Design and Modeling of a Thermoplastic Composite Tail Cone for a Kinetic Energy Penetrator

Transcription

1 Design and Modeling of a Thermoplastic Composite Tail Cone for a Kinetic Energy Penetrator Juan Serrano, Uday Vaidya, Adolfo Villalobos, and George Husman School of Engineering University of Alabama at Birmingham

2 INTRODUCTION Kinetic Energy Penetrator M1A1 tanks have a 120mm smooth bore gun that fires several types of ammunition. Projectile Tailcone Primer Sabot Cartridge Case Propellant

3 DETAIL OF TRAINING ROUND PROJECTILE COMPONENTS Threaded Section Projectile (Body) Tracer Tailcone

4 TAILCONE XM 1002 PROJECTILE CURRENT DESIGN

5 ROLE OF TAIL CONE IN KINETIC ENERGY PENETRATORS Two kinds of rounds: Practice rounds and Combat rounds In combat rounds, the projectile does not have a tailcone, but it is fin-stabilized Purpose of a tailcone is to provide stability and limit the range of the projectile Tail Cone Stabilized Fin Stabilized

6 MOTIVATION Conventional tail cone made of 7075 T6 aluminum adequate properties but expensive (machining) Explore lower cost materials and processing options that yield similar performance Finite Element Analysis is the only efficient way to design such a component

7 LONG FIBER THERMOPLASTICS Fiber aspect ratio ~ Superior mechanical properties than unreinforced TP Higher impact strength Reduced tendency to creep Damping Corrosion resistance High volume processability Ability to fill complex geometries 20 mm

8 BACKGROUND INFO ON THE JOURNEY OF THE TAIL CONE Source: Army Research Laboratory

9 BEFORE DETONATION Propellant Tailcone is the only component that sits inside the chamber Primer Cartridge Case Sabot Projectile Acceleration (g) Pressure (MPa) Time (ms)

10 MAXIMUM PRESSURE AND ACCELERATION (IN BORE) Maximum pressure of 406 MPa at 1.95 ms Maximum acceleration of 44,300 g at 1.95 ms Average temperature of 1980 K You cannot replicate these conditions in the lab, therefore FEA is the most efficient route to address this problem Acceleration (g) Pressure (MPa) Time (ms) 5 6 7

11 OUT OF BORE Projectile takes 6.15 ms to reach the end of the chamber The stresses are various orders of magnitude smaller when compared to the in-bore case Frictional heat when in contact with air Acceleration (g) Pressure (MPa) Time (ms)

12 FINITE ELEMENT ANALYSIS, DESIGN AND VERIFICATION Source: Army Research Laboratory

13 MESHING DETAILS Two (2) dimensional axisymmetric mesh of the tailcone was generated to optimize computational time for solution convergence The use of an expandable 2d model allows for the use of a highly refined finite element mesh Quads were used in the analysis Structural Analysis: PLANE 42 Thermal Analysis: PLANE 55

14 MESHING DETAILS (2) PLANE 42 was used as the element type for the pressure and gravitational simulations. Used for 2-D structural modeling of solid structures. It has capabilities to be used either as a plane element (plane stress or plane strain) or as an axisymmetric element. The element is defined by four nodes having two degrees of freedom at each node: translations in the nodal x and y directions. The element has plasticity, creep, swelling, stress stiffening, large deflection, and large strain capabilities.

15 MESHING DETAILS (3) PLANE 55 was used for thermal analysis of the tail cones. PLANE 55 can be used as a plane element or as an axisymmetric ring element with a 2-D thermal conduction capability. The element has four nodes with a single degree of freedom, temperature, at each node. The element is applicable for steady-state or transient thermal analysis.

16 DETAILED MESH 2d model Axisymmetric expansion Simplifying problem allowed for fine meshing. Computational time was very short. Not more than 2 minutes using a Pentium 4-2.4Ghz 1 GB RAM

17 ALUMINUM TAIL CONE ANALYSIS Thermal analysis for in-bore and outof-bore conditions Property Density (kg/m 3 ) Tensile Strength (MPa) Aluminum Steel 7800 N/A Modulus (GPa) Structural analysis in-bore Poisson's Ratio Thermal Conductivity (W/m*K) Specific Heat (J/kg*K) Melting T (solidus) (K) From:

18 THERMAL ANALYSIS (ALUMINUM) TRANSIENT SOLUTION IN BORE Steel Unknown temperature surfaces Steel 0.40 mm affected steel Temperature in K Initial Temp K Applied Temp 1980 K Aluminum In-bore condition thermal analysis at 6 ms for 7075 aluminum and steel 0.84 mm of molten material Aluminum Boundary conditions Post processing

