Metals Tungsten heavy alloy sequence, there is a high proportion of alloy most prominent feature is the high proportion of that is, we often say that the density. Density tungsten alloy can reach 18g/cm3, steel gravity (7.8g/cm3) 2.3 times, so the heart of a large cross-section density shells, storage capacity and speed of the steel will help improve the penetration capability of flying.

Tungsten core machine gun was developed in the 1970s after an excellent machine gun. This machine gun warhead shelling principle adopted a new structure and a high-density tungsten alloys, new materials, with a high muzzle velocity, trajectory and low elongation, the flight time is short, high hit accuracy, penetration force, etc., can effectively deal with fast moving target; their shells heart section density, and hardened steel or tungsten carbide core penetration bombs in the course of the entire heart broken contrary, tungsten alloy shells heart malleability better to splash piercing, with excellent secondary penetration characteristics, the large angle, and multi-layer sandwich structure composite armor piercing effect is more obvious. At home and abroad have been widely used in the large-caliber bullets and small-caliber artillery, ammunition, armored personnel carriers as deal with armed helicopters, light armored targets.

84 type of tungsten core 12.7mm machine gun equipped for 77 12.7mm machine gun style, common to 54-type 12.7mm machine gun, bullet mass 28g, playing mind quality 22g, the quality is warheads 78.6% projectile core diameter 7.9mm , the second aperture ratio (i.e., d1/d2, dl is core diameter shells, d2 is the diameter of the warhead) is 0.62, muzzle velocity 1150m / s, at 45 ° with 1 000m angles may impose breakdown homogeneous steel plate 15mm thick, the same 45 ° the angle, the maximum distance can breakdown homogeneous alloy steel plate 20mm thick for 150m. The 9.5m-made 54-style shooting at 12.7mm armor-piercing incendiary ricochet from steel is produced, which can only penetrate to 30 ° forward angle 15mm thick steel plate at 830m, 125m at penetrating 20mm thick steel. Visible, 12.7mm machine gun in the tungsten core with a large angle of steel armor-piercing capability.


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1.4 Calculation of numerical simulation

For a long time, the kinetic energy of the process of the target plate armor projectile impact analysis mainly rely on a large number of test results, with the increasing depth study of the phenomenon of piercing, some of the other methods used in the analysis of the role of projectile and target, such as empirical, theoretical analysis and numerical simulation method. Among them, the numerical simulation method provides a more comprehensive response to changes in the middle of the process parameters and physical piercing, using numerical simulation computer graphics technology design can also be visually illustrated throughout the piercing process various parameters (shape, stress, strain, etc.) changes; addition, the use of the computer program can select different physical and geometrical parameters are calculated for the various parameters obtained shells, the impact target interaction, which can give a more comprehensive analysis of the test results.

Michael et tungsten simulation results indicate that the internal stress field, tungsten alloy binder phase does not only occur in the stress concentration, but the first in the high-intensity tungsten particles [18]. High-density housing and other research Wenbin tungsten alloy hot hydrostatic extrusion process using numerical analysis methods, indicating hot hydrostatic extrusion at high temperatures, can significantly reduce the squeeze pressure and squeeze greater than [19] .荣吉利 other studies of penetration and fragmentation properties of tungsten alloy Fragile kinetic energy penetrators, based on the establishment of a tungsten alloy Fragile Projectile finite element analysis model, simulated with different tensile - compressive strength of tungsten alloy penetrators penetrating than the target penetration and crushing process plates at [20].

程兴旺 such as tungsten alloy casing vertical penetration through concrete target experiments, to obtain strain tungsten alloy casing dangerous section at the - time course curve, providing models and numerical verification standard penetration estimates for housing design [21]. Progress in any of the rain and other composite laminated reviewed the impact of the model for the design optimization of composite protective structure together proposed a new approach [22].

