Super compressed detonation method and device to effect such detonation

Abstract

 A method and apparatus (20) for high pressure compression of materials and for detonation of the compressed material by cylindrical implosion followed by an axial detonation to a detonation velocity several times that of TNT and a detonation pressure in excess of ten times that of TNT. The device provides a conical metal flyer shell (5) within which is disposed a cylindrical anvil (10) surrounded by explosive (7). The anvil (10) retains a sample material (11) to be compressed and detonated. A first detonation of explosive by impact of the flyer shell (5) generates a reverberating oblique shock wave system for sample compression. Axial detonation of the compressed sample (11) through any length of a sample (11) is achieved following the principal of matching the axial velocity and compression time of the oblique shock wave system to the detonation rate and induction delay time of the compressed sample (11). The method and apparatus (20) are also applicable to enhancing the effect of anti-armour and anti-hard-target munitions. The apparatus is also applicable to inert sample compression to the megabar range without using the axial detonation.

Description

Field of the invention

[0001] The present invention relates to super compressed detonation and more particularly, the present invention relates to detonation of super-compressed materials to alter the physicochemical and detonation properties and a device to effect this result.

Prior art

[0002] In the most general sense, the effectiveness of munitions that involve detonation of explosive materials largely depends on the detonation velocity and pressure in the explosion phase of the detonation.

[0003] Existing technologies deliver detonation velocities and pressures in the range of a few kilometres per second and several hundred kilobars, respectively. A panoply of efforts have been purported to amplify these parameters by physically modifying explosive material by compression.

[0004] Exemplary of the techniques having been established include the use of diamond anvil technology for the compression of molecular solid hydrogen above 3 megabars. The process was useful in terms of generating a significant density increase and phase transformations. This work was further augmented by others where solid nitrogen was compressed into the megabar range where it was then observed to provide a semi-conducting polymeric phase. Two-stage light gas gun technology has been employed as an alternative approach to pursue compression of liquid hydrogen into the megabar range where the hydrogen becomes conductive. These techniques are limited to the observation of very small samples in several to tens of micrometers at megabar pressures.

[0005] In terms of the parallel contemporary progress in this field, compression of large samples has been achieved most recently using explosive based cylindrical methods, one method of which employs magnetic flux and explosive implosion. These processes, when unified, have also produced extremely high pressures in materials.

[0006] It was subsequently discovered that a cylindrical metal liner could be imploded by an explosive to compress the magnetic flux in the annular gap between a liner and sample tube. It was determined that by increasing the magnetic field, the metal sample tube was compressed which, in turn, isentropically compressed the hydrogen fluid contained in the sample tube. Radiography was employed to determine diameter changes and by this technology, it was observed that the hydrogen density was increased fourteen-fold. Further compression systems employing cylindrical explosive implosion devices without magnetic flux have also advanced the art.

[0007] One of the most common features to such arrangement is that the implosion generally occurs simultaneously along the length of the sample and is driven by a converging detonation wave propagating at a direction normal to and toward the axis.

[0008] In contrast, other conducted studies of cylindrical implosion of a sample have been set forth in which a Chapman-Jouguet (CJ) detonation propagating through an explosive parallel to the axis compresses the sample in an axially sequential fashion. When these latter implosion systems are compared with those driven by radially propagating detonation, they are found to be easier to implement, but result in lower compression. Between the two limits of an explosive detonation propagating normally to the axis and that propagating parallel to the axis, there exist cylindrical compression systems driven by oblique explosive detonation propagating at an angle to the axis as discussed by Zerwekh et al. (Zerwekh, W.D., March, S.P. and Tan T.-H., AIP Conference Proceedings 309:1877-1880, 1994). They developed a phased shock tube system, in which a cylindrical steel flyer was explosively propelled inward and impinged on a conical aluminum-phasing lens. This initiated an oblique detonation wave in a cylindrical shell of high explosive and resulted in a Mach disk shock propagating in an axial cylinder of foamed polystyrene sample. The device functioned like a shock tube and the Mach disk shock created has been employed to propel a 1.5 mm thick steel disk above 10 km/s. Recently, Carton et al. employed a two-layer explosive configuration to obtain an oblique detonation wave, whose angle is determined by the ratio of the fast detonation velocity of the outer explosive over the slow detonation velocity of the inner explosive (Carton, E.P., Verbeek, H.J, Stuivinga, M. and Schoomnan, J., J. Appl. Phys. 81:3038-3045, 1997). This device has been used for dynamic compaction of powders and the axial compaction wave velocity is limited to the CJ detonation velocity of the outer explosive.

