WO2014095989A1

WO2014095989A1 - Warhead with shrapnel and method for producing same

Info

Publication number: WO2014095989A1
Application number: PCT/EP2013/077075
Authority: WO
Inventors: Christophe Bar; Eroan BENADE; Alain Dousset
Original assignee: Tda Armements S.A.S
Priority date: 2012-12-21
Filing date: 2013-12-18
Publication date: 2014-06-26
Also published as: FR3000192A1; FR3000192B1

Abstract

A warhead (10) comprising an explosive (E), detonating means (9) and a metal shrapnel generator (1) in the form of a tube delimited by two longitudinal faces (2, 3), said tube surrounding the explosive (E), said shrapnel generator (1) being intended to break under the effect of the explosion of the explosive in order to form said shrapnel. The shrapnel generator (1) comprises at least one closed honeycomb structure that defines therein a network of closed internal cavities arranged in a reproducible manner, the closed honeycomb structure forming said shrapnel by breaking under the effect of the explosion.

Description

MILITARY LOAD WITH SHADES AND METHOD OF MANUFACTURE

This invention is in the field of military fragmentation loads.

A fragmentation military charge consists mainly of a tubular metal splinter generator that is designed to break under the detonation of the explosive to form metal chips. The chip generator surrounds the explosive whose energy is used to break the chip generator to produce and propel the shards. The energy reservoir constituted by the explosive is initiated by a priming system.

In mortar or artillery shells, splinter generators are usually not pre-fragmented. These are solid metal bodies that break naturally under the effect of detonation. A disadvantage is that the templates of the fragments from these generators are not controlled. Their fragmentation is random.

To solve this problem, pre-fragmented fragment generators are used. By pre-fragmented generator is meant a generator having local weakenings (or local weakenings) intended to promote its rupture and to calibrate the chips in optimal size and mass guaranteeing the functional or structural destruction of the target. The chips do not exist as such within the chip generator before the explosion of the explosive, they are generated during the rupture of the generator under the effect of detonation of the explosive.

Many solutions are known to pre-fragment a chip generator. Here is mentioned the grooving of the chip generator on its inner surface facing the explosive and / or on its outer surface facing the outside of the load. Thus the generator is made in the form of a grooved shell surrounding the explosive.

The generator can also be made in the form of a stack of notched rings, that is to say grooved, surrounding the explosive or by the winding of a toothed bar around the explosive.

The grooves are conventionally made by machining or by laser cutting. The grooves as well as the thickness of the ferrule, rings or toothed bar, define the size and number of future chips. In other words, the coming chips are generally defined by grooves, the inner face and the outer face of the generator. This means that the thickness of the chips necessarily corresponds to the thickness of the tube.

The consequence of this characteristic is to limit in size and, in particular in thickness, the variety of chips generated.

The object of the invention is to overcome the aforementioned drawbacks. For this purpose, the subject of the invention is a military load comprising an explosive, firing means and a metal fragment generator in the form of a tube delimited by two longitudinal faces, said tube surrounding the explosive, said generator being intended to break under the effect of the explosion of the explosive to form said chips. The fragment generator according to the invention comprises at least one closed cellular structure which delimits within it an array of closed internal cavities arranged in a reproducible manner, said at least one closed cellular structure forming said chips by breaking under the effect of the explosion.

Advantageously, the closed internal cavities comprise at least one network of rows of closed internal cavities, said rows of a network being distributed over the circumference of the tube.

Advantageously, the rows of a network extend along different generatrices of the same cylinder.

Advantageously, the military load comprises a plurality of networks of rows of closed internal cavities distributed over the thickness of the chip generator.

Advantageously, the internal cavities are arranged within the structure so as to generate chips of the same caliber.

Advantageously, the structure is configured so that its rupture under the effect of the explosion of the explosive is initiated preferentially at predetermined locations of said envelopes.

Advantageously, the structure comprises envelopes comprising at least one salient angle constituting a rupture primer. Advantageously, the structure comprises envelopes comprising at least one edge and / or at least one vertex and / or comprises polyhedral envelopes.

Advantageously, the structure comprises at least one solid longitudinal metal face provided with grooves and / or cavities.