1.5 Preparation of technical

Refined tungsten particles become a new hot spot study of high-density tungsten alloy by mechanical alloying (MA), condensation drying method, chemical vapor deposition method, spray drying, sol - gel method and other methods for the preparation of pre-alloyed powder, and using a suitable process can be made very fine powder. Furthermore, the reaction process may be spray-step synthesis of fine grain, multi-component, the total of the pre-tungsten alloy powder, the powder can be well below the melting temperature of the binder phase sintering to achieve full density [23]. Fan Jinglian and other processes with MA Nanocrystalline tungsten alloy composite powder hydrogen atmosphere at normal pressure sintering and densification during sintering tungsten grain growth behavior, indicating MA nanocrystalline powders can promote densification temperature densification reduced by about 100 ~ 200 ℃, when the solid-phase sintering temperature can be generally obtained as a fine crystalline grain size of 3 ~ 5μm high strength alloys [24]. They also nano-tungsten alloy injection molding were studied in 1350 ~ 1450 ℃ showed solid phase sintering that reached full density, grain final alloy is about 3μm, tensile strength greater than 1200MPa [25].

罗述东 other studies of tungsten alloy powder warm compaction behavior at different temperatures, indicating that the temperature and pressure can significantly improve the green density, temperature and pressure radial contraction of less than room temperature blank blank radial contraction, and temperature and pressure can improve tungsten alloy microstructure organization [26]. Sample cold isostatic pressing of Lee letters buried in Al2O3 powder, placed in a sintering furnace heating and air after 30min pre-oxidation heat, and then sintered at different temperatures; results showed that the use of pre-oxidized tungsten alloy activated sintering can reduce the sintering temperature, reducing the alloy deformation and get dense tungsten alloy, and can improve the tensile strength and elongation of tungsten alloy [27].
 

References

[18] Michael, Lau Siu-ling, Zhao Baorong, and so on. Tungsten alloy internal stress field numerical simulation [J]. Ordnance Material Science and Engineering, 2005,28 (2) :51-54.

[19] House Wenbin, Oscar Wilde, Hu Lianxi, and so on. High-density tungsten alloy hot hydrostatic extrusion flow numerical viscosity Germany [J]. Rare Metal Materials and Engineering, 2005,34 (1) :33-36.

[20] Rongji Li, in the heart of the construction, Liu Bin, et al. Fragile kinetic energy penetrator armor-piercing tungsten alloy simulation and finite element analysis [J]. Beijing Institute of Technology, 2004,24? (3) :193-196.

[21] Chengxing Wang, Wang Fu shame, Lu Wang, et al. Experimental testing of tungsten alloy shell casing process penetrating concrete target strain [J]. Ordnance, 2004,25 (1) :102-105.
 
[22] any rain, ZHU Xi, Mei Zhiyuan. Composite laminates impact models [J]. Ordnance Material Science and Engineering, 2005,28 (4) :59-67.

[23] Ye passers-Ming Yi Jian Hong, and microstructure of, and so on. New Progress in the study of high-density tungsten alloy [J]. Powder Metallurgy Materials Science and Engineering. 2003,8 (2) :134-140.

[24] Fan Jinglian, Huang Baiyun, Qu Hui, et al. Densification and grain nanocrystalline tungsten alloy powder during pressureless sintering [J]. Powder Metallurgy Materials Science and Engineering, 2001,6 (2) :83-88.

[25] Huang Baiyun, Fan Jinglian, Qu Hui, et al. Research and Application of Nano-tungsten alloys [J]. China Tungsten Industry. 2001,2001,16 (5-6) :38-43.

[26] Luo Shudong, Tang Xinwen, Cao Zhenghua, high density tungsten alloy powder warm compaction behavior [J]. Powder Metallurgy Materials Science and Engineering. 2003,8 (1) :23-27.

[27] Li Xin, wusheng. Pre-oxidation of high-density sintered tungsten alloy [J]. Rare Metal Materials and Engineering, 2002,31 (4): 319.


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In order to avoid military material to the environment, pollution, military tungsten alloy products are gradually replacing lead and depleted uranium armor-piercing bullets and used. In the military field. Tungsten alloy military products are becoming more common. Tungsten alloy military products can be made into excellent armor-piercing performance, non-toxic projectile. Tungsten alloy penetrators rationale Want the material.

