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Rolled homogeneous armour (RHA) is a type of vehicle armour made of a single steel composition hot-rolled to improve its material characteristics, as opposed to layered or cemented armour. Its first common application was in tanks. After World War II, it began to fall out of use on main battle tanks and other armoured fighting vehicles intended to see front-line combat as new anti-tank weapon technologies were developed which were capable of relatively easily penetrating rolled homogeneous armour plating even of significant thickness.
Today, the term is primarily used as a unit of measurement of the protection offered by armour on a vehicle (often composed of materials that may not actually contain steel, or even contain any metals) in equivalent millimetres of RHA, referring to the thickness of RHA that would provide the same protection. Typically, modern composite armour can provide the same amount of protection with much thinner and lighter construction than its protective equivalence in RHA. Likewise, the term is also used as a unit of measurement of penetration capability of armour-piercing weaponry, in terms of the millimetres of RHA that the weapon system can reliably penetrate.
Armoured steel must be hard, yet resistant to shock, in order to resist high velocity metal projectiles. Steel with these characteristics is produced by processing cast steel billets of appropriate size and then rolling them into plates of required thickness. Hot rolling homogenizes the grain structure of the steel, changing the crystalline structure of the steel and normalizing it.
RHA is homogeneous because its structure and composition are uniform throughout its thickness. The opposite of homogeneous steel plate is cemented or face-hardened steel plate, where the face of the steel is composed differently from the substrate. The face of the steel, which starts as an RHA plate, is hardened by a heat-treatment process.
From the invention of tanks through to the Second World War, tank armour increased in thickness to resist the increasing size and power of anti-tank guns. A tank with sufficient armour could resist the largest anti-tank guns then in use.
RHA was commonly used during this period (combined with other plate alloys and cast steel armour), and the power of anti-tank guns was measured by the thickness of RHA they could penetrate. This standard test has remained in use despite the modern usage of many other types of armour, some of which do not include steel or any other metals.
RHA was in common use as primary armour until after World War II, during which a new generation of anti-tank rounds using shaped charges came into use instead of heavy high-velocity projectiles.
Since World War II, because of a reduction in effectiveness against new weapons (mainly shaped charges and improved kinetic energy penetrators), RHA has largely been superseded by composite armour, which incorporates air spaces and materials such as ceramics or plastics in addition to steel, and explosive reactive armour.
For the testing and calibration of anti-tank guns, the term rolled homogeneous armour equivalency (RHAe) is used when giving an estimate of either the penetrative capability of a projectile or the protective capability of a type of armour which may or may not be steel. Because of variations in armour shape, quality, material, and case-by-case performance, the usefulness of RHAe in comparing different armour is only approximate.
Currently, most armoured vehicles have their basic structures formed from RHA to lend general strength and toughness.
For current United States Army use, RHA is produced to military standard MIL-DTL-12560 [1] by several manufacturers. Another standard is MIL-DTL-46177; [2] however, this standard has been inactivated, and all new designs use MIL-DTL-12560. MIL-DTL-46177 RHA is nearly identical to AR500 in terms of tensile and yield strength. [3] The typical Brinell Hardness range of MIL-A 12560 is 302-400, making it weaker than AR500 which is in the 477-534 range. [4]
Armour or armor is a covering used to protect an object, individual, or vehicle from physical injury or damage, especially direct contact weapons or projectiles during combat, or from a potentially dangerous environment or activity. Personal armour is used to protect soldiers and war animals. Vehicle armour is used on warships, armoured fighting vehicles, and some mostly ground attack combat aircraft.
A rocket-propelled grenade (RPG) is a shoulder-fired missile weapon that launches rockets equipped with an explosive warhead. Most RPGs can be carried by an individual soldier, and are frequently used as anti-tank weapons. These warheads are affixed to a rocket motor which propels the RPG towards the target and they are stabilized in flight with fins. Some types of RPG are reloadable with new rocket-propelled grenades, while others are single-use. RPGs are generally loaded from the front.
Reactive armour is a type of vehicle armour that reacts in some way to the impact of a weapon to reduce the damage done to the vehicle being protected. It is most effective in protecting against shaped charges and specially hardened kinetic energy penetrators. The most common type is explosive reactive armour (ERA), but variants include self-limiting explosive reactive armour (SLERA), non-energetic reactive armour (NERA), non-explosive reactive armour (NxRA), and electric armour. NERA and NxRA modules can withstand multiple hits, unlike ERA and SLERA. A second hit in exactly the same location may potentially penetrate any of those, as the armour in that spot is compromised.
Armour-piercing ammunition (AP) is a type of projectile designed to penetrate armour protection, most often including naval armour, body armour, vehicle armour.
Composite armour is a type of vehicle armour consisting of layers of different materials such as metals, plastics, ceramics or air. Most composite armours are lighter than their all-metal equivalent, but instead occupy a larger volume for the same resistance to penetration. It is possible to design composite armour stronger, lighter and less voluminous than traditional armour, but the cost is often prohibitively high, restricting its use to especially vulnerable parts of a vehicle. Its primary purpose is to help defeat high-explosive anti-tank (HEAT) projectiles.
