Patent Publication Number: US-10760145-B1

Title: Apparatus and method for outer surface enhancement and compaction of an object using glass failure generated pulses in an explosive arrangement

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The following description was made in the performance of official duties by employees of the Department of the Navy, and, thus the claimed invention may be manufactured, used, licensed by or for the United States Government for governmental purposes without the payment of any royalties thereon. 
    
    
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to U.S. Pat. No. 10,639,696, filed concurrently with the instant application, herein incorporated by reference, entitled “Apparatus and Method for Outer Surface Enhancement and Compaction of a Cylindrical Structure Using Glass Failure Generated Pulse,” by inventors Philip Dudt and Roshdy George Barsoum. 
     This application is related to the pending U.S. Non Provisional patent application Ser. No. 15/719,951 filed concurrently with the instant application, herein incorporated by reference, entitled “Apparatus and Method for Outer Surface Enhancement and Compaction of a Spherical Structure Using Glass Failure Generated Pulse,” by inventors Philip Dudt and Roshdy George Barsoum. 
     This application is related to U.S. Pat. No. 10,633,718, filed concurrently with the instant application, herein incorporated by reference, entitled “Apparatus and Method for Inner Cylindrical Surface Enhancement and Compaction of a Structure Using Glass Failure Generated Pulse,” by inventors Philip Dudt and Roshdy George Barsoum. 
     TECHNICAL HELD 
     The following description relates generally to an apparatus and method for treating articles, using glass failure generated pulses. In particular, the apparatus and method is directed towards the hardening and compaction of a glass-covered elongated object that is impacted by a flyer plate having a shape that is complimentary to that of the elongated object, thereby initiating an explosive glass failure that hardens and compacts the elongated object. 
     BACKGROUND 
     There is always a need for stronger and harder alloys to improve the performance and lifetime of structures and platforms. Engineers are looking for high strength materials to improve performance and safety, while maintaining low weight requirements. Strength limitations directly affect how industrial parts are used, Engineers are actively looking for alloys with material properties sufficient for manufacturing and use, while providing fatigue, fracture, and corrosion resistance, while maintaining or improving mechanical properties. 
     Fatigue and fracture strengths of machinery parts, non-moving parts such as gun barrels, and weldments can be improved by generating high compressive strengths on their surface. The benefit is that the compressive stresses must be overcome before tension strains can be produced leading to crack initiation and extension. A number of known methods are used industrially for enhancing the surface strength profile. This includes the application of plastic stresses imparted using large rolling machines, carbonizing, shot peening, and explosive detonation. Explosive detonations are also employed for explosion welding, in which arrangements are also used to 
     Many industrial parts, which cannot be otherwise produced by casting, rolling or forging can be fabricated using powder metallurgy techniques. The parts, such as gears, shafts, and brackets etc., are compacted and the powder with matrix portions are bonded together using hot isostatic pressing (HIP), along with follow-on heat application. Dynamically compressing parts under high dynamic loading is a useful process. 
     Another known technique for treating the surfaces of industrial parts to improve fatigue and fracture properties is shot peening. This technique enables a rise in the hardness of a surface layer of a work piece and introduction of compressive residual stress into the surface layer. This technique is widely used in the industrial fields of automobiles, aircrafts, etc. 
     Yet another known technique is laser shock hardening. This involves irradiating the surface of a solid material, such as a metal or a ceramic, with pulsed laser beam through a liquid to adjust surface of internal characteristics of the material, such as structure, hardness and residual stress. Generally speaking, laser shock hardening has a higher effect than shot peening and in addition has various excellent advantages that shot peening does not have, such as capability of contactless operation, no involvement of reaction force and capability of precise control of laser irradiation conditions and laser irradiation sites. 
     Regarding surface treatment that involves the bonding of two industrial parts together, it is known to employ explosion welding, particularly when the parts are metallic. In explosion bonding, two structures are placed on each other or in close proximity to each other, with a layer of explosive material positioned above the arrangement. When the explosion material is ignited and explodes, the two structures are pressed together powerfully to such extent that they melt together in the attachment zone. This melding of the two objects together and the accompanying deformation is not desired for the general machining and treatment of industrial parts. 
