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ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Robust Design9.0
Robust Design9.0
Ray Browell, ANSYS Inc.Ray Browell, ANSYS Inc.
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Why Robust Design?
“Lockheed Martin used to spend an average of 200 work-hours trying to get a part that covers the landing gear to fit. For years employees had brainstorming sessions, which resulted in seemingly logical solutions. None worked. The statistical discipline of Six Sigma discovered a part that deviated by one-thousandth of an inch. Now corrected, the company saves $14,000 a jet.”1
1: Firms aim for Six Sigma efficiency; [FIRST Edition] Del Jones. USA TODAY. McLean, Va.: Jul 21, 1998. pg. 01.B1: Firms aim for Six Sigma efficiency; [FIRST Edition] Del Jones. USA TODAY. McLean, Va.: Jul 21, 1998. pg. 01.B
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Why Robust Design?
“It will keep the company (Allied Signal) from having to build an $85 million plant to fill increasing demand for caprolactam used to make nylon, a total savings of $30 - $40 million a year.”1
Raytheon figures it spends 25% of each sales dollar fixing problems when it operates at four sigma, a lower level of efficiency. But if it raises its quality and efficiency to Six Sigma, it would reduce spending on fixes to 1%.”1
1: Firms aim for Six Sigma efficiency; [FIRST Edition] Del Jones. USA TODAY. McLean, Va.: Jul 21, 1998. pg. 01.B1: Firms aim for Six Sigma efficiency; [FIRST Edition] Del Jones. USA TODAY. McLean, Va.: Jul 21, 1998. pg. 01.B
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Why Robust Design?
“The reason to do DFSS is ultimately financial. It generates shareholder value based on delivering customer value in the marketplace. Products developed under the discipline and rigor of a DFSS-enabled product development process will generate measurable value against quantitative business goals and customer requirements. DFSS helps fulfill the voice of the business by fulfilling the voice of the customer.”2
2: Design for Six Sigma in Technology and Product Development, C.M. Creveling, J. L. Slutsky, and D. Antis, Jr.2: Design for Six Sigma in Technology and Product Development, C.M. Creveling, J. L. Slutsky, and D. Antis, Jr.
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
–Background of Robust Design• What is Robust Design, DFSS, …?• Design for Quality• Robust Design in Engineering Analysis• Illustration Example• Sources of Uncertainty• Effects of Uncertainty• Compare Deterministic and Probabilistic Approach• Enabling Technologies
–Demonstration• Overview of Application Example• Demo
–Questions
Robust Design Overview
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Background of Robust Design What is Robust Design, DFSS, etc.?
• Uncertainty AnalysisQuantify the effect of uncertainties on the performance of a product (mean value, standard deviation, etc.)
• Reliability AnalysisQuantify the reliability (failure probability, defects per million)
• Robust Design or Design For Six Sigma (DFSS)Optimize the design such that it is insensitive to unavoidable uncertainties (e.g. material,loads,…)
• Reliability-based OptimizationOptimize the design such that reliability is maximized or failure probability (defects per million) is minimized
Robust Design is often synonymous to “Design for Six Sigma” or “Reliability-based Optimization”
Robust Design is often synonymous to “Design for Six Sigma” or “Reliability-based Optimization”
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Background of Robust Design Design for Quality
Six Sigma Quality = Only 3.4 out of 1’000’000 parts fail
Six Sigma Quality is inherently a probabilistic statement
Gaussian Distribution
-6 -4 -2 0 2 4 6
Sigma-Value
Area =
Failure Probability
Product is ...
Bad Good
LSL USL
Product is ...
Good Bad LSL = Lower
Specification Limit
USL = Upper Specification Limit
P.S.: Gaussian distribution is not realistic, but does convey the idea correctly
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Background of Robust Design Design for QualitySix Sigma = Optimize manufacturing processes such
that they automatically produce parts conforming with six sigma qualityquality
Design For Six Sigma = Optimize the design such that the parts conform with six sigma qualityquality, i.e. qualityquality and reliability are explicit optimization goals
Design for Six Sigma:• Achieve “Designed-In”
quality as opposed to letting customers find out about quality problems
• Make informed decision that are critical to quality early in the development process0.1
1
10
100
1000
Research Design DevelopmentPrototypeTests
Production
Product Development Phases
Re
l. C
os
t o
f D
es
ign
Ch
an
ge
0%
20%
40%
60%
80%
100%
Design For Six Sigma Six Sigma
De
gre
e o
f F
red
om
to
aff
ec
t th
e P
rod
uc
t L
ife
tim
e C
os
ts
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
FROM:Reactive Quality
Management
• Extensive Design Rework• Assess Performance by
“build-test-build-test-…”• Fix performance/quality
problems after manufacturing
• Quality is “Tested-In”
TO:Predictive Quality
Management
• Controlled Design Parameters
• Estimate likelihood/rate of performance problems in design & development
• Address quality problems in design & development
• Designed for robust performance and quality
• Quality is “Designed-In”
Background of Robust Design Design for Quality
Robust Design is a Paradigm Shift …
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Purpose of Robust Design
InputInputInputInput ANSYSANSYSANSYSANSYS OutputOutputOutputOutput
Material PropertiesGeometryBoundary Conditions
DeformationStresses / StrainsFatigue, Creep,...
