Topology Optimization of Engine Mount Brackets Dr. Dirk Sprengel Ford Werke GmbH

Transcription

1 Topology Optimization of Engine Mount Brackets Dr. Dirk Sprengel Ford Werke GmbH Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 1 ( 21 )

2 EMS Bracket Funktion EMS: Engine Mount System Link between engine and body EMS bracket assembled with: Cylinder Head Engine mount Alternator (Cover) Durability crash, extreme driving conditions NVH, driving comfort no transfer, amplification of engine vibrations, no eigenmodes in driving range Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 2 ( 21 )

3 Problem Definition, Task Conventional bracket design: EMS involved into several engine eigenmodes Local EMS frequency below target of 500 Hz (example: 420, 470 Hz) Run Topology Optimization to Improve modal behaviour of bracket ( f i > 500 Hz ) ( Ensure durability ) Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 3 ( 21 )

4 Define Optimization Volumes and Design Rules Draw directions Obstacles ~ elements regular voxel mesh Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 4 ( 21 )

5 Optimization Submodel, Boundarys, Loads Cylinder Head Alternator Static: loads F bolt 50 kn + F h 10 kn + F h - 10 kn + F v 10 kn + F v - 10 kn + F l 10 kn 5x Engine Block EMS Ring Dynamic: max. Eigenfreq.: Alternator horz. + EMS EMS local (>500Hz) Alternator vert. Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 5 ( 21 )

6 Optimization Run Design Recommendation Run OptiStruct Min. Static Loads 5x Max. Eigenfrequencies No. 1,2,3 Volume: 30% of design space (~ old bracket volume) Iteration 19 Density >= 0.3 Color: casting constraints Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 6 ( 21 )

7 Robustness Check of Optimization Run Single Optimization Frequency (w/o static loads) Check balance between: Min. compliance ( static ) Max. Eigenfrequencies ( modal) Influence of Volumefrac target : 20% instead of 30% Change of boundary conditions or loads Change of draw directions Other OptiStruct features (maxmb) Main features with small design changes Changed weight factor: 10x small design changes 20% results in weaker design with same design features Not checked Not checked: Not used (model size) The optimization seems to be robust, the final design was useful. Base features have been recommended for new CAD geometry. Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 7 ( 21 )

8 Opti CAD Geometry FE check new part CAD / FE Modal analysis of complete P/Train: Reduced participation of EMS 1. Local EMS Mode from 470 Hz to 681 Hz No check of stress distribution Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 8 ( 21 )

9 Next Task: Changed Engine Installation Angle, Position Prototype (449 Hz, local stress concentrations) improve it! Changed bolt position results in a sharp corner near a thread Stress concentration Changed bolt position results in a deep hole ( cast draw ) Stress concentration Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 9 ( 21 )

10 Bracket II Optimization Task Dynamic: Static : 500 Hz Min. compliance Topology Optimization + Stress reduction OptiStruct + Engineering Judgement!! The definition of design space + draw rules should lead to an optimization result with feasible stress distribution. Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 10 ( 21 )

11 Bracket II Optimization Model: Single / Split Draw Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 11 ( 21 )

12 Optimization Model: Final Cut Design space Cut out to avoid stress concentration or to reduce mass concentration Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 12 ( 21 )

13 Bracket II Optimization Run CAD OptiStruct CAD Added features ( lifting eye, cover flange, ) Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 13 ( 21 )

14 Dynamic Performance Modal behaviour CAD FEM remeshed, complete P/Train EMS 1. Mode: 538 Hz (Prototype: 449Hz, Target: 500Hz) general: reduced modal EMS participation Stress distribution No direct optimization task, driven by model features see next pictures Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 14 ( 21 )

15 Stress Analysis: Bolt foces 50 kn + EMS vertical 10 kn Prototype Design Final Design Critical high tension at corner Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 15 ( 21 )

16 Stress Analysis: Bolt foces 50 kn + EMS vertical 10 kn Prototype Design Final Design Stress Analysis Bolt foces 50 kn + vertical EMS load 10 kn Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 16 ( 21 )

17 Successful EMS Evolution High improvement of part functionality Bracket I Modal 681 Hz Robustness study (optimization model, loads, parameters) Bracket II : Modal 538 Hz Stress distribution durable Based on bracket I model, experience Well prepared for stress reduction Lecture What structure do we really need? Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 17 ( 21 )

18 Start Product Development with Optimized Design Target setting Cost of changes Design changes Concept Product Development Job 1 Time Base design features by Optimization First in Chain! + Short time reaction with Optimization tool Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 18 ( 21 )

19 Education Process Management Opti CAD CAE First in Chain! CAE: Optimization Take the lecture! Improve process Persuade people What structure do we really need? All Update Engineering Judgement No Design by Rules Design by Need Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 19 ( 21 )

20 Final Message Optimize! Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 20 ( 21 )

21 Thank You! Dr. D. Sprengel 6/2007 Topology Optimization of EMS Bracket 21 ( 21 )