Download - AUDI Optimization
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Dr. Eckhard Plank, AUDI AGAntoine Guellec, AUDI AG
Willem van Hal, MSC Software
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.20072
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Optimization and correlation with nastran has been d one since a few decades
– Optimizing and correlating multi-millions of design variables in dynamics is of interest in European automotive
– Optimizing large assemblies puts extra strain on op timizer and solver and hardware
The Challenge
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.20073
New methods for optimization and correlation NVH in the Full Vehicle AnalysisThe optimization / correlation process
Meshing
Design Variables
Optimization/Correlation Goal and Constraints Solving
Postprocessing
CAD Redesign
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.20074
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Topology optimization has been used since a decade to determine optimal constructions within a given design space i n static and nlstatic loadcases in competitive products on a part level.
– Topology optimization in the area of modal/frequenc y/acoustics has been extended since Nastran sol 200 was enhanced wi th topology functionality and a new optimizer: BIGDOT as well a s powerfullsolvers.
– The method shown in this presentation is the start to extend theclassical topology optimization from „parts“ toward s assemblies in the area of modes, frequency response and acoustic s for optimizing as well as correlating models with test data.
Topology Optimization in a nutshell
?
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.20075
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Topometry is a way to optimize each single reference d element values like thickness, damping, youngs modulus, density.
– Topometry helps to correlate analysis models with te st data when E,Ge or T is defined
– Topometry can also help to improve the design by def ining where the element thickness can be increased or reduced on an element level
Topometry Optimization in a nutshell
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.20076
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Topology can be used within the designspace, the no n-designed part of the structure
– Topometry can be used on the designed part of the st ructure
Topology vs. Topometry
T
E=f(rho)
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.20077
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Topology (Topvar), Topometry (Tomvar) are a conveni ent way to define millions of design variables in sol 200 by j ust a few lines of input, no preprocessor support is needed
– New responses (frmass,compliance) and manufacturing constraints (extrusion, cast, member thickness and symmetry) ha ve been implemented
– Output can be written to a p2.5 asci file which can be read by many 3rd party software like Fegraph, Animator, Meta Pos t and MSC products, SimX and Patran
Topology / Topometry implementation in nastran
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.20078
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Topology optimization of the AUDI TT threshold prof ile (extruded Al.)
– BIW model correlation : application of topometry opt imization
– Concept investigations with application of large to pology and topometry optimization – body structure design
– Example of topology optimization for an acoustic ap plication
Application of topology and topometry optimization w ithin nastran sol 200 in AUDI projects
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.20079
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Topology optimization of the AUDI TT threshold prof ile (extruded Al.)
– BIW model correlation : application of topometry opt imization
– Concept investigations with application of large to pology and topometry optimization – body structure design
– Example of topology optimization for an acoustic ap plication
Application of topology and topometry optimization w ithin nastran sol 200 in AUDI projects
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200710
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Aluminum casting parts
Aluminum extruded profiles
panels load path investigation
AUDI TT- Roadster Use of topology optimization in TT’s space frame des ign
AUDI TT-Roadster full car model
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200711
New methods for optimization and correlation NVH in the Full Vehicle Analysis
result of the optimization
last design (serie)
► the functional benefit to the previous design is a reduction of the BIW mass of 2 kg while increasing the entire car to rsion mode of 0,8Hz
optimization model
previous design
Targeting
• increase global torsion mode
• constraint on global mass
Conditions
• 650.000 variables
• extrusion and symmetry design constraint
AUDI TT- Roadster topology optimization of the threshold profile (ext ruded Al.)
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200712
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Topology optimization of the AUDI TT threshold prof ile (extruded Al.)
– BIW model correlation : application of topometry opt imization
– Concept investigations with application of large to pology and topometry optimization – body structure design
– Example of topology for an acoustic application
Application of topology and topometry optimization w ithin nastran sol. 200 in AUDI projects
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200713
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Description
FE-Modell
Test-Modell FRAC Criterion
0,472
0,346
0,4900,888
0,716
0,488
0,631
0,471
0,557
0,291
0,492
0,359
0,598
0,222
Sum Shaker 1
Sum Shaker 2
Sum Shaker 3
MAC Criterion
AUDI TT- Roadster BIW model correlation / application of topometry opt imization
► Very good correlation of the modes frequency range. Bad correlation of vectors and amplitudes
TestFE
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200714
New methods for optimization and correlation NVH in the Full Vehicle Analysis
{ } { }{ } { }( ){ } { }( )H
XT
XH
AT
A
HX
TA
HHHH
HHFRAC
2
=
{ }AH - the analytical frequency responsefunction matrix
{ }XH - the experimental frequency responsefunction matrix
Targeting of the topometry optimization
AUDI TT- Roadster BIW model correlation / application of topometry opt imization
► Optimization of the joint stiffness as a way invest igating which are the sensitive parts of the structure to differences between test and
simulation
Variables : Young-Modulus of the joints
Objective : maximization of FRAC
Results : Sensitivities to a better correlation of FRFs
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200715
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Results of the Optimization
AUDI TT- Roadster BIW model correlation / application of topometry opt imization
►joint optimization shows main discrepancies around the aluminum casting parts. The modelization inconsistencies of t he casting parts
were investigated more in detail in a second optimi zation of shell thicknesses. A refinement of the mesh confirmed this result.
