EP0494469B1 - Method of assembling a hollow charge - Google Patents

Abstract

A shaped-charge round has a precision explosive charge (12) which is surrounded on one hand externally by a metallic sleeve (11) and, on the other hand, is clad internally with an insert (13). During assembly, there is a risk that gaps, cavities or cracks between the three parts (11, 12, 13) may occur as a result of thermal expansion. This is avoided in that the precision explosive charge (12) is first cooled, the sleeve (11) is heated and the precision explosive charge (12) is inserted into the sleeve (11), in that the surrounded precision explosive charge (12) is subsequently heated, the insert (13) is cooled and the insert is pressed into the precision explosive charge (12). The parts (11, 12, 13) assembled in this way, are brought to room temperature. <IMAGE>

Description

The invention relates to a method for assembling a shaped charge containing a precision explosive charge, a metallic shell and an insert, wherein at least the precision explosive charge is cooled and introduced into the metallic shell using the thermal expansion of the parts mentioned, and application of the method and shaped charge produced thereafter.

The above-mentioned inlays, also called liners, serve to form beams in shaped charges.

It is an assembly process, i.e. to assemble a shaped charge known (DE -C-3 434 847), in which the lining and the explosive charge are resiliently pressed together. When assembling according to this DE -C 34 34 847, the explosive charge is reduced to the lowest operating temperature. cooled down to at least minus 40 ° C and the explosives, insert and other constituents, which are in the supercooled state, are simultaneously inserted into the heated or normal temperature casing and a ring is flanged. When the whole is subsequently heated to normal temperature, the charge is forcibly clamped in the shell.

Although this method avoids gaps between the shell and the explosive charge, no measures are provided to reliably avoid gaps between the explosive charge and the lining, especially if the latter is not exactly conical.

It is also known to pressurize a body of an explosive mixture of hexogen and TNT into a Press the mold, cool it and then heat the lining to 85 ° C to 95 ° C and press it into the cavity of the body while cooling (DE-A-3 236 706). There are air pockets between the body and the insert prevented, however, the entire lining cannot be heated due to the risk of detonation in the laboratory. Air gaps between the lining and the body can therefore hardly be avoided.

Another method for producing shaped charge projectiles is known, the explosive charge being pre-pressed and cooled to -30 ° C. (FR -A-2 563 517). The explosive charge, together with its lining, is pressed into the shell under high pressure at ambient temperature. A fastening ring is then screwed into it, which fixes the lining with a force fit. After the temperature equalization, there are high mechanical tensions inside the floor, which act on the individual components.

In the known methods, the explosive charge is pressed in on one side when the ammunition is processed under pressure. Although the risks involved in the manufacture of the projectiles are considerably lower than in the FR-A-2 563 517 process, the projectile casing must have a wall which is strong enough to be able to withstand the forces which occur during the pressing. Experience has shown that only shell casings that are relatively thick-walled and often tend to form fragments can be used. Under no circumstances can projectiles for missiles and missile projectiles be produced using the above method, since the wall of such projectiles in particular is to be made as thin as possible for reasons of weight.

The usual materials of these three components - precision explosive charge, metallic shell and lining - mostly have different values with regard to modulus of elasticity, Poisson's ratio and thermal expansion coefficient. A light metal alloy or steel is usually used for the metallic shell, copper is suitable for the lining, and the explosive charge is made from the HMX (octogen) or RDX (hexogen) designated plastic or wax-bound explosives.

The invention has for its object to provide a method that ensures a crack and gap-free assembly of a precision explosive charge with an outer thin-walled metallic shell and an inner shaped charge lining.

The precision explosive charge can only be fully effective if it is enclosed on both sides by the casing and the lining without any space, this requirement should be met at a temperature range of -35 ° C to + 63 ° C. Since the temperature behavior of the materials mentioned is different, there is a risk of gaps or gaps that must be avoided.

This object is achieved in that the method has the features in the characterizing part of claim 1.

In this method, it is advantageous, according to claim 3, that the thermal expansion coefficient of the explosive in the whole or at least in the upper part of the required temperature range exceeds the thermal expansion coefficient of the lining and the casing.

In this method, it is advantageous, according to claim 4, that the thermal expansion coefficient of the explosive is the same in the whole or at least in the upper part of the required temperature range as the thermal expansion coefficient of the lining and the casing.