Due to the high hardness and high temperature tungsten alloys, as early as the 1940s, tungsten alloy products for military began widespread use. Today, military tungsten alloy products more Is widely used in the military field, mainly for bullets, armor-piercing bullet, grenade, artillery, tanks, guns, etc. One of the main purposes of military tungsten alloy products Kinetic energy penetrator warhead as to replace the depleted uranium. Surface military researchers, armor-piercing depleted uranium has a high ability to reason is due to depleted uranium. In the piercing process, will produce adiabatic shear effect, causes the material to sharpen, armor-piercing warhead in the process will not be labeled mushroom shape, thus enhancing the Piercing sex. Therefore, military researchers believe that if the upgrade adiabatic shear effect of tungsten alloy, tungsten alloy can replace the depleted uranium (DU will Cause serious environmental pollution generated).


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1.2 deformation strengthening research

Currently, the tensile strength of powder metallurgy method of preparing high density tungsten alloy (sintered) is generally up to 900 ~ 1000Mpa, elongation between 20% to 30%; while later after plastic deformation strengthening, its strength can greatly improve plasticity declined. After plastic deformation, can exceed the strength of tungsten alloy 1400MPa, the elongation can be maintained at about 10% [9].

Rolling, rotary forging, torsional deformation, hydrostatic extrusion deformation strengthening is to improve the strength of tungsten alloy material and ensure effective way certain toughness, but also the effective grain refinement [10]. Forging deformation is used to improve the strength of tungsten alloy technology, conventional deformation of about 15%. With the strength of tungsten alloy and increase the amount of deformation increases, the greater the amount of deformation of the tungsten particles larger deformation, and the deformation increases the degree of breakage will result in the transfer to the tungsten particles [11]. Rolling can also achieve greater deformation of the deformation and to ensure uniformity, and to make a large grain broken into small grains, and to obtain uniform distribution of the microstructure; rolling can increase the density and reduce the tungsten rod porosity, increase productivity and reduce manufacturing costs. However, due to the small amount of deformation and rolling a billet temperature and the final rolling temperature is higher, and surface oxidation is relatively serious pollution, high energy consumption, and therefore subject to a certain limit in actual production.

Rotary forging effects also increase the strength and armor-piercing tungsten alloy, after multi-pass swaging, the mechanical properties of strength and hardness of tungsten alloys have a more substantial increase than before swaging, but low elongation will. Large deformation makes spherical tungsten particles are elongated become fibrous tissue, can be greatly improved mechanical properties compared to the material. Quiet night extrusion technology is a hard plastic deformation of materials processing technology, mainly divided into cool liquid extrusion and hot hydrostatic extrusion, it is one of the most effective tungsten alloy deformation strengthening the current method, which can be obtained with a larger deformation strain and can greatly improve the characteristics of the material strength. At 3 under hydrostatic extrusion to compressive stress, not only can effectively prevent breakage and cracking of the material in the deformation of tungsten particles within the material is conducive to the healing of the original microscopic pores while being able to refine the microstructure conducive nearly net shape, improve efficiency, reduce costs and improve generation efficiency [12]. After the tungsten alloy using hydrostatic extrusion deformation strengthening and annealed, and breaking the material in the solution to form particles of tungsten high dislocation density cell structure in the material, its deformation after the tungsten particles were directional arrangement, cleavage fracture based. Hydrostatic extrusion deformation strengthening each to force uniform, material deformation process less prone to deformation defects, no heating, a large deformation, a 93W maximum deformation up to about 50% [13].
 

1.3 adiabatic shear Research

Adiabatic shear within the material or component of shear strain is highly concentrated narrow area that is under high strain rate loading conditions of material deformation and fracture of a special mechanism. Adiabatic shear deformation localization is widely present in the high-speed deformation process all kinds of metal, rock and polymer materials in the explosion suffered, penetration, high-speed collisions, wear high-speed cutting and high-speed strain rate loading, the increase in tungsten alloy material adiabatic shear properties to enhance the performance of tungsten alloy rod projectile penetration is currently one of the hotspots. Two of the five Institute, Chinese Academy of Mechanics, China University of Technology and Polytechnic University and other units Quote conducted a number of studies.

