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Noise & Vibrations (N&V) for
Automotive System
Umashankar G
Center for Simulation Excellence (CSE)
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Automotive N&V
N&V Simulation Landscape
Body N&V
Powertrain N&V
Other Areas
Interior (cabin) and exterior noise
Noise due to surface vibrations of
components such as crank case, fuel
pump, manifold,covers...
Brakes (squeal, for example)
Tires (cavity resonance)
Engine mounts (vibration isolation)
Fuel tank vibrations
…..
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15 Why SIMULIA for N&V
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Unified FEA for Multiple Attributes System-Level Analyses
Durability -- Speed bump analysis Durability -- Pothole analysis
Crash -- USNCAP Frontal Impact 35 mph, etc. NVH -- Modal Analysis
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N&V Capabilities in Abaqus
Complete set of linear dynamic analysis procedures
• Natural frequency extraction
• Complex frequency extraction
• Steady state dynamics
• Transient modal dynamics
• Substructures
• Structural Acoustics
• Random Response Analysis
• Nastran-to-Abaqus translation
Support for industry-unique features:
• Preload effects, including contact/friction
• Rolling tire effects
• Acoustic-structural coupling
• Frequency-dependent behavior
• Damping options
High performance SIM architecture
• AMS eigensolver with SMP parallelization support
• AMS eignesolver with GpGPU support
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Key differentiators of Automotive NVH in Abaqus
• With increasing degrees of freedom (dof)
• With increasing modal content
• With increasing modal response and multiple load cases
• With large retained mode and retained dof substructures
Performance
• Customer features consistent with “Best in Class” offerings
• General matrix representations
• Full damping representations
• Connection with other softwares (e.g. AVL / EXCITE)
Functionality
• Nonlinear / Unsymmetric effects
• Frequency-dependent behavior
Advanced mechanics (“standard” feature to be)
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15 Performance
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AMS eigensolver Dramatically faster in medium- to large-models ( > 1M DOF) and large number of modes ( > 500)
Benefits to other classes of problems including noticeable speed improvements even with small models
13.7M DOF Vehicle Body Model: 600Hz cutoff frequency, 5190 structural modes with selective recovery, 266 acoustic
modes with full recovery, and 266 RHS vectors (residual modes) Intel Westmere-EX (4x10 cores) with 128GB memory
1 1.8
3.1
4.6
6.1 6.2 5.7
1 1.95
3.75
6.7
11 11.3
9.6
0
2
4
6
8
10
12
0
50
100
150
200
250
300
1 2 4 8 16 24 32
Spe
ed
up
Fac
tor
Wal
l-Ti
me
(m
in.)
Number of Cores
FREQ Time (6.12)
AMS Time (6.12)
FREQ Speedup (6.12)
AMS Speedup (6.12)
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Example 1: 13M DOF
Powertrain Model
• Machine Information
– Intel Xeon Westmere X5690 (3.4GHz)
– 2x6 cores
– 96 GB memory
– 1.5TB disk space
• Model Information
– 13M DOFs with free-interface
– Number of retained DOFs: 1188
– Number of dynamic modes: 490 (below 10kHz)
– Substructure size: 1678
2.35 1.70
9.70
0.003
9.06
1.94
0
5
10
15
20
25
Abaqus 6.13 Abaqus 6.13
Conventional AMS-based
Wal
l-T
ime
(hrs
.)
Condensed Operators
Dynamic Modes
Constraint Modes
Frequency Extraction
Selective recovery
~14x
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Example 2: 10M DOF
Vehicle Body Model
• Machine Information
– Intel Xeon Westmere X5690 (3.4GHz)
– 2x6 cores
– 96 GB memory
– 1.5TB disk space
• Model Information
– 10M DOFs with free-interface
– Number of retained DOFs: 336
– Number of dynamic modes: 571 (below 300Hz)
– substructure size: 907
0.48 1.48
4.71
0
1
2
3
4
5
6
7
Abaqus 6.13 Abaqus 6.13
Conventional AMS-based
Wal
l-T
ime
(hrs
.)
Condensed Operators
Dynamic Modes
Constraint Modes
Frequency Extraction
Full recovery
~4x
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GPU Acceleration of the AMS Eigensolver
6.14 AMS can utilize fast GPU
devices
There are three AMS phases
As the first release, only AMS
reduced eigensolution phase can
use GPU devices
Two other phases (AMS reduction
phase and AMS recovery phase) will
be supported in the next releases
AMS Recovery Phase - Recover full/partial eigenmodes
AMS Reduction Phase - Reduce the structure onto substructure modal subspaces
AMS Reduced Eigensolution Phase - Compute reduced eigenmodes
AMS
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GPU Acceleration of the AMS Eigensolver 9M DOF Full Vehicle Model (10,743 eigenmodes below 800Hz)
Hardware: Sandybridge (2x8 cores), 2 NVIDIA K20X (Kepler)
1.00
1.50 1.54
1.00
2.30 2.39
0.00
0.50
1.00
1.50
2.00
2.50
3.00
0
200
400
600
800
1000
1200
1400
6.13 6.14 6.14
16 Cores 16 Cores + 1 GPU 16 Cores + 2 GPUs
Spe
ed
up
Elap
sed
Tim
e (
sec.
