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Frédéric Boilard, Application Engineer, MAYA HTT Ltd.
Eric Preissner, Principal, PEC LLC
FEMAP for the Space Industry
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Page 2 Siemens PLM Software
MAYA and PEC Introduction
LDCM/MMS Space Craft Shipping Container Case Study
Femap SA Toolkit
Questions
Agenda Femap SA Toolkit Suite
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Page 3 Siemens PLM Software
MAYA Heat Transfer Technologies
•Leading Simulation Software Development Company
•Over 25 years of experience in design & development of
• Thermal, Flow and Structural simulation software
•Embedded Partner for Siemens PLM Software for over 25 years
•>125 Employees
• Specialists in Heat Transfer, CFD and Structural Analysis
•Main Activities
• Software Design & Development
• Engineering Consulting Services
• Software Implementation & Training
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Page 4 Siemens PLM Software
MAYA Developed Siemens PLM Software Products
I-deas (GUI & Solvers)
• TMG Thermal
• TMG Radiation
• Electronic Simulation
• Laminates
• FE solver translators
• PCB Interface
Femap (GUI & Solvers)
• Thermal
• Flow
NX (GUI & Solvers)
• Thermal and Advanced Thermal
• Flow and Advanced Flow
• Electronic Systems Cooling
• Space Systems Thermal
• Laminate Composites
• FE/Test Correlation
• FE solver environments
• PCB Exchange
• Datacenter Clarity LC
Nastran
• Structural Analysis Toolkit
• Model Update I-deas
• Test
• Sound Quality
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Preissner Engineering & Consulting LLC
• PEC LLC is a customer-focused small business dedicated to advanced
analysis and design support for customers in the aerospace and specialty
transportation fields.
• PEC was founded in 2010, and has successfully completed a variety of
projects ranging across forensic investigations, industrial machinery,
aerospace components, and heavy-haul specialized transports.
• Eric Preissner, Ph.D., PE is the principal at PEC. Eric has over 20 years of
engineering experience in government, private industry, and research
organizations. Eric and PEC are dedicated to excellent customer support, full
team participation, and continuous improvement.
• Eric can be reached at [email protected].
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The Use of Femap on the LDCM / MMS
Modular Spacecraft Shipping Container
FEMAP Symposium 2013 Eric Preissner, Principal, PEC LLC
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Outline
• The modular shipping container was designed to safely transport space vehicles (SVs)
for two NASA projects:
• Landsat: the world's longest continuously acquired collection of space-based moderate-resolution land remote
sensing data (four decades of imagery). The Landsat Data Continuity Mission (LDCM) launched what is now officially
the Landsat 8 spacecraft. (http://ldcm.gsfc.nasa.gov/index.html)
• MMS: the Magnetospheric Multiscale mission to investigate how the Sun’s and Earth’s magnetic fields connect and
disconnect, controlling geospace weather, which has effects on many modern tecnological systems.
(http://mms.gsfc.nasa.gov/about_mms.html)
Text and images courtesy of NASA and USGS
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Program Team
• Project management: NASA Goddard SFC
• Space vehicle: Orbital Sciences Corp.
• Transportation assembly design and build:
Nelson Manufacturing
• Analysis support: PEC LLC www.pec-llc.com
[email protected] Images courtesy of NASA and Orbital
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Page 9 Siemens PLM Software
How Femap & NX Were Used
• Femap: – importing accurate CAD geometry (numerous times as the design evolved)
– parsing, processing, and meshing this geometry (mesh toolbox)
– managing a FE model with multiple configurations and multiple load cases and analysis types
– integrating multiple major sub-components into a single FEM
– incorporating and using a reduced (DMIG) representation of the satellite for accurate stiffness predictions
– quickly and clearly communicating a significant amount of results.
• NX Nastran: – static and dynamic analyses
– dynamic analyses included both modal (target frequencies) and random vibration (MIL-STD-810)
– static analyses included key linear contact regions for accurate assembly modeling
– many element types were used (beam, plate, laminate, RBE, CONM, CBUSH, etc.)
