Chobham và những chiến xa bất khả chiến bại

Chobham armour
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Chobham armour is a composite armour developed at the British tank research centre on Chobham Common. Although the exact composition of Chobham armour remains a secret, it appears to be a composite of ceramic layered between steel armour plating, a combination that is excellent at defeating high explosive anti-tank (HEAT) rounds. Possible ceramics for such armours are: boron carbide, silicon carbide, aluminium oxide (sapphire or "alumina"), titanium boride or Syndie, a synthetic diamond composite. Of these boron carbide is the hardest and lightest, but also the most expensive and brittle. Over the years newer composites have been developed, giving about five times the protection value of the original pure ceramics, the best of which were again about five times as effective as a steel plate of equal weight. The ceramic tiles are encased within a metal (today typically titanium) matrix, either by isostatically pressing them into the heated matrix, or by glueing them with an epoxy resin. A more general name is therefore: CMC or Ceramic Matrix Composite. A titanium matrix is extremely expensive to manufacture but the metal is favoured for its lightness, strength and resistance to corrosion, a constant problem with CMC''s. The Rank company claims to have invented an alumina matrix for the insertion of boron carbide or silicon carbide tiles.
The exact nature of the protection offered by this layering remains classified, but it has been suggested that some part of Chobham armour works in a manner somewhat similar to reactive armour. This may be referring to the effect of sandwiching an inert but soft elastic material such as rubber, between two of the armour plates. The impact of either a shaped charge jet or long-rod penetrator, after the first layer has been perforated and the rubber layer is being penetrated, will cause the rubber to deform and expand, so deforming both the back and front plates. Both attack methods will suffer from obstruction to their expected paths, so experiencing a greater thickness of armour than is there in reality, this lowering penetration. Also for rod penetrations, the transverse force experienced due to the deformation may cause the rod to shatter, bend, or just change its path, again lowering penetration.
Modern tanks also have to face kinetic energy penetrator rounds of various sorts, which the ceramic layer is not particularly effective against: for the original ceramics the resistance against penetrators was about three times, for the newest composites it is about ten times less than against HEAT-rounds. For this reason many modern designs include ad***ional layers of heavy metals to add more density to the overall armor package. The metal used appears to be either tungsten or, in the case of later M1 Abrams tanks, depleted uranium. Some companies offer titanium carbide modules. These metal modules or rods have many perforations or expansion spaces reducing the weight up to about a third while keeping the protective qualities fairly constant.
The effectiveness of Chobham armour was demonstrated in the first Gulf War, where no Coalition tank was destroyed by the obsolete Iraqi armor. In some cases the tanks in question were subject to multiple hits by both KE-penetrators and HEAT rounds, but the old Russian ammunition used by the Iraqis, in their Polish licence built T-72''s, their old T-55''s bought from Russia and upgraded with "enigma" type armour, and T-62 tanks left them completely incapable of penetrating coalition armour. It''s also worth noting that the Iraqis rarely actually hit the coalition tanks, because of lack of training and inferior optics. To date, only 5-10 Chobham-protected tanks have been defeated by enemy fire in combat, including an M1 that was hit on the side skirts, below the turret ring by a PG-7VR, a tandem charge [citation needed] RPG, in the Second Gulf War. The jet penetrated the skirting armour, side hull armour, traversed across the tanks interior and penetrating a further 1.5 to 2 inches into the hull armour on the other side.
The latest version of Chobham armour is used on the Challenger 2 (called Dorchester armour), and (though the composition most probably differs) the M1 Abrams series of tanks, which according to official sources is presently protected by silicon carbide tiles. Given the publicly stated protection level for the earliest M1: 350 mm steel equivalence against KE-penetrators (APFSDS), it seems to have been equipped with alumina tiles. Though it is often claimed to be otherwise, the Leopard 2 does in fact not use Chobham armour, but pure perforated armour, avoiding the horrendous procurement, maintenance and replacement costs of those ceramic armour systems not based on the cheap but rather ineffective alumina. Ceramic modules will corrode their matrix and gradually fracture during driving and the smallest come at over $100,000. For many modern tanks, such as the French Leclerc and the Italian Ariete, it is yet unknown which type is used. There is a general trend away from ceramic armour towards perforated armour; but even many tanks from the seventies like the Leopard 1A3 and A4, the Italian OF-40 and the French AMX-32 and AMX-40 prototypes used the latter system

Depleted uranium (DU) is uranium which contains a reduced proportion of the fissile isotope U-235. It is a byproduct of the enriching of natural uranium for use in nuclear reactors. DU is what is left over when most of the more radioactive isotopes of uranium are removed.