The precision explosive charge, according to claim 5, should be inserted into the casing without tension in order to improve the quality of the projectile.

It is also desirable that the shape of the liner be adapted to the process.

The method has the great advantage that even in the event of temperature fluctuations in the temperature range intended for use, there are no cracks due to tensile stresses in the precision explosive charge, thereby avoiding gaps or voids between the shell, explosive charge and lining.

The invention is also based on the object of specifying a method which ensures an air gap-free fit between the explosive charge and the projectile casing at operating temperatures of the ammunition from -35 ° C to + 63 ° C, and in particular also when the projectile casing is designed so light that it may not be pressed or re-pressed for reasons of strength. At the same time, the object of the invention is to provide a particularly light ammunition body which can be produced using this new method.

Preferably, according to claim 2, the pressed, dimensionally and dimensionally accurate explosive charge is cooled to a temperature of -50 ° C to -100 ° C and the metallic shell is heated to a temperature of + 50 ° C to + 80 ° C, then the jacketed precision explosive charge is warmed up to an intermediate temperature of -15 ° C to -35 ° C, at which the thermal expansion coefficients of the explosive and the metallic shell are the same and the lining is cooled to a temperature of -50 ° C to -100 ° C .

The invention has the enormous advantage that light projectiles can now be produced in very large batches without air pockets. Even the greater dangers in the laboratory, such as premature detonations, can hardly be feared.

It is particularly advantageous in connection with the method according to the invention if the precision explosive charge according to claim 6 is pressed isostatically according to CH-PS 673 704, since this results in a very homogeneous, texture-free, shape and dimensionally accurate explosive charge body.

In order to achieve a sufficiently homogeneous temperature distribution in the explosive charge, it should be cooled together with its protective cover for 2 hours.

A further advantage is obtained if the explosive charge is covered with a protective cover, so that no frost forms on the load during cooling. This also avoids the problems that would otherwise lead to undesirable water inclusions in the laboratory. The protective cover advantageously consists of a plastic film that does not become brittle at low temperatures.

By pressing, in particular isostatic pressing, the explosive charge is sufficiently strong that it can be machined; Claim 9.

In the case of a shaped charge, according to claim 10, ammunition bodies with a casing made of light metal or of glass fiber or carbon fiber reinforced plastics can be produced particularly well.

Such bullets usually have a very thin wall, practically with a thickness of 1.0 mm to 2.0 mm, and thanks to the method described, they do not pose any problems in their laboratory work.

According to claim 11, nitropenta, hexogen (RDX) with or without trinitrotoluene, or octogen (HMX) with a desensitizing additive such as wax or methyl methacrylate have proven particularly useful as explosives for the precision explosive charge of a shaped charge projectile.

The method can, according to claim 12, be used for the production of thin-walled ammunition bodies for anti-aircraft defense and for missile projectiles.

Further advantages result from the description below. There, the invention is explained in more detail with reference to various examples shown in the accompanying drawings.

Fig. 1 a-i

die einzelnen, grundsätzlichen Verfahrensschritte zur Herstellung eines Munitionskörpers,

Fig. 2

einen Längsschnitt durch ein erstes Ausführungsbeispiel des erfindungsgemäss hergestelltes Hohlladungsgeschoss (einstückiger Sprengkörper) und

Fig. 3

einen Längsschnitt durch ein zweites Ausführungsbeispiel (zusammengesetzter Sprengkörper).

Show it:

Fig. 1 ai

the individual, basic process steps for producing an ammunition body,

Fig. 2

a longitudinal section through a first embodiment of the shaped charge projectile produced according to the invention (one-piece explosive device) and

Fig. 3

a longitudinal section through a second embodiment (assembled explosive device).

The powdered explosive 1 is filled into an elastic mold 2, Fig. 1a. The whole is then placed in an autoclave 4, FIG. 1b and isostatically pressed to the precision explosive charge 3 at a pressure of, for example, 300 MPa, cf. Fig. 1c. The details of the isostatic pressing process can be found in CH-PS 673 704. The compressed explosive charge 3 can be machined if necessary, so that an end shape with very narrow tolerances is obtained, FIG. 1d.