19 THERMAL ANALYSIS (ALUMINUM) TRANSIENT SOLUTION OUT OF BORE Frictional heat when in contact with air Steel Steel Applied Temp 550 K Temperature in K Initial Temperature from in-bore analysis Aluminum Transient condition thermal analysis 5 s for 7075 aluminum and steel Aluminum Boundary conditions Post processing

20 STRUCTURAL ANALYSIS (ALUMINUM) LINEAR ELASTIC IN BORE Displacement constrains in X and Y G s Stresses in Pa y Pressure x In-bore condition von Mises analysis for 7075 Aluminum Boundary conditions Post processing

21 DESIGN CONCEPT Metal Insert LFT Tail cone The tail cone is formed by a long fiber thermoplastic molded portion with a metal insert 25 mm Geometry replicates that of the aluminum tail cone (hollow back)

22 LFT COMPOSITE TAIL CONE ANALYSYS Thermal analysis for in-bore and out-ofbore conditions Structural analysis inbore Property Density (kg/m3) Tensile Strength (MPa) Modulus (GPa) Poisson's Ratio Thermal Conduction (W/mK) PA 66 40% GF Specific Heat (J/kgK) 2200 Melting T (K) 271 From:

23 THERMAL ANALYSIS LFT TRANSIENT IN BORE Steel Initial Temp = 300 K Steel Aluminum Aluminum Applied Temp 1980 K In-bore thermal analysis at 6 ms for PA 66 40% GF, 6061 Aluminum and Steel Temperature in K LFT PA 66-40%GF Boundary conditions mm of molten material Post processing

24 THERMAL ANALYSIS LFT DESIGN TRANSIENT OUT OF BORE Steel Aluminum Initial temp from in-bore analysis Aluminum PA 66-40%GF Steel Boundary conditions Applied Temp 550 K Out-of-bore thermal analysis at 5 s for PA 66-40%GF, Aluminum 6061 and Steel The LFT has a small heat affected region, when compared to aluminum Post processing Temperature in K LFT

25 STRUCTURAL ANALYSIS LFT DESIGN LINEAR ELASTIC IN BORE Fully Constrained Normal Constraints Normal Constraints Gravity Failure Criteria Pressure In-bore condition Tsai-Wu ratio analysis for threaded geometry PA 66-40% GF Detail Boundary conditions Post processing

26 INITIAL FIRING TRIALS Observed failure path

27 TRANSITION REGION P i High pressure gas escapes from chamber P 0 P 0 Acceleration (g) Pressure (MPa) Acceleration Pressure Time (ms)

28 TRANSITION REGION Pressure is 1/7th of the pressure inbore P 2 P 0 Difference in pressure cause higher stresses F Moment caused by the force F at a distance L L M

29 STRUCTURAL ANALYSIS (ALUMINUM) LINEAR ELASTIC TRANSITION Failure Region Constraints in X and Y y Pressure x Transition condition von Mises analysis for 7075 Aluminum (without gravitational acceleration) Detail Stresses in Pa Boundary conditions Post processing

30 STRUCTURAL ANALYSIS LFT DESIGN LINEAR ELASTIC TRANSITION Failure Path Transition condition Tsai Wu ratio analysis for threaded geometry PA 66-40% GF (Detail) Failure Criteria Post processing

31 ANOTHER LOOK AT THE FIRING TRIALS Observed failure path

32 REVISED DESIGN CONCEPT: FILLED BACK TAIL CONE The filled back LFT tailcone advantages: Smaller moment arm Larger area subjected to P2 Thicker moment arm P 0 L F P 2 M

33 STRUCTURAL ANALYSIS LFT DESIGN LINEAR ELASTIC TRANSITION Transition condition Tsai-Wu ratio analysis PA 66-40% GF (Detail) Failure Criteria 3 of the 22 threads are failing Probable failure path Post processing

34 STRUCTURAL ANALYSIS LFT DESIGN LINEAR ELASTIC TRANSITION x-displacement plot of the stressed tailcone relative to its original position Displacement (m) Region of maximum displacement of the interface (average of 0.09 mm)

35 SECOND SET OF FIRING TRIALS FILLED BACK LFT COMPOSITE Three part sabot LFT tailcone

36 SUMMARY Design and FEA model developed while simple showed to be accurate enough to represent the complicated loading scenario. A successful full-cycle FEA design of a XM1002 training round utilizing LFT composite was demonstrated. The transition region was found to be the most critical condition during firing. The filled-back LFT tail cone was successful in meeting all the loading conditions LFT material has extremely low thermal conductivity. this makes the LFT polymer less prone to failure from temperature.

37 SUMMARY (CONT) The LFT tail cone is projected to cost 20% that of the aluminum version.

38 ACKNOWLEDGEMENTS Army Research Laboratory Cooperative agreement W911NF James Sands, James Garner and Pete Dehmer, Army Research Laboratory