Numerical and Experimental Methods for. Numerical and Experimental Methods for. Penetrating Glass and Plywood

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1 Numerical and Experimental Methods for Numerical and Experimental Methods for Estimating Impact Acceleration of Small-Caliber Projectile Penetrating Glass and Plywood 49th Annual Fuze Conference April 6, 2005 Sang-Hee Yoon, Young-Ho Lee, Jong-Soo Oh, Seok-Woo Lee Fuze team, Agency for Defense Development Dae-Gil Jeon, Dong-Lib Kim Hanwha Cooperation

2 Introduction Impact acceleration of small-caliber ammunition penetrating soft targets is required for : Structural design of ammunition Structural fracture of ammunition Multi-functional fuze design, especially, PD (Point Detonation) mode and PDD (Point Detonation Delay) mode Malfunction or dud Previous methods to estimate the impact acceleration of ammunition G-t kit (shock recorder) : large size and heavy weight Trial and error : Extracting impact acceleration experimentally High cost and much time We need to develop simple and reliable methods to estimate impact acceleration of small-caliber ammunition penetrating soft targets

3 Project objectives Estimating impact acceleration of the small-caliber ammunition penetrating glass and plywood for application to small-caliber multifunctional fuze with simplicity, low-cost but high-reliability Simulation using Autodyn-2D RBT (Reverse Ballistic Test) technique

4 Simulation using Autodyn-2D What is Autodyn-2D? Interactive non-linear dynamic analysis program Solving complex dynamic behavior problem by discretization of the problem in both time and space Impact acceleration = Fn (ammunition model, muzzle velocity, target model ) Simulation conditions Axisymmetric model 2D analysis Simplified ammunition model Diameter : 20 mm Weight : 100g Material (using material library in Autodyn-2D and material properties at Ogive : Noryl / Ammunition body : Steel & Aluminum / Molding : Kev-epoxy Muzzle velocity : 150 m s, 200 m s Target model Material : flat glass Dimension : Φ 600 mm X t 3 mm Body (Steel) Body (Aluminum) Ogive (Noryl) Molding (Kev-epoxy) Meshing More than 4 meshes in the thinnest element, ogive

5 Simulation using Autodyn-2D (cont.) Simulation Process based on Lagrange technique V o =150 m s V o =200 m s

6 Simulation using Autodyn-2D (cont.) Simulation results V o =150 m s V o =200 m s Max. acceleration : ~4000G Impact duration time : ~20 μs Max. acceleration : ~5500G Impact duration time : ~15 μs

7 Experiments using RBT technique What is RBT technique? Impact test method where a target is fired at a stationary ammunition using a gas gun Why not ballistic test (BT) technique? Impossible to connect the accelerometer in a flying projectile with measuring instruments by a wire Impossible to embed shock recorder within a small-caliber projectile High-cost to measure a impact acceleration using radio telemetry

8 RBT technique (cont.) Experimental setup Before impact After impact

9 RBT technique (cont.) Experiment components 50 mm gas gun Soft catcher Wire

10 RBT technique (cont.) Experiment components Projectile and targets Target 10 mm plywood Projectile 3 mm glass Small-caliber ammunition model Accelerometer

11 RBT technique (cont.) Experiment components Accelerometer 7270A-20KM6, Endevco Piezoresistive accelerometer 10kHz mechanical filter High-resonance frequency Shock survivability Less change in operation characteristics than piezoelectric accelerometer in high-g environment Electric circuit Connected with accelerometer s output line Functions : accelerometer driving, signal amplification, low-pass filtering

12 RBT technique (cont.) Experimental setup Measuring instrument

13 RBT technique (cont.) 1 st RBT Conditions Projectile : Φ 49.8 mm X l 193 mm Muzzle velocity of projectile (target) : 150 m s Impact angle : 90 Target : glass 3 mm thick Measured impact accelerations Measured impact acceleration Trigger signal

14 RBT technique (cont.) 1 st RBT results Max. acceleration : 4890G Impact duration : 15 μs Max. acceleration : 4230G Impact duration : 13 μs

15 RBT technique (cont.) 2 nd RBT Conditions Projectile : Φ 49.8 mm X l 200 mm Muzzle velocity of projectile (target) : 150 m s Impact angle : 90 Target : plywood 10 mm thick Measured impact acceleration Max. acceleration : 3802G Impact duration : 60 μs

16 Operational test Firing test setup Test arms Small-caliber ammunition Target (glass / plywood) Fuze setter Contact cone Cap Spring Small-caliber ammunition W/ multifunctional fuze (underdeveloped) Inertial impact sensor - operation G: 1000G Sawdust catcher

17 Operational test (cont.) Firing test results Mode : PD, Target : ordinary flat glass 3 mm thick Mode: PD, Target : plywood 10 mm thick Mode: PDD, Target: tempered glass 3 mm thick Mode: PD, Target : plywood 10 mm thick

18 Summary and conclusions To develop small-caliber multifunctional fuze, we have estimated the impact acceleration of small-caliber ammunition penetrating glass and plywood based on the simulation results using Autodyn-2D and the experimental results using RBT technique. In simulation, the impact acceleration of small-caliber projectile with the velocity of 150 m s and 200 m s penetrating glass 3 mm thick have been 4000G with the duration of 20 μs and 5500G with the duration of 15 μs, respectively. In RBT test, the impact acceleration of small-caliber projectile with the velocity of 150 m s penetrating glass 3 mm thick and plywood 10 mm thick have been 4500G with the duration of 14 μs and 3800G with the duration of 60 μs, respectively. Firing test results have shown that the simulation using Autodyn-2D and the experiments using RBT technique are suitable for analyzing the impact acceleration of the small-caliber ammunition penetrating soft targets