DCASS presentation V3

Air Force Institute of Technology
Topology Optimization of
Additively Manufactured
Penetrating Warheads
Hayden Richards
Masters Student
Department of Aeronautics and Astronautics
David Liu
AFIT Assistant Professor
Department of Aeronautics and Astronautics
4 Mar 15
Overview
• Problem Overview
• Motivations / Goals
• Research Methodology
• Optimization Strategies
• Design Process
• Results & Discussion
• Preliminary Warhead(s)
• Optimizations & Analysis
• Design, Printing, and Testing Details
• Summary / Conclusions
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Problem Statement
• Problem: Traditionally manufactured penetrator warhead cases have undesirable
fragmentation properties because of their thick walls.
• Question: Can a warhead be designed to maintain penetrative performance while
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Motivation
• Additive Manufacturing ‘3D Printing’
• Lattice Structures
• Topology Optimization
http://www.shining3dscanner.com/en-us/Direct_metal_laser_sintering.html
http://patapsco.nist.gov/imagegallery/details.cfm?imageid=1328
http://www.manufacturingthefuture.co.uk/research/
Sigmund, O. ‘A 99 line topology optimization code written in Matlab’
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Goals
• Primary Goals
• Explore the viability of additive manufacturing as a method
for penetrating warhead production
• Reduce wall thickness for better fragmentation performance
while maintaining penetration capability
• Fabricate and test printed warheads
• Supporting Capabilities
• Introduce lattice structures as possible to reduce mass
• Use topology optimization to influence design decisions
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Research Methodology
1) Fabricate standard design using AM methods
2) Define test parameter loading conditions
3) Produce optimized warhead solution through topology
optimization process
4) Translate solution into actual optimized warhead design
5) Fabricate optimized design using AM methods
6) Perform further analysis and live-fire testing
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Standard Design
• Unitary warhead case
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Mat’l = 15-5 Stainless
Length = 7.50 in
Diameter = 1.00 in
Walls < 0.120 in thick
CRH as specified
• To be closed using traditionally
manufactured end cap
• Designed using Solidworks 2013
• Printed using DMLS on EOS
M270-M280 series
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What is the standard design, explain
Explain three iterations, evolution
Model Generation
• HyperWorks was used for all FEA and optimization work
• Motivation for loading conditions:
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Talk about problem: how do we take the standard case and change its performance? What process was used for this
Have drawing of problem impact
Optimization Generation
• Derivation of optimization parameters:
• Size, shape, C.G., and total mass were conserved
• Design space was inner 50% of the wall thickness and entire interior
area / volume
• Internal volume fraction was used to control mass
• Compliance was used for optimization objective
• Displacement was used as the measure of merit
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Test Parameter Loading
= Applied forces
= Constraints
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Warhead Optimization
• Optimization parameters:
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Decision variable: 2D design property
Responses: comp = total compliance, volfrac = design property
volume fraction
Constraint: volfrac = (0.20-0.30)
Objective: minimize comp
Loadstep: C2-F2 (body, angle), min/max member size 0.5-1.0
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Solution-Design Translation
1) Import solution to Solidworks, identify desired solid
regions (consider printability limitations):
2) Revolve regions to form solid, cut longitudinal channels,
generate outer case wall separately:
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Once we have solution, how do we transform into 3D body?
Solution-Design Translation
3) Develop ideal lattice structure (ensure printability) and
shape to desired volume to fill moderate-density spaces:
4) Combine these two pieces together to generate internal
structure (solid and lattice):
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Solution-Design Translation
• Combine to form entire warhead with case wall in printing
configuration and additional machined end cap:
• Optimized has ~30-40% thinner walls than standard
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Optimized Design Fabrication
• EOS M280 in PH1 / 15-5 stainless steel
Optimized
design (3)
Standard
Design (2)
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Fabrication Overview
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Preliminary Warhead
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Standard Warhead #1 (S1-1, S1-2)
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Standing up, rough stock removed
C.G. location unsatisfactory for test
Standard Warhead #2 (S2-1, S2-2)
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Laying down orientation
Out-of-round, outside tolerance
Standing up, printed to size
Mass, C.G. matched
Optimized Warhead #1 (O1-1, O1-2)
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Standing up, printed to size
Requires further post-processing
Mass, C.G. matched
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Live-Fire Testing
• Goals are:
• Have both AM warheads survive penetration event
• Measure penetration
• Have AM optimized design penetrate deeper than AM
standard design in both obliquity conditions
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Live-Fire Testing