[0009] In summary, recent high-pressure compression technologies have been successful in achieving pressures of a few megabars in molecular fluids. Compression to these pressure levels results in a super-dense fluid, whose density is several to ten-fold the initial density with structural phase transformations and the onset of metallization characterized by electronic band-gap closing and the presence of atomic particles. While complete metallization of a substance to a metastable, monatomic material remains a difficult challenge for theories and technologies, the achievements to date have shown immense potential for use in critical military applications.

[0010] Explosive implosion compression techniques are more attractive than diamond anvil cells and light gas guns from the points of view of sample size and military applications, taking effectiveness and cost into account. However, the survey of current cylindrical explosive implosion techniques detailed herein previously indicates that these have not been applied to investigations of detonation under conditions of extremely high pressure. Furthermore, the available compression systems have mainly operated in two generic driving modes: explosive converging detonation propagating in a direction normal to and towards the axis, or explosive CJ detonation propagating parallel to the axis.

Summary of the invention

[0011] One object of the present invention is to provide an improved method and device for super-compressing materials to effect physicochemical changes.

[0012] The new method and device enhance detonation properties of super-compressed materials and provide a new method and device to effect anti-armour and anti-hard-target munitions.

[0013] A method for effecting physicochemical transformations in a material using super-compression and detonation, comprising:

providing a material to be compressed;

super-compressing the material by exposure to at least one of a normally or obliquely oriented cylindrical imploding shock wave, generated from a first detonation;

effecting transformations from the super-compression in the material including increasing at least material density, structural transformations and electronic band gap transitions relative to a material unexposed to the super-compression;

exposing the super-compressed material to a second detonation; and

effecting transformations from the second detonation in the material including increasing at least detonation pressure, velocity and energy density relative to a material unexposed to the super-compression and second detonation.

[0014] A method for inducing cylindrical reverberating shock waves for compressing a material exposed thereto is based on a principle referred to as "impedance matching", in which the pressure and particle velocity are conserved across the boundary existing between materials when a shock wave passes from one material to another, and comprises:

providing an explosive-clad conical metal flyer shell with an explosive contained therein and an interior cylindrical metal anvil having a central rod and containing a material to be compressed;

detonating the explosive cladding to accelerate the flyer shell;

detonating the contained explosive by impact from the flyer shell to form imploding shock waves impinging the anvil, where the imploding shock waves can be either normal or oblique, depending on the angle of the flyer shell;

compressing the material by the imploding shock wave transmitted through the anvil wall;

implosion of the shock wave at the central rod;

reflecting a diverging shock wave from the implosion through the material for further compression; and

further reverberating shock waves between the anvil wall and central rod to compress the material to a desired high pressure and density.

[0015] It will be appreciated by those skilled in the art that this technology is clearly transferable to material consolidation and structural transformation that would naturally occur as a result of megabar pressure exposure. It is particularly valuable for diamond formation and could also be used for consolidating different materials under high pressure for the purpose of generating new compositions of matter.

[0016] A further object of one embodiment of the present invention is to provide a method for enhancing detonation properties in a material using detonation in super-compresses materials, comprising:

providing a material to be compressed and to be detonated;

super-compressing the material by an obliquely oriented imploding shock wave, generated from a first detonation, and subsequent reverberating shock waves; and

exposing the compressed material to an axially oriented second detonation.

[0017] By the present technology, a completely new strategy was employed which effectively consists of two sequentially timed events. The events include the cylindrical oblique implosion and subsequent reverberating shocks for material compression and axial detonation of the precompressed material to achieve a detonation velocity several times that of TNT and a detonation pressure more that ten times that of TNT. It has been observed that there is a significant increase in the resident energy in the compressed sample which is a direct consequence of the increased material density coming from the sequential wave impact. It has also been recognized that structural transformations in the material together with the liberation of atomic particles also augment the resident energy, and therefore detonation pressure and velocity.

[0018] It will be appreciated by those skilled in the art that this technology is obviously useful in increasing the effectiveness of munitions that depend on the magnitude of detonation velocity and pressure in the detonation phase of explosive materials. Moreover, this technology is clearly transferable to material consolidation and structural transformation.

[0019] As a feature of the instant technology, one principle developed in this invention is particularly important, namely "velocity-induction matching". In this method, a sample material is exposed to compression by an oblique shock wave system that propagates steadily in the axial direction at any given velocity ranging from several kilometres per second to infinity. In addition, variation of the diameter, wall material and thickness of the sample anvil provides a wide range of time during which the sample material is exposed to the compression by the oblique shock wave system. Thus, the device can be designed in a manner such that the compression time and axial velocity of the oblique shock wave system match the induction delay time and the detonation velocity of the compressed sample material. Since the resultant wave structure is substantially stable and self-organizing, a super-compressed detonation can automatically propagate in any length of sample material.

