objective thus posed by proposing a new projectile particularly designed to have the characteristics of precision of shooting of a penetrating projectile and the characteristics of a terminal effectiveness important, without necessarily implementing the presence of an on-board explosive charge.

To achieve the above objectives, the projectile according to the invention is characterized in that it comprises means for fragmenting the body on impact comprising a blind bore delimited by the body and occupied by a mass of compression material subjecting said body to a fragmentation preload.

Various other characteristics will emerge from the description given below with reference to the appended drawing which shows, by way of nonlimiting example, an embodiment of the subject of the invention.

The single figure is a sectional elevation of the object of the invention.

The projectile, as shown, comprises a body 1 made of a dense material, such as, for example, sintered tungsten, depleted uranium, tungsten carbide.

The body 1 is produced in the usual way in length and in size and has an axis of longitudinal symmetry or, again, of revolution x-x ' .

The body 1 is associated with a piercing head 2 , also made of a dense material, such as for example a treated steel. The head 2 is wrapped and covered by a ballistic cap 3 made of a malleable material having a good characteristic of penetration into the air by its shape and its nature, for example in light alloy or in copper alloy. The ballistic cap 3 can be mounted by crimping or shrinking on the body 1 capable of then presenting a low-cut front part or directly on the head 2 when the latter is made integral, by any appropriate means, with the body 1 , as is the case. case of the object represented.

The body 1 and the head 2 are linked by a mechanical connection 4 which comprises, in a preferred, but non-limiting embodiment, a threaded end portion 6 extending, from the rear face 7 of the head 2 , in presenting a diameter which may be equal to or less than that of the latter.

The mechanical linkage comprises, moreover, an internal thread 8 which is provided, from the front part 1a of the body 1, to the input of a cylincrique bore 9 provided axially and blind manner in the body 1. The internal thread 8 is produced in a complementary manner to the thread 6 , so as to allow a connection by traditional screwing of steps to the right or to the left, indifferently.

According to the invention, it is planned to subject the body 1 to a fragmentation preload which is provided by taking advantage of the presence of the bore 9 intended to be occupied by a mass 10 of compression-preload.

Different means of prestressing fragmentation can be retained from the mass 10 .

A first means consists in using, to constitute the mass, a plastic compressible material, that is to say having the characteristic of remaining compressed after compression. Such a material may consist of a metal powder, a mass of chips, a pyrotechnic powder composition, etc. Such a material is compressed in the bore 9 to occupy, if not all, at least the major part. This compression is applied so as to generate a prestress of the body 1 , either only radial, or radial and axial, chosen, in all cases, so that the mechanical strength of the body is preserved. The total prestress must therefore be in a range such that the maximum value respects the initial integrity of the body 1 , but that the minimum value is sufficient to improve the fragmentation of said body on impact.

où Eo,2 % définit la valeur de la limite d'élasticité conventionnelle du matériau du corps 1, c'est-à-dire la valeur de la contrainte donnant une déformation permanente de 0,2 % dudit matériau.It can be considered that the total prestress applied to the body must be between: $$\text{0.1 x Eo, 2\% and 0.4 x Eo, 2\%}$$

where Eo, 2% defines the value of the conventional yield strength of the material of body 1 , i.e. the value of the stress giving a permanent deformation of 0.2% of said material.

For example, a material 10 of tungsten powder compressed between 600 and 800 MPa in a body 1 of sintered tungsten is satisfactory.

où Rm représente la résistance à la rupture du matériau du corps 1.It can also be chosen to subject the material 10 thus compressed to an axial prestress of the order of: $$\frac{\text{Rm}}{\text{3.5}}$$

where Rm represents the breaking strength of the material of the body 1 .

In this first implementation, the material 10 is compressed, after which the head 2 is mounted to close the bore 9 to ensure, preferably, directly by an external extension or by means of an independent piston 11 , contact with the compressed material.

A second implementation variant consists in using a compressible material 10 elastically, such as elastomer. In such a case, the prestressing is obtained by the composition of a radial prestressing and an axial prestressing, the radial prestressing being a consequence of the radial deformation of the rubber subjected to an axial force.

The total prestressing must still be in the area defined above. Such preload is then advantageously applied via the head 2 of the screw type.

Another alternative is to implement a 10-compressible material, such as balls, rollers, paddles, rollers, cylinders. The fragmentation preload is then only of the axial type and is applied to the body 1 by mounting the screwed head 2 . Such axial prestressing is preferably between: $$\frac{\text{Rm}}{\text{3.5}}\text{and}\frac{\text{<figure-callout id="3" label="Rm" filenames="imgf0001.png" state="{{state}}">Rm</figure-callout>}}{\text{3}}$$

The projectile according to the invention undergoes, upon its impact on the target, a release from the prior constraint or constraints which are imposed on it by manufacturing. The shock wave promotes the release of these stresses, which increases the speed and the fragmentation capacity of the body 1 which produces a greater number of shards and a burst of shards than in the case where it would be, by mounting prior, devoid of the initial constraints.

To improve the fragmentation, the body 1 may include zones of least resistance, either axial or, preferably, transverse, as shown in dashed lines and designated by the references 12 .

An improvement in the fragmentation can also be obtained by using, in addition to the axial and / or radial prestressing, a pyrotechnic charge 10 whose explosion is caused by the impact.

The invention is not limited to the example described and shown, since various modifications can be made thereto without departing from its scope.

The invention finds an interesting application to sub-calibrated projectiles.

Claims (9)

1. Armour-piercing, fragmentation projectile of the type comprising a body (1) made of a dense material, a head (2) also made of a dense material, as well as means for fragmenting the body upon impact, characterised in that said means incorporate a blind bore, demarcated by the body and occupied by a mass (10) of compressed material subjecting said body to a fragmentation prestress.
2. Projectile according to Claim 1, characterised in that the mass of material subjects the body (1) to a fragmentation prestress in at least one axial direction.
3. Projectile according to Claims 1 or 2, characterised in that the fragmentation prestress is between 0.1 x Eo.2% and 0.4 x Eo.2%.
4. Projectile according to Claims 1, 2 or 3 characterised in that the mass (10) is formed of compressible materials of a plastic nature, previously compressed in the bore and maintained therein by the presence of a head (2) fitted on the body and covered by a ballistic cap (3).
5. Projectile according to Claims 1, 2 or 3 characterised in that the mass (10) is formed of compressible materials of an elastic nature, previously compressed in the bore and maintained therein by the presence of a head (2) fitted on the body (1) and covered by a ballistic cap (3).
6. Projectile according to Claims 1, 2 or 3 characterised in that the mass (10) is formed of incompressible materials exerting an axial prestress to the body by means of a head (2) fitted onto the body and covered by a ballistic cap (3).
7. Projectile according to Claim 6, characterised in that the axial prestress is between Rm/3.5 and Rm/3.
8. Projectile according to one of Claims 5 to 7, characterised in that the head (2) is screwed to the body and penetrates into the bore (9) by a rear extension (11).
9. Projectile according to one of the above Claims, characterised in that the body comprises zones of lesser strength.

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