     Given what is known, it is still desired to have a method and an apparatus to improve the ability to strengthen and to make more compact, the surface of industrial parts, Such a method may also be used to supplement other forms of surface hardening, such as carburizing, nitriding and cyaniding. 
     SUMMARY 
     In one aspect, the invention is a system for hardening and compacting an elongated object. In this aspect, the system includes a confinement assembly. The confinement assembly includes, an elongated object having an upper surface, a glass sheet contacting and covering the upper surface of the elongated object, the glass sheet having an upper glass surface. The confinement assembly also includes a rigid outer shell encasing the glass sheet and the elongated object therewithin, wherein the rigid outer shell is open at the top so that the upper glass surface is exposed. The system also includes a striker assembly that includes a flyer plate having a flyer plate top surface, and a flyer plate bottom surface. The flyer plate bottom surface is complementary with the upper glass surface of the glass sheet. The striker assembly also includes an explosive composition attached to at least a portion of the flyer plate top surface. In this aspect, the flyer plate is positioned so that when the explosive composition is ignited, the flyer plate strikes the glass sheet of the confinement assembly, shattering the Mass of the glass sheet to create an explosive volume expansion of the glass. Due to the glass being trapped between the flyer plate and the confinement assembly, compressive forces are applied to the surface of the elongated object, thereby hardening and compacting the elongated object. 
     In another aspect, the invention is a method of hardening and compacting an elongated object. In this aspect, the method includes, providing a confinement assembly. The confinement assembly includes an elongated object having an upper surface, and a glass sheet contacting and covering the upper surface of the elongated object, the glass sheet having an upper glass surface. The confinement assembly also includes a rigid outer shell encasing the glass sheet and the elongated object therewithin, wherein the rigid outer shell is open at the top so that the upper glass surface is exposed. The method also includes providing a striker assembly. In this aspect, the striker assembly includes, a flyer plate having a flyer plate top surface, and a flyer plate bottom surface, wherein the flyer plate bottom surface is complementary with the upper glass surface of the glass sheet. The striker assembly also includes an explosive composition attached to at least a portion of the flyer plate top surface. The method further includes the igniting of the explosive composition, so that the flyer plate strikes the glass sheet of the confinement assembly, thereby creating an explosive expansion of the glass. In this aspect, due to the limited space between the flyer plate and the confinement assembly, compressive forces are created and applied to the surface of the elongated object, thereby accomplishing said hardening and compacting of the elongated object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features will be apparent from the description, the drawings, and the claims. 
         FIG. 1  is an exemplary side view of a system for hardening and compacting an elongated object, according to an embodiment of the invention. 
         FIG. 2A  is an exemplary sectional illustration of the system for hardening and compacting an elongated object, according to an embodiment of the invention. 
         FIG. 2B  is an exemplary sectional illustration of the system for hardening and compacting an elongated object, according to an embodiment of the invention. 
         FIG. 2C  is an exemplary sectional illustration of the system for hardening and compacting an elongated object, according to an embodiment of the invention. 
         FIG. 2D  is an exemplary sectional illustration of the system for hardening and compacting an elongated object, according to an embodiment of the invention, 
         FIG. 3  is an exemplary explanatory illustration of a system  100  for hardening and compacting a cylindrical structure, according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an exemplary side view of a system  100  for hardening and compacting an elongated object, according to an embodiment of the invention. It should be understood that  FIG. 1  shows the general arrangement of the elements of the system  100  with respect to each other. As outlined below,  FIGS. 2A-2D  below illustrate the different possible shapes of the elements arranged in  FIG. 1 . 