[0020] Accordingly, the sample material to be compressed and detonated may be selected from materials having a detonation velocity and induction delay time responsive to velocity-induction matching. Suitable examples will be apparent to those skilled in the art.

[0021] A further object of one embodiment of the present invention is to provide a method for maintaining super-compressed detonation in any length of a material using velocity-induction matching, comprising:

providing any length of a material to be compressed and detonated with known detonation velocity and induction delay time under conditions of compression;

providing an explosive-clad conical metal flyer shell with an explosive therein and an interior cylindrical metal anvil having an axis and containing the material;

determining the angle of the flyer shell by matching the axial velocity of an oblique shock wave system to be generated in the material to the detonation velocity of the compressed material;

determining the diameter, wall material and thickness of the anvil by matching the compression time exposed to the oblique shock wave system to the induction delay time of the compressed material;

compressing the material to desired density using the oblique shock wave system generated by reverberation; and

self-initiating and propagating a super-compressed detonation wave following the oblique shock wave system over the entire length of the material.

[0022] Having thus generally described the invention, reference will now be made to the accompanying drawings, illustrating preferred embodiments.

Brief description of the drawings

[0023] 

Figure 1 is a longitudinal cross section of the device in accordance with one embodiment;

Figure 2 is a schematic illustration of the device shown in Figure 1;

Figure 3 is a schematic illustration of the parameters during detonation;

Figure 4 is a schematic illustration of the wave structure parameters;

Figure 5 is a graphical representation of pressure and density as a function of axial position of the compression locus for a given angle of the conical metal flyer shell; and

Figures 6A through 6E are representative of data for pressure and density in the radial direction at various cross-sections within the super-compressed wave structure.

[0024] Similar numerals employed in the text denote similar elements.

Detailed description of the preferred embodiment

[0025] Referring now to Figure 1, numeral 20 globally references the device. The arrangement has a conical metal flyer shell 5, base plate 9 and cone shaped top 3. In use, the device is retained with top 3 in position as depicted.

[0026] The top comprises low density foam and provides sheets of explosive 4, which also clad the flyer shell 5 with the exception of the base plate 9. Mounted at the apex of the top 3 is a detonator 2 secured to the former by holder 1. The device 20 positions a sample holder (discussed herein after) in coaxial relation with the apex of top 3 and consequently detonator 2.

[0027] In greater detail with respect to the sample holder, the holder comprises a metal anvil 10 containing sample material 11. The anvil 10 has a top plug 13 and a bottom plug 14 which locate and retain a centrally disposed rod 12. A centering member 8 ensures coaxial alignment of rod 12 and anvil 10 with top 3 and detonator 2. Sample material 11 is generic such as solid, liquid or powder, etc. In the case of liquid sample material, sealing caps 15 are provided in plug 14.

[0028] Surrounding anvil 10 is high explosive 7, which, in turn, is surrounded by an aluminium casing 6.

[0029] In anti-armour and anti-hard-target applications, bottom plug 14 is replaced by a projectile (not shown).

[0030] In operation, detonator 2 is activated to create a circular wave pattern. The wave propagates through the top 3 and sheets of explosive 4 and through the flyer shell 5. This detonation induces symmetric implosion of the flyer shell 5 to impact casing 6 in a continuous manner with respect to its length from the top to the bottom.

[0031] These activities generate the inception of a normal or oblique detonation wave in high explosive 7, depending on the angle of the conical flyer shell. In super-compressed detonation applications, an oblique detonation wave is required which travels through high explosive 7 resulting in the subsequent transmission of a cylindrical oblique shock wave. This wave is transmitted through the anvil 10 and into the sample for compression of the sample. Implosion of this wave occurs at the rod 12 with reflection of a cylindrical shock wave to the wall of anvil 10. The waves reverberate between the wall and the rod 12 for cyclical compression of the material in anvil 10 to a predetermined density and pressure within a compression zone thickness corresponding to a compression time.

[0032] The wave process will be discussed in connection with Figures 2 and 3. The angle of the flyer shell 5 is selected so that the flyer shell impacts the cylindrical boundary of the high explosive from top to bottom. As discussed previously, an oblique imploding detonation wave is generated and propagates in the explosive with a velocity D₁ at an incident angle Φ to the wall of anvil 10. The oblique detonation wave transmits an oblique shock wave having a front velocity U_s axially along the wall of anvil 10 and into the material in anvil 10. This incident oblique shock wave compresses the material while imploding towards the axis. Implosion at the axis forms a reflected diverging shock wave for further compression.