Chobham armour is the informal name of a composite armour developed in the 1960s at the British tank research centre on Chobham Common, Surrey. The name has since become the common generic term for composite ceramic vehicle armour. Other names informally given to Chobham armour include Burlington and Dorchester. Special armour is a broader informal term referring to any armour arrangement comprising sandwich reactive plates, including Chobham armour.
A high-explosive squash head (HESH), in British terminology, or a high-explosive plastic/plasticized (HEP), in American terminology, is a type of explosive projectile with plastic explosive that conforms to the surface of a target before detonating, which improves the transfer of explosive energy to the target. Squash head projectiles are similar to high-explosive projectiles and are well suited to many of the same targets. However, while HESH projectiles are not armour-piercing, they can defeat armored targets by causing spall, which can injure or kill a vehicle's occupants or detonate some types of ammunition.
Sloped armour is armour that is oriented neither vertically nor horizontally. Such angled armour is typically mounted on tanks and other armoured fighting vehicles (AFVs), as well as naval vessels such as battleships and cruisers. Sloping an armour plate makes it more difficult to penetrate by anti-tank weapons, such as armour-piercing shells and rockets, if they follow a more or less horizontal trajectory to their target, as is often the case. The improved protection is caused by three main effects.
Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fighting vehicles like tanks, aircraft, and ships.
A ballistic plate, also known as an armour plate, is a protective armoured plate inserted into a carrier or bulletproof vest, that can be used stand-alone, or in conjunction with other armour. "Hard armour" usually denotes armour that uses ballistic plates.
The following is a list of ammunition fired by the 125 mm smoothbore gun series used in the T-64, T-72, T-80, M-84, T-90, PT-91, T-14 Armata, and other tanks derived from those designs, as well as the 2A45 Sprut anti-tank gun.
Armour with two or more plates spaced a distance apart falls under the category of spaced armour. Spaced armour can be sloped or unsloped. When sloped, it reduces the penetrating power of bullets and solid shot, as after penetrating each plate projectiles tend to tumble, deflect, deform, or disintegrate; spaced armour that is not sloped is generally designed to provide protection from explosive projectiles, which detonate before reaching the primary armour. Spaced armour is used on military vehicles such as tanks and combat bulldozers. In a less common application, it is used in some spacecraft that use Whipple shields.
The 14.5×114mm is a heavy machine gun and anti-materiel rifle cartridge used by the Soviet Union, the former Warsaw Pact, modern Russia, and other countries.
The Ordnance QF 20 pounder was a British 84 mm (3.307 inch) tank gun. It was introduced in 1948 and used in the Centurion main battle tank, Charioteer medium tank, and Caernarvon Mark II heavy tank. After the 20 pounder gun was found to have inadequate performance against the Soviet T-54 the gun was mostly replaced in service by the larger calibre 105 mm L7 gun.
37 mm anti-tank gun model 1930 (1-K) was a Soviet light anti-tank gun used in the first stage of the German-Soviet War.
Ceramic armor is armor used by armored vehicles and in personal armor to resist projectile penetration through its high hardness and compressive strength. In its most basic form, it consists of two primary components: A ceramic layer on the outer surface, called the "strike face," backed up by a ductile fiber reinforced plastic composite or metal layer. The role of the ceramic is to (1) fracture the projectile or deform the projectile nose upon impact, (2) erode and slow down the projectile remnant as it penetrates the shattered ceramic layer, and (3) distribute the impact load over a larger area, which can be absorbed by ductile polymer or metallic backings. Ceramics are often used where light weight is important, as they weigh less than metal alloys for a given degree of resistance. The most common materials are alumina, boron carbide, and, to a lesser extent, silicon carbide.
A main battle tank (MBT), also known as a battle tank or universal tank, is a tank that fills the role of armor-protected direct fire and maneuver in many modern armies. Cold War-era development of more powerful engines, better suspension systems and lighter composite armor allowed for the design of a tank that had the firepower of a super-heavy tank, the armor protection of a heavy tank, and the mobility of a light tank, in a package with the weight of a medium tank. The first designated MBT was the British Chieftain tank, which during its development in the 1950s was re-designed as an MBT: "Chieftain, which until then had been called Medium Gun Tank No 2, was renamed the Main Battle Tank". Through the 1960s and 1970s, the MBT replaced almost all other types of tanks, leaving only some specialist roles to be filled by lighter designs or other types of armored fighting vehicles.
The Kanchan Armour is the name informally given to a modular composite armour developed by India. The armour got its name from Kanchan Bagh, Hyderabad, Telangana, where the Defence Metallurgical Research Laboratory (DMRL) is located.
Non-explosive reactive armour (NxRA), also known as non-energetic reactive armor (NERA), is a type of vehicle armor used by modern main battle tanks and heavy infantry fighting vehicles. NERA advantages over explosive reactive armor (ERA) are its inexpensiveness, multi-hit capability, and ease of integration onto armored vehicles due to its nonexplosive nature.
The Obiekt 490 "Poplar", or Object 490, was an experimental Soviet tank developed in the early 1980s. Two versions of the vehicle existed under the same project name, however the designs were radically different, with the second being one of the most unusual designs in the history of tank development. The vehicle was designed by Eugenie Morozov, who was the son of Alexander Alexandrovich Morozov. The project was cancelled in 1991 following the collapse of the USSR and Morozov's death.