EP0376838B1 - Apparatus for cutting solid structures from a distance by the directed projection of splinters - Google Patents

Description

The invention relates to a device for the remote cutting of solid structures, in particular thick metal plates by oriented splinters.

A number of documents describe various machining, forming or plating processes in which the energy produced by an explosion is exploited. It is known, for example, to put a punch in motion or to project a coating plate onto a surface to cover it with a brazing due to heating.

The use of hollow charges is also known, where an explosive charge is hollowed out according to a conical imprint and furnished with a projectile in the form of a conical envelope with the same opening. The implosion of this cone by detonation of the explosive creates a threadlike metallic jet on the axis of the charge. This metallic jet has the property of perforating thick solid targets over great depths. These shaped charges are mainly used to perforate shields. We note during the trajectory that the energy of the explosion makes the projectile plastic and that its matter is animated by a centripetal component, so that it ends up accumulating in the form of a thin jet on the axis of the trajectory and that the cone is almost abolished. Such a hollow charge is the subject of American patent 4,702,171. Another is described in French patent 2,041,498. It is also possible to note American patent 4,649,828 where a spherical cap is formed from contiguous lamellae which are deformed into points of explosion arrow.

The invention rather aims to perforate the target along a closed contour such as circular, which causes greater damage and, in the case of plates, allows cuts to diameters decided by the user.

The device according to the invention comprises a projectile and an explosive charge located behind the projectile relative to the solid and separated from it by a damping layer. The projectile is in the form of a disc having a circular perimeter or not analogous to the closed contour, a pierced center and a thickness decreasing from the perimeter towards the center; the explosive charge is itself capable of producing a substantially planar shock wave towards the plate.

The projectile thus possibly has a conical concave face. It can be fitted with lines of least radial or circumferential resistance.

The explosive charge is advantageously provided with a substantially planar face directed towards the projectile and separated from the latter by a layer of air.

• La figure 1 est une coupe diamétrale d'une réalisation du dispositif présentant une symétrie de révolution ;
• La figure 2 explique le fonctionnement du dispositif ; et
• Les figures 3 à 6 représentent de face diverses formes pour le projectile.

The invention will now be described in more detail with the aid of the figures annexed by way of illustration and not limitation:

• Figure 1 is a diametrical section of an embodiment of the device having a symmetry of revolution;
• Figure 2 explains the operation of the device; and
• Figures 3 to 6 show various shapes of the projectile from the front.

We distinguish in Figure 1 an explosive charge 1 of cylindro-conical shape having a cylindrical part 2 at the front and a frustoconical part 3 limited by a rear face 6 at the rear, constituting the plane detonation wave generator. A detonator 5 is located on the rear face 6. The cylindrical part 2 is terminated by a flat front face 7; a spacer ring 8 separates it from a disc-shaped projectile 10 which exactly covers the front face 7. The gaseous layer 9 between the charge 1 and the projectile 10 makes it possible to avoid the almost immediate disintegration of the latter at moment of the explosion and therefore constitutes a shock absorber.

The projectile 10 has an outer perimeter 11 and a bore 12 established on its central part. The thickness of the projectile 10 gradually decreases from the perimeter 11 to the bore 12; it is noted there Ep and Ec respectively. This can be achieved by building it with a flat rear face 13 and a concave front face 14 of conical shape.

Figure 2 shows that following the explosion the projectile 10, initially in the form of a disc 10a as we have just seen, deforms plastically by opening as it approaches of the target, here a plate 20 to be cut along a circular contour 21, to take the form first of a cone 10b then finally of a crown 10c. More precisely, the plane shock wave created by the explosive charge 1 projects the material of the projectile 10 at an increasing speed with the proximity of the bore 12, so that the material which was at the beginning in the center comes to the front and is is moreover animated by a centrifugal speed which makes it progressively approach the trajectory followed by the points of the perimeter 11. We witness approximately, for each radial section of the projectile 10, a rotation in the plane of the section around the part adjacent to perimeter 11; no bead of material appears. The centrifugal speed of the points located near the perimeter 11 is low or zero.