• Test Data:
• Instrumented:
• Flight attitude information
• Penetration depth and character
• Warhead recovery
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Flight Attitude HSDCs
• Side:
• Top:
• Target:
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HSDC flight videos
• Side, O1-1
• Overhead, S2-1
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(FH, S7)
(FO, S4)
Penetration Performance
• Penetration Data:
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Penetration HSDC videos
• O1-2:
• S2-2:
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T S5
T S6
Warhead Recovery
• First Standard Warhead Designs:
• S1-1:
• S1-2:
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Warhead Recovery
• 0º Oblique Warhead Designs:
• S2-1:
• O1-2:
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Warhead Recovery
• 20º Oblique Warhead Designs:
• S2-2:
• O1-1:
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Summary
• Problem Overview
• Motivations / Goals
• Research Methodology
• Optimization Strategies
• Design Process
• Results & Discussion
• Preliminary Warhead(s)
• Optimizations & Analysis
• Design, Printing, and Testing Details
• Summary / Conclusions
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Lessons Learned
• Specific lessons learned during design processes:
• Regarding topology optimization:
• Consider and recognize all assumptions and simplifications used to
generate models and perform analyses / optimizations
• Trust the optimization routine to generate a valid result, but only
provided the input parameters are valid and appropriate
• Regarding design for additive manufacturing:
• Design for 3D printing requires many iterations
• Design to printer capabilities and accept complications
• Take advantage of machine capabilities
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Project Conclusions
• Additive manufacturing is the only suitable method for the
production of complex geometries such as those used in this
research
• However, there are still limitations due to specific additive
manufacturing techniques which resulted in design
compromises
• Cost can rely heavily on design
• Additive manufacturing can produce parts generated by
topology optimization techniques
• Empirical testing is the best method of confirming analytical
results, especially given the dynamic nature of this problem
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Sponsors
• This research was sponsored by:
• Damage Mechanisms, Munitions
Directorate, Air Force Research
Laboratory, and
• Joint Aircraft Survivability Program
Office.
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Questions?
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Abstract
Research at the Air Force Institute of Technology explored the viability of producing
penetrating warheads using 3D printing.
Three different warhead designs were
developed in this research, all with constant outer diameter, length, mass, and center of
gravity location. Two of the designs, referred to as the “standard designs,” were unitary
with a constant-thickness case wall representing typical penetrating warhead designs.
The third warhead design, referred to as the “optimized design,” was developed based on
topology optimization solutions under loading conditions reflective of penetration events.
The optimized warhead design, to improve fragmentation characteristics, reduced case
wall thickness by 40% by relocating the mass removed from the unitary walls to internal
structures within the warhead. Lattice structures occupied moderate-density regions
within the topology optimization solution. Based on Finite Element Analysis (FEA)
calculations, the optimization solution guiding the optimized warhead design reduced
total warhead compliance by 90.1% compared to the two unitary models. Two warheads
were produced for each of the three different designs. The finished warheads were livefire tested at Eglin Air Force Base, Florida and tested against 5 ksi semi-infinite contained
concrete targets at 0º and 20º angles of obliquity (AoO). For 0º AoO tests, the standard
warheads demonstrated the effectiveness of 3-D printed steels by penetrating similarly to
equivalent wrought steels. For 20º AoO tests, significant “tail slap” was observed and
caused significant structural damage to both warheads. The results of this test helped to
support AFRL/RW research on the use 3D printing for future Air Force munitions.
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200word abstract V3
References
•
3DSystems, “3DS Phenix Systems Datasheet” 3D Systems, Inc., Rock Hill, SC, 2013. URL: http://www.
3dsystems.com/sites/www.3dsystems.com/files/phenix-metal-3d-printers-usen.pdf [cited 30 May 2014].
•
3D Systems Inc. Direct metal production 3D printers. 2014. Available: http://www.3dsystems.com/sites/www.
3dsystems.com/files/direct-metal-brochure-0214-usen-web.pdf.
•
Hao, L., Raymont, D., Yan, C., Hussein, A., and Young, P., “Design and Additive Manufacturing of Cellular Lattice
Structures” College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, United
Kingdom, 2012. URL: http://www.manufacturingthefuture.co.uk/research/ [cited 29 May 2014].
•
M. F. Ashby. The properties of foams and lattices. Philos. Trans. A. Math. Phys. Eng. Sci. 364(1838), pp. 15-30.
2006. . DOI: 10.1098/rsta.2005.1678 [doi].
•
Wadley, H.N.G., “Cellular Metals Manufacturing” Advanced Engineering Materials 2002, Vol. 4, No. 10, 2002, pp.
726-732.
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M. P. Bledsoe and O. Sigmund, "Topology Optimization; Theory, Methods, and Applications," pp. 2, 2003.
•
EOS GmbH – Electro Optical Systems, “EOS StainlessSteel PH1 for EOSINT M270” Material Data Sheet, EOS
GmbH, Munich, Germany, 2008.
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