     The system  100  of  FIG. 1  includes a confinement assembly  110  and a striker assembly  130 . The confinement assembly  110  includes an elongated object  115 , which may be a plate or the like. As shown, the elongated object  115  has an upper surface  116  and a lower surface  114 , The elongated object  115  is to be hardened and compacted, as outlined below. The object  115  may be made from metallic materials such as 1015 steel, 4140 steel, and the like, and may be used as an industrial part in a mechanical operation, for example, and thus may be sized in accordance with the application. The object may have a thickness T of about 0.25 in to about. 3.0 in 
     The confinement assembly  110  also includes a glass sheet  120  contacting and covering the upper surface  116  of the elongated object  115 . The glass sheet  120  has an upper glass surface  121  and a lower glass surface  119 . According to one embodiment of the invention, the glass sheet  120  is a solid glass plate, According to another embodiment of the invention, the glass sheet  120  is made up of densely packed glass particles. The glass may be for example, any known type of glass such as silica glass, fused silica, fluoride glass, alumino silicate glass, phosphate glass, borosilicate glass, or flint glass. The glass sheet  120  may include solid or densely packed glass particles. 
       FIG. 1  also shows a rigid outer shell  122  encasing both the glass sheet  120  and the elongated object  115 . The rigid outer shell  122  may be a thick containment vessel, and may be open at the top so that the upper glass surface  121  is exposed.  FIG. 1A  shows the striker assembly  130  having a flyer plate  140  with a flyer plate top surface  141 , and a flyer plate bottom surface  139 . As outlined below, the flyer plate bottom surface  139  is complementary with the upper glass surface  121  of the glass sheet  120 . The striker assembly  130  also includes an explosive composition  150  attached the top surface  141  of the flyer plate  140 , Although  FIG. 1  shows the explosive composition  150  covering the entire flyer plate  140 , it should be understood that the explosive composition  150  is applied to the top surface  141  in an amount that facilities the requisite explosive output, and thus the explosive composition may only cover a portion of the top surface  141  of the flyer plate  140 . The explosive composition may include pentotite, C-4, or other known explosives. 
       FIG. 1  shows striker assembly  130  at an angle Θ, with respect to the confinement assembly  110 . As shown, the flyer plate  140  contacts the glass sheet  120  at a contacting section  142 , thereby creating the angle Θ of the striker assembly  130  with respect to the confinement assembly  110 . Force arrows shown at  170  indicate the direction in which the striker assembly is propelled, and in particular the direction the flyer plate  140  accelerates towards the glass sheet  120  of the confinement assembly  110 , when the explosive composition  150  is ignited.  FIG. 1  does not show a spacer which defines a standoff distance, but it is understood and known that one or more spacers may be employed to hold the striker assembly at an angle. The angle Θ may be any known angle used in explosion welding, as the instant embodiment operates under the same general explosion principle. According to a particular embodiment, angle Θ may be about 2 degrees to about 45 degrees. It should be understood that although in the arrangement as depicted in  FIG. 1 , the striker assembly  130  is at the angle Θ, with respect to the confinement assembly  110 , it is also known to set up the striker assembly  130  spaced-apart and substantially parallel to the confinement assembly  100 , so that the flyer plate bottom surface  139  is parallel to the upper glass surface  121  of the glass sheet  120 . 
       FIG. 2A  is an exemplary sectional illustration of the system  100  for hardening and compacting an elongated object, according to an embodiment of the invention in which the elongated object  115  is a flat plate. The exemplary sectional illustration of  FIG. 2A  is taken through AN shown in  FIG. 1 .  FIG. 2A  also shows all the accompanying elements of the confinement assembly  110  and a striker assembly  130  being planer/flat as well. Thus, according to this embodiment, each of the flyer plate  140 , and the glass sheet  120  are flat. As stated above, the glass sheet  120  may be a solid sheet, or may be made up of densely packed glass particles. 
       FIG. 2A  also shows the rigid outer shell  122  encasing both the glass sheet  120  and the flat plate  115 . It should also be noted that when the explosive composition  150  is ignited, and the flyer plate is projected into the glass sheet  120 , the flyer plate, in combination with the rigid outer shell  122 , completely cover and encase the glass sheet  120  and the flat plate  115 , to facilitate the hardening and compacting of the flat plate  115 . 
