design and modeling of a thermoplastic composite tail …...design and modeling of a thermoplastic...
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Design and Modeling of a Thermoplastic Composite Tail Cone for a Kinetic Energy Penetrator
Design and Modeling of a Thermoplastic Composite Tail Cone for a Kinetic Energy PenetratorJuan Serrano, Uday Vaidya, Adolfo Villalobos, and George HusmanSchool of EngineeringUniversity of Alabama at Birmingham
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INTRODUCTION
Kinetic Energy PenetratorM1A1 tanks have a 120mm smooth bore gun that fires several types of ammunition.
ProjectileTailcone Primer
Sabot Cartridge Case Propellant
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DETAIL OF TRAINING ROUND PROJECTILE COMPONENTS
Projectile (Body)
Tailcone
Threaded Section
Tracer
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TAILCONE XM 1002 PROJECTILECURRENT DESIGN
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ROLE OF TAIL CONE IN KINETIC ENERGY PENETRATORS
Two kinds of rounds: Practicerounds 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
Fin Stabilized
Tail ConeStabilized
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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
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LONG FIBER THERMOPLASTICS
• Fiber aspect ratio ~ 600-2400• 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
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BACKGROUND INFO ON THE JOURNEY OF THE TAIL CONE
Source: Army Research Laboratory
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BEFORE DETONATION
05000
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0 1 2 3 4 5 6 7050100150200250300350400450
Acceleration (g) Pressure (MPa)
Time (ms)
ProjectilePrimer
Sabot
Cartridge Case
PropellantTailcone is the only component that sits inside the chamber
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MAXIMUM PRESSURE AND ACCELERATION (IN BORE)
Maximum acceleration of 44,300 g at 1.95 ms
Maximum pressure of 406 MPa at 1.95 ms
Average temperature of 1980 K
05000
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Acceleration (g) Pressure (MPa)
Time (ms)
You cannot replicate these conditions in the lab, therefore FEA is the most efficient route to address this problem
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OUT OF BORE
05000
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Acceleration (g) Pressure (MPa)
Time (ms)
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
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FINITE ELEMENT ANALYSIS, DESIGN AND VERIFICATION
Source: Army Research Laboratory
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Two (2) dimensional axisymmetric mesh of the tailcone was generated to optimize computational time for solution convergenceThe use of an expandable 2d model allows for the use of a highly refined finite element mesh Quads were used in the analysis
MESHING DETAILS
Structural Analysis: PLANE 42
Thermal Analysis: PLANE 55
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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.
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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 transientthermal analysis.
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DETAILED MESH
Simplifying problem allowed for fine meshing.
Computational time was very short.
Not more than 2 minutes using a Pentium 4 - 2.4Ghz 1 GB RAM2d model Axisymmetric expansion
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ALUMINUM TAIL CONE ANALYSIS
• Thermal analysis for in-bore and out-of-bore conditions
• Structural analysis in-bore
100805Melting T (solidus) (K)
500960Specific Heat (J/kg*K)
50130Thermal Conductivity (W/m*K)
0.270.33Poisson's Ratio
20071.7Modulus (GPa)
N/A503Tensile Strength (MPa)
78002810Density (kg/m3)SteelAluminumProperty
From: www.matweb.com
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THERMAL ANALYSIS (ALUMINUM)TRANSIENT SOLUTION IN BORE
Steel
Aluminum
Initial Temp - 300 K
Applied Temp1980 K
Unknown temperature surfaces
Temperature in K
0.84 mm of molten material
Steel
AluminumIn-bore condition thermal analysis at 6 ms for 7075 aluminum and steel
0.40 mm affected steel
Boundary conditions Post processing
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Transient condition thermal analysis 5 s for 7075 aluminum and steel
Temperature in K
Steel
Aluminum
Applied Temp 550 K
Steel
Aluminum
Initial Temperature from in-bore analysis