The precision explosive charge 3 is placed in a freezer 6 and cooled to -50 ° C to -100 ° C, preferably -90 ° C, cf. Fig. 1e. In order to prevent the explosive charge 3 from becoming brittle and / or showing cracks, the temperature should not be lower than -100 ° C. Any cracks in the explosive charge 3 reduce the final ballistic performance of the ammunition produced, which must be usable in a temperature range from -35 ° C to + 63 ° C. To cool down, the explosive charge 3 is loosely covered with a protective cover 5 and the seam of the protective cover 5 is sealed. Plastic films which have not proven to become brittle, particularly at low temperatures, have proven to be a protective cover 5.

According to the invention, the residence time in the freezer 6 should be at least 2 hours and is dependent on the charge size. However, a continuous cooling machine can also be used as the freezer 6, the precision explosive charge 3 being slowly moved on a conveyor belt through the tunnel of the machine, i.e. for at least 2 hours. At the same time, the metallic shell 7 is heated in a furnace 8 to a temperature of + 50 ° C to + 80 ° C, preferably + 60 ° C, Fig. 1f.

The protective casing 5 is then removed from the explosive charge 3 and the cold precision explosive charge 3 and the warm projectile casing 7 are immediately labored without tension, i.e. assembled without using any additional components and without external pressure, cf. Fig. 1g. The structure consisting of the explosive charge 3 and the casing 7 is brought to an intermediate temperature, thereby creating an air gap-free press fit between the explosive charge 3 and the metallic projectile casing 7, which remains easily maintained in the prescribed working temperature range from -35 ° C to + 63 ° C. This intermediate temperature depends on the explosive and the shell material used and is usually between -35 ° C and -15 ° C. This intermediate temperature is -31 ° C when the octogen, which has been desensitized with methyl methacrylate, is used as the explosive and the Perunal as the shell material.

Then the lining 9, cooled to -50 ° C. to -100 ° C., preferably -80 ° C., is inserted into the explosive charge 3, 1h and 1i. This last operation is carried out under slight pressure, so that an air gap-free fit is created between the explosive charge and the shell and the lining, which is retained at higher temperatures.

The method described above for the production of ammunition bodies is particularly suitable for the manufacture of projectiles for anti-aircraft defense and of missile projectiles, since particularly explosive explosive charges such as nitropenta, hexogen with or without tinitrotoluene or octogen are used in these.

In such projectiles, primarily light metal sheet, such as aluminum, or glass fiber or carbon fiber reinforced plastics are used. The wall of the metallic shell 7 is between 1.0 and 2.0 mm, preferably about 1.5 mm.

The two practical exemplary embodiments, FIGS. 2 and 3, differ from one another by the additional elements present in FIG. 3, a transfer charge and a barrier, as will be explained in more detail below.

According to FIG. 2, the shaped charge bullet 10 produced according to the invention has a housing or a metallic shell 11 in which an explosive device or a precision explosive charge 12 is located. This precision explosive charge 12 is provided with an insert 13 on the inside. The housing or the metallic shell 11 has at one end an internal thread 14 into which a threaded ring 15 is screwed.

According to FIG. 3, in addition to the elements mentioned, in particular the shell 11, the precision explosive charge 12, the insert 13, the threaded ring 15, the shaped charge bullet 10 produced according to the invention also has a transfer charge 16 and a barrier 17. Preferably form the precision explosive charge 12, the barrier 17 and the transfer charge 16 form a single body which is inserted as a whole into the shell 11.

• a) die Präzisionssprengladung 12 abzukühlen
• b) die Hülle 11 zu erwärmen
• c) die abgekühlte Präzisionssprengladung 12 in die erwärmte Hülle 11 einzuführen
• d) die von der Hülle 11 ummantelte Präzisionssprengladung 12 auf Zwischentemperatur zu erwärmen
• e) die Einlage 13 abzukühlen
• f) die abgekühlte Einlage 13 in die Präzisionssprengladung 12 hineinzupassen
• g) das entstandene Gebilde mittels Gewindering anzupressen
• h) die derart zusammengeführten Teile auf irgendeine Umgebungstemperatur innerhalb des Einsatzbereiches zu bringen.

The method according to the invention now consists in:

• a) to cool the precision explosive charge 12
• b) to heat the casing 11
• c) insert the cooled precision explosive charge 12 into the heated casing 11
• d) to heat the explosive charge 12 encased by the envelope 11 to an intermediate temperature
• e) cool the insert 13
• f) to fit the cooled insert 13 into the precision explosive charge 12
• g) to press the resulting structure using a threaded ring
• h) to bring the parts brought together in this way to any ambient temperature within the area of use.