It’s a reality that input parameters are subjected to scatter => automatically the
output parameters are uncertain as well!!
Background of Robust Design Robust Design in Engineering Analysis
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Questions answered with Robust Design:
• How large is the scatter of the output parameters?• What is the probability that output parameters do not fulfill design
criteria (failure probability – defects per million)?• How much does the scatter of the input parameters contribute to the
scatter of the output (sensitivities – critical-to-quality)?
Background of Robust Design Robust Design in Engineering Analysis
ANSYS ANSYS DesignXplorerDesignXplorer
ANSYS ANSYS DesignXplorerDesignXplorer
Purpose of Robust Design
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Property SD/Mean %
Metallic materiales, yield 15
Carbon fiber composites, rupture 17
Metallic shells, buckling strength 14
Junction by screws, rivet, welding 8
Bond insert, axial load 12
Honeycomb, tension 16
Honeycomb, shear, compression 10
Honeycomb, face wrinkling 8
Launch vehicle , thrust 5
Transient loads 50
Thermal loads 7.5
Deployment shock 10
Acoustic loads 40
Vibration loads 20Source: Klein, Schueller et.al. Probabilistic Approach to Structural Factors of Safety in Aerospace.
Proc. CNES Spacecraft Structures and Mechanical Testing Conf., Paris 1994
Background of Robust Design Sources of Uncertainty
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
CFD
FEMCAD
FEMGeometry
Materials,Bound.-Cond.,
Loads, ...
Materials,Bound.-Cond., ...
Materials,Bound.-Cond.,
Loads, ...
LCF
Materials
± 0.1-10%
±5-50%
±5-100%
±30-60%
±??%
±5-100%
Thermal Analysis
Structural Analysis
Background of Robust Design Effects of Uncertainty
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Influence of Young’s Modulus and Thermal Expansion Coefficient on thermal stresses:
thermal = E · ·T
Deterministic Approach:
Mean = EMean · Mean · T Mean = typically used results
Probabilistic Approach:
Probability that ( thermal >= 105% Mean) ( thermal >= 110% Mean)
‘E’ scatters ±5% 16% (~1 out of 6) 2.3% (~1 out of 40)
‘E’ and ‘‘ scatter ±5% 25% (~1 out of 4) 8% (~1 out of 12)
‘E’, ‘‘ & ‘T’ scatter ±5% 28% (~1 out of 4) 13% (~1 out of 8)
Background of Robust Design Effects of Uncertainty
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Turbine What-If Analysis Series
Background of Robust Design Compare Deterministic/Probabilistic
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Background of Robust Design Enabling Technology: Parameterization
• Robust Design for all parameters including:
– APDL Parameters
/syp,parabatch.exe,'testpb.rsx','testpb.cdb','location',%value%,'testpb_mod.cdb'
/inp,testpb_mod,cdb ! Input the modified geometry
Paramesh db Initial mesh
Parameter name
Parameter value
Output mesh
Import Output mesh
CAD Parameters (Workbench)CAD Parameters (Workbench) APDL ParametersAPDL Parameters
ParaMesh ParametersParaMesh Parameters
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Background of Robust Design Enabling Technology: DesignXplorer
DesignXplorer manages the parameters and the uncertainties
DesignXplorer manages the parameters and the uncertainties
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
CAD Geometry FEM MeshFEM Boundary
Conditions
Robust Design Demonstration Overview of Application Example
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Results for Maximum Principal StressPressure Side Suction Side
Peak Value s
Tang. Leaning
AxialLeaning
Dove TailWidth
MaterialDensity
(Gaussian)
Fillet Radius(Lognormal)
Mass
Design Variables and Uncertainties
Imbalance: (p – s)2 Avg.Stress: 0.5(p + s)
Peak Value p
Robust Design Demonstration Overview of Application Example
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Robust Design DemonstrationTurbine Blade Workshop
Robust Design Demonstration Demonstration
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
DesignXplorer Family9.0
DesignXplorer Family9.0
Ray Browell, ANSYS Inc.Ray Browell, ANSYS Inc.
