Download - Claudia-Raffaldini ENG Rev2
Claudia Raffaldini
Design Development
Structural optimization
Testing
Product design cycle
Structural re-design of engine components
Product knowledge
Design freedom
Structural optimization
University of Parma 2/18
Claudia Raffaldini
Design Development
Structural optimization
Testing
Product design cycle
Structural re-design of engine components
Structural optimization
Optimized design
Max stress
Initial design
University of Parma
Kaya N., Karen I., Ozturk F., Re-design of a failed clutch fork using topology and shape optimization by the response surface method, Materials and Design 31, 2010.
Failure
3/18
Claudia Raffaldini
Design Development
Structural optimization
Testing
Product design cycle
Structural re-design of engine components
Structural optimization
ALTERNATOR BRACKET
ENGINE SUPPORT
Two applications examined in thesis work:
METHOD
University of Parma 4/18
finite element density [0,1]
0
Claudia Raffaldini
Numerical optimization method implemented by FEA software Altair HyperMesh (OptiStruct)
Topological optimization: material redistribution applying the SIMP Method (Solid Isotropic Material with Penalization):
Selective material removal from the design volume, made by OptiStruct
University of Parma
Geometry to be optimized
Initial design volume Optimized geometry
Kaya N., Karen I., Ozturk F., Re-design of a failed clutch fork using topology and shape optimization by the response surface method, Materials and Design 31, 2010.
Boundary conditions assigned to the FEM model of the component to be optimized
Extension of the initial design volume, according to the BCs
5/18
Claudia Raffaldini
Settings of the optimization parameters
- Technological and manufacturing constraints
- Hardware limitations
Widespread, useful for every optimization process
Structural analysis of the component to be
optimized
- CAD/FEM model - Boundary/loading conditions
- Experimental data
Input data
Definition of initial geometry of the component
Setting up of the Design Region
Analysis and modification
Analysis of results
University of Parma
First check: parameters quality
Second check: initial geometry quality
x
x
6/18
Claudia Raffaldini
Bracket used to connect the alternator to the engine
TARGET
CONSTRAINT
ωRI > 250 Hz
Mass ≤ Initial mass
Density 2,7 g/cm3
Elastic modulus 70000 MPa
Poisson’s ratio 0,3
Material data (AlSi7)
Constraints
University of Parma
The bracket is subjected to dynamic loading that could make the system oscillate at its resonance frequencies. To avoid this, the system’s natural frequency of the normal mode I (ωRI) must be increased over an assigned treshold, possibly reducing the weight of the structure. This is the aim of the optimization.
7/18
Claudia Raffaldini
Bracket used to connect the alternator to the engine
TARGET
CONSTRAINT
ωRI > 250 Hz
Mass ≤ Initial mass
Original Design Region Optimized
Meshing
University of Parma
Overall view of the optimization process made on the bracket:
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Mode I Mode II Mode III
244 Hz 435 Hz 757 Hz
Claudia Raffaldini
Pre-processing
Simulation
Post-processing
Modal analysis of the orginal design
University of Parma
Deformed shapes for the first 3 normal modes
9/18
Claudia Raffaldini
Pre-processing
Simulation
Post-processing
Change in the geometry
Setting up of the Design Region
Excluding the bolt seats
University of Parma
Analysis of results
Geometry reconstruction and modal analysis OptiStruct automatically elimiminates FEs that don’t have a structural function
ωRI = 273 Hz
Density plot treshold = 0,3 Geometry reconstructed using the OSSmooth tool
10/18
Claudia Raffaldini
Structural verification
Outcome: design improvement Increase of the natural frequency of the normal mode I maintaining the initial mass
University of Parma
Uniform distribution of the Element Strain Energy (at a reasonable distance from the fixed nodes)
Original bracket Optimized bracket
Variation (%)
Mass (g) 702 702 0
ωRI (Hz) 244 273 12
11/18
Claudia Raffaldini University of Parma
Fixing nodes on the bolt holes
Fixing nodes on the highlighted surfaces
Extending the Design Region
Test with different boundary conditions
Optimization could sometimes generate unfeasible designs, requiring an iteration of the parameters’ setttings step in the overall process.
12/18
Claudia Raffaldini
Engine support to fasten the engine base on the car frame
TARGETS
CONSTRAINT
ωRI > 300 Hz Minimize the stresses
Mass ≤ Initial mass
Density 2,6 g/cm3
Elastic modulus 77000 MPa
Poisson’s ratio 0,3
Ultimate tensile strenght 240 MPa
Yield strenght 180 MPa
Material data (AlSi7)
Constraints
University of Parma
The aim of the optimization is to minimize the stresses on the support, possibly reducing the weight and increasing its natural frequency of the normal mode I (ωRI) over an assigned treshold.
13/18
Claudia Raffaldini
Iterative change of the Design Region to satisfy the second check on the initial geometry quality
Loading
Rigid element (RBE2)
FY
Fz
FX
University of Parma
Component to be optimized Initial design – 1st version Initial design – 2nd version Initial design – 3rd version
Loadcases: Bump (4g acceleration along y axis) + steering dx/sx
14/18
Original support Original support
Claudia Raffaldini
Structural strength improvement (3rd version of the initial design)
Optimized support Original support
University of Parma
Better stress distribution (at a
reasonable distance from the fixed nodes)
15/18
Sensitivity to optimization parameters:
- Design Region extension
- Average element size
- Draw direction
- Minimum/maximum member size
Claudia Raffaldini University of Parma
Influence of the settings of the parameters on the design variations
1
1
2
2
3
3
4
4
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Claudia Raffaldini
Outcome: design improvement
Original support Optimized support
Variation (%)
Mass (Kg) 2,82 2,95 5
ωRI (Hz) 1382 1275 -8
Max Von Mises stress (MPa)
81 43 -46
University of Parma 17/18
Significant stress reduction, despite little variations on mass and natural frequency of the first mode.
Claudia Raffaldini
Method successfully applied to automotive components (alternator bracket, engine support)
Stiffness targets met, satisfying mass requirements
Possible expansion: - Improvement of the Design Region setting up step
- Fatigue analysis
- Other components
- Other optimization algorithms
- Software benchmarking
Faster optimization
University of Parma
Settings of the optimization parameters
Structural analysis of the component to be
optimized
Definition of initial geometry of the component
Analysis and modification
Analysis of results
First check: parameters quality
Second check: initial geometry quality
x
x
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