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MSC Software Confidential MSC Software Confidential
Full vehicle early-phase concept optimization for
premium NVH comfort at BMW 2012 Regional User Conference
Presented By: Dr. L. Cremers - BMW AG, Naji El Masri – Noesis Solutions
Tommaso Tamarozzi, Laurens Coox - KU Leuven,
Maximilien Landrain, Bram Vanderheggen - Noesis Solutions.
May 7-8, 2013
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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FULL VEHICLE NVH COMFORT OPTIMIZATION.
OUTLINE.
The BMW Structural Dynamic Analysis Group.
Beams and shells modeling for early-phase car body concept optimization.
Overview of current process and Optimus integration.
• Application case 1: Car body ‘material switch’.
• Application case 2: Car body stiffness vs. wheel base.
Full vehicle NVH concept optimization.
• Application case 3: Design exploration and optimization using an NVH
full vehicle model.
Conclusions.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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Seite 3
FULL VEHICLE NVH DEVELOPMENT & OPTIMIZATION.
STRUCTURAL DYNAMIC ANALYSIS GROUP.
Integral 4
~ 560 Parameter
Doppelquerlenker
~ 320 Parameter
Allrad
~ 230 Parameter
M 57D30 / 6HP26
~ 160 Parameter
GFZG
~ 1500 Parameter
Integral 4
~ 560 Parameter
Doppelquerlenker
~ 320 Parameter
Allrad
~ 230 Parameter
M 57D30 / 6HP26
~ 160 Parameter
GFZG
~ 1500 Parameter
Structure borne
noise
Vibration comfort.
Structural dynamic
analysis
Test & Integration Concept development
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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FULL VEHICLE NVH DEVELOPMENT & OPTIMIZATION. ROLE OF STRUCTURAL DYNAMICS.
Road induced vibrations in secondary Ride
& Comfort: noticeable vibrations of the car
body at the floor panel, seat, door etc. after
crossing minor road bumps
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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EARLY-PHASE CAR BODY OPTIMIZATION.
BEAMS & SHELLS CONCEPT MODELLING.
condensed flexible car body
models for full vehicle multi-
body vibration comfort
simulation.
Static and dynamic car body stiffness: - global static load cases. - local dyn. stiffness at connection points. - car body eigenfrequencies.
Structural dynamic car body development through numerical beam structure optimization.
NVH car body target setting. Early-phase functional development, evaluation and optimization of the car body regarding acoustic
and vibration comfort requirements. Beam & Shell FEM with simplified beam connection methods. Parametric beam barrier structure.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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Seite 6
EARLY-PHASE CAR BODY OPTIMIZATION.
BEAMS & SHELLS CONCEPT MODELLING.
1500 design variables
MSC Nastran SOL200
optimization.
Functional targets
Minimum weight
25 load cases
Roll-over
Crash
Steering
wheel
vibrations
Static stiffness Dynamic
stiffness
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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EARLY-PHASE CAR BODY OPTIMIZATION.
BEAMS & SHELLS CONCEPT MODELLING.
Design model: creation of large number of desvars, geometrical responses and constraints with
OptiCenter.
Application region
Desvars for outer
dimensions and wall
thicknesses
Geometrical
responses and
constraints
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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EARLY-PHASE CAR BODY OPTIMIZATION.
BEAMS & SHELLS CONCEPT MODELLING.
Responses and
constraints for
dynamic stiffnesses
Responses and
constraints for static
stiffnesses
Weighting factors
Design model: creation of functional responses, constraints and objective
function with OptiCenter.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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BEAMS & SHELLS CONCEPT MODELLING.
OPTIMIZATION PROCESS USING OPTIMUS
FE concept model
Nastran DESVARs
Interfacing design variables from
MSC.Nastran using Optimus Interfacing Outputs from
MSC.Nastran using Optimus
w
h
t(1)
t(2)
t(3)
MSC.Nastran
PBxSECT design var
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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EARLY-PHASE CAR BODY OPTIMIZATION.
BEAMS & SHELLS CONCEPT MODELLING.
changes in wall thickness
Post-processing: visualization of optimization results.
change in construction space.
Optimization history (global static stiffness).
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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BEAMS & SHELLS CONCEPT MODELLING.
APPLICATION CASE 1: ‚MATERIAL SWITCH‘.
Steel
Al
Change in weight and functional performance after
one-to-one material switch.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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Seite 12
BEAMS & SHELLS CONCEPT MODELLING.
APPLICATION CASE 1: ‚MATERIAL SWITCH‘.
Change in construction space.
Change in wall thickness
Aluminum car body optimization
Target:
Equal global static and dynamic car body stiffness in
comparison with steel body.
Design space:
full car body beam structure (red)
Geometric constraints:
construction space max. +50%
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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Seite 13
BEAMS & SHELLS CONCEPT MODELLING.
APPLICATION CASE 1: ‚MATERIAL SWITCH‘.
