FEMAP for the Space Industry - Femap y NX Nastran · FEMAP for the Space Industry . Unrestricted ©...

Unrestricted © Siemens AG 2013 All rights reserved.

Frédéric Boilard, Application Engineer, MAYA HTT Ltd.

Eric Preissner, Principal, PEC LLC

FEMAP for the Space Industry


Siemens PLM Software

MAYA and PEC Introduction

LDCM/MMS Space Craft Shipping Container Case Study

Femap SA Toolkit

Questions

Agenda Femap SA Toolkit Suite



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



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



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].



The Use of Femap on the LDCM / MMS

Modular Spacecraft Shipping Container

FEMAP Symposium 2013 Eric Preissner, Principal, PEC LLC



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



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



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.



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



Transport Assembly, Full View

Front

gooseneck

Cover

Pallet

Rear

gooseneck

Steerable

rear dolly

Transport

frame and SV



Transport Assembly, STF + SV

STF + SV

STF fully

assembled

Bolted

joints

SV Mount

plane / pads

Hangar

bracket attach




• STF – FE model overview (~140k elem)

SV DMIG representation




• 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



• STF – FE model details


Isolator mount plate

Solid elements for

crush tubes and lift

provisions

Bolts as beams with

RBE2 connections to

structure



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



Extensive use of Linear Contact

FG lift tower

RG lift tower

Rear steering

turntable

Cover-to-base



• Full vehicle (~465k elem)

Transport Assembly, Full View

Front

gooseneck

Cover

Pallet

Rear

gooseneck

Steerable

rear dolly



• A variety of analysis configurations

Managing Multiple Submodels With Femap

Static - RG

Static - FG

Static - PL

Vibe - PL

Static &

vibe - STF



Envelope and Plot Stress Results

• Rear gooseneck + bogie – stress plot



Envelope and Plot Stress Results

• STF – lifting configurations



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



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



Dynamic Analysis, Reporting

• MIL-STD-810 random vibration studies – base+STF+SV

Curves 4-6 are attached to SV

Curves 4-6



Proof Test – STF

Image courtesy of Nelson Manufacturing



Proof Test – Road Configuration

Image courtesy of Nelson Manufacturing



Delivery & Launch

Image courtesy of NASA GSFC / VAFB


Frédéric Boilard, Application engineer

Femap SA Toolkit Suite



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



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



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)




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




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




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




MS Excel

Perfect for notching or

other processing

HTML

Perfect for quick view

and reports



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



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



Modal Processor (Cont'd)



Energy Processor

Efficiently identify groups with high energy in complex models, on

a mode by mode basis

• Process both kinetic and strain energy



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



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



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



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



Grid Point Force Processor (Cont'd)



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

http://www.plm.automation.siemens.com/en_us/products/velocity/femap/nxNastran/structural_analysis.shtml



http://www.mayahtt.com/resource-center/resource-satk








http://behindtheblack.com/behind-the-black/essays-and-commentaries/the-costs-of-space-cargo

















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