Advantageously, the chip generator is monobloc.

Advantageously, the structure is rigid.

The invention also relates to a method of manufacturing a military load according to the invention, comprising a step of producing the honeycomb structure by additive manufacturing.

Advantageously, the method comprises a step of modeling the cellular structure of three-dimensionally modeling the shape and dimensions of the structure (s) as well as the shapes, the dimensions and the arrangement of the cavities within the structure. splinter generator. The method also comprises a step of producing the structure (or structures) in which the structure is produced by metal deposition in successive layers on a substrate from a metal powder that is heated by means of a laser for fusing or sintering the metal powder outside the areas intended to form the cavities of the structure so as to obtain a structure having said geometry.

Other features and advantages of the invention will appear on reading the detailed description which follows, given by way of non-limiting example and with reference to the appended drawings in which:

FIG. 1 schematically represents a military load according to the invention shown in a longitudinal section,

FIG. 2 represents a section of the military load of FIG. 1 along a plane perpendicular to the longitudinal axis;

FIG. 3 diagrammatically represents a cavity of the structure represented in FIG. 1,

FIG. 4 represents a flowchart of the method according to the invention, FIG. 5 represents a flow chart of a step of producing a closed cellular structure according to the invention by additive manufacturing,

FIG. 6 schematically represents an enlargement of FIG. 2 in the zone delimited in dotted lines,

FIG. 7 represents an enlargement of a variant of the generator of FIG. 2.

From one figure to another, the same elements are identified by the same references.

FIG. 1 represents a military load 10 according to the invention shown in a longitudinal section, comprising a splinter generator intended to form the metal chips under the effect of the explosion of the explosive, that is to say under the combined effect of the shock wave created by the explosion and the pressure of the decomposition gases exerted. The chip generator 1 is metallic and pre-fragmentation. It has a tubular shape extending longitudinally along a longitudinal axis x.

The tubular form, and the explosive E are symmetrical of revolution about the longitudinal axis x. The chip generator 1 has a thickness e which can be fixed or variable along the longitudinal axis and around the longitudinal axis x.

Depending on the shape that one wants to give the sheaf of chips, the generator 1 may have a cylindrical shape as shown in Figure 1 or concave or convex

The chip generator 1 is made of a metal material which is a metal or a metal alloy. For example, steel, cast iron, aluminum or tungsten can be used.

The chip generator 1 is delimited by two longitudinal faces 2, 3 extending longitudinally along the longitudinal axis x. These longitudinal faces 2, 3 comprise an inner face 2 facing the explosive and an outer face 3 facing outwardly 4 of the load 10. The inner face 2 is the longitudinal face which has the lowest average radius among the two longitudinal faces 2, 3.

A flange 5 is attached to each end of the generator 1. The explosive charge E is surrounded by the chip generator 1. In other words, the inner face 2 and the flanges 5 delimit an interior volume 8 within which the explosive E is confined. The explosive E has a break that is adapted to cause, under the combined effect of the shock wave created by the explosion and the pressure of the decomposition gases exerted on the inner face of the cylinder, the rupture of the chip generator 1 and the propulsion of the chips.

The internal volume 8 also comprises means for firing the explosive or priming means 9. These firing means can also be deported outside the volume defined by the tube.

As shown in Figures 1 and 2, the chip generator according to the invention consists of a closed cellular structure forming said chips breaking under the effect of the explosion. Closed cellular structure is understood to mean a honeycomb structure which delimits inside it closed internal cavities 13. By closed internal cavity is meant a cavity which communicates neither with the other internal cavities nor with the outside of the structure. These internal closed cavities 13 are delimited by all-metal envelopes 14 which are entirely located at a distance from the longitudinal faces 2, 3. Envelope means the surface delimiting a cavity. In other words, these internal cavities 13 do not open on the longitudinal faces 2, 3 nor on the unnumbered transverse faces and facing the flanges 5. The cavities and their envelopes are at a distance from these faces.

Moreover, the cavities are arranged in a reproducible manner, that is to say in a controlled manner. In other words, the generator has an internal porosity whose value and arrangement are controlled.

