Fragment Patterns Behind Concrete Structures Caused by KE Projectiles

Fragment Patterns behind Concrete Structures caused by KE Projectiles R. Jeanquartier, D. Hoffmann*, S. Lampert and B. Lehmann armasuisse, Science & Technology Departement, Thun, Switzerland *IBH Consulting Services, Schramberg, Germany Overview Interest of Swiss Army: to know more about … effectiveness of ammunition against urban targets (concrete, brick wall) especially medium caliber ammunition (APDSFS and FAPDS) Computer Model (PANZKI3) for vulnerability assessments Modul of ammunition effectiveness against urban targets: Effects of concrete fragments are not yet taken into consideration Aim of present study - learn more about risk for people exposed to concrete fragments - describe the dynamics of concrete fragments in a realistic model - Focus on perforation of concrete walls by KE projectile (APFSDS) 22 nd ISB, 2005 Model projectile mass 152 g Rod material: Tungsten-alloy Y 925 Fin material: Aluminum φ9 M10 x 0.75 φ9 φ 19 20 57 140.6 58 22 nd ISB, 2005 Laboratory gun Acceleration of model projectile smooth barrel powder gun Caliber 38 mm 22 nd ISB, 2005 Specifications of concrete 1 m3 391 kg, 20 V% Bebbles Ø 4 – 8 mm ρ = 2432 kg/m3 586 kg, 30 V% Bebbles Ø 8 – 16 mm Compressive Strength ≈ 40 MPa 977 kg, 50 V% Sand 325 kg Cement + 325 kg Cement + 153 kg Water 153 kg Water 22 nd ISB, 2005 Concrete wall (dim) 1.5 - 2 20 cm 3 3 1.5 - 2 15 x 15 500 cm 1.5 - 2 22 nd ISB, 2005 15 x 15 500 cm Experimental set-up 20mm Styrofoam Reinforced Concrete vi = 900 – 1600 m/s 3mm card board 1mm aluminum 20 cm 0.9 m High Speed Cam 5000 i/s 22 nd ISB, 2005 flash x-ray Soft Catcher Soft catcher (1) 20mm Styrofoam - Small pebbles and concrete lumps were stopped - Mass of stopped fragments is only 5 % of the total crater mass 22 nd ISB, 2005 Soft catcher (2) 3mm card board Perforations were registered, mainly caused by pebbles (in the ring) 22 nd ISB, 2005 Soft catcher (3) bulges perforation holes 1mm aluminum - No perforations of concrete fragments could be observed - only perforations of projectile fragments 22 nd ISB, 2005 High speed recordings Impact velocity of model projectile: vi = 1600 m/s 0.4 ms 0.6 ms 1.4 ms 115 ms 1000 m/s 70 m/s 1440 m/s 500 m/s 22 nd ISB, 2005 x-ray pictures Empirical Formulas x1 x2 “Perforation of Concrete Targets by an eroding Tungsten-alloy Rod“ by Lampert and Jeanquartier 1. x-ray picture k1 = 1.85m k 2 = 1.86 2. x-ray picture −1 L1 L2 vr = 1 − k1 ⋅ d k2 ⋅ vi    k   1+ 4   d Lr = L0 ⋅ 1 − k3 ⋅ d ⋅ exp−     vi     vcrit         d ⋅k 5 ( ) Residual velocity of projectile vr = x1 + x2 ∆t Residual length of projectile Lr = L1 + L2        22 nd ISB, 2005 Residual velocity of projectile Normalized residual velocity versus normalized impact velocity vi vr 1.5 1.4 1.3 1.2 d =20 cm d =20 cm (45°) d = 40 cm vi vr vr/vcrit 45° 1.1 1 0.9 0.8 0.7 vi vr 0.6 0.5 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 vi/vcrit vcrit = 1000 m/s (determined by experiments) 22 nd ISB, 2005 Residual length of projectile Normalized residual length versus normalized impact velocity vi Lr 1.0 0.9 0.8 0.7 Lr/L0 vi 45° 0.6 0.5 0.4 0.3 0.2 d = 20 cm d = 20 cm (45°) d = 40 cm d = 60 cm 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 vi Lr 0.1 0.0 vi/vcrit vcrit = 1000 m/s (determined by experiments) 22 nd ISB, 2005 Fragments of projectile half cone angle ~ 8 ° 1mm Aluminum Plate Residual Projectile Lr Projetile Fragments vr 22 nd ISB, 2005 Excavation crater Cumulative Mass (cone) [kg] Cumulative Mass [kg] 4 m/ s 3 15 80 2 αmax 1 m 950 /s 0 0 10 20 30 40 50 13 50 60 αmax 20 cm α [°] half cone angle 22 nd ISB, 2005 m /s Concrete fragment model (2-dim.) vi vmax vmax v Velocity of concrete fragment v = f3(α) α γ γmax (direction of fragment flight) 22 nd ISB, 2005 Intact Concrete γmax vmax αmax γ = f1(α) γ = f2(α) γ mmax m2 mmax= f4(α) approximation Maximum mass of a largest fragment α γmax = αmax / 2 m1 0 α = γmax αmax α Example Impact velocity: vi = 1350 m/s → vr = 1230 m/s → Lr = 0.83 · L0 → vmax = 1/3 · vr = 410 m/s 350 300 250 E (Joule) 200 150 100 50 0 Maximum possible Energy of a single fragment depending on angle γ 30° < α ≤ 60° x = 10 m x=0m 0° < α ≤ 30° 0 22 nd ISB, 2005 5 10 15 20 25 γ (°) 30 γmax Summary vi γmax vR Lr Residual Projectile with enormous perforation potential ….. and the remaining fragments of projectile ( half cone angle ~ 8°) represent the major threat The fastest concrete fragments are small and the biggest fragments are very slow (half cone angle ~ 30°) From energetic point of view the concrete fragment cloud does not represent a dramatic threat for people But low-energy concrete fragments (unfractured pebbles) are dangerous for an unprotected person and also dust can affect eyes and respiratory organs 22 nd ISB, 2005 Thank you 22 nd ISB, 2005