Rocker panel
Roof carrier
-235,1
-64,4
-11,9
Masse [kg] Statik [%] Dynamik [Hz]
E90 Alu
E90 Alu optimiert
-235,1
-64,4
-11,9
-168,6
-1,2
7,2
Masse [kg] Statik [%] Dynamik [Hz]
E90 Alu
E90 Alu optimiert
At the cost of construction
space!
in what areas is it useful to introduce light
weight materials?
Aluminum
Opt. Aluminum
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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Question:
How does the global car body stiffness change with increasing wheel base?
Parameter study using MSC.Nastran & Optimus, monitoring both global
static and dynamic stiffness (eigenfrequencies)!
Seite 14
BEAMS & SHELLS CONCEPT MODELLING.
APPLICATION CASE 2: STIFFNESS VS WHEEL BASE.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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BEAMS & SHELLS CONCEPT MODELLING.
APPLICATION CASE 2: STIFFNESS VS WHEEL BASE.
Optimus workflow including mode tracking based on mode correlation.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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BEAMS & SHELLS CONCEPT MODELLING.
APPLICATION CASE 2: STIFFNESS VS WHEEL BASE.
incre
asin
g w
he
el b
ase
change in
weight (kg)
change in static
torsion stiffness (%) change in global
torsion mode (Hz)
MAC
value
de
cre
asin
g g
lob
al
stiff
ne
ss
? ?
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
BMW 3Series full-vehicle NVH multi-body simulation model. ‘simplified’ model without doors, lids, roof, front and rear windows!
NVH Design exploration and
optimization by varying engine and
gearbox mount stiffnesses.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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Competing NVH-requirements for engine and gearbox mount stiffness.
Low stiffness for maximum structure-borne noise isolation.
low frequency vibrations of car body and power train for optimal vibration comfort.
e.g. engine idle vibrations, start/stop vibrations, engine judder…
FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
Local dynamic
car body stiffness
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
Engine idle vibration comfort.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
Full vehicle 4-poster simulation: sine sweep torsion excitation 0-60Hz.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
Optimus work flow
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
Methodology for design exploration and optimization:
•DOE: 3 Level Full Factorial.
•RSM: Quadratic Least Squares.
•DOE: Verification Latin-Hypercube.
•Optimizations:
Evolutionary Multi-Objective on RSM and validation of optimal points.
Evolutionary Multi-Objective on analysis.
Target based Single Objective on RSM.
Objective:
Minimize car body and steering wheel vibrations (RMS), while constraining relative motion
between engine and car body.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
Correlations based on 3-level full factorial DOE
Inputs - Outputs Outputs - Outputs
Stiffness in X and Z are dominant.
All output have to be considered.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
.
FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
RSM: Quadratic Least Squares
Least Squares Quadratic is
accurate enough.
Error prediction is below 6% for
worst case scenario.
Acc
Engine
Z (RMS)
Acc
Body
Z
(RMS)
Mount
Stiffness Z
Mount
Stiffness
X
Mount
Stiffness
X
Mount
Stiffness
Z
Ste
eri
ng
wh
eel acc Z
(RM
S)
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
.
FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
Multi objective optimization results
Conflicting
objectives
Acc
Body
Z
(RMS)
Acc
Engine
Z
(RMS)
Acc
Steering
wheel
Z (RMS)
Acc
Steering
wheel
Z (RMS) Acc
Engine
Z (RMS)
Acc Body Z (RMS) Acc Body Z (RMS)
Acc S
teeri
ng
wh
eel
Z
(RM
S)
Acc
Engine
Z (RMS)
Acc
Body
Z (RMS)
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
.
FULL VEHICLE NVH OPTIMIZATION.
APPLICATION CASE 3: MOUNT STIFFNESS OPTIMIZATION.
Multi objective optimization results
Mount stiffness X
Mount stiffness X
Mo
un
t sti
ffn
ess Z
Acc
Body
X (RMS)
Acc
Body
Z
(RMS)
Acc
Body
X
(RMS)
Eigenfrequency shifts are evaluated based on full vehicle
vibration comfort ‚finger print‘!
Engineering task is to find the best compromise amongst all
functional requirements!
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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FULL VEHICLE NVH COMFORT OPTIMIZATION.
SUMMARY.
multi-objective concept optimization has become a very important task
in automotive NVH development.
Advanced optimization processes are used on both component an
system level to explore the design space in search of optimal designs.
MSC.Nastran & Optimus software play herein an important role to
capture the simulation process and accelerate the optimization
schemes (SOL 200, Global Optimizer, Multi-Objective Optimizer with
Pareto fronts). The wide range of post-processing capabilities
facilitates the exploration of the design space of complex systems in a
multi-objective and even multi-disciplinary context.
MSC Software Confidential MSC Software 2013 Users Conference Americas., May 7-8, 2013.
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THANK YOU VERY MUCH FOR YOUR ATTENTION!
Dr. L. Cremers
BMW AG
80788 München