imac10 component
DESCRIPTION
Presentation at IMAC 2010TRANSCRIPT
Using component modes in a system design process.
G. Vermot, JP Bianchi, E. Balmes, SDTools, Arts et Metiers ParisTechR. Lemaire, T. Pasquet Bosch, Chassis System Brakes
IMAC 28, Jacksonville
Requirements & architecture
Component design and NVH
Concept : a device that decelerates
Component designIntegration, test, verification
Operation
System, verification & validation
Component design and NVH
Component redesign
Sensitivity, energy analysis
1. Which system features are important for NVH
2. Classify sensitivity and energy contributions of component modes
3. Redesign component
Outline• Motivation• Method : a reduced model using modal
coordinates of components• Illustrate the use
– Validate the ability to do parametric analysis
– See how this can be used for design
• Conclusion
Reduction method• Disjoint components with interface energy
• Rayleigh-Ritz reduction of each component using– free/free real modes (explicit DOFs)– trace of the assembled modes on the component
• Nominal system modes are predicted exactly
+
Reduced model• Reduction basis diagonal by block• specific topologies are obtained
– K split in elastic + interactions– Mass is identity, Kel is diagonal– Kint has blocks ≠0 where component interaction exists
• Free mode amplitudes are DOFs• Change component mode frequency ⇔ change the
diagonal terms of Kel
Disc
OuterPad
Inner Pad
Anchor
Caliper
Piston
Knuckle
Hub
ωj21
[M] [Kel] [KintS] [KintU]
Reduction validation• Assembled real modes are explicitly in the model
• Reduced and full models show identical real modes• High frequency precision depends on the solver
convergence• Low frequencies show an increasing difference due to a
shift in the Abaqus results
Validation – 1. Disc Young Modulus• First terms of the reduced elastic
matrix are varying• E disc +10% 2% accuracy (compared to
Abaqus full)
• Stability diagram well predicted
Nom.+10% +20%
-20%
Nom.+10% +20%
-20%
Validation – 2. Anchor Mass Modification• 9 grams added to anchor handle• Anchor mode frequencies up to -6%• Error on system modes
less than 1 %
1%
Validation – 3. Lining Transverse Young Modulus• Lining Ezz is a common updating parameter (material
parameters accuracy)• Matrix stiffness interpolation between two states• 2 reduction bases possible, high or low Ezz• Same basis for both matrices• The modified matrix is not diagonal
Ezz= 275 MPa
Ezz= 3000 MPa
Lining Ezz tuning• Cross interpolation tested• Curves are globally overlaying
• Differences are due to the reduction basis used• Using the high Ezz (+, +) is better• Low Ezz ( ) computation loses high values accuracy
Component Mode Tuning 1• Analysis of energy contribution can target a
singlecomponent mode• Most unstable mode at 12 Bar is mode 55,
involves pad mode 7• Mode 51 is also sensitive to pad mode 7
Mode 51 @ 3560 Hz 0% Mode 55 @ 4056 Hz -2.3%
Component Mode Tuning 2• The first pad bending mode has no real effect on mode 55• Decreasing its frequency by 2.5 % is enough to trigger
mode 51 instability• A few percent of variation is likely to append in the
production process
• Robustness studies can be easily performed
Sensitivity Analysis - 1• A nominal design point does not show the
variability of the solution• Robustness is improved if sensitive modes
are spotted• The sensitivity is given by
• Scanning each component mode for each assembled mode is a quick computation
• Gives direction for component tuning analyses by spotting relevant modes
Sensitivity Analysis - 2• Assembled modes are
sensitive to a few component modes at a time
• Piston has no sensitivity (excepted piston cap modes)
• Hub has very limited sensitivity
• Pad are sensitive at rather high frequencies (>4kHz)
• Knuckle show great sensitivity but mainly limited to local fixation areas contribution
Disc (c10001ds)
Interaction Tuning• Interaction tuning for penalized contact• Robustness of the static computation• Pad spring example (Mode 55)• Involves comp. interaction AND material
compression• Some variation observed• Applicable to any interaction
+
Friction Analysis• Instability from asymmetric coupling due to friction
forces driven by μ• Test from 0.7 to 0.3 ; Reduction basis at 0.6• A stiff transition is observed between
μ=0.4 to 0.5• A few modes are
sensitive
0.70.6
0.3
0.7 0.6
0.3
Other applications• Multi-stage cyclic symmetry
(SNECMA). – Which stage, which diameter, …– Mistuning (which blade)
• Damping design (PSA)– Fixed system modes, component
redesign
Conclusion• Reduced model with component modes and
exact system modes• Enables parametric studies
– Low computation times– Validated accuracy (vs. full Abaqus recomputation)– Access to physical and modal parameters– Sensitivity analysis– Modal energy useful to understand motion
• Illustrated for brake squeal• Lots of other possible applications
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