Aluminum casting parts in the AUDI TT
body structure
First step : joint stiffness optimization
2nd step : shell thicknesses optimization
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200716
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Topology optimization of the AUDI TT threshold prof ile (extruded Al.)
– BIW model correlation : application of topometry opt imization
– Concept investigations with application of large to pology and topometry optimization – body structure design
– Example of topology for an acoustic application
Application of topology and topometry optimization w ithin nastran sol 200 in AUDI projects
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200717
New methods for optimization and correlation NVH in the Full Vehicle Analysis
0,01
0,1
1
10 12 14 16 18 20 22 24 26 28 30
frequency (Hz)
Sum
func
tion
body
base variant
rigid body
AUDI A3 Concept investigations – body structure design
Strategy / load case
►The important influence of the body elasticity on c omfort relevant vibrations in a low frequency range in combination with light weight
requirements dictate to track the right energy flow s in the structure in order to design a robust body.
road excitation: body acceleration
A3 full car NVH model
Excitation
Response
influence of body
elasticity
Res
pons
e
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200718
New methods for optimization and correlation NVH in the Full Vehicle Analysis
0,01
0,1
1
10 12 14 16 18 20 22 24 26 28 30
frequency (Hz)
Sum
func
tion
body
base variant
result optimization
rigid body
AUDI A3 Concept investigations – body structure design
Strategy / target Topology
Combination topology and topometry
Topometry
► The goal of the optimization is a reduction of the maximal amplitude of a sum function on a relevant frequency range.
Comparison of 3 optimization strategies (topometry, topology, both combined)
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200719
New methods for optimization and correlation NVH in the Full Vehicle AnalysisAUDI A3 Concept investigations – body structure design
Results
topology
topometry
combination of topology and topometry
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200720
New methods for optimization and correlation NVH in the Full Vehicle AnalysisAUDI A3 Concept investigations – body structure design
Results – comparison of the 3 strategies
– Topology and topometry optimization provide good res ults, fast convergence and easy interpretation
– Best strategy would be combination of topology and topometryoptimization: it allows to investigate the best cho ice between shear fields and profile structure
– Bad convergence of a combined topometry and topology optimization. Results are still difficult to be int erpreted
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200721
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Topology optimization of the AUDI TT threshold prof ile (extruded Al.)
– BIW model correlation : application of topometry opt imization
– Concept investigations with application of large to pology and topometry optimization – body structure design
– Example of topology optimization for an acoustic ap plication
Application of topology and topometry optimization w ithin nastran sol 200 in AUDI projects
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200722
New methods for optimization and correlation NVH in the Full Vehicle Analysis
1,00E-02
1,00E-01
1,00E+00
1,00E+01
80 83 86 89 92 95 98
Example of beta optimization in low frequency acous tics
Sou
nd p
ress
ure
leve
l (dB
)Frequency (Hz)
Trimmed body acoustic model
Result topology optimization
Structure enhancement around the critical panel
Acoustic cavity
Sensitive panel
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200723
New methods for optimization and correlation NVH in the Full Vehicle Analysis
First step, focus on the right solver
Second step, focus on the right parallel method
Solver method selection
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200724
New methods for optimization and correlation NVH in the Full Vehicle Analysis
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
1 10 100 1000 10000 HzHz
Statics:
– Sparse (assemblies)
– Casi, element based iterative solver (solid parts, red uced assembliesdmig)
Modes, Modal frequency response:
– SMP Lanczos, single shift
– DMP dof domain Lanczos
Acoustics / Driving point responses:
– DFreq DMP
– Mfreq ACMS
Solving methods selection, Topology
AU
TO
MO
TIV
E A
SS
EM
BLY
AU
TO
MO
TIV
E A
SS
EM
BLY
LanczosLanczos
ACMSACMS
DFREQDFREQ
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200725
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– The decision should be made upon amount of subcases and conditioning of the K matrix
– The type of sensitivities can influence the solver selecti on
Statics: Sparse Decomp vs Iterative methods
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200726
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– In statics we can choose between a 2 Iterative solve rs and a sparse solver
– In Nastran the sparse solver is default. The Iterat ive solver can be chosen in the case control section by:
– SMETHOD= ELEMENT $ For the CASI element based itera tive solver
– SMETHOD= MATRIX $ For the matrix based iterative so lver
______________________________________________________________
Due to the mix between shells and solids we used th e sparse solver for the Audi TB.
When the just the design space is run, 6mil element s can be run in 20min/SC on IT2 with casi.