For half a century, the study of adiabatic shear deformation, mainly in three aspects: first, starting from the material constitutive relations, the establishment of adiabatic shear deformation localized buckling model to explore the adiabatic shear instability propagation law criterion and adiabatic shear bands; Second, microstructure, starting to explore the different components of the structure, microstructure features adiabatic shear band of tissue material within the organization as well as its nucleation and micro factors grew up; first Third, the use of computer simulation technology evolution of adiabatic shear band and should stand the strain and temperature field studies [14].

Wei Zhigang and other devices with a split Hopkinson pressure bar for oblique cylindrical specimen after pre-torsion impact test, not only observes the adiabatic shear band, while observing that if the maximum shear stress direction and orientation of the tungsten particles are consistent, then the failure is tungsten particles of brittle fracture, damage to the binder phase, tungsten - tungsten and tungsten interface separation - the result of both interfacial bonding separation of several damage mechanisms [15]. Hsu Shu-hua, etc. No pre-twisting and twisting tungsten alloy rod ballistic missile test and the residual microscopic tissue fragments were analyzed and found to reverse the pre-tungsten alloy with tungsten grain deformation direction close to the maximum shear stress direction, so projectile and target impact process in favor of adiabatic shear deformation and shear failure occurs. Observed from the remnants of warheads to adiabatic shear bands described in the pre-penetration bombs to reverse the process is easier than playing not to reverse the self-sharpening, which is pre-torsion rod projectile into the root causes of increased capacity [16]. Tan Chengwen, etc. In order to quantitatively evaluate the different materials on the sensitivity of the adiabatic shear deformation, can extend the use of adiabatic shear - adiabatic shear sensitive factor to characterize this difference, and to establish the corresponding experimental test system to solve the adiabatic shear quantitatively evaluate and test the sensitivity of the issue [17]. (To be continued)

References

[9] Zhang Baosheng, Kang Zhijun. Piercing characteristics of high-density tungsten alloy and its application [J]. China Tungsten Industry, 1999.14 (5-6) :178-185.

[10] Wilde, Yu Yang, Hu Lianxi, and so on. Advances in technology W-Ni-Fe based high-density tungsten alloy deformation strengthening [J]. Powder Metallurgy Technology, 2004,22 (5) :303-307.

[11] Shi Honggang, QI Zhi Wang, Xu Jie, et al. Affect the amount of deformation of tungsten alloy forging material properties Tak [J]. Ordnance Material Science and Engineering, 1998,21 (4) :3-6.

[12] Wang Yu change before David, the Qian Mei. Intensification of hydraulic extrusion technology [J]. Advanced materials and manufacturing technology. 1998, (5) :1-5, 25.

[13] Liu Zhiqiang, Yangguo Yi, Zhao Hongmei, et al. Analysis [J] high-density tungsten alloy hydrostatic extrusion tissue defect. Ordnance Material Science and Engineering, 2004,27 (4) :40-43.

[14] Tancheng Wen, WANG Fu-chi, Li Shukui. Adiabatic shear deformation localization research progress and development trend [J]. Ordnance Material Science and Engineering, 2003,26 (5) :62-67.

[15] Wei Zhigang, Hu SS, Lee pool. Experimental study of localized adiabatic shear deformation of powder sintered tungsten alloy [J]. Metal Journal, 1999,35 (8) :829-833.

[16] Hsu Shu-hua, Zhanggang Ming, Wang Xiaojun, et al. MICROMECHANICS pre-tungsten alloy rod projectile into reversing capability [J]. Explosion and Shock, 2000,20 (2): 143.

[17] Tancheng Wen, WANG Fu-chi, Liu Yuanhong, and so on. Adiabatic shear sensitivity study materials characterization and testing methods [J]. Beijing Institute of Technology, 2004,24 (5) :377-379.


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