       FIG. 2B  is an exemplary sectional illustration of the system  100  for hardening and compacting an elongated object, according to an embodiment of the invention in which the elongated object  115  is a polymer membrane or foil  216  filled with a powdered/granular material  217  for compaction. The pre-form powder material can also contain ceramic particles such as boron nitride, silica, alumina, and silicon carbide, and particles of cobalt and nickel. Particles of lower melting point alloys, such as aluminum and tin may be included to facilitate and preserve high hardness polymorphs formed during glass shock loading of a silicate pre-form, According to an embodiment of the invention, the powdered/granular material  217  may also include fiber materials. 
     As shown, the polymer membrane or foil  216  filled with the powdered/granular material  217  is laid out as a flat plate, similar to what is shown in  FIG. 2A , Similarly, regarding  FIG. 2B , each of the flyer plate  140 , and the glass sheet  120  are flat. As outlined above, the glass sheet  120  may be a solid sheet, or may be made up of densely packed glass particles. The rigid outer shell  122  encases both the glass sheet  120  and the elongated object  115 . When the explosive composition  150  is ignited, and the flyer plate is projected into the glass sheet  120 , upon impact, the flyer plate in combination with the rigid outer shell  122 , completely cover and encase the glass sheet  120  and the elongated object  115 , which is made up of the membrane or foil  216  and the granular material  217 , to facilitate the hardening and compacting of the flat plate  115 , The exemplary sectional illustration of  FIG. 2B  is taken through AA′ shown in  FIG. 1 . 
       FIG. 2C  is an exemplary sectional illustration of the system  100  for hardening and compacting an elongated object, according to an embodiment of the invention in which the elongated object  115  is a curved plate that has a curvature as if a top portion of a cylinder. The exemplary sectional illustration of  FIG. 2C  is taken through AA′ shown in  FIG. 1 .  FIG. 2C  also shows all the accompanying elements of the confinement assembly  110  and a striker assembly  130  having complementary curvatures. Thus, according to this embodiment, each of the flyer plate  140  and the glass sheet  120  are all curved as a top portion of a cylinder. As stated above, the glass sheet  120  may be a solid sheet, or may be made up of densely packed glass particles, 
       FIG. 2C  also shows the rigid outer shell  122  encasing both the glass sheet  120  and the curved plate  115 . It should also be noted that when the explosive composition  150  is ignited, and the flyer plate is projected into the glass sheet  120 , the flyer plate  140 , in combination with the rigid outer shell  122 , completely cover and encase the curved glass sheet  120  and the curved plate  115 , to facilitate the hardening and compacting of the curved plate  115 . 
       FIG. 2D  is an exemplary sectional illustration of the system  100  for hardening and compacting an elongated object, according to an embodiment of the invention in which the elongated object  115  is a curved plate that has a curvature as if a bottom portion of a cylinder.  FIG. 2D  is not necessarily a section of  FIG. 1 , but represents a reverse curvature, as compared to the illustration of  FIG. 2C , and is another possible embodiment of the system  100 . Thus, the illustration of  FIG. 2D  shows the elongated object  115   FIG. 2D  also shows all the accompanying elements of the confinement assembly  110  and a striker assembly  130  having complementary curvatures, Thus, according to this embodiment, each of the flyer plate  140 , and the glass sheet  120  are all curved as a bottom portion of a cylinder. As stated above, the glass sheet  120  may be a solid sheet, or may be made up of densely packed glass particles. 
       FIG. 2D  also shows the rigid outer shell  122  encasing both the glass sheet  120  and the curved plate  115 . It should also be noted that when the explosive composition  150  is ignited, and the flyer plate is projected into the curved glass sheet  120 , the flyer plate  140 , in combination with the rigid outer shell  122 , completely cover and encase the curved glass sheet  120  and the curved plate  115 , to facilitate the hardening and compacting of the curved plate  115 . 