As a radioactive byproduct otherwise requiring long term storage as low level nuclear waste, depleted uranium is an inexpensive but controlled material. It is useful for its extremely high density, which is only slightly less than that of tungsten. However, it has extremely poor corrosion properties, is pyrophoric (it will burn spontaneously when small particles are exposed to air[1]), and since it is a teratogen and a neurotoxin as well as being radioactive, the facilities for processing it need to monitor and filter dust, airborne particles, combustion products, vapors, and fumes. Disadvantages also include the need for depleted uranium to be handled with care as a toxicant radioactive heavy metal, and the fact that it spalls easily during metalworking.
Production and availability
Natural uranium metal contains about 0.71% U-235, 99.28% U-238, and about 0.0054% U-234. Depleted uranium contains only 0.2% to 0.4% U-235, the remainder having been removed and concentrated into enriched uranium through the process of isotope separation. The enrichment process does not create U-235 but merely separates the different isotopes of uranium. Therefore the process leaves large amounts of U-238 uranium as a byproduct. This byproduct is refered to as depleted uranium. For example producing 1 kg of 5% enriched uranium requires 11.8 kg of natural uranium, leaving about 10.8 kg of depleted uranium with 0.3% U-235.
The Nuclear Regulatory Commission (NRC) defines depleted uranium as uranium in which the percentage of the 235U isotope by weight is less than 0.711 percent (10 CFR 40.4). The military specifications designate that the DU used by DoD contain less than 0.3 percent 235U (AEPI, 1995). In actuality, DoD uses only DU that contains approximately 0.2 percent 235U (AEPI, 1995).
Most of the depleted uranium produced to date is being stored as UF6 in steel cylinders in the open air in so-called cylinder yards located adjacent to the enrichment plants. The cylinders contain up to 12.7 tonnes of UF6. In the US alone, 560,000 metric tonnes of depleted UF6 have accumulated until 1993; they are currently stored in 46,422 cylinders. Meanwhile, their number has grown by another 8,000 new cylinders.
World Depleted Uranium Inventory
Country Organization DU Stocks (000 Kg) Reported
USA DOE 480,000 2002
Russia FAEA 460,000 1996
France COGEMA 190,000 2001
UK BNFL 30,000 2001
Germany URENCO 16,000 1999
Japan JNFL 10,000 2001
China CNNC 2,000 2000
South Korea KAERI 200 2002
South Africa NECSA 73 2001
TOTAL 1,188,273 2002
Source: WISE Uranium Project
Uses
Nuclear energy applications
Breeder reactors
Depleted uranium is not usable directly as nuclear fuel. Depleted uranium can be used as a source material for creating the element plutonium. Breeder reactors carry out such a process of transmutation to convert "fertile" isotopes such as U-238 into fissile plutonium. It has been estimated that there is anywhere from 10,000 to five billion years worth of Uranium-238 for use in these power plants [2]. Breeder technology has been used in several reactors [3].
As of December 2005, the only breeder reactor producing power is BN-600 [4] in Beloyarsk, Russia. The electricity output of BN-600 is 600 megawatts. Russia has planned to build another unit, BN-800, at Beloyarsk nuclear power plant. Also, Japan''s Monju breeder reactor is planned for restart, having been shut down since 1995, and both China and India have announced intentions to build breeder reactors.
Radiation shielding
DU is also used as a radiation shield â?" its alpha radiation is easily stopped by the non-radioactive casing of the shielding and the uranium''s high atomic weight and high number of electrons is highly effective in absorbing gamma radiation and x-rays. However, DU is not as effective as ordinary water for stopping fast neutrons. Both metallic depleted uranium and depleted uranium dioxide are being used as materials for radiation shielding. Depleted uranium is about five times better gamma ray shield than lead, so a shield with the same effectivity can be packed into a thinner layer.
DUCRETE, a concrete made with uranium dioxide aggregate instead of gravel, is investigated as a material for Dry cask storage systems to store radioactive waste.
Downblending
The opposite of enriching is downblending. Surplus highly enriched uranium can be downblended with depleted uranium to turn it into low enriched uranium and thus suitable for use in commercial nuclear fuel.