The elements mentioned, in particular the precision explosive charge 12, the metallic shell 11 and the insert or lining 13 are assembled in such a way that no cracks occur in the explosive charge 12 and that on the one hand between the precision explosive charge 12 and the metallic shell 11 and on the other hand between the precision explosive charge 12 and the insert 13 no gaps or gaps arise.

Calculation example

• 1. Calculation approach
  The assembled metallic parts of the shaped charge have dimensions and tolerances that are valid for a temperature of 20 ° C (room temperature).
  The bonds between the explosive device and the metallic parts only allow the transfer of compressive stresses, not tensile and / or shear stresses.
  A firm bond is assumed for the separating surface between insert 13 and threaded ring 15.
  With the separating surface between the insert 13 and the metallic shell 11, freedom from binding and radial freedom from tension are assumed in the axial direction.
• 2. Simulation of thermoelastic processes
• 2.1 Determining the required amount of explosives
  The model defined in the calculation approach is cooled to the temperature at which the thermal expansion numbers of the explosive and the metallic shell are the same (at approx. -30 ° C).
  The resulting gaps between the explosive device 3 and the metallic shell 7 or lining 9 are filled with explosives in such a way that there is pressure-free contact at the intermediate temperature of approximately -30 ° C.
  The model corrected at approx. -30 ° C is further cooled down to the minimum operating temperature (-35 ° C). Any gaps that arise are also filled with explosives.
  The shaped charge thus defined is warmed up to 20 ° C (room temperature).
• 2.2 Determination of the mechanically machined outline of the explosive charge
  The practical outline of the explosive charge 3 is determined from the above simulation by removing the metallic parts of the shaped charge, such as the shell 7 and the lining 9.
  The manufacturing tolerances at 20 ° C of both the explosive charge and the metallic parts should be taken into account, which leads to a small excess of the explosive to be machined.
• 2.3 Determination of the compressive stress in the explosive device and in the metallic shell
  The stress distribution, in particular the distribution of the pressures on the explosive device and shell, are determined at the maximum operating temperature (+ 63 ° C). The dimensional deviations are set to zero and the resulting stresses or pressures are calculated according to VON MISES.
  It should be noted that the compressed explosive charge does not deform plastically if the stresses or pressures in the explosive do not exceed the pressure.
• 3. Numerical example
  The numerical calculation of a shaped charge of caliber 120 mm was carried out with the finite element program ABAQUS (trading program by the company HIBIT, KARLSSON & SORENSON, Inc., Providence, Rhode Island, USA).
  The following thermoelastic parameters were used
  • for the explosives, octogen phlegmatized with methyl methacrylate:
    The electricity module E _s = 1,200 N / mm², constant in the relevant temperature range.
    The POISSON number = 0.1
    The coefficient of thermal expansion α _s , function of temperature, is represented by a third degree polynomial
    
    ${\text{α}}_{\text{s}}{\text{= (4.08 + 0.0625Θ + 0.00028Θ² - 0.00000104Θ³) x10⁻⁵ 1 /}}^{\text{O}}\text{K}$
    
    
    
    
  • for a light metal cover made of ASTM 7'075 alloy:
    The elastic modulus E _h = 70,000 N / mm², constant in the relevant temperature range.
    The POISSON number = 0.3
    The coefficient of thermal expansion α _h = 2.36x10⁻⁵ 1 / ^o K, constant in the relevant temperature range.
  • For the lining made of pure electrolytic copper:
    The modulus of elasticity E _Cu = 125,000 N / mm², constant in the relevant temperature range.
    The POISSON number = 0.3
    The coefficient of thermal expansion α _Cu = 1.9x10⁻⁵ 1 / ^o K, constant in the relevant temperature range.
    The calculation resulted in a maximum dimensional deviation of 0.12 mm for the lining base. Here the thickness of the explosive charge is 2 mm (measured radially) and that of the metallic shell is 1 mm.
    However, the highest three-dimensional compressive stress that occurs in the explosive charge lies at the lining tip and is
    
    $\text{2.43 N / mm²}$
    
    
    
    calculated by VON MISES. This value is below the pressure at which the explosive charge was compressed (approx. 200 N / mm²). The maximum stress on the shell occurs at a maximum temperature of 63 ° C, a corresponding three-dimensional stress is
    
    $\text{110 N / mm²}$
    
    
    
    and is still in the elastic range of the aluminum alloy.

