Requirements regarding Fatigue Tests of a Composite Wheel with Integrated Hub Motor

Transcription

1 Requirements regarding Fatigue Tests of a Composite Wheel with Integrated Hub Motor Functional and Innovative Lightweight Concepts and Materials for HEVs Switzerland, Oct. 09th-10th 2014 HEV 2014 Fraunhofer LBF A. Büter, D. Laveuve, O. Schwarzhaupt Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF Seite 1

2 Summary Example: Design and manufacturing of FRP-wheel with integrated hub motor Workflow Design methodology Manufacture Special considerations regarding durability-tests for FRP-wheels Influencing parameters Challenge: Damage equivalence Outlook Testing of combined functionality of hub-motor driven wheel Seite 2

3 Example: Fraunhofer Systemforschung Elektromobilität Seite 3

4 Multifunctional design of an FRP wheel with hub-motor 1. CAD-design 6. Testing 5. Manufacturing Requirements: 2. Identification of critical areas strength, space, mass, 4. Mold design & fabrication integration of electric drive 3. Optimization Load case analysis Lay-up definition Seite 4

5 Multifunctional design of an FRP wheel with hub-motor electric motor Motor Power: 4kW (Voltage: 2*24,5V) Seite 5

6 Composite Wheel With Integrated Hub-motor - Summary Wheel size: 6,5 x 15 Wheel mass: Basic wheel: ca. 3.5kg Motor-housing: ca. 1.4kg Wheel load: 450kg (static) Load cases: Straight driving F v = 10,2 kn F h = ± 3,15 kn Cornering F v = 8 kn F h = 6,2 kn Seite 6

7 Calculation and Identification of the Optimal Ply Layup Area, Area Location and Fiber Orientation Seite 7

8 Simulation and Visualization of Draping in CAD Spoke 45 -ply Spoke 0 -ply Offset 45 -ply Offset 0 -ply Seite 8

9 Tooling - Design of the Mold Part 1 Rim region Part 2 Spoke region Seite 9

10 Patches for the Spokes Flat-patterns Cut prepreg Seite 10

11 CFRP-Wheel With Hub-motor: Manufacturing Seite 11

12 Seite 12

13 Classification of Components Considering Safety And Functionality Depending of component-class, different requirements for design and testing apply. Seite 13

14 Loading of Safety-components And Possible Effects Structural durability of safety-components Operational loading Fatigue strength / stiffness-/strength-evolution Eigenmodes / eigenfrequencies Special event / misuse Buckling Yielding Impact behavior Environmental conditions Ageing Seite 14

15 Mechanical Failure Criteria Fracture No failure due to cyclic loading during designlife (approx km) Stiffness degradation No exceedance of allowable deformation (usability) Residual strength Endure the maximum operational load at any time (also at the end of design-life time; No Sudden Death ) Quelle: Grubisic Seite 15

16 Requirements For A Reliable Durability Proof Service-like deformation of the entirely assembly, including the influences from environmental conditions, wear and long term service Service-like load program with typical load cases (e.g. cornering, straight driving, bad road driving, breaking operations, temperature, centrifugal forces etc.) Correct load correlations for individual load-cases Damage equivalence between test load program and usage under operational conditions Therefore: Fatigue test on component must be checked, if the design, the material or the manufacturing technique changed! Standard of Valuation: Damage Equivalence Seite 16

17 Zweiaxialer Radprüfstand (ZWARP) Test Spectra: Standardized Load Spectra (damage equivalent synthetic test spectra) Challenge: Test spectra (originally developed for metal wheels) need to be adapted for FRP to ensure damage equivalence. Seite 17

18 Multiaxial Stress-states + Inhomogenous and Anisotropic Material (Composite) F z F F x Different local stress-spectra for running wheel (simplified) Node x Node y Load Spectrum Requirement: For each point of the wheel the accumulated damage caused by test spectrum must be similar to the damage due to design spectrum! Seite 18

19 Outlook: Electro-mechanical System-reliability Seite 19

20 For multifunctional composite parts, test-methods need to be reconsidered. Seite 20

21 Thank you for your attention! Questions? Seite 21

22 Fraunhofer LBF - Lightweight Structures Mean Areas of LBF Load analysis and -monitoring considering fatigue Characterisation of new lightweight materials considering the manufacturing methods Design and Structural Optimisation Stability, Durability and Reliability Investigations based on testing and numerical calculations Functional expansion such as Adapronics and Structural Health Monitoring Services and Products Determination of fatigue life Development of adapted failure models and strength theories Optimisation of components and Structural Systems Design of Fail Safe Structures Evaluation of Joints Evaluation of manufacturing and repair techniques Durability tests of lightweight structures & components (exp. & num.) Development of adapted SHM Systems for lightweight structures LBF Wing Mock-Up with 18 DMS; 16 FOBGs, Sensor coating, 8 Piezo-Modules Seite 22

23 Prof. Dr.-Ing. Andreas Büter Head Light-Weight Design Fraunhofer-Institute for Structural Durability and Systemreliability LBF Bartningstr. 47, Darmstadt, Germany Tel.: Fax.: Seite 23