[0033] As mentioned in the text, when a boundary exists between materials to which are exposed a shock wave, pressure and particle velocity are maintained. This property can be exploited in a process known as "impedance matching", in which the appropriate choice of anvil and central rod materials and component thicknesses, including the high explosive, can result in controlled reverberating shock waves between the sample anvil wall and the central rod that compress the sample to a desired high pressure and density. These multiple dynamic compressions heat the sample quasi-isentropically and result in a final temperature lower than would be achieved by a single shock resulting in the same final pressure. The compression time t_c in which the sample material is compressed to a desired density can be controlled via impedance matching and the selection of thickness of components so that it is sufficiently long to achieve equilibrium, yet does not exceed the induction delay time for a given sample material. The latter is important to avoid premature chemical reactions.

[0034] To achieve a stable detonation in the super-compressed sample material in any length, a critical method called "velocity-induction matching" is developed in this invention and described below. If designing the device for a known sample material such that: (i) the compression time t_c equals the induction delay time ti of the material, and (ii) the shock front velocity U_s equals the energy release velocity U_D of the material at the desired state of compression, a detonation wave can be automatically initiated at the compression time tc and can propagate quasi-steadily with a velocity U_D = U_s. Since the wave structure is quasi-steady and self-organizing, the resultant super-compressed detonation wave can propagate in any desired length of sample material. The structure of the quasi-steady, super-compressed detonation wave is illustrated in Figure 4, for which the following relations are obeyed:





where U_s, is axial velocity of the oblique shock front at the sample periphery;

D₁, is high explosive detonation velocity;

ϕ, wave incident angle with respect to the axis;

L_C, thickness of the compression zone;

t_C, compression time;

t_I, the induction delay time; and

U_D, detonation velocity in the super-compressed sample material.

[0035] Shock front velocity U_s can be matched to the detonation wave velocity U_D for a given material by selection of a value for the angle of the conical flyer shell 5. This is the case because, by increasing the angle of the flyer shell, the shock front velocity U_s can be varied continuously from a value just above the CJ detonation velocity of the high explosive to infinity. The latter situation corresponds to the normal cylindrical implosion in which the detonation wave in the high explosive propagates in the normal direction towards the axis. Within the range of conical angles between zero degree and the value which gives a normal cylindrical implosion, there exists a unique solution for the shock front velocity U_s for a given angle of the conical flyer shell. Matching the compression time tc to the induction delay time t_I for a given test material can be done by changing the compression time via the impedance matching and the selection of specific thickness of the device components, and also by changing the induction delay time via the addition of chemical additives that can alter the material sensitivity.

[0036] Figure 5 is a graphical representation of sample material pressure and density as a function of axial position of the compression locus for a given angle of the conical flyer shell.

[0037] Axial propagation history of the sample material density and pressure were obtained experimentally and averaged over the cross-section of the maximum compression locus. The density was obtained from X-ray radiographs by measuring the change in the internal diameter of the sample anvil. For this purpose, the volume change caused by the increase in the sample anvil length was neglected. In the experiments, sample anvil length variations did not exceed 4%. Having obtained the densities, the corresponding pressures were calculated according to the known experimental double-shocked equation of state for the sample material.

[0038] Figure 5 indicates that the quasi-steady wave structure is established after an initial axial propagation distance of 3 to 4 cm, after which the maximum compression is achieved resulting in three times the initial density and a pressure of 1.24 megabars. Detailed measurements of the pressure and density profiles in the super-compressed wave structure would be considerably difficult and expensive using currently available diagnostic methods.

[0039] Figures 6A through 6E display numerically calculated pressure and density profiles in the radial direction at four cross sections corresponding to axial distances of x = 2.2 cm, 3.7 cm, 4.2 cm and 4.7 cm, where x = 0 refers to the cross-section at which the oblique shock front enters the sample material. These profiles clearly indicate the reverberating oblique waves between the central rod and the wall of the sample anvil. When the reflected shock wave off the central rod approaches the anvil wall, the maximum compression is achieved. The pressure and density profiles remain relatively uniform in the radial direction following the point of maximum compression.

Claims

1. A method for effecting physicochemical transformations in a material using super-compressed detonation, characterized in that the method comprises the steps of:

providing a material to be compressed;

super-compressing said material by exposure to at least one of a normally or obliquely oriented cylindrical imploding shock wave, generated from a first detonation;

effecting transformations from said super-compression in said material including increasing at least material density, structural transformations and electronic band gap transitions relative to a material unexposed to super-compression;

exposing super-compressed material to a second detonation; and

effecting transformations from the second detonation in the material including increasing at least detonation pressure, velocity and energy density relative to a material unexposed to the super-compression and second detonation.

