Structural re-design of engine components

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2 Structural re-design of engine components Product design cycle Design Development Testing Structural optimization Product knowledge Design freedom 2/18

3 Structural re-design of engine components Product design cycle Design Development Testing Structural optimization 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, Initial design Optimized design Failure Max stress 3/18

4 Structural re-design of engine components Product design cycle Design Development Testing Structural optimization ALTERNATOR BRACKET METHOD ENGINE SUPPORT Two applications examined in thesis work: 4/18

5 Numerical optimization method implemented by FEA software Altair HyperMesh (OptiStruct) 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, Geometry to be optimized Initial design volume Optimized geometry Boundary conditions assigned to the FEM model of the component to be optimized Extension of the initial design volume, according to the BCs Selective material removal from the design volume, made by OptiStruct Topological optimization: material redistribution applying the SIMP Method (Solid Isotropic Material with Penalization): density [0,1] finite element 0 5/18

6 Widespread, useful for every optimization process Input data - CAD/FEM model - Boundary/loading conditions - Experimental data Structural analysis of the component to be optimized Setting up of the Design Region Definition of initial geometry of the component - Technological and manufacturing constraints - Hardware limitations Settings of the optimization parameters Analysis and modification Analysis of results First check: parameters quality Second check: initial geometry quality x x 6/18

7 Bracket used to connect the alternator to the engine 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 (ω RI ) must be increased over an assigned treshold, possibly reducing the weight of the structure. This is the aim of the optimization. Constraints TARGET ω RI > 250 Hz CONSTRAINT Mass Initial mass Material data (AlSi7) Density 2,7 g/cm 3 Elastic modulus MPa Poisson s ratio 0,3 7/18

8 Bracket used to connect the alternator to the engine TARGET ω RI > 250 Hz CONSTRAINT Mass Initial mass Meshing Overall view of the optimization process made on the bracket: Original Design Region Optimized 8/18

9 Modal analysis of the orginal design Pre-processing Simulation Post-processing Mode I Mode II Mode III 244 Hz 435 Hz 757 Hz Deformed shapes for the first 3 normal modes 9/18

10 Change in the geometry Setting up of the Design Region Excluding the bolt seats Pre-processing Simulation Post-processing Density plot treshold = 0,3 Geometry reconstructed using the OSSmooth tool ω RI = 273 Hz Analysis of results Geometry reconstruction and modal analysis OptiStruct automatically elimiminates FEs that don t have a structural function 10/18

11 Structural verification Uniform distribution of the Element Strain Energy (at a reasonable distance from the fixed nodes) Outcome: design improvement Increase of the natural frequency of the normal mode I maintaining the initial mass Original bracket Optimized bracket Variation (%) Mass (g) ω RI (Hz) /18

12 Test with different boundary conditions Fixing nodes on the bolt holes Fixing nodes on the highlighted surfaces Extending the Design Region Optimization could sometimes generate unfeasible designs, requiring an iteration of the parameters setttings step in the overall process. 12/18

13 Engine support to fasten the engine base on the car frame 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 (ω RI ) over an assigned treshold. TARGETS ω RI > 300 Hz Minimize the stresses CONSTRAINT Mass Initial mass Constraints Material data (AlSi7) Density 2,6 g/cm 3 Elastic modulus MPa Poisson s ratio 0,3 Ultimate tensile strenght Yield strenght 240 MPa 180 MPa 13/18

14 Iterative change of the Design Region to satisfy the second check on the initial geometry quality Component to be optimized Initial design 1st version Initial design 2nd version Initial design 3rd version Loading Rigid element (RBE2) Loadcases: Bump (4g acceleration along y axis) + steering dx/sx F X F z F Y 14/18

15 Structural strength improvement (3rd version of the initial design) Better stress distribution (at a reasonable distance from the fixed nodes) Optimized Original support Original support 15/18

16 Influence of the settings of the parameters on the design variations Sensitivity to optimization parameters: Design Region extension - Average element size - Draw direction - Minimum/maximum member size 16/18

17 Outcome: design improvement Original support Optimized support Variation (%) Mass (Kg) 2,82 2,95 5 ω RI (Hz) Max Von Mises stress (MPa) Significant stress reduction, despite little variations on mass and natural frequency of the first mode. 17/18

18 Structural analysis of the component to be optimized Method successfully applied to automotive components (alternator bracket, engine support) Definition of initial geometry of the component Stiffness targets met, satisfying mass requirements Settings of the optimization parameters Faster optimization Analysis and modification Analysis of results First check: parameters quality Second check: initial geometry quality x x Possible expansion: - Improvement of the Design Region setting up step - Fatigue analysis - Other components - Other optimization algorithms - Software benchmarking 18/18