Depleted uranium is also used (with recycled plutonium) from weapons stockpiles for making mixed oxide fuel (MOX) which is now being redirected to become reactor fuel. This dilution, also called downblending, means that any nation or group that acquired the finished fuel would have to repeat the (very expensive and complex) enrichment and seperation processes before assembling a weapon.
Military applications
Incendiary projectile munitions
Depleted uranium is very dense; at 19050 kg/mÂ, it is 70% denser than lead. Thus a given weight of it has a smaller diameter than an equivalent lead projectile, with less aerodynamic drag and deeper penetration due to a higher pressure at point of impact. DU projectile ordinance is often incendiary because of its pyrophoric property. DU munitions, in the form of ordnance, tank, and naval artillery rounds, are deployed by the armed forces of the United States, United Kingdom, Israel, France, China, Russia, Pakistan, and others. DU munitions are manufactured in 18 countries.
Most military use of depleted uranium has been as 30 mm and smaller ordnance, primarily the 30 mm PGU-14/B amour-piercing incendiary round from AH-64 Apache helicopters and the GAU-8 Avenger cannon of the A-10 Thunderbolt II[5] by the U.S. Army and Air Force. 25 mm DU rounds have been used in the M242 gun mounted on the U.S. Army''s Bradley Fighting Vehicle and LAV-AT. The U.S. Marine Corps uses DU in the 25 mm PGU-20 round fired by the GAU-12 Equalizer cannon of the AV-8B Harrier, and also in the 20 mm M197 gun mounted on AH-1 helicopter gunships.
Another use of DU is for kinetic energy penetrators for the anti-tank role. Kinetic energy penetrator rounds consist of a long, relatively thin flechette surrounded by a discarding sabot. Two materials lend themselves to flechette construction: tungsten and depleted uranium, the latter in designated alloys known as staballoys. The US Army uses DU in an alloy with around 3.5% titanium. Staballoys, along with lower raw material costs, have the advantage of being easy to melt and cast into shape; a difficult and expensive process for tungsten. Depleted uranium is favoured for flechette because it is self-sharpening and pyrophoric. On impact with a hard target, such as an armoured vehicle, the nose of the flechette rod fractures in such a way that it remains sharp. The impact and subsequent release of heat energy causes it to disintegrate to dust and combust when it reaches air because it is pyrophoric (compare to ferrocerium). After a disintigrated DU penetrator reaches the interior of an armored vehicle, it explodes, often igniting ammunition and fuel, burning the crew, and causing the vehicle to explode. DU is used by the U.S. Army in 120 mm or 105 mm calibre by the M1 Abrams and M60A3 tanks. The Russian military has used DU munitions in tank main gun ammunition since the late 1970s, mostly for the 115 mm guns in the T-62 tank and the 125 mm guns in the T-64, T-72, T-80, and T-90 tanks.
DU was used during the mid-1990s in the U.S. to make 9mm and similar caliber armor piercing bullets, grenades, cluster bombs, and mines, but those applications have been discontinued, according to Alliant Techsystems. Whether or not other nations still make such use of DU is difficult to determine.
The US Navy used DU in its 20 mm Phalanx CIWS guns, but switched in the late 1990s to armor-piercing tungsten for this application, because of the fire risk associated with stray pyrophoric rounds.
The DU content in various munitions is 180 g in 20 mm projectiles, 200 g in 25 mm ones, 280g in 30 mm, 3.5 kg in 105 mm, and 4.5 kg in 120 mm penetrators. It is used in the form of Staballoy, alloyed with small proportion of other metals.

Đạn DU đã bất khả chiến bại thế nào và tương lai ra sao thì còn bàn. Nhưng ở đây Tuất đính chính lại bác MiGKiller chút.
Depleted uranium is very dense; at 19050 kg/m³, it is 70% denser than lead
(Uranium nghèo DU có mật độ rất cao, đạt 19,05, cao hơn chì 70%).
Thực chất, người ta không sử dụng DU đúc để làm đạn. Đạn DU là một composite hai lớp. Lớp ngoài là hợp kim 3/4 titanium, 1/4 uranium, hợp kim này được gọi là hợp kim 3/4 titan. Lớp vỏ này chiếm 3% đến 10% thanh xuyên. Bên trong là uranium nén. Vỏ titan cực bền, dự ứng lực, làm viên đạn rất cứng. Lõi tạo dự ứng lực cho vỏ, nén lại nên mới đạt được mật độ cao.