     In operation, the explosive composition  150  in the striker assembly  130  is ignited, projecting the flyer plate  140  at a high velocity in the direction shown by force arrows  170 , impinging on the glass sheet  120 . The flyer plate  140  contacts the glass while moving at speeds between 700 feet per second to about 20,000 feet per second. This generates explosive forces for several reasons. First, due to the phenomenon called “Reynolds Dilatancy” in which multiple cracks force the volume occupied to increase as the cracks rupture and expand the molecular structure. The glass experiences this Reynolds Dilatancy when impacted by the high velocity flyer plate  140 , The pressure created by the ruptured glass trapped between the flyer plate  140  and the confinement assembly  110 , serves to pressurize the elongated object  115 , thereby hardening and compacting the object  115 , Elongated objects  115  that are treated as outlined above could have different sizes and shapes, and could be solid or granular, as shown in  FIGS. 2A, 2B, 2C, and 2D . 
     Additionally, the impact by the high velocity flyer plate  140  on the glass causes failure waves.  FIG. 3  is an exemplary explanatory illustration of a system  100  for hardening and compacting a cylindrical structure, according to an embodiment of the invention.  FIG. 3  shows the failure waves  310 , which are waves that propagate so the glass material is intact ahead of the wave and comminuted behind the wave. In embodiments in which the glass sheet  120  comprises glass particles, it is preferred that the glass particles are more granulated, as opposed to fine powdered, in order to create more substantial failure waves  310 . The large amount of kinetic energy stored ahead of the wave must then appear in comminuted form. The failure is explosive, and due to the confined area of the confinement assembly  110 , creates intense pressurization forces on the elongated object  115 . This hardens and compacts the object  115 . 
     The impact by the high velocity flyer plate  140  on the glass may involve a third phenomenon which occurs when the high velocity impact of the flyer plate  140  on the glass is so forceful that coesite, stishovite, or seifertite, which are denser forms of silicate, are created. Stishovite has a density of about 4.6 gm/cc as compared to 2.6 gm/cc. It is understood that when the stishovite-type polymorphs rupture they may convert to an amorphous state. It is generally understood that polymorphs that initially form under the high pressure in the glass have smaller volume contents. Then they appear to revert to the larger volume condition, this volume change helping to create the hulking. This rebound effect increases the applied pressure via the volume expansion. It should also be understood that in response to the impact of the high velocity strikers, the coesite, stishovite, and seifertite may be created simultaneously, but at different locations. The highest pressures producing stishovite and seifertite, and areas of relatively lower pressures producing coesite. 
     On average, due to the different phenomenon outlined above, i.e., on account of Reynolds Dilatancy, the formation of failure waves, and the creation of coesite or stishovite, the volume expansion could be up to 40 percent or even greater. Specifically regarding stishovite, expansions of around 77 percent at high pressures may occur. It should be noted that only a limited amount of the material would likely change to this polymorph. Again, as stated above, due to the glass being confined between the flyer plate  140  and the confinement assembly  110 , the explosive volume expansion created by the flyer plate  140  impacting the glass creates intense pressurization forces on the object  115 . This results in the hardening and compacting of the elongated object  115 , with higher and more intense pressures created with the formation of coesite, stishovite, and seifertite, producing a more hardened object  115 . It should be understood that this applies to all shapes of the object  115 , i.e., whether it is flat/planer or curved as shown in  FIGS. 2A, 2C, and 2D , and applies regardless of whether the elongated object is solid or granular as shown in  FIG. 2B . 
     What has been described and illustrated herein are preferred embodiments of the invention along with some variations. The terms, descriptions and figures used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention. For example, in addition to planar and curved elongated objects, cylindrical pipes may also be treated according to the principles outlined in the instant invention. Additionally, as opposed to the illustration in  FIG. 1 , it is also known to set up the striker assembly  130  spaced-apart and substantially parallel to the confinement assembly  100 . The invention including the stated variations is intended to be defined by the following claims and their equivalents, in which all terms are meant in their broadest reasonable sense unless otherwise indicated.