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Presentation titleCDH/OPT and NX/NASTRANa industry leading solution
Mladen CharginCDH [email protected]
PLM World ‘06
Premium Partners:
CDH/OPT
• What is CDH/OPT?– An extension to NX/NASTRAN– Requires User Modifiable NX/NASTRAN (V3)
• Reasons to use:– Solve problems not possible with standard
NASTRAN– Focused on NVH optimization for automotive
industry– Generally faster and uses less disk space
CDH/OPT - Capabilities
• Frequency Dependent Elements/Properties– Important for frequency range 100-300+ Hz
• Engine, Body, Exhaust Mount Optimization• Radiated Noise Optimization by
– Coupling of NASTRAN with BEM– Engine, Oil Pan, Valve Cover, etc.
Freq. Dependent Properties
• Different from standard NASTRAN • Any element w/Pxxxx can be frequency
dependent• Used for modeling hydromounts, rubber
bushings• Modeling mid-frequency response of
damped structural panels (floor pan)• Extremely efficient modal solution scheme• Used as a foundation for other options
Typical Hydromount Prop.
300
350
400
450
500
550
600
650
1
1
2
2
3
3
4
0 5 10 15 20 25 30
Real
Imag
Rea
l Stif
fnes
s
Imaginary Stiffness
Frequency (Hz)
Full System Model
3028262422201816141210864200.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
No Freq. Dep.With Freq. Dep. - NASTRANWith Freq. Dep. - CDH/OPT
Frequency (Hz)
Acc
eler
atio
n
Frequency Dependent Hydromounts
CPU Comparison
• DOFs 6.7M DOFs• Modes below 200 Hz. - 1767• Excitation frequency 0 - 30 Hz in 0.25
Hz inc.• CPU time (SGI/Altix) sec
– No Freq. Dep. 7097
– NX/NASTRAN 16736
– CDH/OPT 7146
Typical Floor Pan Properties
2.50 1011
2.60 1011
2.70 1011
2.80 1011
2.90 1011
3.00 1011
0.06
0.07
0.08
0.09
0.10
0.11
0 100 200 300 400 500 600 700 800
Effective Young's Modulus
Damping Factor
Stiff
ness
(mN
t/mm
^2)
Structural Dam
ping Factor
Frequency (Hz)
Acoustic Damping Test
Comparison NoFD vs FD
10-4
10-3
10-2
10-1
100
101
0 50 100 150 200 250 300
30044_T2_NOFD:45030044_T2_FD:45030044_T2_FD:55030044_T2_FD:650
Vel
ocity
Frequency (Hz)
Mount Optimization
• Two step reduction procedure– FRF representation for most of the structure– Dynamic reduction to a minimal physical DOFs– Reduce a 106 order problem to ~ 20-50 DOFs– Resulting matrices are frequency dependent
• Needs CDH/OPT freq. dependent capability• ~10 iter. in SOL 200 require few minutes • Potential for global optimum by using many
starting designs
Radiated Noise Optimization
• Requires frequency dependent capability in CDH/OPT
• Unique capability where BEM is used as a preprocessor to NASTRAN
• BEM not in the optimization loop– for thickness changes– addition or removal of stiffeners– assume no (or small) shape changes
• Output limited for points in the far-field– Radiated power obtained from DRESP2– Simulate the qualification tests in anechoic chamber
NASTRAN-BEM Coupling• New Methodology
BE ModelInitial
StructuralDesign
BEMAnalysis
AcousticTransferFunctions
AcousticTransferFunctions
NASTRAN StructuralResponse & Acoustic
Performance Eval.
Optimum?
Exit
ChangeDesign
Yes
No
Air Cleaner ApplicationAir FEM Model for the Interior (42524 DOFs)
Helmholtz Resonator
Air Cleaner
Air Cleaner-Structure FEM
406128 DOFs
Structural Design VariablesHousing walls DV Rib/stiffener DV
Total 125 DV
Location of Field Points
1
2
3
4
5
Optimized Response
100 150 200 250 300 350 400 450 500
FPoint 1 - OptFPoint 2 - OptFPoint 3 - OptFPoint 4 - OptFPoint 5 - Opt
Pre
ssur
e
Frequency (Hz)
10 dB
β=1.0
β=0.162
Conclusion
CDH contribution to faster and improved NVH analysis and optimization has been, and will continue to be, very significant
Global Warming Explained