Presentation titleCDH/OPT and NX/NASTRANa industry leading solution

Mladen CharginCDH AGchargin@garlic.com408-848-5716

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

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