2. The method as set forth in claim 1, characterized in that said method further includes the step of exposing compressed material from said first detonation to reverberating shock waves from said first detonation.

3. The method as set forth in claim 2, characterized in that said material exposed to said imploding shock wave and subsequent reverberating shock waves is compressed to a pressure of between one and ten megabars.

4. The method as set forth in claim 2, characterized in that detonation of said super-compressed material results in a detonation velocity more than three times that of TNT and a detonation pressure greater than ten times the detonation pressure of TNT.

5. The method as set forth in claim 1, characterized in that said first detonation and said second detonation are sequential.

6. The method as set forth in claim 1, characterized in that said first detonation, when an oblique imploding detonation wave, results in an oblique shock wave being transmitted through said material to be compressed.

7. The method as set forth in claim 6, characterized in that said oblique shock wave induces reverberating shock waves in said sample for a plurality of sequenced compression phases.

8. The method as set forth in claim 7, characterized in that said method further includes the step of controlling said sequenced compression phases.

9. The method as set forth in claim 8, characterized in that said sample is quasi-isentropically heated from said sequenced compression phases.

10. The method as set forth in claim 1, characterized in that said material is selected with detonation velocity and induction delay time responsive to velocity-induction matching.

11. A method for inducing reverberating shock waves for compressing a material exposed thereto, characterized in that said method comprises:

providing an explosive-clad conical metal flyer shell with an explosive contained within said shell and an interior cylindrical anvil having an axis and containing a material to be compressed;

detonating said explosive cladding to accelerate said flyer toward said explosive contained within said flyer shell;

detonating said explosive by impact from said flyer to form imploding shock waves impinging said anvil;

compressing said material by exposure to said imploding shock waves transmitted through said anvil wall;

imploding said converging shock wave at said axis;

reflecting a divergent shock wave from said implosion through said material for further compression; and

reverberating shock waves between said anvil wall and axis to compress said material to a predetermined high pressure and density.

12. A method of velocity-induction matching for maintaining super-compressed detonation in any length of a material, characterized in that said method comprises:

providing a length of a material to be compressed and detonated having known detonation velocity and induction delay time under conditions of compression;

providing an explosive-clad conical metal flyer shell with an explosive within said shell and an interior cylindrical anvil having an axis and containing material to be compressed;

determining the angle of said conical flyer shell by matching the axial velocity of an oblique shock wave system to be generated in said material to said detonation velocity;

determining the diameter, wall material and thickness of said anvil by matching the time exposed to said oblique shock wave system to said induction delay time;

compressing said material using oblique shock wave system generated by reverberation; and

self-initiating and propagating a super-compressed detonation wave following said oblique shock wave system through the length of said material.

13. The method as set forth in claim 12, characterized in that said method includes adjusting said angle of said conical flyer shell to achieve a selected high detonation velocity above the CJ velocity of said explosive to near infinity.

14. The method as set forth in claim 12, characterized in that said method includes controlling a stable and self-organizing wave structure for exposure to said material.

15. The method as set forth in claim 12, characterized in that said material is selected with detonation velocity and induction delay time responsive to velocity-induction matching.

16. A method for effecting anti-armour and anti-hard-target munitions, characterized in that said method comprises:

providing said anti-armour or anti-hard-target projectiles;

detonating a material under super-compression;

propelling and shaping said projectile by super-compressed detonation; and

enhancing said projectile penetration capabilities including increasing at least kinetic energy and flying body velocity.

17. A device for high pressure compression of materials and for detonation of super-compressed materials, comprising:

a flyer shell having a substantially conical cross section;

a lid on said flyer shell including explosive material and a detonator therefor;

a sample anvil disposed within said conical flyer shell for retaining a sample to be compressed or detonated, said anvil being substantially surrounded by explosive material; and

alignment means for maintaining alignment of said explosive material, said anvil and said conical flyer shell.

18. The apparatus as set forth in claim 17, wherein said detonator in said lid is axially aligned with said alignment means.

19. The apparatus as set forth in claim 17, wherein said flyer shell and said lid are surrounded with explosive material.

20. The apparatus as set forth in claim 17, wherein said explosive material surrounding said anvil is retained within a casing.

21. The apparatus as set forth in claim 17, wherein said alignment means comprises a centering sleeve.

22. The apparatus as set forth in claim 17, wherein said anvil includes removable plugs.

23. The apparatus as set forth in claim 17, wherein said removable plugs retain a central rod.

Drawing