The internal cavities 13 weaken the chip generator 1. They facilitate its rupture when it is subjected to the combined effects of the shock wave and the pressure of the decomposition gases on its internal face since the chip generator 1 is thinned near the envelopes of these internal cavities.

In addition, the internal cavities also have a function of breaking initiation during the fragmentation phase. Breakthrough initiation means a place where a crack will occasionally be initiated when the chip generator is subjected to a tensile stress or expansion caused by the explosion of the explosive. Cracks initiated at adjacent cavities will spread, meet. Their meeting draws the contours of the fragments and leads to the rupture of the generator of splinters and the generation of splinters. By arranging the incipient fractures within the tube itself at a distance from the longitudinal walls of the tube, that is to say by embedding the internal cavities 13 in the chip generator, it is possible to obtain chips which have a thickness less than that of the tube.

This characteristic makes it possible to choose the thickness of the fragments by an appropriate arrangement of the internal cavities. It allows to obtain several chips calibrated on the thickness of the generator.

It also makes it possible to obtain a less random fragmentation than that of a generator of the prior art of the same thickness. Indeed, the fragmentation of a generator on a smaller thickness (that is to say on a portion of the thickness of the generator) is easier and is done according to better controlled lines.

As the chips have a thickness less than that of the generator, these chips have a smaller size than the chips generated by a structure having identical dimensions and grooves on one of its longitudinal faces. This has the effect of increasing the number of splinters generated and thus improve the flow of chips.

Furthermore, the chips from a chip generator of a load according to the invention have mastered calibres. The size of the future chips and their number depend on the arrangement, the size and the shape of the cavities within the chip generator that are controlled. It is therefore possible to obtain chips having different sizes and in different numbers depending on the choice of these parameters. It should be known that the control of the distribution of the calibres of the fragments obtained according to the target which is assigned to the load is an essential parameter of the efficiency of the load.

The invention also makes it possible to considerably increase the number and size of chips that can be obtained with respect to those that can be obtained from a chip generator of the prior art realized in the form of a tube having identical dimensions, in particular an identical thickness. This advantage is obtained in a simple manner without complicating the structure of the chip generator. The proposed solution does not require the provision of means to assemble rigidly several tubes on the thickness of the chip generator. It also makes it possible to obtain chips having different thicknesses on the circumference but also on the height of the tube.

In the example shown in Figures 1 and 2, the internal cavities 13 are arranged in a regular manner within the honeycomb structure so as to generate chips of the same caliber.

There are several types of regular layouts. An example is given in Figures 1 and 2. As shown in Figures 1 and 2, the inner cavities 13 advantageously but not necessarily the same shape and the same dimensions which allows to promote the homogeneity of templates and shapes of splinters to come. The regularity of the arrangement of the cavities and the homogeneity of the configuration of the cavities also make it possible to facilitate the production of the chip generator.

However, with an additive manufacturing process it is possible to realize irregular cavities in a complex way if the mission requires it.

Advantageously, the chip generator 1 comprises a plurality of arrays of rows of internal cavities 13 distributed over its thickness e. The cavities of the same row are spaced in the longitudinal direction with a curvature identical to the curvature of the inner faces 2 and outer 3. The rows of the same network are distributed over the circumference of the tube. They are spaced along the circumference of the tube, the networks being spaced according to the thickness of the tube.

In the embodiment of FIGS. 1 and 2, the chip generator 1 comprises two arrays 13b, 13c of rows 13a of internal cavities 13. The arrays 13a of the same array 13b or 13c extend according to different generators of the same cylinder d or respectively c2 whose axis is the longitudinal axis x. The internal cavities 13 forming a row 13a are spaced in the longitudinal direction of the cylinder. The internal cavities 13 are advantageously regularly spaced along the longitudinal axis of the cylinder over the entire length thereof. And the rows 13a of the same network 13b or 13c are regularly spaced on the circumference of the cylinder. In addition, the rows of arrays are spaced apart over the thickness of the tube so as to generate chips having substantially the same thickness. This regular arrangement makes it possible to obtain a regular rupture of the chip generator during the explosion with pieces of the same caliber.

In a variant, the generator comprises a single array of rows of internal cavities 13 over its thickness e. The greater the number of networks, the more the thickness of the chips relative to the thickness of the tube is reduced.