Solver method selection STATICS
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200727
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Modal methods are needed if modes need to be tracked
– Modal methods may run into numerical side effects due to ch angesin modal densities:
ρρρρ = ρρρρo x
E = Eo xp
– Direct can be an advantage if little excitations have to be calculatedand/or if dmp is possible
MODAL vs DIRECT Methods
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200728
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Modal method selection
– In modes calculation, there are 2 general economic possibilities: ACMS and Lanczos
– The decision which solver to choose will be depende nt on 2 variables: amount of solids, amount of modes.
– In general below 70-100 Hz or upto 70 modes, the Lan czos solver will be as good as acms and will outperform acms for the c ase the amount of solids increases.
– ACMS will be the choice when many modes are calcula ted and a limited amount of very dense solids.
– A Full Vehicle up to 50 hz with 3 mil solid topo vari ables is done best by Lanczos whereas an acoustic model with a double l ayer of shells (for stiffness or damping) for acoustics is handled faster by ACMS.
– High frequency domain with acoustics and solids mig ht be covered by sol 108 as well.
______________________________________________________________
Most Audi models shown, were run with the SMP varia nt from lanczos. This choice was made based on robustness and perfor mance and modal density.
Solver method selection MODES / MFREQ
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200729
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Lanczos: the choice for problems with little modal d ensity and increasingly dense problems
– Lanczos can be run in SMP,DMP (dof,freq,geom) mode.
– SMP (2 cpu) mode is economical when 1 shift can be used and most time is spend in decomp.
– Factorization cost go up if many dense solids are ad ded
– 50-70% speedup is possible on 2 cpu´s for the situat ion that factorization is the major cost factor
– DMP: DOMAINSOLVER MODES (partopt=dof) could be an alternative as well as ACMS and is a working solutio n for most TB/GFZ Models.
Lanczos Performance
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200730
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Avoiding changes in the modal density in order to a void performance problems:
– When K drops faster then M, the modal density might increase at once resulting in a dramatic performance decrease (SQRT( K/M)).
– K and M can be influence by:
A) Topvar , power variable (field 8).
B) E and Rho on the mat1 card.
Under the assumption that we will add little mass, a material with reduced rho is beneficial for the performance AND wh en you want to know where you could add material without adding a significant amount of mass then the assumption be valid.
C) Dynamic dampers can be avoided by this assumptio n
DFREQ (sol 108) wouldn't show this problem and is a viable option for the higher frequency domain.
Modal (lanczos and acms) Performance (2)
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200731
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Modes up to 50hz,
– 8 frequencies, 1 subcase sum over max of acceleration of 10 grids.
– Determine where to stiffen between 2 spring struts
– 6.2 Mil design elements (12.4 mil desvar)
– 12 mil dof (G), 8 mil dof (A)
– 20H/ cycle 85% solving 15% optimizing
– I8 with 14gb memory used in SMP mode
– Extremely dense design space
Example MFREQ, TB (not shown) + Design Space Topolo gy in dynamics
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200732
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Dfreq can be a economical choice if:
– The modal density get’s too high as design elements go down the highest request frequency
– DFREQ can be run in DMP with an almost linear speed up
– DFREQ can be used economical to combine Topology wi th acoustics.
Direct frequency response: DFREQ
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200733
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Mostly shell based, or dominated structures, no extra d of are added ornumerical difficulties are not to be expected
Statics
– Sparse, Sparse smp/dmp
Modes, Dynamics / Acoustics
– ACMS > 100 Hz in both smp or dmp mode
– Single shot lanczos (1 shift) < 70 Hz
– I8 might be beneficial for mfreq with many excitation frequ encies forspeeding up adjoint sensitivities
– Dfreq
Solving methods selection, Topometry
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200734
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Large assemblies can be optimized with multi millio n desvar due to efficient solvers for various problems and efficien t optimizers
– Topology optimization can be used to determine load path within the non-designed structure
– Topometry can be used to define model improvements w ithin the designed structure
– Topometry can be used to easily define design variab les for correlation
Conclusion
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200735
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Glueing might be a good way to easily define design space s as congruent meshes are not needed
– Frac and Mac values should be considered as responses in nastran as well as a more simplified test data input.
– Relative/percentage output
– Ease of use topometry interface: TOMVAR (MD2.1) to b e released
Outlook and possible enhancements
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200736
New methods for optimization and correlation NVH in the Full Vehicle Analysis
– Special thanks to ..
Ludger Lagerman, EDAG for the meshing efforts and
Nastran Devl: Xiaoming Yu, Shenghua Zhang, Joe Cole, Peter Schartz, Mike Reymond and Erwin Johnson for enhancing Nastran in t he area of performance and functionality.
– The credits, for the correlation data method, go to Andreas von Mach / Von Mach engineering.
Credits
Dr. E. Plank AUDI AG, A. Guellec AUDI AG, W. Van Hal MSC Software – NVH Symposium, Detroit, 10.10.200737
New methods for optimization and correlation NVH in the Full Vehicle Analysis
Thank you !! Questions?