– NX provided rapid solution times for models up to ~3M DoF to enable numerous design iterations in a short period of time.
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Brief Requirements Overview
• Maximum payload of 16 000 lb
• Container internal volume sized to accept LDCM SV plus transport /
roll-over frame (STF)
– Approximately 11 ft H x 12 ft W x 17 ft L
• Static loads:
– Road transport: 2.0g down, 1.0g fwd/aft, 0.75g lat, lifting
– Safety factors: SFy=2, SFy=3 (road), SFy=3, SFy=5 (lift)
• Dynamic loads:
– Frequency goal for SV + STF (high to avoid resonance)
– Frequency goal for container + transport goosenecks (medium for
isolation)
– MIL-STD-810 over-the-road truck transport vibration for transmissibility
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Page 11 Siemens PLM Software
Transport Assembly, Full View
Front
gooseneck
Cover
Pallet
Rear
gooseneck
Steerable
rear dolly
Transport
frame and SV
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Transport Assembly, STF + SV
STF + SV
STF fully
assembled
Bolted
joints
SV Mount
plane / pads
Hangar
bracket attach
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Transport Assembly, STF + SV
• STF – FE model overview (~140k elem)
SV DMIG representation
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Transport Assembly, STF + SV
• STF – FE model details
Bolting pads for SV
mounting plate
Lifting provision (RBE2
element)
Refined mesh in localized
areas, mainly near joints
Connection at removable
diagonal; welds represented
with plate elements
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• STF – FE model details
Transport Assembly, STF + SV
Isolator mount plate
Solid elements for
crush tubes and lift
provisions
Bolts as beams with
RBE2 connections to
structure
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Page 16 Siemens PLM Software
Plotting Model Properties
• Front gooseneck – FE model material distribution
All plate and fabricated
sections with thickness more
than 0.5” are ASTM A514
steel, “T1,” 100 ksi yield
Deck surface is 3/16” 6061
Aluminum tread plate
All plate and formed sections with
thickness of 0.5” or less are
Domex 100XF steel, 100 ksi yield
Th
ickn
ess d
istr
ibu
tio
n
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Page 17 Siemens PLM Software
Extensive use of Linear Contact
FG lift tower
RG lift tower
Rear steering
turntable
Cover-to-base
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• Full vehicle (~465k elem)
Transport Assembly, Full View
Front
gooseneck
Cover
Pallet
Rear
gooseneck
Steerable
rear dolly
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Page 19 Siemens PLM Software
• A variety of analysis configurations
Managing Multiple Submodels With Femap
Static - RG
Static - FG
Static - PL
Vibe - PL
Static &
vibe - STF
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Page 20 Siemens PLM Software
Envelope and Plot Stress Results
• Rear gooseneck + bogie – stress plot
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Page 21 Siemens PLM Software
Envelope and Plot Stress Results
• STF – lifting configurations
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Page 22 Siemens PLM Software
Interface Force Extraction
• STF – other calculations – welds
Location of weld
for force resultant
1.25” thick
mount block 0.25” thick
tube
Rigid element
connection and grid
point for SV DMIG
Location of weld
for force resultant
0.188” thick
tube
Rigid element
representation of lift
point
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Page 23 Siemens PLM Software
Dynamic Analysis
• MIL-STD-810 random vibration studies – base+STF+SV
Large mass for acceleration input
MIL-STD-810 truck transport input curves. Vetical curve (blue) has max
value of 0.015 g2/Hz
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Dynamic Analysis, Reporting
• MIL-STD-810 random vibration studies – base+STF+SV
Curves 4-6 are attached to SV
Curves 4-6
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Page 25 Siemens PLM Software
Proof Test – STF
Image courtesy of Nelson Manufacturing
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Page 26 Siemens PLM Software
Proof Test – Road Configuration
Image courtesy of Nelson Manufacturing
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Page 27 Siemens PLM Software
Delivery & Launch
Image courtesy of NASA GSFC / VAFB
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Page 28 Siemens PLM Software
Delivery & Launch
Image courtesy of NASA GSFC / VAFB
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Page 29 Siemens PLM Software
Delivery & Launch
Image courtesy of NASA GSFC / VAFB
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Frédéric Boilard, Application engineer
Femap SA Toolkit Suite
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Page 31 Siemens PLM Software
What is the Femap SA Toolkit Suite?