Frictional heat when in contact with air
THERMAL ANALYSIS (ALUMINUM)TRANSIENT SOLUTION OUT OF BORE
Boundary conditions Post processing
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STRUCTURAL ANALYSIS (ALUMINUM)LINEAR ELASTIC IN BORE
Pressure
Displacement constrains in X and Y
x
y
Stresses in Pa
In-bore condition von Mises analysis for 7075 Aluminum
Boundary conditions Post processing
G’s
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DESIGN CONCEPT
• The tail cone is formed by a long fiber thermoplastic molded portion with a metal insert
• Geometry replicates that of the aluminum tail cone (hollow back)
Metal Insert
LFT Tail cone
25 mm
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LFT COMPOSITE TAIL CONE ANALYSYS
• Thermal analysis for in-bore and out-of-bore conditions
• Structural analysis in-bore
271Melting T (K)
2200Specific Heat (J/kgK)
0.52Thermal Conduction (W/mK)
0.4Poisson's Ratio
13.79Modulus (GPa)
221Tensile Strength (MPa)
1460Density (kg/m3)
PA 66 – 40% GFProperty
From: www.rtpcompany.com
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In-bore thermal analysis at 6 ms for PA 66 – 40% GF, 6061 Aluminum and Steel
Temperature in K
Aluminum
Steel
LFT
0.065 mm of molten material
THERMAL ANALYSIS LFT TRANSIENT IN BORE
Steel
Aluminum
Initial Temp = 300 K
Applied Temp 1980 K
PA 66 -40%GF
Boundary conditions Post processing
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THERMAL ANALYSIS LFT DESIGNTRANSIENT OUT OF BORE
Steel
Aluminum
Initial temp from in-bore analysis
PA 66 - 40%GF
Out-of-bore thermal analysis at 5 s for PA 66 -40%GF, Aluminum 6061 and Steel
Steel
LFT
Aluminum
The LFT has a small heat affected region, when compared to aluminum
Temperature in K
Applied Temp 550 K
Boundary conditions Post processing
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STRUCTURAL ANALYSIS LFT DESIGNLINEAR ELASTIC IN BORE
Pressure
Gravity
Fully Constrained
Normal Constraints
Normal Constraints
In-bore condition Tsai-Wu ratio analysis for threaded geometry PA 66 - 40% GFDetail
Failure Criteria
Boundary conditions Post processing
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INITIAL FIRING TRIALS
Observed failure path
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TRANSITION REGION
05000
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Acceleration (g)
Time (ms)
Acceleration
Pressure
Pressure (MPa)
P0
P0
High pressure gas escapes from chamber
Pi
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• Pressure is 1/7th of the pressure in-bore
• Difference in pressure cause higher stresses
• Moment caused by the force F at a distance L
TRANSITION REGION
P2
P0
M
F
L
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STRUCTURAL ANALYSIS (ALUMINUM)LINEAR ELASTIC TRANSITION
Pressure
Constraints in X and Y
x
y
Stresses in Pa
Transition condition von Mises analysis for 7075 Aluminum (without gravitational acceleration)Detail
Failure Region
Boundary conditions Post processing
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Failure Criteria
Transition condition Tsai Wu ratio analysis for threaded geometry PA 66 - 40% GF(Detail)
Failure Path
STRUCTURAL ANALYSIS LFT DESIGNLINEAR ELASTIC TRANSITION
Post processing
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ANOTHER LOOK AT THE FIRING TRIALS
Observed failure path
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REVISED DESIGN CONCEPT:FILLED BACK TAIL CONE
• The filled back LFT tailcone advantages:
– Smaller moment arm– Larger area subjected
to P2– Thicker moment arm
F
M
L
P0
P2
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STRUCTURAL ANALYSIS LFT DESIGNLINEAR 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
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x-displacement plot of the stressed tailcone relative to its original position
Region of maximum displacement of the interface (average of 0.09 mm)
Displacement (m)
STRUCTURAL ANALYSIS LFT DESIGNLINEAR ELASTIC TRANSITION
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SECOND SET OF FIRING TRIALSFILLED BACK LFT COMPOSITE
Three part sabot
LFT tailcone
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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.
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SUMMARY (CONT)
• The LFT tail cone is projected to cost 20% that of the aluminum version.
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ACKNOWLEDGEMENTS
• Army Research Laboratory Co-operative agreement W911NF-04-2-0018
• James Sands, James Garner and Pete Dehmer, Army Research Laboratory