The effect of the Chieftain tank's high-explosive armor-piercing shells on armor
We have previously published some rather interesting reports on the testing of the British tank A Chieftain tank, which fell into the hands of Soviet researchers virtually undamaged during the Iran-Iraq War. Another article in this series examines the effects of this tank's 120mm high-explosive armor-piercing shells on armor and compares them with domestic high-explosive fragmentation tank shells.
From a practical standpoint, this report may not be so interesting, since the British have already abandoned the use of this ammunition in favor of installing a smoothbore gun on the Challenger 3, and the only modern non-British tank capable of firing the BFS is the Indian Arjun, which is in limited supply. Nevertheless, at least in historical In terms of material, it's quite good.
The effect of armor-piercing high-explosive shells on armor
The Chieftain Mk5P tank's ammunition load includes L31A7 high-explosive armor-piercing shells (HES), which, when fired into a tank with monolithic armor, cause fragments to break off from the rear of the armor, causing damage inside the tank, and the impact action can cause damage to the tank's internal equipment.
The performance of the L31A7 BFS was studied on composite and monolithic armor in comparison to the impact of high-explosive fragmentation projectiles (HEF). The impact response (impact spectra) of measuring transducers (MT) with various natural oscillation frequencies f₀, which serve as a dynamic analogue of shock-absorbing components and instruments of internal equipment with a linear elastic characteristic, was examined.
The response of such impulse sensors is proportional to the projectile's impulse to the armor element. The measuring transducer is an inertial mass weighing between 0,4 kg and 8 kg, mounted on dual shock absorbers such as the APN-675 (f₀ = 50–95 Hz) or on shock absorbers such as the ATRM-20/50 (f₀ = 22–44 Hz). Two to four piezo accelerometers such as the IS-313A or ABC-06-02 are mounted on the inertial mass using epoxy compound.
Accelerations were recorded using N-115 light-beam oscilloscopes with IS-943A and IS-1301 preamplifiers. The operating frequency band of the measuring circuit was 15–2000 Hz. The process under study was recorded on photographic paper and processed using graphic smoothing to isolate the primary component of the shock-oscillatory motion.
To obtain data on the impact action of the BFS, at various points on the rear surface of the combined armor of the upper frontal plate and the turret of the tank, IPs with natural frequencies of 22, 44, 50, 70 and 85 Hz were installed on welded booms, and on plates of monolithic armor - with frequencies of 50 and 95 Hz.
During the experimental determination of the damaging effect of the BFS on the spall destruction of the rear surface of monolithic armor, the shelling of armor plates of different thicknesses was carried out at an angle of 60° to the normal, and on a plate with a thickness of 160 mm, the action of the BFS was simultaneously assessed based on the reaction of the IP.
The results of the study of the reaction of the inertial particle blast to the impact of a 120-mm BFS shell in the central zone of the upper frontal plate and in the right part of the turret of a tank with composite armor are compared with the reaction to the impact of 115 and 125 mm caliber HE shells (Figs. 1, 2), and the reaction of the inertial particle blast to the shelling of an armor plate measuring 2750 × 2800 × 160 mm at an angle of 60° from the normal is compared with the reaction to the shelling of 100, 115 and 125 mm caliber HE shells (Table 1). The same table (see Fig. 1) presents the results of the calculated assessment of the reaction of the inertial particle blast to the impact of a 125-mm HE shell in the center of the upper frontal plate of the Chieftain tank.
Fig. 1. Experimental values of the reaction force (acceleration J) to an impact when firing at the upper frontal plate of a tank with combined armor with a BFS and an HEFS (1 — 120 mm BFS at a speed of vₚ = 645 m/s; 2 — 125 mm HEFS, vₚ = 850 m/s; 3 — 115 mm HEFS, vₚ = 780 m/s) and the calculated values of the reaction force when hitting the upper frontal plate of the Chieftain tank with a 125 mm HEFS (curve 4). Fig. 2. Experimental values of the reaction force to an impact when firing at the turret of a tank with combined armor with a BFS and HEFS at course angles of 23–30°: 1 — 120 mm BFS, vₚ = 645 m/s; 2 — 125 mm OFS, vₚ = 850 m/s; 3 — 115 mm OFS, vₚ = 780 m/s.
The results of an experimental assessment of the after-armor impact of 120mm BFS and 115mm and 125mm HE shells on a tank hull with composite armor show that the dynamic loads from the 120mm BFS are, on average, 15% lower than those from the 125mm HE shell and 5-10% higher than those from the 115mm HE shell. When hitting the frontal portion of the turret, the dynamic loads from the 120mm BFS are, on average, 15% higher than those from the 125mm HE shell and 50% higher than those from the 115mm HE shell.
When hitting a turret, the reduced effectiveness of the HEFS compared to the BFS is explained by the difference in their operating principles. The BFS operates through the mechanical impact of the projectile body against the obstacle before the explosive charge detonates, and the detonation momentum of the explosive charge. Therefore, the load is distributed locally, and the projectile's impact momentum is almost completely transferred to the obstacle.
The primary effect of the HEFS is to create a stream of high-velocity fragments distributed over a large area, generated by the shell's detonation. However, since the turret has a relatively low profile, a significant portion of the effective fragment stream misses the turret, and only a portion of the shell's full momentum is transferred to it.
The results of the studies of the damaging effect of the 120 mm BFS on spall destruction of the rear surface of homogeneous armor, in which the spall velocity was determined using a high-speed movie camera and target frames (Table 2), showed that the maximum plate thickness at which spall destruction occurs when fired at an angle of 60 degrees to the normal by the 120 mm BFS is 150 mm, and due to the detonation of the flattened explosive, the dent reaches a depth of 10 mm and a diameter of approximately 2,2 calibers.
Conclusions
1. The behind-the-armor impact effect of the 120-mm armor-piercing high-explosive projectile of the Chieftain Mk5P tank on composite armor is approximately equivalent to the effect of a 125-mm high-explosive fragmentation projectile on this armor.
2. When a 120 mm high-explosive armor-piercing shell from a Chieftain Mk5P tank hits a 150 mm thick homogeneous armor plate at an angle of 60 degrees from the normal, the rear surface of the armor breaks off, and fragments can hit internal equipment and the tank crew.
Source:
"The Effect of an Armor-Piercing High-Explosive Projectile on Armor." V.V. Gayun, A.V. Grishkun, O.P. Gusev, et al. Scientific and technical collection "Problems of Defense Technology," series VI, issue 5 (111). Declassified by the expert commission of the Federal State Autonomous Educational Institution of Higher Education "SPbPU": act No. 2 of November 23, 2016.
Information