)
STD Time
AMS Time
STD Speedup
AMS Speedup
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15 Functionalities
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Linear Problems with Nonlinear Preloading
Numerous examples demonstrate the importance of nonlinear effects
Expanding on traditional Abaqus domains
Tires
Suspension
Brakes
Powertrain
More accurate solution due to
Nonlinear geometry
Inertial effects
Structural-acoustic coupling
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Front Corner Module Modal Analysis
Goal is to capture accurate stiffness and modes
Nonlinear:
Brake lining/pads/contact
Shock spring
Shock damper
Shock bushing
Linear:
Upper and lower arms
Knuckle
Anti-sway bar
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Shock spring assembly frequency (Hz) Suspension system
test (Hz) Mode Linear
analysis no preload
Abaqus preload prescribed
Spring first axial 34 70 70
Spring second axial 100 132 131
Spring third axial 164 192 192
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Unsymmetric Dynamic Substructures Stiffness matrix can be unsymmetric
Viscous damping matrix can be unsymmetric
Important use case: Substructure representation of rolling tires
Substructure generation for the base state obtained from the steady-state transport analysis of a rotating tire in contact with the road
Stiffness matrix can be unsymmetric due to the contact friction
Viscous damping matrix can be unsymmetric due to the Coriolis terms
Abaqus workflow for tires:
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Nonlinear static analysis of a
stationary tire including
inflation and contact footprint
calculation
Steady-state transport
analysis of a rolling tire
Generation of an
unsymmetric dynamic
substructure for a
rotating tire
Using tire substructures in
the full vehicle simulations
Linear dynamic
analysis of a single tire
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Example: Frequency Response of a Tire at 60 km/h
FE model: 430 K degrees of freedom
Substructure: 180 dynamic modes, 2 retained nodes
FE model compared with tire substructure models
Significantly different results for rotating vs. stationary
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Full Vehicle with Rotating Tire Effects
3.4 M degrees of freedom
Structural material damping
3,200 modes extracted
Rotating tire effect taken into account using unsymmetric substructure
AMS eigenvalue extraction and modal frequency response analysis
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Rotating Tire Effects
Stationary tire (blue) vs. rolling tire (red)
Roof vertical deflection
Tire patch lateral response
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Dramatic
differences
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Brake Squeal Analysis Complex Frequency Solver: A single-bore disc
brake with a low frequency squeal at 2.9 kHz
Animation
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
-200 -100 0 100 200
Real Part of Eigenvalue
Freq
uenc
y (H
z)
mu_a = 0.0
2.9kHz
Positive values indicate
squeal modes
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Brake Squeal Analysis Nonlinear Transient Approach using Abaqus/Explicit
Apply
pressure Maintain pressure
1.E+02
1.E+03
1.E+04
1.E+05
0 1 2 3 4 5 6 7 8 9 10
Frequency (kHz)
Vel
ocity
Am
plitu
de
2.9kHz Answer 3864
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1. Abaqus provides substructures (or linear elastic bodies) for crankshaft, engine block, etc.
2. AVL / Excite (Power Unit) provides nonlinear joints/bearing/mounts with gas forces and piston and timing drive impact forces; the nonlinear bearing forces and moments can be calculated due to actual dynamics of parts of the assembled multi-body system.
Substructure – Abaqus-Excite Workflow
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Squeak & Rattle simulation Challenges
Predict squeak & rattle (S&R) using simulation
Products
Abaqus/Standard
Methodology
Linear Dynamics procedure
Connector elements used as sensors
Scripting to automatically create connectors
Benefits
Innovative use of connector technology to predict S&R accurately IDIADA, Spain, SCC 2011
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Noise & Vibration simulation N&V simulation enabled cheaper and
faster with AMS
Transient Dynamics
Including fatigue analysis
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Road Noise Simulation with Tires Modeled as Substructures
The tire model needs to have a fine mesh to capture high frequency content, a deformable wheel (significant after 300 Hz or so), and the tire acoustic cavity (significant above 200 Hz).
The tire model thus calibrated will need to be converted to substructures before using in an implicit dynamics simulation or steady state dynamics simulation along with the vehicle model.
Abaqus-Adams Workflow for Full Vehicle
Insert Abaqus substructures in Adams for calculating time transient load data at the attachment points.
Perform transient linear/nonlinear dynamics and/or steady state dynamics with Adams loads. For example, friction with strut is an area of potential energy loss that could be critical.
Weakly and Strongly Coupled Structural-Acoustics
Lanczos or AMS uncoupled modes approach for weakly-coupled cases
Lanczos coupled modes approach for strongly-coupled cases
NVH Technology Trends
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