This type of structure can be obtained by additive manufacturing. Additive manufacturing is defined as an assembly process for making three-dimensional objects from three-dimensional models by depositing one or more layer-by-layer materials in opposition to subtractive fabrication such as machining or cutting.

The invention also relates to a method of manufacturing an explosive charge according to the invention.

A flow chart of the process steps is shown in FIG. 4. This process comprises a step 50 for manufacturing the honeycomb structure (or honeycomb structures) of chips.

It also comprises a step 51 consisting in inserting the explosive E and possibly the priming means 9 in the interior volume 8 delimited by the cylinder so that the chip generator 1 has a longitudinal inner face 2 facing towards the explosive E and a longitudinal outer face 3 facing outwardly 4 of the load 10.

The step 50 of manufacturing the honeycomb structure can be performed by additive manufacturing.

It then comprises, as visible in FIG. 5, a step 60 for modeling the geometry of the desired structure consisting in three-dimensionally modeling the shape and the dimensions of the chip generator 1 as well as the shapes, the dimensions and the arrangement of the cavities within the structure.

This step is conventionally performed by computer-aided design or CAD.

The manufacturing method comprises a step 61 of making each metal structure 1 as such in which the piece is made by metal deposition in successive layers on a substrate to from a metal powder that is heated by means of a laser to fuse or sinter the metal powder outside the areas intended to form the cavities of the structure so as to obtain a structure having the desired geometry that was previously defined.

The melting or sintering can be carried out before or after the deposition of each layer.

The metal powder is a powder of the material forming the chip generator 1.

The step of producing the chip generator can be implemented in different ways. It can be carried out by direct additive laser (CLAD) or DLMS, an acronym for the term "Direct Laser Metal Sintering", consisting of fusing metal powders injected coaxially with a laser beam to produce metal deposits in successive layers. . It can be performed by selective sintering by laser or SLS (acronym for the English expression "selective laser sintering"). It can also be performed by selective laser melting SLM (acronym for the English expression "selective laser melting").

Additive manufacturing makes it possible to produce a chip generator integrating cavities of various sizes and / or shapes, controlled and reproducible according to very diverse, controlled and reproducible arrangements defined by modeling. The shapes and arrangement of the internal cavities may be chosen to generate chips of different sizes depending on the targets that are assigned to the load.

The closed cavities may contain metal powder, especially when the melting or sintering of the powder of a metal layer is carried out after the deposition of the metal powder layer.

Advantageously, the method comprises a step of removing the powder disposed in the cavities or at the places intended to form the cavities after the melting or the sintering of the successive layers. In this case, the internal cavities are filled with gas.

The process shown in Figure 5 does not exhibit this removal step. The cavities obtained by this process house metal powder. However, the apparent density of the metal powder is lower than that of the fused metal powder. During the explosion, there is thus finds multiple reflections of the shock wave produced by the explosion which promotes the fragmentation of the chip generator.

Advantageously, the honeycomb structure is configured so that its fragmentation, under the effect of the explosion of the explosive is initiated at predetermined locations envelopes delimiting said internal cavities. This makes it possible to better control the fragmentation and therefore the number and size of the chips to come.

Advantageously, the structure 1 comprises envelopes comprising at least one salient angle. It is at the level of the salient angles that the cracks are in fact firstly initiated. The projecting angles constitute breakaway primers. They also determine the direction in which the crack propagates. This propagates in fact globally perpendicular to the salient angle.

Advantageously, the structure comprises envelopes having a stop and / or a vertex. The ridges and summits have indeed a function of initiation of rupture.

Advantageously, as shown in FIG. 3, the structure of FIG. 2 comprises closed internal cavities 13 having a cubic shape. In general, the structure advantageously has cavities (open and / or closed) polyhedral. Thus their envelopes have salient angles.

The cracks initiated by the cubic cavities are on diagonal cubes. It can therefore be expected that the cracks initiated in the structure of FIG. 2 extend in the directions shown in FIG.

The cavities may have all kinds of polyhedral shapes such as, for example, a hexagonal diamond or parallelepipedic shape. The greater the number of faces of the polyhedron, the greater the fracture of the structure is favored and the number of initiated crack initiation is important which multiplies the number of future chips and decreases their mass.