Primarily used for its very efficient and accurate Random Processor Performs random and sine solutions (both from a base excitation) from NX NASTRAN normal modes results with exact Von Mises stresses Efficient post-processing of Nastran results
• Ranking, sorting, enveloping, filtering • Summaries by groups, subcases, etc. • Margins of safety for different failure types • Direct manipulation of .op2 file data • Extremely efficient for large models
Automatic Report Generation
• Femap neutral, HTML, MS Excel® and ASCII
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Random Vibration Processor
Exact Von Mises stress calculation using optimized Segalman
approach corresponding to desired probability (3 sigma rule)
• Von Mises stresses do not usually form a Gaussian distribution
(the stress components always do)
• It is incorrect to multiply RMS results by 3, as stated in Segalman
paper [1]
• As seen in this table, if stress components are of the same
magnitude, your 3 sigma stress would be 27% too conservative
From [1] p.47
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Random Vibration Processor (Cont'd)
State-of-the-art integration schemes
No need to specify integration frequencies, the software does it automatically!
• Don’t have to worry about defining too few or too many (FREQx Cards)
• You don’t need to trade-off accuracy and performance
Residual flexibility / Residual vectors option to account for modal truncation effects
Absolute and relative displacements
Number of positive zero crossings
Processes nodal and elemental stresses
Stress margins of safety automatically calculated on groups of elements using
specified factor of safety (if desired)
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Random Vibration Processor (Cont'd)
Performance metrics from a small model
• 18K nodes, 18K elements
• 225 normal modes more than 95% effective mass, 3 axes
• Residual vectors used
• Process centroid and corner stresses
• Op2 file size: 1.52 GB
Largest model ever used internally
• Exact 3s peak Von Mises stress for all elements
• Process centroid and corner stresses
• 980k nodes, 600k elements
• 250 modes, 1 axis
• Op2 file size: 77 GB
• Time to completion: ~ 9h30
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Page 35 Siemens PLM Software
Random Vibration Processor (Cont'd)
The following table compares Nastran and SAToolkit solution times • Sol 103 time (98 sec) was removed from Nx Nastran Solution (Sol
111) but then multiple by 3 to account for the 3 axes.
Note that a couple of FREQx card iterations were made in Nx Nastran to minimize the solution time while matching results with Femap SA Toolkit. Spec of pc used (my laptop, Lenovo W530): • MS Windows 7 64 bits SP1 • Intel Core i7 @ 2.60 GHz • 16 Gb DDR3 (664 MHz) • 500 Gb SATA Toshiba hard drive
Accelerations Exact 3σ Margin of safety
(Corner nodes used)
Nx Nastran 8.5 53 min 54 sec N/A
Femap SA Toolkit 5.0 2 min 03 sec 28 min 06 sec
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Page 36 Siemens PLM Software
Random Vibration Processor (Cont'd)
What benefit is SAToolkit providing for this part?