Đó là đạn uran ngày nay. Ban đầu, đạn uran nghèo được làm bằng carbua uranium (carbide ??). Vật liệu này rất cứng và mật độ cũng khá cao. Nhưng do nhiều nghuyên nhân, đạn làm bằng vật liệu này không được triển khai nhiều. Đến giữa thật niên 1970, khi xe tăng Soviet đã đạt đỉnh cao với việc xuất hiện T-72, các nỗ lực chống lại nó được tăng cường. Đạn uranium có vỏ titan nén được người Anh phát triển, sau đó, được sản xuất số lượng lớn ở Mỹ. Một trong những thiết bị chống tăng lúc đó được phát triển là máy bay A-10. Vũ khí ban đầu của máy bay này là khẩu G-8, 20 mm, bắn đạn DU. Nó cũng chỉ xuyến được phần nóc tăng T-72, nhưng bắn rất khó. 20 năm sau, chiến tranh Nam Tư, duy nhất báo công một tăng bị A-10 dùng súng này hạ, có điều kết quả kiểm tra sau đó xác nhận, đạn bắn vào một cái xe đã cháy.
Một trong những ứng dụng hết sức cần thiết của DU là hệ thống tác chiến tầm ngắn. Tức là các hệ thống phòng không tầm ngắn, nhiệm vụ lớn nhất là đánh chặn tên lửa bảo vệ chiến hạm. Ngày từ thế chiến, loại bom chú bé cồng kềnh đã có vỏ thép dầy trên 100mm. Rõ ràng, đến nay, ngoài DU, không thứ nào chống được loại đạn này. Ngay cả DU cũng không được ứng dụng nhiều do hiệu quả vẫn rất thấp. Nhưng vào những năm 1980, khi mà các tên lửa chống chiến hạm siêu âm Nga trở nên chính xác và rẻ thì DU là một hy vọng sáng sủa.

Chào tất cả mọi người và các MOD!
Đúng ra thì MiGKiller này cũng định dịch hai tài liệu trên sang tiếng Việt để các bạn không có khả năng Anh ngữ có thể hiểu,nhưng nghĩ lại thấy không cần thiết.Lý do...???...
-Nếu nói về Khoa Học và Kỹ Thuật,hơn nữa lại muốn tìm hiểu về khoa học và kỹ thuật Quân sự trên thế giới,mà người muốn tìm hiểu lại không có khả năng về Nga ngữ hay Anh ngữ...thì hiểu biết sẽ rất hạn chế...đơn giản vì họ chỉ có thể tham khảo những tài liệu đã được dịch sang tiếng Việt.
(Lưu ý) Tại sao chỉ Nga hoặc Anh ngữ? Tự hiểu...!
-Ngày nay,nhờ có Internet nên việc tìm hiểu,trao đổi thông tin cũng thuận tiện hơn nhiều.Nhưng những thông tin trên Internet chỉ có giá trị Tham Khảo,nhất là các tin tức liên quan đến Quốc Phòng.
-Việc tìm hiểu và trao đổi thông tin sẽ giúp mở rộng kiến thức.Nhưng tự học và biết lắng nghe là cách tốt nhất để tồn tại rồi mới nói đến Phát triển mà theo kịp thời đại.Xin phép được nói thêm một chút về tự học.Khi chúng ta tìm hiểu các kiểu máy bay tiêm kích đánh chặn hiện đại của Nga và Mỹ rồi đem so sánh,có bạn trong Forum này quả quyết con MiG25 Foxbat và MiG39 là Vô địch (The Champ) vì con MiG25 Foxbat bay nhanh nhất và vô địch thủ,nó thực sự là vô địch trong 40 năm kể từ khi được sử dụng...v,v ...còn con MiG39 có thể bắn hạ Vệ tinh.Đến vệ tinh nó còn bắt hạ thì....F chẳng là cái đinh rỉ gì...Hehehehehe!!!!
Nếu là một người thực sự hiểu biết về lĩnh vực này thì...ngượng đến đỏ cả mặt cho tác giả của những tuyêt bố hùng hồn trên.Lý do...???...Xin hẹn đến bài sau...
Chào thân ái và tam biệt.

lol chuyện thường ngày ở huyện rồi đó mà! Nói chung là đồ Âu Mỹ Nhật toàn là đồ bỏ đi hết thôi! lol