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:

8/18

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

16/18

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

18/18