• With the finite element model as-is (push-button tet mesh)
• Solution without SAToolkit not feasible
• Disk space and/or CPU time prohibitive
• Using traditional workflow
• Spend effort meshing
• De-feature, abstract and use different element types, or
• Use a coarse mesh except at hot-spots where you will
recover stresses
• Break up the modal solution into specific frequency ranges
• One or more ranges
• Combine RMS results from multiple ranges
• Extra effort
• Results accuracy
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Page 37 Siemens PLM Software
Random Vibration Processor (Cont'd)
MS Excel
Perfect for notching or
other processing
HTML
Perfect for quick view
and reports
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Page 38 Siemens PLM Software
Sine Vibration Processor
Uses efficient modal approach with option to account for modal
truncation
Phase-consistent Von Mises Stresses (Nx Nastran doesn't)
• Stress tensor is complex
• Von Mises stress is a real value
• Maximum possible Von Mises stress is computed for any
phasing of the stress tensor components
Stress margins of safety automatically calculated on groups of
elements using specified factor of safety
Accurate results
• Nastran eigenvectors are used
• We are computing Nastran results, except faster and
Same results capabilities as the Random Vibration Processor
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Page 39 Siemens PLM Software
Modal Processor
To provide all information required in preparation of modal base-excitation analysis For each mode • Effective mass • Maximum response estimation for excitation in all 3 translational
directions, for user-selected node groups for an harmonic excitation of 1G at natural frequencies
Summary of all the modes that pass the following criteria: • User-defined minimum effective mass • User-defined minimum dynamic response
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Page 40 Siemens PLM Software
Modal Processor (Cont'd)
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Page 41 Siemens PLM Software
Energy Processor
Efficiently identify groups with high energy in complex models, on
a mode by mode basis
• Process both kinetic and strain energy
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Page 42 Siemens PLM Software
Stress Processor
• Summarizes margins of safety for many element groups, several subcases and
different safety factors
• Supported failure theories:
• Von Mises, Laminates, Honeycomb Sandwich
• For each each group one can specify:
• Factor of safety, Allowable Stress, MS threshold, Failure criteria
• Dynamic stresses are combined in a phase consistent fashion
• Resulting margins of safety can processed as contour plots
• Composites and honeycomb panels
• First ply failure, margins of safety using NASTRAN PCOMP output
• Facesheet instability [3]
• Wrinkling
• Intracell buckling
• Shear crimping
• Facesheet Stresses
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Page 43 Siemens PLM Software
Stress Processor (Cont'd)
Summary Worksheet
• Summarize margins of safety for many element groups, several
Nastran subcases and different safety factors
Detail Worksheet
• As many worksheets as there are combinations of subcases and
user-defined stress cases
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Page 44 Siemens PLM Software
Element Force Processor
Efficiently summarizes forces on elements for many element
groups and several subcases, component by component
• Force output varies depending on element type
• Summaries make it easy to identify critical component and
element
123 RaRs
MS Excel output of
spring forces
Example of bolt
margin
calculation in MS
Excel using
spring force data
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Page 45 Siemens PLM Software
Grid Point Force Processor
Synthesize forces on groups of elements in complex geometries, for several subcases
• Extract resulting forces at a grid point resulting from a user
specified group of elements
• MPC, SPC forces and applied loads optionally considered
• Complex grid point forces are accounted for in frequency response analyses (SOL 108 and 111)
• Resulting forces may be in a coordinate system other then the grid displacement coordinate system
• Typically used for bolt and joints detailed hand calculations
• Also used for laminate/composite joint analyses
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Page 46 Siemens PLM Software
Grid Point Force Processor (Cont'd)
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Questions,
References, Resources & Help
Web Site Links -SATK
• http://www.plm.automation.siemens.com/en_us/products/velocity/femap/n
xNastran/structural_analysis.shtml
• http://www.mayahtt.com/resource-center/resource-satk
References [1] Dan Segalman & cie, "Estimating the Probability Distribution of von Mises Stress for Structures Undergoing
Random Excitation", Journal of Vibration and Acoustics, Vol 122, January 2000
[2] "The costs of space cargo", http://behindtheblack.com/behind-the-black/essays-and-commentaries/the-costs-of-
space-cargo, June 2nd 2011
[3] NASA CR1457, "Manual For Structural Stability Analysis Of Sandwich Plates And Shells", December 1969