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
• DesignXplorer & DesignXplorer VT– Robust Design
• GUI Structure• Parameterize DFSS Results• Optimize DFSS results
– New Trade-Off Study– Genetic Algorithm for Sample Generation
• Variational Technology (DesignXplorer VT)– Support of Discrete Variables in Workbench– RSX File Viewing– Additional Contact Support– Frequency dependent material properties– Support inertial load parameters– 2D Analysis
DX Family 9.0 New Features
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
DX Family 9.0 New Features Robust Design - GUI Structure
DFSS Charts and Table PagesMeasures of robustness
CDF Plot Y-Axis can be scaled as Gaussian, Log-Normal, Weibull, Exponential
CDF Plot Y-Axis can be scaled as Gaussian, Log-Normal, Weibull, Exponential
Statistics Available
Customize Tables (add, delete)
Sigma-Level in Tables
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
New“Robust Design”
View
New DFSS Parameters showing upin Parameter
View
DX Family 9.0 New Features Parameterize DFSS Results
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
DX Family 9.0 New Features Optimize DFSS results
1)
2)
2) Design Variables: Useable for Robust Design Optimization
1) Random Variables: Uncontrollable – used to obtain DFSS results
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Same optimization functionalityas for GDS
DX Family 9.0 New Features Optimize DFSS results
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
DX Family 9.0 New Features Trade-Off Studies
Mouse-OverResults
Conflicting goals lie along the Pareto Front, Tradeoffs
Studies occur here
Both 2D and 3D Tradeoff Plots are available
Both 2D and 3D Tradeoff Plots are available
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Mouse-Over
Results
Pareto Frontfor Conflicting
Goals
Infeasible Points in Pareto Front
InfeasibleInfeasibleFeasibleFeasible
DX Family 9.0 New Features Trade-Off Studies
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Choice of Basic (Screening), which is pseudo-random sampling method typically done first, or Advanced (Genetic) Algorithm which is typically done second
Choice of Basic (Screening), which is pseudo-random sampling method typically done first, or Advanced (Genetic) Algorithm which is typically done second
DX Family 9.0 New Features Genetic Algorithm Sample Generation
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
Advanced sample optionsAdvanced sample options
DX Family 9.0 New Features Genetic Algorithm Sample Generation
Screening SamplesScreening Samples Advanced SamplesAdvanced Samples
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
DesignXplorer VT 9.0 Support of Discrete Variables in Workbench
• Variational Technology is much faster than DOE for discrete parameters
• Supports:– Spot Welds– Solid Bodies– Sheet Bodies– Line Bodies– Parts
Time for a 30 minute base solve
0.001
0.1
10
1000
100000
1E+07
1E+09
1E+11
1E+13
1E+15
0 5 10 15 20 25 30 35 40 45 50
Num ber of Boolean Param eters
Time (
Days)
DOE
DXVT
1 Day
1 Year
1 Decade
1 Century
1 Millennium
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
• Efficient Postprocessing– Multi-objective Boolean
optimizer based on Bayesian sampling faster optimization of discrete parameters
– Boolean scatter chart representing the solution points of all the parameter combinations of the selected parameters.
DesignXplorer VT 9.0 Support of Discrete Variables in Workbench
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
DesignXplorer VT 9.0 Support of Discrete Variables in Workbench
6 Supports
None Suppressed
6 Supports
None Suppressed
6 Supports
4 Suppressed
6 Supports
4 Suppressed
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
• Allows user to view Variational Technology results from a variety of sources including– DesignXplorer VT
(of course)– ANSYS using VT
DesignXplorer VT 9.0 RSX File Viewing
Hoover model solved with VT within the ANSYS EnvironmentHoover model solved with VT within the ANSYS Environment
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
• For harmonic analyses, VT supports frequency dependant modulus and damping
DesignXplorer VT 9.0 Support of Frequency Dependent Properties
Modulus of Elasticity vs. Frequency
1.0E+07
1.2E+07
1.4E+07
1.6E+07
1.8E+07
2.0E+07
2.2E+07
2.4E+07
2.6E+07
2.8E+07
3.0E+07
0 100 200 300 400 500 600 700 800
Frequency (Hz)
Mo
du
lus
of
Ela
stic
ity
Imaginary Modulus Damping Ratio vs. Frequency
0.0%
0.5%
1.0%
1.5%
2.0%
2.5%
3.0%
3.5%
0 100 200 300 400 500 600 700 800
Frequency (Hz)
Ima
ng
ina
ry M
od
ulu
s D
am
pin
g R
ati
o
Frequency Response
0.0001
0.001
0.01
0.1
1
10
0 100 200 300 400 500 600 700 800
Frequency (Hz)
Y D
isp
lac
em
en
tVariable E
E for 0 Hz
E for 800 Hz
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
DesignXplorer VT 9.0 Inertial Load Paramenters & 2D Analysis
• Support Inertial Load Parameters– Acceleration (Magnitude and Components)– Rotational Velocity (Magnitude and Components)– Rotational Acceleration (Magnitude and
Components)
• Allows Variational Technology analysis of 2D Simulation studies to include:– Axisymmetric– Plane Strain– Plane Stress
ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.
DesignXplorer and DesignXplorer VT
• Thank you!• Questions?
– Additional Questions:
Ray Browell(724) [email protected]
– Additional Information:
http://www.ansys.com/