Advantageously, the chip generator 1 is monoblock. It consists of a closed honeycomb structure that forms the metal chips breaking under the effect of the explosion. This embodiment presents the advantage of being simple to implement, inexpensive and allow to perform connection functions with other elements of the projectile in which is included the load subject to a particular arrangement.

In a variant, it comprises several closed cellular structures that form the chips by breaking under the effect of the explosion. It is advantageously constituted by a plurality of individual closed cellular honeycomb structures. These structures are assembled to form a tubular structure. The generator is, for example, consisting of a stack of rings in the longitudinal direction.

Advantageously, the chip generator is arranged to be rigid.

Advantageously, each cellular structure constituting the generator is rigid. The rigidity of the generator allows it to resume the forces applied to the load along the longitudinal axis without breaking. It avoids having to install stiffening means that would be causing additional chips that would not have the same size as the chips from the chip generator as claimed such as ferrules. The generator according to the invention is advantageously constituted by at least one closed cellular structure and without ferrules.

In the embodiment of Figure 1, the inner faces 2 and outer 3 of the chip generator 1 are metal walls. These surfaces are smooth.

In a variant, as visible in FIG. 7, the inner face 2 and / or the outer face 3 of the chip generator 1 is a solid metal wall provided with grooves and / or cavities 17 or hollow opening towards the explosive and / or or respectively to the outside of the tube. These grooves and / or cavities have functions of breaking initiation. They are arranged and configured to promote initiation and propagation of cracks in predetermined directions. These cavities advantageously have notches shapes with projecting angles or parallelepiped cavities.

Claims

A military load (10) comprising an explosive (E), firing means (9) and a metal chip generator (1) in the form of a tube defined by two longitudinal faces (2, 3), said tube surrounding the explosive (E), said chip generator (1) being intended to rupture under the effect of the explosion of the explosive to form said chips, characterized in that the chip generator (1 ) comprises at least one closed cellular structure which delimits therein an array of internally closed cavities (13) arranged in a reproducible manner, the closed cellular structure forming said chips by breaking under the effect of the explosion, and in that the closed internal cavities comprise a plurality of arrays (13b, 13c) of rows (13a) of closed internal cavities distributed over the thickness of the chip generator.

Military load according to the preceding claim, wherein for each network (13b, 13c) of rows (13a) of closed internal cavities, said rows (13a) are distributed over the circumference of the tube.

Military load according to the preceding claim, wherein, said rows (13a) of a network (13b, 13c) extend according to different generatrices of the same cylinder.

A military load according to any one of the preceding claims, wherein the internal cavities are arranged within the chip generator so as to generate chips of the same size.

A military load according to any one of the preceding claims, wherein the cellular structure is configured such that its rupture under the effect of the explosion of the explosive is initiated preferentially at predetermined locations of said envelopes (14).

6. Military load according to any one of the preceding claims, wherein the cellular structure comprises envelopes comprising at least one salient angle constituting a breaking primer.

7. Military load according to the preceding claim, wherein the cellular structure comprises envelopes comprising at least one edge and / or at least one vertex and / or polyhedral envelopes.

8. Military load according to any one of the preceding claims, wherein the generator comprises at least one solid longitudinal metal face provided with grooves and / or cavities.

9. Military load according to any one of the preceding claims, wherein the chip generator and monobloc.

A military load according to any one of the preceding claims, wherein the closed cellular structure is rigid.

1 1. A method of manufacturing a military load according to any one of the preceding claims, comprising a step of producing the closed honeycomb structure by additive manufacturing.

12. A method of manufacturing a military load according to the preceding claim, comprising:

a step (60) for modeling the geometry of the closed cellular structure consisting in three-dimensionally modeling the shape and dimensions of the structure as well as the shapes, the dimensions and the arrangement of the cavities within the chip generator ,

a step (61) for producing the closed cellular structure by metal deposition in successive layers on a substrate from a metal powder which is heated by means of a laser to fuse or sinter the metal powder by outside the areas intended to form the cavities of the structure so as to obtain a structure having said geometry.