• a) ein riss- und spaltfreies Zusammenbauen einer Präzisionssprengladung mit einer äusseren, dünnwandigen Hülle und einer inneren Hohlladungsauskleidung und
• b) bei Einsatztemperaturen der Munition von -35°C bis +63°C einen luftspaltlosen Sitz zwischen Sprengladung und Geschosshülle

zu gewährleisten, absolut exakt gelöst werden können. Somit zeigt das Berechnungsbeispiel, dass sowohl bei sehr tiefen als auch bei sehr hohen Temperaturen keine Risse oder Spalten im erfindungsgemäss hergestellten Hohlladungsgeschoss auftreten werden und somit auch die geforderte Qualität des Geschosses gewährleistet ist.This calculation example shows that the two tasks set out at the beginning, namely:

• a) a crack and gap-free assembly of a precision explosive charge with an outer, thin-walled shell and an inner shaped charge lining and
• b) at ammunition operating temperatures from -35 ° C to + 63 ° C an air gap-free seat between the explosive charge and the shell

to ensure can be solved absolutely precisely. The calculation example thus shows that there are no cracks or gaps at very low or very high temperatures will occur in the shaped charge storey produced in accordance with the invention and thus the required quality of the storey is guaranteed.

Claims (12)

1. Method for the fissure-free assembly of a hollow charge projectile, taking account of the various coefficients of thermal expansion of the precision explosive charge (12), metallic casing (11) and insert (13) through the introduction of the precision explosive charge (12) and insert (13), which are in the supercooled state, into a casing (11) which has been heated or is at normal temperature, characterised in

   - that first the pressed precision explosive charge (12), which is of a precise shape and mass, is cooled, the metallic casing (11) is heated and the precision explosive charge (12) is introduced into the metallic casing (11) in a stress-free manner,

   - that the sheathed precision explosive charge (12) is then heated, the insert (13) is cooled and the insert (13) is pressed axially and fixed into the sheathed precision explosive charge (12) in a friction-tight manner,

   - that the thus assembled parts (11, 12, 13) are then brought to any ambient temperature.
2. Method according to claim 1, characterised in that the pressed precision explosive charge (12), which is of a precise shape and mass, is cooled to a temperature of -50 °C to -100 °C, and that the metallic casing (11) is heated to a temperature of +50 °C to +80 °C, that the sheathed precision explosive charge is then heated to -35 °C to -15 °C and the insert is cooled to a temperature of -50 °C to -100 °C.
3. Method according to claim 1, characterised in that the coefficient of thermal expansion of the explosive (12) in all or at least in the upper portion of the required temperature range exceeds the coefficient of thermal expansion of the insert (13) and of the casing (11).
4. Method according to claim 1, characterised in that the coefficient of thermal expansion of the explosive (12) in all or at least in the upper portion of the required temperature range is the same as the coefficient of thermal expansion of the lining (13) and of the casing (11).
5. Method according to claim 1, characterised in that the precision explosive charge (12) is introduced into the casing (11) in a stress-free manner.
6. Method of introducing a precision explosive charge into a metallic casing according to claim 5, characterised in that the precision explosive charge (12) is pressed and/or isostatically pressed.
7. Method of introducing a precision explosive charge into a metallic casing according to claim 5 or 6, characterised in that the precision explosive charge (12) is cooled for at least 2 hours.
8. Method of introducing a precision explosive charge into a metallic casing according to claim 7, characterised in that the precision explosive charge (12, 3) is enclosed by a protective casing (5) during the cooling.
9. Method according to one of the preceding claims, characterised in that the shapes and dimensions of the precision explosive charge (12) are obtained, at least partly, by machining.
10. Hollow charge projectile produced using the method according to claim 1, characterised in that the casing (7, 11) of the thin-walled ammunition body consists of a light metal, such as an aluminium or magnesium alloy, or of a plastic reinforced with glass fibre or carbon fibre.
11. Hollow charge projectile produced using the method according to claim 1, characterised in that the precision explosive charge (3, 12) of the thin-walled ammunition body consists of nitropenta, hexogen with or without trinitrotoluene, or octogen with a phlegmatising additive, such as wax or plastic, such as methylmetacrylate.
12. Use of the method according to one of claims 1 to 9 for producing thin-walled ammunition bodies for anti-aircraft defence and for rocket projectiles.

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