In a concrete example, we sought to drill a target 20 of 40 mm armor steel thick. Load 1 and projectile 10 were placed 1 m from target 20. The load was approximately cylindrical, 150 mm in diameter and composed of 2.5 kg of Octolite. The projectile 10 was also 150 mm in diameter, its thickness Ep was 5 mm and its thickness Ec 2.5 mm. The angle C was 2 ° and the diameter of the hole 10 mm. We observed a cut 21 of almost 150 mm in diameter on the target 20. Many other acceptable solutions are of course possible.

où Z est égal à la racine carrée de 1+(32r/27), r désignant le rapport de la masse surfacique locale de la charge sur celle du projectile, perpendiculairement au front d'onde, U_c la vitesse de détonation de la charge et U_p la vitesse locale du projectile.We will be able to use for other digital applications the results obtained from simulations from two-dimensional hydrodynamic calculation codes or by applying for example the formula usable for the projection of a planile projectile by a frontal detonation: $${\text{U}}_{\text{p}}{\text{/ U}}_{\text{vs}}\text{= (Z-1) / (Z + 1)}$$

where Z is equal to the square root of 1+ (32r / 27), r denoting the ratio of the local surface mass of the charge to that of the projectile, perpendicular to the wavefront, U _c the detonation speed of the charge and U _p the local velocity of the projectile.

By increasing or on the contrary by decreasing the angle C, one can reduce or on the contrary strongly increase, by several meters for example, the optimal distance d of perforation indicated on figure 2.

This optimal distance d corresponds to the flight distance of the flakes from which they are almost aligned in a crown.

The opening of the projectile 10 can be favored by having lines of least resistance therein (FIG. 3). These lines can be radial 22 and extend from the perimeter 11 to the central bore 12, or circumferential 23 and extend over a closed curve between the perimeter 11 and the central bore 12. They can be made by mechanical grooving, electronic bombardment or by laser.

We have so far spoken of projectiles in the form of circular discs. As shown in FIGS. 4 to 6, the projectile can be in the form of a non-circular disc: FIG. 4 shows an equilateral triangular projectile 104, FIG. 5 a square 105 projectile and FIG. 6 a hexagonal projectile 106. Any irregular or non-irregular polygonal shape is admissible. All of the above description applies to these projectiles. Their interest is to allow cuts to be made according to closed contours similar to their respective perimeters 114, 115 and 116.

The front face of the load 2 may not be perfectly conical and have a slight curvature in one direction or the other.

The method can be used, in addition to cutting plates, in particular from composite materials, for destroying elements of concrete structures (dismantling of installations) or shielding or for perforating the casing of a well as well as for disintegrating. around this well the rocks impregnated with petroleum.

Claims (5)

1. Device for long-range cutting of solid structures and in particular for cutting a plate (20) along a closed contour (21) comprising a projectile (10) and an explosive charge (1) situated behind the projectile (10) with respect to the solid (20) characterised in that the explosive charge (1) is separated from the projectile (10) by a damping layer (9), and in that the projectile (10) is shaped like a disc having a circular or other perimeter (11) similar to the closed contour (21), a perforated centre (12) and a thickness diminishing from the perimeter towards the centre, and in that the explosive charge (1) is able to produce a substantially plane shock wave heading for the plate.
2. Device according to Claim 1, characterised in that the explosive charge (1) has a substantially plane face (7) turned towards the projectile (10) and separated from the projectile (10) by a layer of gas (9).
3. Device according to either one of Claims 1 or 2, characterised in that the projectile has a concave face (14).
4. Device according to any one of Claims 1 to 3, characterised in that the projectile (10) is endowed with lines of least resistance (22) joining the perimeter (11) to the centre (12).
5. Device according to any one of Claims 1 to 4, characterised in that the projectile (10) is endowed with closed-contour lines of least resistance (23) between the perimeter (11) and the centre (12).

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